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2015v1.0
Imaging Physics
CASE REVIEW SERIES
Series Editor
David M.Yousem, MD, MBA
Vice-Chairman Radiology, Program Development
Associate Dean, Professional Development
Department of Radiology
Johns Hopkins School of Medicine
Baltimore, Maryland

Volumes in the CASE REVIEW Series

Brain Imaging
Breast Imaging
Cardiac Imaging
Duke Review of MRI Physics
Emergency Radiology
Gastrointestinal Imaging
General and Vascular Ultrasound
Genitourinary Imaging
Head and Neck Imaging
Imaging Physics
Musculoskeletal Imaging
Neuroradiology
Non-Interpretive Skills for Radiology
Nuclear Medicine and Molecular Imaging
Obstetric and Gynecologic Ultrasound
Pediatric Imaging
Spine Radiology
Thoracic Imaging
Vascular and Interventional Imaging
Imaging Physics
CASE REVIEW SERIES

R. Brad Abrahams, DO, DABR

Interventional and Diagnostic Radiologist
Radiology Consultants of the Midwest
Assistant Clinical Professor of Radiology
Creighton University
Omaha, Nebraska

Walter Huda, PhD

Professor of Radiology
Geisel School of Medicine at Dartmouth College
Director of Physics Education
Dartmouth-Hitchcock
Lebanon, New Hampshire

William F. Sensakovic, PhD

Diagnostic Medical Physicist
Florida Hospital
Associate Professor of Medical Education
University of Central Florida
Orlando, Florida
IMAGING PHYSICS: CASE REVIEW SERIES ISBN: 978-0-323-42883-5
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For my wife Jen, my parents, and all of my teachers
-RBA
For my wife Joyce
-WH
For Jen, Bohdan, and Evie
-WFS
This page intentionally left blank

     
 FOREWORD

I am so excited about the launch of this new edition of the in preparing to tackle radiological physics…and the American
Case Review Series. We had not, until now, been able to bring a Board of Radiology Core and Certifying exams.
comprehensive imaging physics volume to the series. We have, The approach here is unique in that it is case-based and relies
however, had the excellent Duke Review of MRI physics edi- on imaging studies to make the teaching points, as opposed to
tion that was published in 2012 and is due for another release lots of equations and diagrams and dry text. Perfect for the Case
shortly. There was a gap. Review Series.
Who better to write the content for this new volume than Welcome to the series, gentlemen!
the person whose name is associated with great teaching on the Please enjoy!
subject—Professor Walter Huda. Huda and physics go together David M. Yousem, MD, MBA
like salt and pepper. He was the best “catch” of the Case Review Professor of Radiology
Series, and we have benefited from it. He asked for the support Director of Neuroradiology
of Drs. R. Brad Abrahams and William Sensakovic to create the Russell H. Morgan Department of Radiology Science
dynamic trio.We feel certain that these stellar authors have cre- The Johns Hopkins Medical Institutions
ated an edition that will assist residents and trainees at all levels Baltimore, Maryland
This page intentionally left blank

     
 PREFACE

The incorporation of radiological physics into the American followed by a short discussion. There is an illustrated figure
Board of Radiology Core and Certifying examinations has made or artifact simulation paired with each discussion to comple-
a dramatic impact on radiology physics education. This has ment the topic. Despite the intimate relationship of physics
been a welcome change to the many clinically minded trainees and mathematics, we have attempted to limit the appearance of
and educators in the field of radiology. Despite the abundance numbers and equations in this book. Although the memoriza-
of high-quality physics resources, few authors have framed tion of certain numbers is unavoidable, most of the numbers
the discussion of physics using a case-based and image-rich provided in the following cases were added to give a “ballpark”
approach. We hope that the addition of this book to the Case idea of values or to illustrate specific examples.
Review Series will fill this gap. There is an ever-increasing focus on patient safety in medi-
Although physics is the foundation of radiology, many of us cine, and it is our responsibility to balance the clinical benefit
often overlook its importance in our daily clinical work. There and the negative consequences of imaging studies. While the
can sometimes be a disconnect between the granularity of phys- first 12 chapters of this book focus on the physics of radiologi-
ics and the real-world needs of patient X on our exam table. cal modalities, the last two chapters are dedicated to radiation
Even though there is not always a direct connection between doses and safety topics. These chapters will be a great resource
every clinical image and physics principle, understanding the for both exam preparation and the clinical practice of radiology.
underlying concepts of radiological physics will pay dividends Unlike other topics in radiology, radiological physics is not
to the reader for years to come. Throughout your career you something that can be predominantly learned at the worksta-
will be tasked with optimizing image quality, troubleshooting tion. Combining didactics, reading, self-study, practice ques-
artifacts, purchasing equipment, and building on your knowl- tions, and clinical learning is the best approach to mastering
edge as new technologies emerge. the basic principles of radiological physics. We hope that you
This book follows the familiar structure of other books in the enjoy this case-based approach to learning and wish you the
Case Review Series. The chapters are generally broken down best in your exciting career.
into modalities, with each case highlighting a specific topic.
The case begins with a clinical image and several multiple- R. Brad Abrahams
choice questions pertaining to the physics principle of interest. Walter Huda
The answers and explanations are shown on the reverse page, William F. Sensakovic
This page intentionally left blank

     
 CONTENTS

Radiographic Imaging 1

Mammographic Imaging 27

Fluoroscopy With Image Intensifiers 51

Interventional Radiology With Flat-Panel Detectors 73

Computed Tomography Basics 99

Computed Tomography Imaging 125

Gamma Cameras 151

Single-Photon Emission Computed Tomography and Positron Emission Tomography Imaging 177

Magnetic Resonance Basics 211

Magnetic Resonance Imaging 237

Ultrasound Basics 273

Ultrasound Imaging and Doppler 297

Radiation Doses 319

Radiation Safety 353

Index 381
This page intentionally left blank

     
CHAPTER 1 Radiographic Imaging

C A S E 1 .1

A B
Fig. 1.1

1. What is most likely to be affected by the choice of a radio- 3. What is most likely reduced when focal spot size is in-
graphic focal spot size? creased?
A. Radiographic mottle A. Grid artifacts
B. Lesion contrast B. Image mottle
C. Spatial resolution C. Lesion contrast
D. Image artifacts D. Motion blur
2. Increasing what parameter will most likely result in the 4. What radiographic examination most likely uses a small fo-
largest increase in focal spot blur? cal spot?
A. Geometric magnification A. Extremity
B. X-ray tube voltage B. Skull
C. X-ray tube current C. Chest
D. Exposure time D. Abdomen

1
ANSWERS

C A S E 1 .1
Tungston target
Focal Spot Heated filament (anode)
Fig. 1.1 Chest radiograph in an adult patient (A) using a large focal (cathode) Anode angle
spot and hand radiograph of a pediatric patient (B) using a small (15°)
Electrons
focal spot.
X-ray beam
C. Spatial resolution is the image quality metric that is af-
1. 
fected by the focal spot because a larger focus increases Fig. 1.2 Electrons flow from the cathode to the anode, colliding with
focal spot blur, especially when there is geometric magnifi- the tungsten target and producing x-rays.
cation.The focal spot has no effect at all on mottle, contrast,
or artifacts.
A. Focal spot blur always increases with increasing geomet-
2. 
ric magnification. When magnification mammography is
performed, it is essential to use a very small focal spot (0.1
mm) to reduce focal spot blur. Increasing the tube voltage,
tube current, and exposure time will have no significant ef-
fect on focal spot blur.
D. When the focal spot is increased, this usually means that
3. 
the power incident on the target can be increased. Increas-
ing power will mean that exposure time can be reduced,
which helps to minimize motion blur. Focal spot size will
not affect grid artifacts, mottle, or contrast in radiographic
images.
A. Use of a small focal spot in an extremity exam is impor-
4. 
tant to reduce focal blur and improve the chance of de-
tecting (small) hairline fractures. Large focal spots are used
in the skull, chest, and abdomen to reduce exposure times,
and where detection of small features is unlikely to be a
major diagnostic task.
Comment
The focal spot in radiography is the size of the x-ray tube Fig. 1.3 With no geometric magnification, there is no focal spot blur
region that produces x-rays. When electrons hit the target (upper image). When the object-to-detector distance is increased,
located in the x-ray tube anode, x-rays are produced. The the image is magnified and blurred (middle image). Switching from
power used in x-ray tubes is much greater than in an aver- a large focal spot to a small focal spot is essential to reduce image
age domestic home (e.g., 100 kW vs. 4 kW), and overheating unsharpness with geometric magnification (lower image).
issues can be important in radiologic imaging. For this reason,
the target is arranged to be at a small angle (e.g., 15 degrees) small focal spot power limit. In most of radiography, the key
so that a large area is irradiated but appears relatively small issue is a reduction of the exposure time and thereby the corre-
when viewed from the patient perspective (Fig. 1.2). The sponding amount of motion blur. Accordingly, a large focal spot
size of the focal spot influences image sharpness (blur), with is essential where exposure times must be minimized (chest).
larger focal spots typically resulting in blurrier images than When the amount of image detail becomes important, such
small ones (Fig. 1.3). The focal spot poses a fundamental limit as detection of hairline fractures in extremity imaging, a small
on the sharpness of any image. Once such a limit is reached, focal spot is used. When the imaged body part is not very
use of smaller pixels will not translate into improved imaging attenuating, the amount of radiation required to penetrate the
resolution performance. patient will be less. Although using a small focal spot in extrem-
The amount of focal blur is critically dependent on the ity imaging increases exposure time, this is counteracted by
amount of geometric magnification. The amount of geometric improved radiation penetration so that motion blur does not
magnification is determined by the distance from an object to become problematic.
the image receptor, relative to the distance from the focal spot
to the image receptor. As geometric magnification increases, References
focal spot blur also increases, requiring the use of smaller focal Bushberg JT, Seibert JA, Leidholdt EM Jr, Boone JM. X-ray production, x-ray tubes,
spots (see Fig. 1.3). Geometric magnification is sometimes used and x-ray generators. In: The Essential Physics of Medical Imaging. 3rd ed.
in interventional neuroradiology and requires special x-ray Philadelphia: Wolters Kluwer; 2012:181–184.
tubes with exceptionally small focal spots. Huda W. Image quality. In: Review of Radiological Physics. 4th ed. Philadelphia:
Wolters Kluwer; 2016:36–37.
Most conventional x-ray tubes use two focal spot sizes, a
Huda W. Radiography. In: Review of Radiological Physics. 4th ed. Philadelphia:
small one (0.6 mm) and a large one (1.2 mm). The power limit Wolters Kluwer; 2016:91–99.
on the large focal spot (100 kW) is four times greater than the

2
C A SE 1. 2

Fig. 1.4

1. What is impacted the most when milliampere-seconds (mAs) 3. Which of the following detectors is expected to be quan-
is adjusted? tum mottle limited for chest radiography?
A. Mottle A. Scintillator (cesium iodide)
B. Contrast B. Photoconductor (selenium)
C. Sharpness C. Photostimulable phosphor (PSP) (BaFBr)
D. Artifacts D. A, B, and C
2. Which radiographic examination most likely uses the low- 4. How will quadrupling the mAs used to perform a bedside
est mAs? radiograph affect the amount of noise (mottle) in the im-
A. Skull age?
B. Extremity A. Quadrupled
C. L-spine B. Doubled
D. Abdomen C. Halved
D. Quartered

3
ANSWERS

C A SE 1. 2 Comment
Consider a conventional chest x-ray where the selected x-ray
Tube Output and Mottle tube voltage is set at 120 kV.The x-ray tube current will be sev-
eral hundred mA (e.g., 400 mA), and the exposure time will be
Fig. 1.4 Chest radiograph with extremely low mAs. Note the visible very short (e.g., 2.5 ms).The total x-ray intensity (x-ray tube out-
noise in the image.
put) is the product of the tube current and exposure time and,
in this instance, equal to 1 mAs. For an abdominal radiograph,
A. The number of photons used to create any radiographic
1. 
the tube current would likely be several hundred mA (say, 400
image will affect only the amount of mottle. Quadrupling
mA), but the exposure time would be much longer to penetrate
the number of photons will halve the amount of mottle.
the much thicker body part (say, 50 ms). The total x-ray inten-
The mAs generally has no effect on contrast, sharpness, or
sity in this abdominal radiograph would be 20 mAs, or 20 times
the artifacts in the resultant image.
greater than the chest x-ray. When more radiation is required,
B. An extremity would use an mAs that is very low and
2.  this is achieved by increasing the tube current, the exposure
much less than a skull, L-spine, or abdomen. Two useful time, or both.The ideal scenario is to increase the tube current,
benchmarks in radiography are 1 mAs for a chest radio- but because focal spot power loading (i.e., heating) will also
graph (posteroanterior [PA]) and 20 mAs for an abdomen increase, this may not always be possible.
(anteroposterior [AP]). The former is one of the low values The mAs is a relative indicator of x-ray tube output and is
implemented in radiography, and the latter is one of the increased whenever “more radiation” is required to create a
high values. radiologic image. It is important to note that knowledge of the
mAs does not permit a definitive determination of the amount
D. All medical imaging systems are normally operated at ex-
3.  of radiation that is being emitted. X-ray tube output depends
posure levels that guarantee that they are quantum mottle on a number of additional factors, including x-ray tube design,
limited. What this means is that the only technical way to tube voltage, and x-ray beam filtration. The absolute amount of
reduce mottle is to use more photons to create the image, radiation incident on the patient is given by the entrance air
which will also increase the patient dose. kerma (Kair), which is approximately 1 mGy for a lateral skull
C. The noise is halved when the number of photons is qua-
4.  x-ray. The absolute amount of radiation incident on the image
drupled. When four images are added together, the signal is receptor is much lower than entrance Kair and typically 3 μGy.
quadrupled. Because noise is random, adding four images The radiation intensity at the image receptor is much lower
together will only double the noise. The overall improve- because of patient attenuation, increased distance from the
ment by adding N images together in any imaging modality focus, and losses in the antiscatter grid. It is helpful to think of
is usually given by N0.5. mAs as analogous to the tachometer in a car, where increasing

Electrons

mAs
(quadruple)

Target

Photons

Noise
(half )

Fig. 1.5 Quadrupling the mAs will result in a fourfold increase in the number of x-rays produced but will reduce image noise only by half.
Increasing mAs will not increase the photon energy or beam quality, and so the contrast of all lesions will remain exactly the same. On the left,
lesion contrast is the same as on the right, but lesion visibility is inferior because of higher noise.

4
revolutions per minute (rpm) will increase car speed. However, Random noise is important because it limits the visibility
it is the speedometer that tells you the absolute speed, which of low-contrast lesions. Noise is irrelevant when the lesion
depends on engine design and the gear you are in (≡ Kair). has high contrast, irrespective of whether the lesion is large
Noise is any unwanted signal in a medical image and can be or small. However, to assess the visibility of any lesion, it is
considered to be structured or random. A rib cage in a chest important to take into account both the amount of contrast
radiograph may mask a lung lesion, as an example of structured and the corresponding level of noise.The contrast-to-noise ratio
(or anatomic) noise. When a detector is uniformly irradiated, (CNR) is a number that is used to assess how lesion visibility is
not every pixel has exactly the same value, and there will be a affected when radiographic techniques (kV and mAs) are modi-
salt-and-pepper appearance that is called mottle (noise). Quan- fied. When mAs is increased, contrast is unchanged and noise
tum mottle results from the discrete nature of x-ray photons is reduced, so the CNR increases and the lesion becomes more
and is the only important source of random noise in x-ray– visible. When automatic exposure control (AEC) systems are
based imaging. The only technical way to reduce the amount used, noise is “fixed” so that lesion CNR is solely determined by
of mottle in an x-ray–based image is to increase the number the choice of voltage. For AEC exposures, high voltages reduce
of photons interacting with the detector, either by improving contrast and vice versa.
detection efficiency or by using more photons (Fig. 1.5). The References
latter method of using more photons by increasing the mAs
Huda W. Image quality. In: Review of Radiological Physics. 4th ed. Philadelphia:
used will also increase patient dose. It is possible to reduce the
Wolters Kluwer; 2016:33–40.
apparent mottle using image-processing techniques, but these Huda W, Abrahams RB. Radiographic techniques, contrast, and noise in X-ray imag-
come at a cost in terms of imaging performance. For example, ing. AJR Am J Roentgenol. 2015;204(2):W126–W131.
averaging four pixels together will result in less random inter-
pixel fluctuations, but spatial resolution performance will also
be reduced.

5
This page intentionally left blank

     
C A SE 1.3

A B
Fig. 1.6

1. X-ray beam quality is independent of which x-ray beam fac- 3. Which parameter is generally independent of lesion con-
tor? trast?
A. Tube voltage (kV) A. Tube output (mAs)
B. Tube output (mAs) B. Tube voltage (kV)
C. Filter thickness (mm) C. Beam filtration (mm)
D. Filter atomic number (Z) D. Grid ratio (10:1)
2. What will happen to patient dose and lesion contrast when 4. How will reducing the display window width impact lesion
0.1 mm Cu is added as a filter in a pediatric x-ray examina- contrast in the image?
tion performed using an AEC system? A. Increase
A. Increase; Increase B. No effect
B. Increase; Decrease C. Reduce
C. Decrease; Increase
D. Decrease; Decrease

7
ANSWERS

C A SE 1.3 Comment
When x-rays interact with patients, the two most important
Beam Quality and Contrast processes are photoelectric absorption and Compton scatter.
As photon energy increases in the human body, the likeli-
Fig. 1.6 (A) and (B) Frontal chest radiograph in a patient with mul- hood of an interaction decreases. As a result, increasing photon
tiple metastatic pulmonary masses. The image taken at higher kV (B)
has lower soft tissue contrast.
energy will increase the amount of radiation that is transmitted
through the patient. The penetrating power of an x-ray beam,
B. Tube output (mAs) has no effect on x-ray beam quality.
1.  which reflects its average energy, is quantified by the thickness
Voltage and beam filtration are important variables that of aluminum (mm) that attenuates half of the x-ray beam inten-
radiologists have to adjust the beam quality in any radio- sity. For example, the average voltage in abdominal radiography
graphic examination. Average x-ray beam energy can also is 80 kV, where the corresponding beam quality is approxi-
be adjusted by changing the filter thickness or x-ray beam mately 3 mm aluminum. If the average energy is reduced, less
filter atomic number. aluminum is required to halve the x-ray beam intensity, and
when the average energy increases, more aluminum would be
D. The addition of 0.1 mm Cu to an x-ray beam will prefer-
2.  required to halve the x-ray beam intensity. X-ray beam quality
entially eliminate low-energy photons, resulting in a more affects patient dose for examinations performed using AEC with
penetrating beam. To maintain the same radiation intensity a fixed Kair at the image receptor. As the x-ray beam becomes
at the image receptor, less radiation is required to be inci- more penetrating, fewer photons need to be used to achieve
dent on the patient, so the dose is reduced. The difference the required Kair at the image receptor, resulting in a decrease
in transmitted radiation between a lesion and the surround- in patient dose.
ing background is always reduced when energy increases, A lesion must transmit more or less radiation than the sur-
so contrast goes down. rounding tissues to be observable. The lesion will appear darker
when more radiation is transmitted. Conversely, the lesion
A. The mAs used to generate a radiographic image never
3.  will appear lighter when less radiation is transmitted. Photon
affects contrast. If a lesion transmits 10% less radiation than energy is the most important determinant of subject contrast
do the surrounding tissues, this will be true at 1 mAs and at in radiography, with lower photon energies increasing contrast
1000 mAs. Contrast is reduced when voltage and filtration and vice versa. Photon energy increases with increasing x-ray
increase and is reduced when the amount of scatter in an tube voltage, as well as increasing x-ray beam filtration. These
image is increased, which occurs at lower grid ratios. increases would generally be expected to reduce the amount
A. When the window width is reduced, contrast in the
4.  of contrast in all radiographic images (Fig. 1.7).
displayed image will increase. Conversely, wide windows Changes in contrast are highly dependent on the atomic
­always reduce displayed image contrast. number of the lesion relative to that of soft tissues (Z = 7.5).

Low kV, High mAs High kV, Low mAs

Number of x-rays

Energy (keV) Energy (keV)

High contrast, high dose Low contrast, low dose

Fig. 1.7 This retained surgical lap pad can be easily seen in the left image, where kV is low and mAs is high. Patient dose is high because of the
need to use a lot of radiation to achieve a given amount at the image receptor. Raising the kV markedly reduces the contrast between the sponge
and surrounding tissue, but very little radiation is now needed because of the increased penetration to achieve the same radiation intensity at
the image receptor.

8
When the lesion atomic number is similar to that of tissue, with 200 in the surrounding tissues. The appearance of a lesion
changes in contrast with x-ray photon energy will be modest. in any radiographic image can always be adjusted by modify-
However, for high (or low) atomic number lesions, increas- ing the display characteristics (window/level settings). In chest
ing photon energy will markedly reduce lesion contrast. For computed tomography (CT), a narrow window is used to visu-
example, angiographic studies performed at high voltages (120 alize soft tissues. When a wide chest CT window is used to see
kV) will have very poor contrast in comparison with those per- all the tissues within the lung, perceived differences between
formed at an optimal voltage of 70 kV that matches the average soft tissues in the displayed image will “disappear.”
photon energy to that of the iodine K-edge (i.e., 33 keV).
Scatter reduces contrast but does not influence resolution References
or mottle. A lesion that transmits 50 photons compared with Huda W. Image quality. In: Review of Radiological Physics. 4th ed. Philadelphia:
100 for surrounding tissues has a 50% contrast. Adding 100 scat- Wolters Kluwer; 2016:31–33.
ter photons to all locations of this image would reduce the con- Huda W, Abrahams RB. Radiographic techniques, contrast, and noise in X-ray imag-
trast to 25% because there are now 150 in the lesion compared ing. AJR Am J Roentgenol. 2015;204(2):W126–W131.

9
This page intentionally left blank

     
C A SE 1.4

Fig. 1.8

1. What is most likely to be adversely affected by an increase 3. What is the typical exposure index (EI) for an adult body
in exposure time in radiography performed using AEC? radiograph?
A. Noise (mottle) A. 3
B. Patient dose B. 30
C. Geometric magnification C. 300
D. Image sharpness D. 3000
2. What improves when exposure time is increased on a table- 4. Which radiographic examination is most likely to make use
top examination (i.e., no AEC)? of AEC?
A. Lesion contrast A. Skull
B. Image mottle B. Extremity
C. Gridline artifacts C. Infant body
D. Motion blur D. Bedside chest

11
ANSWERS

C A SE 1.4 radiographs, typical exposure times are tens of milliseconds

and generally result in images with negligible motion blur.
Most radiographic examinations are performed using an
Exposure Time and Automatic Exposure AEC system (Fig. 1.9). The x-ray beam quality is selected by
Control the operator by adjusting the tube voltage (kV) and adding or
Fig. 1.8 Image blur from patient motion in a trauma patient. The removing filtration at the collimator. The examination is termi-
stationary backboard is sharp, whereas the projection of the patient nated when a radiation detector located at the image receptor
is blurred due to motion. registers a predetermined amount of radiation based on anat-
omy of interest (e.g., 3 μGy). This mechanism ensures that the
D. Image sharpness may be lost when exposure times in-
1.  right amount of radiation is used to generate each radiographic
crease, because of voluntary and involuntary motion by the image and avoids the problems of increased mottle (underex-
patient. Noise and patient dose stay the same when an AEC posed), patient dose, and risk (overexposed).
system is used because this fixes the amount of radiation In 2010 an agreement was reached between vendors and
at the receptor. With an AEC, a lower tube current would the imaging science community to standardize the way that EI
result in a longer exposure and vice versa (i.e., fixed mAs). is defined and transmitted to clinical practitioners. A radiation
Geometric magnification is not dependent on exposure intensity of 1 μGy would be expressed as an EI of 100, which is
time. directly proportional to the image receptor Kair. For each radio-
graphic examination the responsible radiologist should identify
B. A tabletop examination does not use an AEC system, so
2.  the target Kair with appropriate input from technologists, ven-
increasing the exposure time means that more radiation is dors, and imaging scientists. All state-of-the-art commercial sys-
incident on the patient and more is used to create the image. tems will generate a number (deviation index [DI]) to inform
As the mAs increases, mottle is reduced and patient dose will operators how closely a given radiograph actually met the target
also increase. Contrast will not be affected, whereas resolu- EI value (e.g., 300).A DI of −3 means that half the required radia-
tion due to motion blur (artifacts) will get worse, not better. tion was used, 0 means the target value was met, and +3 means
C. The radiation at the image receptor for most radiographic
3.  that twice the required amount was used. Values of EI and DI
examinations such as skull, chest, and abdomen is approxi- can be selected for display on workstations and are also located
mately 3 μGy, which will be recorded in the DICOM header as in the DICOM header associated with each radiographic image.
an EI of 300 and can be displayed on any PACS workstation. A radiation intensity (Kair) of 3 μGy would generate a good
radiographic image and is commonly used in all digital radiog-
A. Skull x-rays are generally performed using AEC systems.
4.  raphy of the head and body. Accordingly, the target EI value for
Extremity and infants can be exposed on the tabletop with most radiographic examinations is 300. If 1 μGy (EI = 100) were
no grid or AEC. AEC systems are impractical at the patient used, the mottle would be too high. If 6 μGy (EI = 600) or more
bedside in an intensive care unit (ICU) setting. were to be used, the patient would have been exposed to twice
the radiation than is actually needed for diagnostic purposes.
Comment
In extremity radiography, the EI value is usually set higher, at
The total time electrons are hitting the target to create x-rays approximately 1000. Extremities use very low-energy photons
is called the exposure time. This is an important protocol generated at 60 kV and deposit less energy into the x-ray detec-
parameter that impacts image quality, as well as the radiation tors. The higher EI ensures that the image quality (mottle) in
dose received by the exposed patient. Increasing the expo- extremities is comparable to that in conventional (screen-film)
sure time increases the number of photons that are incident radiographic imaging by ensuring that the same amount of
on the patient. Quadrupling the exposure time therefore will x-ray energy is absorbed in the radiographic detector.
quadruple the patient dose but will also halve the amount of
mottle in the resultant image. However, increasing exposure References
time also increases the likelihood of motion by the patient and American College of Radiology. ACR–AAPM–SIIM practice parameter for digital
is therefore more likely to result in a more blurred image. Chest radiography. Revised 2017. https://www.acr.org/-/media/ACR/Files/Practice-
x-rays have exposure times of a few milliseconds to minimize Parameters/rad-digital.pdf?la=en. Accessed March 1, 2018.
unavoidable heart motion, which goes through a complete Huda W. X-rays. In: Review of Radiological Physics. 4th ed. Philadelphia: Wolters
Kluwer; 2016:11–12, 96.
cardiac cycle in approximately 0.5 to 1 second. For abdominal

X-ray
timer

AEC ionization chamber

A B Image receptor

Fig. 1.9 (A) The rectangles illustrate the typical location of the automatic exposure control (AEC) detectors in chest radiography. (B) The AEC
detects the radiation intensity at the image receptor (air kerma) in predefined regions, which enables the exposure to be terminated when the
correct amount of radiation has been reached. In this way, the amount of mottle in the image is always fixed so that the right amount of radia-
tion is always used to create an image.

12
C A SE 1. 5

A B
Fig. 1.10

1. What part of an x-ray tube produces differential x-ray at- 3. What should be reduced to minimize the heel effect in radi-
tenuation that is called the heel effect? ography?
A. Cathode A. SID
B. Housing B. Anode angle
C. Filter C. Cassette size
D. Target D. A, B, and C
2. Changing what parameter is unlikely to influence the mag- 4. In what type of radiograph would x-ray tube orientation be
nitude of the heel effect in radiographic imaging? most important?
A. Tube output (mAs) A. Chest
B. Source-to-image receptor distance (SID) B. Skull
C. X-ray tube anode angle C. Abdomen
D. Radiographic receptor size D. Extremities

13
ANSWERS

C A SE 1. 5 toward the cathode pass through less of the target than those
that travel toward the anode.The tungsten target has a very high
atomic number (Z = 74), which attenuates almost as much as lead
Heel Effect (Pb) (Z = 82). As a result, the x-ray beam intensity at the anode
Fig. 1.10 (A) and (B) Frontal views of the abdomen demonstrating side of an x-ray tube has a reduced intensity when compared
how the appearance of an image changes when an x-ray tube is ro- with the corresponding radiation intensity at the cathode side
tated through 180 degrees. The top part of image B is more exposed of an x-ray tube. All commercial x-ray tubes label the anode side
(darker) due to increased exposure at the cathode side of the x-ray on the tube housing to enable operators to “know” the direction
tube (i.e., heel effect). with the highest (cathode) and lowest (anode) intensities.
As the anode angle is reduced, there is a greater differential
D. It is the differential attenuation in the tungsten target
1.  distance in path lengths that travel in the anode and cathode
that causes the heel effect. X-rays traveling in the anode directions, which increases the heel effect. Conversely, increasing
direction traverse much more of the strongly attenuating the anode angle will reduce the magnitude of the heel effect, but
tungsten (Z = 74), which results in a weaker x-ray intensity this is never eliminated (see Fig. 1.11). The heel effect increases
at the anode side of the x-ray tube (Fig. 1.10). The filter will with increasing distance from the central axis, so it is much more
attenuate all x-rays equally, and the cathode and housing pronounced with large cassette sizes. A small cassette size will
play no role in x-rays that are directed toward the patient. capture the central region of the x-ray beam where differences
A. The heel effect is not affected by the mAs used in radiog-
2.  in path length between opposite edges will be reduced (smaller
raphy. When the anode side is 25% weaker than the central heel effect). As the SID increases, an image receptor will increas-
beam, this will be true at 1 mAs and 1000 mAs. The heel ef- ingly capture only the central part of the x-ray beam, where the
fect increases with reduced SID, reduced anode angle, and magnitude of the heel effect is smaller. It is only at shorter SIDs
for larger image receptors based on irradiation geometry. that the heel effect becomes of increased importance.
The heel effect is always present in all x-ray–based imaging
C. When the cassette size is reduced, it is only the central
3.  systems and is used to improve the resultant imaging perfor-
region of the x-ray beam that is being used, which is more mance. In chest radiography, the more intense cathode side is
uniform than the larger beam. Reducing the SID and anode directed toward the abdomen, which attenuates much more
angle will increase the heel effect. than the chest and benefits from increased x-ray intensities.
A. In a chest x-ray, the anode should point toward the upper
4.  The less intense anode side is directed toward the upper tho-
chest region, which is much less attenuating. In all the other racic region, where x-ray attenuation is much lower than in the
examinations, the patient is “more uniform” than the chest, abdomen. Similarly, in mammographic imaging, the cathode
and the orientation of the x-ray tube (heel effect) is thus of side points toward the chest wall, whereas the anode side is
less importance. directed toward the nipple. In CT, the anode-cathode axis is ori-
ented perpendicular to the axial image plane to ensure that the
Comment detected projections are not influenced by the heel effect.
X-rays are produced when energetic electrons interact with References
tungsten atoms in the target that are embedded within an anode. Bushberg JT, Seibert JA, Leidholdt EM Jr, Boone JM. X-ray production, x-ray tubes,
These energetic photons are produced at some depth (<1 mm) and x-ray generators. In: The Essential Physics of Medical Imaging. 3rd ed.
in the tungsten and are attenuated as they emerge from the pro- Philadelphia: Wolters Kluwer; 2012:184–186.
duction site and travel toward the patient. Because the target is Huda W. Radiography. In: Review of Radiological Physics. 4th ed. Philadelphia:
angled at approximately 15 degrees (Fig. 1.11), x-rays that travel Wolters Kluwer; 2016:92–94.

Anode (+) Cathode (-)

Lower Higher
radiation radiation
intensity intensity

Fig. 1.11 In the upper right image, the heel effect occurs because photons produced in the tungsten target are attenuated as they exit and
move toward the patient. If the photon exits toward the cathode (1), there is less tungsten and therefore less attenuation along its path. If the
photon exits toward the anode (2), it is attenuated by a longer path within the target. In the radiograph, the lower intensity on the anode side
is directed to the less attenuating part of the patient (chest), and the higher intensity cathode side is directed to the more attenuating part of
the patient (pelvis).
C A SE 1.6

A B
Fig. 1.12

1. Which radiographic examination is most likely to use a scat- 3. What percentage (%) of primary x-ray photons is typically
ter removal grid? lost in grids used when performing adult abdominal radiog-
A. Skull raphy?
B. Extremity A. 10
C. Infant body B. 30
D. Bedside chest C. 70
D. 90
2. Which grid ratio is typically used to perform a chest x-ray
on a dedicated departmental imaging system? 4. What is the most likely dose reduction (%) in infant radia-
A. 2:1 tion dose when a grid is removed for a follow-up AEC radio-
B. 5:1 graph?
C. 10:1 A. 5
D. 20:1 B. 15
C. 50
D. 90

15
ANSWERS

C A SE 1.6 Primary beam Scatter

Grids
Fig. 1.12 Frontal views of the pelvis with a grid (A) and simulated
without a grid (B), where the latter showed a dramatic reduction in
contrast because of high scatter. Without the grid, for every primary
photon transmitted there are five scattered photons that dramati-
cally reduce image contrast.

A. Skull x-rays are performed with a grid, likely 10:1. Grids

1. 
are optional for thin anatomy such as an infant or an ex-
tremity, where the amount of scatter radiation is relatively 70% 90%
low. Aligning a grid at the bedside is very difficult, and scat- of primary beam of scatter
ter is usually reduced by the use of a lower x-ray tube volt- transmitted absorbed
age (80 vs. 120 kV).
Fig. 1.13 Grid septa transmit 70% of the primary beam while ab-
C. Most departmental radiographs, including chest x-rays
2.  sorbing 90% of scatter radiation. If the grid ratio is increased, more
on a dedicated unit, would use a 10:1 grid. A 5:1 grid is of the primary and scatter radiation will be absorbed by the grid and
used in mammography, and there are no 2:1 or 20:1 grids in vice versa.
current clinical practice.
B. Approximately 70% of the primary x-rays that are inci-
3.  scatter photons incident on the image receptor. When primary
dent on a grid will be transmitted through the gaps, and photons hit the septa, these are invariably lost, and in a 10:1 grid
the remaining 30% are lost in the Pb or W strips (Fig. 1.13). approximately 30% of the primary photons are attenuated (lost)
Losses could never be as low as 10% or as high as 70% in so that only approximately 70% are transmitted through to the
any clinical scatter removal grid. image receptor (see Fig. 1.13). Increasing the grid ratio improves
C. For an infant, the Bucky factor (BF), which is defined
4.  scatter removal but also increases primary photon losses and
as the incident/transmitted radiation through a grid, is ap- vice versa. The grid ratio is a useful guide to imaging perfor-
proximately 2. When the grid is removed, there is twice as mance but does not account for the overall size of the septa. An
much radiation incident on the AEC, so the radiation has to ­alternative approach to assessing grid performance is to con-
be reduced to 50% of the initial value. sider the amount of Pb used (areal thickness in gm/cm2), where
increased Pb content would likely improve scatter removal.
Comment In abdominal radiography, where the scatter-to-primary ratio
The amount of scatter radiation in abdominal radiography is is approximately 5:1, the use of a grid markedly reduces how
very high, amounting to up to five scattered photons for every much of the radiation intensity exiting the patient gets transmit-
primary photon transmitted through the patient. This amount ted through to the image receptor. The BF is the ratio of the
of scatter markedly reduces image contrast and would render incident radiation to that transmitted through the grid. A typi-
most radiographs “nondiagnostic.” Antiscatter grids are used cal BF in adult abdominal radiography is approximately 5, and
to reduce the amount of scatter radiation reaching an image this value has a special importance for radiographic imaging.
receptor, which dramatically improves image contrast. Grids Consider an AEC radiograph obtained without a grid and then
consist of strips (septa) of Pb or other high attenuating mate- repeated with a grid. Because only one-fifth of the radiation is
rial (e.g., tungsten) that are separated from each other with an transmitted when the BF is 5, the mAs must now be increased
intergrid material such as aluminum that will transmit most of fivefold to achieve the required Kair at the image receptor. The
the incident primary photons. The strips are angled to point BF is therefore correlated to the increase in patient dose when
toward the source of x-ray photons (focus). Artifacts may be a grid is introduced in AEC radiography. Grids are optional
caused by using the grids at distances other than the focal dis- when the patient thickness is less than 12 cm, and in infants
tance. Grids are not observed on radiographic images because the BF is typically approximately 2. Accordingly, adding a grid
these move (oscillate) during the exposure in a device known in an infant AEC radiograph to improve image quality (contrast)
as a Bucky system. Grid suppression image processing also will double the infant’s radiation exposure.
helps to remove gridlines from images. References
The septa have a length of approximately 1 mm or so, a sep- Huda W. Radiography. In: Review of Radiological Physics. 4th ed. Philadelphia:
tal thickness of approximately 50 μm, and an interspace gap of Wolters Kluwer; 2016:97–98.
approximately 0.1 mm. The grid ratio is the most important grid Huda W. X-ray imaging. In: Review of Radiological Physics. 4th ed. Philadelphia:
characteristic, is defined as the length divided by the interspace Wolters Kluwer; 2016:18–19.
gap, and is generally approximately 10 or so in radiographic Radiological Society of North America. RSNA/AAPM physics modules. Projection
imaging. The grid frequency is the number of grid septa per x-ray imaging: basic concepts in radiography. https://www.rsna.org/RSNA/
AAPM_Online_Physics_Modules_.aspx. Accessed March 1, 2018.
centimeter, which is generally approximately 60 lines/cm.
­Typical grids have 10:1 ratios, which will remove 90% of the

16
C A SE 1.7

A B
Fig. 1.14

1. Which type of detector is most likely to result in the lowest 3. Image sharpness in digital radiographic imaging is indepen-
patient dose in an abdominal radiograph (80 kV)? dent of which parameter?
A. Gas chamber (xenon) A. Focal spot size
B. Photoconductor (selenium) B. Pixel size
C. Scintillator (cesium iodide) C. Scintillator thickness
D. PSP (BaFBr) D. Technique (kV and mAs)
2. Which type of detector is most likely to result in the sharp- 4. Increasing what parameter is most likely to improve spatial
est images? resolution?
A. Scintillator A. Matrix size
B. PSP B. Focal spot size
C. Photoconductor C. Scintillator thickness
D. A ≈ B ≈ C D. Imaging time

17
ANSWERS

C A SE 1.7 Comment
Scintillators (cesium iodide) absorb x-rays and convert the
Imaging Plates and Resolution absorbed energy into light photons. The magnitude of the
detected light signal, which is then converted into charge for
Fig. 1.14 The chest radiograph (A) uses a larger physical cassette
quantitative detection, is directly proportional to the absorbed
size compared with the foot radiograph (B). With a similar matrix
size of 2000 × 2500, the smaller cassette offers improved spatial x-ray energy. Photoconductors (selenium) absorb x-rays and
resolution (5 line pairs [lp]/mm vs. 3 lp/mm). produce a charge that is collected in a “charge detector” by
the application of a voltage across the photoconductor. Charge
C. A cesium iodide scintillator is an excellent absorber of
1.  produced in photoconductors is directly measured, whereas in
incident x-rays because the K-edges of Cs and I (i.e., 36 and scintillators the light produced is subsequently converted into
33 keV, respectively) generally match a typical radiographic charge (i.e., indirect detection). PSPs (BaFBr) absorb and store
beam generated at 80 kV. A typical cesium iodide flat panel a fraction of the absorbed x-ray energy incident during a radio-
detector would likely absorb most (>80%) of the incident graphic examination. The stored energy is released by the appli­
radiation, far higher than current xenon, selenium, and BaF- cation of a (red) laser and emits light that is blue. The detected
Br detectors. blue light is a measure of the energy absorbed in each pixel and
is used to generate the radiographic image.
C. When a photoconductor absorbs x-rays, the charge that
2.  The type of detector used will influence the amount of detail
is produced is collected by an electric field. This charge in the resultant image. Photoconductors are most likely to result
does not spread out in the way light spreads out in a scintil- in the sharpest images because the charge that is produced at
lator or a PSP. the x-ray interaction site does not diffuse very far before it is
collected by the “charge detectors.” Scintillators generally have
D. kV, mAs, and beam quality have no practical direct effect
3. 
average resolution because the light produced at the interac-
on the maximum achievable spatial resolution. In all radio-
tion site diffuses before being detected, which results in blurred
graphic imaging, the imaging system resolution is affected
images. The thicker the scintillator, the greater the light spread-
by the focal spot and the important detector characteristics
ing before being intercepted by the “light detectors” and vice
of detector thickness, as well as the pixel size.
versa (Fig. 1.15). PSPs have the poorest resolution because the
A. Only a larger matrix in the same field of view (i.e., small-
4.  incident light used to “read out” the stored data is also subject
er pixels) may improve resolution. However, at some matrix to scattering and can therefore release light in adjacent pixels,
size, one must reach the intrinsic limits to resolution based reducing the resultant image sharpness. Because of the light
on focal blur and the detector characteristics (i.e., thick- scatter problems, there is a limit to the thickness of any PSP
ness). As focal spot size, scintillator thickness, and imaging detector used in radiographic imaging.
time increase, the resultant images will likely be less sharp.

Photons Photons

Thick scintillator
Thin scintillator

High patient dose Low patient dose

Sharp image Blurry image
A B

C D
Fig. 1.15 When the number of absorbed photons in the detector is kept constant as in the above examples, the patient dose will be lower with
the thicker scintillator (B) than with the thinner scintillator (A). The thin scintillator image (C) is sharper than the thick scintillator image (D)
because of lower light spreading.

18
 Different types of detectors have different efficiencies Most digital detectors used in chest radiography (35 × 43 cm)
in absorbing photons, which will influence the radiation have 175-μm pixels, which results in a limiting resolution of
dose because a specified number of absorbed photons are 3 lp/mm.When the cassette physical size is reduced, the matrix
needed to create an image. Cesium iodide is an excellent size is normally unchanged (2000 × 2500) so that a 20 × 25 cm
x-ray absorber because these atoms have K-edge energies of cassette has smaller pixels (100 μm) and improved spatial reso-
33 and 36 keV, which are close to the average photon ener- lution (5 lp/mm). To appreciate these spatial resolution values,
gies generated by 80-kV x-ray voltages. On the other hand, the human eye has a limiting resolution of 5 lp/mm at a nor-
selenium is a very poor absorber because the K-edge is only mal viewing distance of 25 cm (approximately arm’s length).
13 keV, and this material has poor x-ray absorption, especially ­Radiographic technique factors of kV and mAs, which are of
at higher photon energies. BaFBr in PSP plates is intermedi- paramount importance in influencing a lesion CNR, have no
ate between the good absorption of cesium iodide and the direct effect on spatial resolution in radiographic imaging.
poor absorption of selenium at energies used in radiography.
References
Although the atomic number of BaFBr is much higher than
that of selenium, the read-out mechanism (light lasers) limits Bushberg JT, Seibert JA, Leidholdt EM Jr, Boone JM. Radiography. In: The Essen-
the thickness of material that may be used to ensure ade- tial Physics of Medical Imaging. 3rd ed. Philadelphia: Wolters Kluwer;
2012:231–235.
quate spatial resolution performance. In radiographic imag-
Huda W. X-ray imaging. In: Review of Radiological Physics. 4th ed. Philadelphia:
ing normally performed using x-ray tube voltages ranging Wolters Kluwer; 2016:22–25.
between 60 and 120 kV, indirect cesium iodide detectors will Huda W, Abrahams RB. X-ray-based medical imaging and resolution. AJR Am J
likely result in the lowest patient doses and direct selenium Roentgenol. 2015;204:W393–W397.
detectors will likely result in the highest doses when image
quality (mottle) is kept fixed.

19
This page intentionally left blank

     
C A SE 1. 8

A B

C D
Fig. 1.16

1. What is the most likely cause of the artifact depicted in Fig. 3. What is the most likely cause of the artifact depicted in Fig.
1.16A? 1.16C?
A. Ghosting A. Ghosting
B. Grid B. Grid
C. Barium (Ba) spill C. Ba spill
D. Motion D. Motion
2. What is the most likely cause of the artifact depicted in Fig. 4. What is the most likely cause of the artifact depicted in Fig.
1.16B? 1.16D?
A. Ghosting A. Ghosting
B. Grid B. Grid
C. Ba spill C. Ba spill
D. Motion D. Motion

21
ANSWERS

C A SE 1. 8 When the technologist or radiologist uses an x-ray system, they

assume that it is functioning properly. A malfunctioning detector
can result in ghost images (see Fig. 1.16A), patches of uneven uni-
Artifacts formity, or even areas of complete signal loss (dead pixels). These
Fig. 1.16 A) Radiograph of the femur demonstrating image ghost- problems are often corrected by recalibrating the detector and
ing. (B) Radiograph of the pelvis demonstrating grid artifact. (C) Ra- image processing (usually performed by the physicist or vendor
diograph of abdomen demonstrating a barium spill. (D) Radiograph service). Damage from physical collisions can result in artifactual
of a pediatric chest demonstrating motion artifact. marks on the image due to bent grids, gouged detector covers, or
debris in the x-ray tube. If these artifacts are severe and impede
A. Radiograph of the femur demonstrating image ghosting.
1.  diagnosis (or mimic pathology), then the damaged components
A highly attenuating implant from a previous exam is super- must be replaced. Proper quality control carried out by technolo-
imposed on top of the current image. When a region of an gists and medical physicists is vital to identifying and correcting
image has received an unexpectedly high (or low) exposure, system malfunctions before they create artifacts in clinical images.
this area of the receptor can have a different sensitivity for a A properly functioning system does not guarantee an arti-
short period after the exposure. When the next radiograph fact-free image. The radiologist or technologist must position
is taken, the different sensitivities cause a “ghost” image of the patient correctly and ensure that proper technique is used
the previous exposure to appear in the current image. throughout the imaging procedure. Poor positioning can result
B. Radiograph of the pelvis demonstrates grid artifact. Grid
2.  in grid cutoff (see Fig. 1.16B), too much or too little anatomy in
artifacts can manifest as repeating coarse or fine lines (see the field of view, or even patient motion due to discomfort. When
vertical lines in the inset image) and nonuniform intensity such artifacts occur in clinical practice, it is the decision of the
across the image (note overall intensity from right to left radiologist whether to retake the images to ensure diagnostic
side of the image), caused by grid cutoff when the SID does quality at the cost of extra patient dose. When contrast media is
not match that of the grid or when the grid is not aligned used, suboptimal images can occur due to spills, extravasation,
correctly. Grids need to be correctly aligned to transmit pri- and incorrect volume or injection rates. Finally, the human visual
mary x-rays over the entire image. system can create the perception of artifacts that are not actu-
ally present in the images. Mach bands are perceived bands of
C. This radiograph of the abdomen demonstrates a Ba spill.
3.  light and dark near high-contrast edges that are created in our
The highly attenuating Ba appears bright white on the im- eye but are not actually present in the pixel values of the images.
age and may render an image nondiagnostic if it obscures Technique can impact the appearance of artifacts. Longer
or fails to opacify the desired anatomy. Objects worn by exposure times can lead to increased motion artifact (see Fig.
patients (false teeth, necklaces, hairpins) can also mask im- 1.16D); thus short acquisitions are especially important in non-
portant anatomy or even simulate pathology. compliant patients such as infants and those with diminished
intellectual capabilities. Proper kV must be selected to ensure
D. This radiograph of a pediatric chest demonstrates mo-
4. 
that the K-edge of contrast media is used. Image processing can
tion artifact. The image blurs as the patient moves during
impact contrast, resolution, and noise, causing any one of them
acquisition. Although it may appear that a radiograph is
to be suboptimal, depending on the settings. Grid artifacts may
created instantaneously, in reality it takes several to tens
be present if the grid is not aligned and set up properly and if
of milliseconds. If the patient moves during this time, then
grid suppression image processing is not active (see Fig. 1.16B).
the anatomy will smear along the direction of motion like a
Grid cutoff may also occur if the grid is installed upside down
blurred photograph. Minimizing exposure time is crucial to
(Fig. 1.17). Image processing can also create artifactual “halos”
minimizing motion artifacts.
around metal implants if edge enhancement is improperly set.
Comment References
An artifact is something observed that is not actually present. Huda W. Radiography. In: Review of Radiological Physics. 4th ed. Philadelphia:
The creation of a diagnostic image requires that all components Wolters Kluwer; 2016:100–101.
of the imaging system are functioning correctly and that all Walz-Flannigan A, Magnuson D, Erickson D, Schueler B. Artifacts in digital radiogra­
aspects of the imaging chain are properly implemented. Failure phy. AJR Am J Roentgenol. 2012;198:156–161.
of one or more aspects can result in artifacts that degrade image Zylak CM, Standen JR, Barnes GR, Zylak CJ. Pneumomediastinum revisited. Radio-
Graphics. 2000;20(4):1043–1057.
quality and may even result in missed or false diagnoses.
Photons

Grid

(Correct) (Reversed)

Imaging plate

Grid cutoff

Fig. 1.17 When a grid is installed upside down, the central region will have a normal appearance but appear white (i.e., grid cutoff) toward
the edges.
C A SE 1.9

Fig. 1.18

1. Radiographic examination of what body part likely has the 3. What type of follow-up examination is most likely to use
lowest x-ray tube voltage? decreased x-ray tube output (mAs)?
A. Skull A. Scoliosis
B. Chest B. ICU chest
C. Abdomen C. Extremity
D. Extremity D. Abdomen
2. Radiographic examination of what body part likely has the 4. Decreasing what parameter is most likely to increase the
highest x-ray tube voltage? lesion CNR in radiographic imaging performed using AEC?
A. Skull A. Current (mA)
B. Chest B. Voltage (kV)
C. Abdomen C. Exposure time (s)
D. Extremity D. Focus (mm)

23
ANSWERS

C A SE 1.9
Radiographic Techniques and Diagnostic
Task
Fig. 1.18 Frontal view of the spine in a patient with idiopathic sco-
liosis. Because the clinical question pertains only to high-contrast
bony anatomy, radiation exposure can be reduced because in-
creased noise will not impact diagnosis.

D. Extremity exams are generally performed at 55 to 65

1. 
kV, which is lower than for a skull (80 kV), dedicated
chest (120 kV), or abdomen (80 kV). The thin extremi-
ties generally are easy to penetrate, and thus low kV can
be used. Thicker structures such as the abdomen require
higher kV.
B. Dedicated chest exams are generally performed at 120
2. 
kV with heavy filtration, which is higher than an extremity
(60 kV) or skull/abdomen (80 kV). Although the attenua-
tion of the lungs is relatively low, a high kV is used in digital
radiography to reduce attenuation of ribs and thus improve
visibility of underlying tissue.
A. A follow-up scoliosis examination is primarily concerned
3.  Fig. 1.19 Although high image noise may prevent detection of soft
with any changes in the curvature of the spine, which are tissue abnormalities, this displaced supracondylar fracture is easily
very easy to see. If the radiation intensity (mAs) was re- detected. Image quality would thus be very poor for detection of soft
duced by 90%, this would be unlikely to affect diagnostic tissue abnormalities but adequate for detection of a major fracture.
performance. Because this examination is most often per-
formed in children, this offers substantial and worthwhile
patient dose savings. of radiographic techniques and whose absolute value has no
significance whatsoever. X-ray beam quality (kV) influences the
B. When an examination is performed using AEC, the mot-
4.  amount of radiation that penetrates the patient, lesion contrast,
tle in the image will always be exactly the same, no matter and the amount of scatter that is produced. Low beam quali-
how kV, mA, or s is changed. The only change can be to the ties will reduce penetration and increase lesion contrast. On
amount of contrast. If the kV goes down and the AEC is the other hand, quantity (mAs) influences only the amount of
working, noise will stay the same but contrast will increase. noise in the resultant image. Changing the quantity of radia-
As a result, CNR will also increase. tion used will have absolutely no effect on lesion contrast.
Comment When the effect of any technique changes on lesion CNR is
fully taken into account, an increase in this metric means the
One of the most important lessons provided by imaging sci- lesion is more visible and vice versa.
entists is that, in the absence of a defined imaging task, there A diagnostic departmental chest x-ray needs to be high quality
is no such thing as “image quality.” This can be illustrated by to diagnose a range of pathologies and accurately assess the size
considering a very mottled image where it would be virtually of the heart. High voltages (120 kV) and high filtration reduce the
impossible to detect a subtle low-contrast lesion but simple to patient dose and help visualize a wide range of tissues types, and
measure the dimension of some anatomic structure (Fig. 1.19). the SID in PA projections is increased to 180 cm to minimize geo-
The image is “terrible” for detecting a subtle lesion but per- metric magnification of the heart.A 10:1 grid is used to minimize
fectly adequate if the diagnostic imaging task happens to be scatter, and phototiming is used to guarantee the right intensity
obtaining the anatomic dimension for a surgeon. at the image receptor (Kair). Bedside radiographs are obtained
Imaging scientists have investigated the issue of whether primarily to monitor the placement of tubes, lines, and catheters.
a given lesion would likely be detected by a trained observer An AP projection is used with a reduced SID (100 cm) and man-
(radiologist). This question can be answered in an objective ual techniques. Because of alignment difficulties, grids are gener-
manner provided that the key aspects of imaging performance ally not used and the tube voltage is reduced to 80 kV to help
(lesion contrast, noise, and resolution performance), as well as minimize scatter. Optimal performance would also process the
the characteristics of the human visual system, are taken into resultant images using unsharp mask enhancement to improve
account. For a specified lesion, a radiographic signal-to-noise the visibility of sharp edges associated with all inserted devices.
ratio (SNR) can be computed, where this number provides an
objective measure of the likelihood of an observer detecting References
the lesion. Imaging scientists would consider a lesion with a Huda W. Radiography. In: Review of Radiological Physics. 4th ed. Philadelphia:
radiographic SNR of 1 to be “invisible” but a radiographic SNR Wolters Kluwer; 2016:94–96.
of 5 to be detected by any human observer. Huda W. Understanding (and explaining) imaging performance. AJR Am J Roent-
genol. 2014;203(1):W1–W2.
SNR is a highly technical absolute measure of the chance
Huda W. X-rays. In: Review of Radiological Physics. 4th ed. Philadelphia: Wolters
of a specified lesion being detected. Conversely, the CNR is a Kluwer; 2016:11–13.
relative measure of lesion visibility that is influenced by choice

24
C A S E 1 .1 0

A B
Fig. 1.20

1. What is the patient entrance Kair (mGy) for a lateral skull 3. How many adult body radiographic examinations would be
radiograph? needed to give the same amount of radiation as a typical
A. 0.1 fluoroscopy-guided gastrointestinal (GI) study?
B. 1 A. 1
C. 10 B. 10
D. 100 C. 100
D. 1000
2. What is the kerma area product (KAP) (Gy-cm2) for an AP
skull x-ray examination? 4. How many adult body radiographic examinations would be
A. 0.1 needed to give the same amount of radiation as a typical
B. 1 interventional radiologic procedure?
C. 10 A. 1
D. 100 B. 10
C. 100
D. 1000

25
ANSWERS

C A S E 1 .1 0
Incident Air Kerma and Kerma Area Product
Fig. 1.20 Lateral (A) and frontal (B) radiographs of the skull in a
patient with Gorlin syndrome.
Beam
B. For an adult lateral skull x-ray, 1 mGy is most likely inci-
1.  area (A)
dent on the patient. The amount that reaches the detector
will be much lower (0.003 mGy) because of attenuation in
the patient and inverse square law drop in intensity, as well
as loss of primary photons in the grid.
B. An AP skull x-ray examination in an adult will likely use
2. 
1 Gy-cm2 of radiation. Chest x-rays would likely be two or
three times lower and abdominal radiographs two or three
times higher.
B. A KAP in a GI/genitourinary examination is at least 10
3.  Entrance
Gy-cm2, which is an order of magnitude higher than in radi- air kerma (kair)
ography.
Kerma Area Product (KAP) = kair x Area
C. A KAP in an IR procedure is at least 100 Gy-cm2, which is
4. 
Fig. 1.21 The intensity of the x-ray beam (i.e., photons per mm2) is
two orders of magnitude higher than in radiography. given by air kerma (kair) and is measured in mGy. The corresponding
Comment x-ray beam area (A) is measured in cm2. The kerma area product
(KAP) is expressed in Gy-cm2, where 1 Gy-cm2 is 1000 mGy-cm2.
Patient entrance Kair values generally depend on x-ray tube The KAP is often referred to as the dose area product (DAP), and
characteristics, x-ray technique (mAs and kV), and distance these two terms are synonymous.
from the focus to the patient entrance. The radiation intensity
from any source falls off according to the Inverse Square Law
(1/[distance]2), where doubling the distance reduces the inten- of 3 higher. In pediatric radiography, entrance Kair is lower
sity by a factor of 4. The entrance Kair for a lateral skull x-ray is because patients are thinner and KAP is much lower because
approximately 1 mGy and about twice this value for the more the corresponding x-ray beam areas are also lower.
attenuating AP projection when radiographs are obtained with Radiologists and technologists are responsible for the x-ray
systems that employ an AEC. Radiographs of much less attenuat- beam quantity and quality that is incident on a patient. These
ing body parts (PA chest) require an entrance Kair of approxi- factors will depend on patient characteristics, and the specified
mately 0.1 mGy, whereas those for much more attenuating diagnostic imaging task for which the examination is being per-
regions (lateral lumbar spine) would require a Kair of about 10 formed. Medical physicists can convert values of incident radia-
mGy. Kair is independent of the x-ray beam cross-sectional area tion into corresponding patient doses and risks. To do this, it is
and therefore cannot account for the total amount of radiation essential that account is taken of both technical factors such as
used in any radiographic examination. the x-ray beam quality and quantity, as well as exam type that
When the average Kair (mGy) value of the x-ray beam inci- includes the body region (e.g., chest) and the specific projec-
dent on the patient is multiplied by the corresponding x-ray tion used (e.g.,AP).A complete assessment of patient doses and
beam cross-sectional area (cm2), one obtains the KAP. The KAP, risks should also include the important patient characteristics
also known as the dose area product (DAP), measures the total including size and patient demographics.
amount of radiation incident on the patient because it accounts
for the beam area (Fig. 1.21). When the value of Kair is 1 mGy, References
and the x-ray beam has an area of 1000 cm2 (approximately 30 Huda W. Kerma-area product in diagnostic radiology. AJR Am J Roentgenol.
× 30 cm), the KAP is 1 Gy-cm2. The average KAP for a complete 2014;203(6):W565–W569.
radiographic examination is 1 Gy-cm2. Chest x-ray examinations Huda W. Patient dosimetry. In: Review of Radiological Physics. 4th ed. Philadel-
phia: Wolters Kluwer; 2016:47–48.
are approximately a factor of 3 lower than this average value,
Huda W. Radiography. In: Review of Radiological Physics. 4th ed. Philadelphia:
and abdominal x-ray examinations are approximately a factor Wolters Kluwer; 2016:100.

26
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Title: Sink or swim?

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Author: Mrs. Houstoun

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Original publication: London: Tinsley Brothers, 1868

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 CHAPTER I., II., III., IV., V., VI., VII., VIII., IX., X., XI.,
XII., XIII., XIV., XV., XVI., XVII., XVIII., XIX., XX., XXI.,
XXII.

SINK OR SWIM?
A Novel.

BY THE AUTHOR OF

“RECOMMENDED TO MERCY,”

ETC.

IN THREE VOLUMES.

VOL. I.

LONDON:
TINSLEY BROTHERS, 18 CATHERINE ST. STRAND.
1868.

[The right of translation and reproduction is reserved.]

LONDON:
ROBSON AND SON, GREAT NORTHERN PRINTING WORKS,
PANCRAS ROAD, N.W.

SINK OR SWIM?
 CHAPTER I.

WHAT THEY SAID IN THE VILLAGE.

“If I hadn’t heard it from Mrs. Clay herself, I never would have believed it!
To think that John Beacham, who’s a sensible man as men go, should be
marrying an Irishwoman! If Honor Blake was English-born now, one
wouldn’t blame him so much; but to choose a girl that comes of people
who, as everyone knows, you can’t trust farther than you can see them, is
what I call a sin and a shame.”
The speaker was a woman of low stature, elderly, and sharp of voice and
feature. She was seated at a round old-fashioned mahogany table, on which
a teapot of the material known as Britannia metal steamed with a pleasant
warmth, while the odour of buttered toast, “hot and hot,” filled the little
room in which she and a chosen chum and gossip had met together to talk
over the domestic affairs of their friends and neighbours.
The name and title of the first-mentioned lady was Mrs. Thwaytes, and
she, being at the present time a widow, and highly respected, kept a small
general shop in an old-fashioned village, to which I shall give the name of
Switcham. This village, situated near the grandest and most imposing of
England’s rivers, could be reached by express train in something a little
under an hour and a half from London. It was, considering this proximity,
rather a behindhand village. Progress had not hitherto made any gigantic
strides in the old-world-looking place, where not a single house was less
than a century old, and where the aged inhabitants of the quiet spot had not
as yet ceased to speak of crinoline as an abomination, and the absence (on
young women’s heads) of that decent article called a cap as a sign and
symbol of a lost and abandoned soul.
The guest of the widow Thwaytes was qualified in many ways to be that
highly-respected personage’s confidential friend and favourite gossip. A
widow indeed she was, forlorn and desolate by her own account, but
comfortable withal in outward circumstances, and possessed of a portly
person, and a complexion indicative of good cheer and inward content. Mrs.
Tamfrey, for that was the relict’s name, had been left (like the congenial
friend above named) with an only daughter to solace her declining years;
and, after duly casting that young woman upon her own resources as a
domestic servant, she—the widow of the deceased Mr. Tamfrey, a
journeyman carpenter in a comfortable way of business—had entered upon
the attractive career of a monthly nurse. In this lucrative profession she had
met with marked and flattering success. Endowed with a low voice, a
caressing manner, and a universal fund of anecdote, as well as considerable
powers of invention, “Mrs. Tam,” as she was habitually called, made her
way very successfully among the matrons, young and middle-aged, of the
district; and over a cup of a “woman’s best restorer, balmy tea,” the widow
Tamfrey was very generally allowed to be—during the pauses between her
professional engagements—very excellent company.
The room in which these well-suited friends had met for the purpose (not
openly avowed, but nevertheless existent) to which I before alluded was a
snug but not very spacious apartment running parallel with, and having easy
access to, the shop. Miss Thwaytes, the widow’s only daughter, and a young
person verging on forty, was occupied in the said shop—waiting upon
customers and keeping up the credit of the establishment by civil speeches
and oft-repeated remarks on the beauty of the weather and other such banal
topics of conversation. A wonderfully useful person in her way was Esther
Thwaytes; a thorough woman of business, keen-eyed, calculating, and with
only the very smallest of soft spots in the woman’s heart beating under her
maidenly bosom. But there was yet another purpose besides that of business
utility to which Miss Esther Thwaytes was daily put. With her the aged
mother, who possessed but that one ewe lamb, was always indulging in, not
sweet converse, gentle reader—not the interchange of soul with soul, nor
the pleasant fellowship of congenial trencherwomen—but the inexhaustible
enjoyment, the indescribable satisfaction of what we have heard described
in five single letters as “words.” They were both—the daughter of forty and
the parent of sixty-five—essentially “naggers.” The daily food of snip-snap,
the eternal picking of bones, was as necessary to them as the air they
breathed. Deprived of wholesome excitement, the lives of these two women
would have been horribly flat and uninteresting; a vis inertiæ, despite the
busy shop, the cheering tea-drinkings, and the friendly intercourse with that
unfailing gossip Mrs. Tamfrey, the monthly nurse of Switcham.
That exemplary village functionary was pouring out her third dish of tea
when, with a wheezy sigh, she commenced a reply to her friend’s comment
on the approaching marriage.
 “As sure as I sits here, Jane Thwaytes,” she said oratorically, “if John
Beacham marries that Irish gurl he’ll come to trouble. There’s that about
Miss Blake as speaks a vollum. It isn’t that she’s, so to speak, aither bold or
forrard; I couldn’t say that of her—no, not if I was to be put upon my Bible
oath; but what I do say is, that she’s got a look with her eyes that I would
have whipped my daughter out of before she was twelve years old, or I
would have known the reason why.”
“It’s singular now, ain’t it,” suggested Mrs. Thwaytes, “that one can’t
learn more about who she is, and where she comes from? A nussery
governess too isn’t much to boast of neither, and I don’t wonder as the old
lady is a bit put out. The Beachams have allers held their heads high, and
John’s mother hasn’t been behindhand with ’em. She’s not the woman, I’m
thinking, to like being mother-in-law to a gurl who may, for anything that’s
known, be a gentleman’s love-child. And, pretty as she is—I must say that
for her—and like a lady too, Miss Blake had to dress the children, and hem
the pincloths, and all that sort of thing at Clay’s Farm.”
“All that sort of thing! I should think so, and a precious deal more to
that. Why from the first moment that Mrs. Clay was took in labour—and
that’s been twice in the two years that Miss Blake’s been at the farm—the
most of the head-work fell upon Honor. There was this to be thought of, and
that to be done—the children to be kep from noise, and the master from
being put out because the baking was spoiled. Everything, morning, noon,
and night—and I used to think it was a bit too much for such a mere girl as
she is—fell upon the nussery governess.”
“And that’s true, I believe, or the Clays, one and all, wouldn’t make so
much of her as they do; and the old lady ought to think of that, proud as she
is, for she’ll be a rare help, will Honor, at the Paddocks. A good headpiece
of her own, and not above making herself useful; and add to that that John’s
getting on for forty, and is particular in his ways—so he is. He means
honourable, does Mr. Beacham, and stands high with rich and poor, and
what’s more, he can take his wife to as good a home as any in the country.”
“Better, maybe, for his wife if it was a poorer one,” said Mrs. Tamfrey,
who knew something of the world and of human nature. “When a young
gurl that’s been used to work marries a man that can keep her without it, ten
to one that she gets into mischief. I don’t say, if she gits a family about her,
which it’s a’most certain she will,” continued Mrs. Tam, speaking, as was
only natural, in the interests of her profession, “that Mrs. John Beacham
won’t settle down; but she’s but a giddy thing at present, always laughing—
I declare it’s the prettiest thing to hear her, and makes one laugh, too, for
company; but if she don’t have a family—and John Beacham’s nearly old
enough to be her father—and if the young men get about her, why”—and
Mrs. Tam, deeming, probably, that she had said enough to enlighten the
feminine mind of her auditor, wound up her prognostications with a very
suggestive sigh.
“I hope not. It would be a sad thing, indeed, if mischief came of this
grand marriage of hers. I should be sorry for John Beacham if it was to,”
mumbled the widow Thwaytes, whose mouth was fuller than was altogether
becoming of well-salted buttered toast. “I should be sorry as sorry could be
for John if trouble was to come upon him that way. Ah well! if the Squire
had only lived! Such a gentleman as he was for advising and keeping things
straight! There isn’t a day nor yet an hour that the parish doesn’t feel the
want of him. If Squire Vavasour had been spared, things would have gone
on, as we’ve all on us said a hundred times, in quite another guess sort of
fashion. There would have been more living at the Castle then, and a
precious sight more money spent in the parish. The Castle then would have
been a proper house for young people to live in, and be married out of; and
now what is it? As Mrs. Shepherd says—and she ought to know that’s been
housekeeper these twenty years at the great house—there’s as much
skinflinting there as if milady hadn’t as many pounds as she has thousands.
‘I declare,’ says she to me, which it will be a week to-morrow, the day I was
taking tea with her up at the Castle,—‘I declare,’ says she, ‘it’s a sin and a
shame how little’s been spent this five years at Gillingham Castle. The
Chace itself and the game and all has been let to go to rack and ruin. Next
to no labourers employed, no parties given where there used to be a’most
open house kep, and such a home made for the young gentlemen as it’s no
wonder they should run a little wild when they was let out like.’”
“There’ll be a change now, I’m thinking,” suggested Mrs. Tamfrey after
a pause; “the young ladies are getting on, you know, and Mr. Arthur coming
of age next year will make something of a stir, in course.”
The widow shook her head with a dreary air of superior wisdom. “From
what Mrs. Shepherd tells me”—and the words were said in one of those
ominous whispers that are intended to imply even more of knowledge than
is expressed—“from what Mrs. Shepherd says, there’s no coming of age yet
awhile for the air aperient of Gillingham. There’s something out of the
common, it appears, though what it is Mrs. Shepherd couldn’t speak to
exactly, in the last entail. Anyway, milady—which seems odd, don’t it? she
having been the heiress—hasn’t got, after a certain day—that’s pos—
anything to do with the estate and property. It’s that, folks say—them as
knows something about the matter—as puts her out so. And it’s to be, some
says, when Mr. Arthur is five-and-twenty that his mamma will have to walk
out of her own house like a private person, after all the money and land that
she was born to.”
“Let milady alone,” put in Mrs. Tam decidedly; “she’ll be rich enough, if
all’s true, whatever happens. There’s a pretty long purse a-filling
somewhere, I’ll be bound. It’s little besides her name that she gives to all
them mad-houses and county ’ospittles that there’s such a talk about. No,
no; Milady Millicent isn’t one to be short of cash, whoever else goes to the
wall—but,” interrupting herself, “my gracious! Jane Thwaytes, if there ain’t
two parties a-waiting in the shop, and no one in life to serve them but
Esther!”
Startled by this appeal to her love of gain and order, the widow, after a
hurried wipe of her lips with the corner of her apron, bustled into the
adjoining shop with a sharp rebuke already on her tongue. It was a tidy and
very prosperous establishment that of which Esther Thwaytes was the prop
and mainstay. In it you could obtain all that the heart of a reasonable
woman of simple tastes and habits ought to desire. On one side, the counter
was strewed with cheap ribbons, snowy cap-fronts, artificial flowers more
gaudy than artistic, with occasionally a tempting novelty in the shape of the
last new thing in bonnets. The other side of the widow’s flourishing “store”
contained goods that were more useful than ornamental. Tea, coffee,
tobacco, and snuff, together with other articles of home and colonial
produce, were procurable at “the” shop in the main street of Switcham. As a
matter of course, the widow, enjoying the benefit of a monopoly, drove a
thriving trade; and, equally as a matter of course, incessant were her
jeremiads on the disjointedness of the times, the dearness of provisions, the
iniquity of subordinates, and the general decadence of all things since the
days which she was pleased to call “her time.” And yet, at scarcely any
hour of the day from the early hour of opening was the little shop devoid of
customers; while towards the witching time of evening, and that more
especially on a Saturday night (for the widow was no advocate for early
closing), her house was one, it may be said, of “call”—a regular rendezvous
for the busy and the idle, for the sweethearts and the gossips, of the village
where the much-respected widow had been born and bred.
 CHAPTER II.

THE ANTECEDENTS OF MILADY.

The Lady Millicent Vavasour, whose proceedings were thus so freely
commented upon by her inferiors, was the only child of the rich and potent
Earl of Gillingham. That nobleman, who survived the Countess, his wife,
but little more than a year, bequeathed at his decease, with restrictions and a
good deal à contre cœur, all that he possessed, in land, mines, personalty,
and otherwise, to his only child, the Lady Millicent aforesaid and in the last
chapter duly commented upon.
The income produced by the above-mentioned properties—of all of
which the heiress came into undisputed possession at the age of twenty-
three—amounted at a moderate computation to thirty thousand pounds per
annum. The Lady Millicent Vavasour therefore took her stand on the
platform of public estimation with the prestige of being one of the richest
heiresses in England.
As might naturally be expected, the eyes of the world and eke the
monster’s tongue had from her earliest womanhood a good deal to look and
say on the subject of the Lady Millicent’s future disposition in marriage.
That she would—like the Maiden Queen of mighty memory, or the banker’s
heiress of nineteenth-century renown—be content to enjoy her power alone,
no one appeared for a single moment to imagine. There exist, always have
existed, and probably always will exist, a large proportion of the bolder sex
of whom it is averred, and safely too, that they are not “marrying men;” but
whoever in his or her experience—and I say it without prejudice—has
heard of a “non-marrying woman”? Such a being, if it were discovered to
exist, would be an anomaly, a lusus naturæ, a freak, so to speak, of the
mighty mother who has done all things not only wondrously, but “decently
and in order.”
But if there be a class of females likely to “go in,” as the saying is, for
celibacy, that class is the genus heiress. There are causes too numerous to
mention that may account for this established fact: the watchfulness alike of
friends and foes; a natural as well as a cultivated suspicion that “men are
not (always) what they seem;” the difficulties attendant on an embarras de
choix; and last, but by no means least in importance, the fear of being
reduced to a second-rate power,—may all be cited as good and sufficient
reasons for the delay which so frequently occurs in the “going off” of an
heiress. As regarded the Lady Millicent Vavasour, the rich partie par
excellence of this story, the last-mentioned cause was, far and away beyond
the rest, the one to which might be attributed the important fact that she had
reached the age of twenty-four while still a single woman.
There is much to be said in excuse for the almost proverbial arrogance
and love of power which marks the woman who is born to greatness. She is
so often taught—if not indeed by words, at least by the deference of those
around her, by the inevitable yielding to her will, and by the kotooing of
dependents—that she is, in her way, a Queen, that it would be rather
surprising if any humbler ideas of her own position should find entrance
into her mind. A great deal has been advanced and written on the
importance of public schools as tending to the discovery of that imaginary
line known as a young gentleman’s “level;” but whether this hoped-for
good is ever attained, and if attained whether it be worth the high price
often paid for its possession, must remain an open question; the distressing
truth however cannot, I fear, be disputed, that the “level” of a young lady
possessed of forty thousand pounds per annum is never likely to be found,
save and except in rare cases of matrimonial felicity—in those exceptional
cases, I mean, where there is no struggle for power, where the Salic law as
exemplified in the nineteenth-century wife is virtually set aside, and where
(but this is a sine quâ non) the husband is in every way worthy of this
heroic act of voluntary self-abnegation.
That the Lady Millicent Vavasour was very far from being the model
woman whose price is far above rubies will very speedily be seen. She was
a cold and unattractive child, and she grew up to be in many respects a cold
and unattractive woman; but that she was so must in a great measure be
attributed to the peculiarity of her “bringing up,” and, strange to say, to the
regretable fact that she was not born to be a man. The Earl and Countess of
Gillingham were both what I must be permitted to describe as “family-
mad.” That the Vavasours were the most ancient, the noblest, and most
exalted of all the races of men upon earth, this elderly and highly
respectable couple religiously believed. Previously to her union with the
last male of this ancient family, the Lady Caroline M‘Intyre (the respected
mother of Lord Gillingham’s heiress) had entertained a foolish
prepossession in favour of the old Scottish blood which ran in her own blue
veins; but the engrafting of her northern race in the still nobler stock of the
Vavasours of Gillingham was sufficient to inoculate her with every
prejudice entertained by Richard, eleventh earl of that most princely house.
They were not—barring this one folly—either a particularly silly or an
especially objectionable pair. They were a little grand and distant to those
who might be so daring as to claim equality with themselves, but to their
clearly-marked inferiors and to the actual poor they were kind, generous,
and “pleasant.”
Perhaps the person who suffered the most from the “madness” which
may be said to be inherent in the Vavasour blood was their only child—the
Lady Millicent, whose career will form one of the subjects of these pages.
To her, without intending to be otherwise than affectionate and kind, the
behaviour of both father and mother was invariably cold and distant. She
was never forgiven for the “sin” of her birth—never pardoned, poor
unconscious child, for the guilt of being a girl! As the last male descendant
of the Vavasours, Lord Gillingham would willingly have given ten years at
least of his vast rent-roll, for a son in whose person the grand old title might
be perpetuated; and the Countess his wife fully shared in what she deemed
his very natural discontent. To bear without murmuring this crumpled rose-
leaf on their luxurious couch was not in the nature of either; so instead of
making the best of the only child with which Providence had blessed them,
they did precisely the contrary; and the little Lady Millicent, deprived of the
caresses and the softening influence of a gentle mother’s love, grew up as I
have described her to be—cold, arrogant, and unamiable.
The young lady herself was fully capable of appreciating the wrong that
had been done, not only to her family but to society at large, by the
deplorable accident of her birth. As one of the richest heiresses in England,
and as the bearer of a name so noble and so honoured, she was of course a
“personage;” and as one of the uppermost (that could not be denied) of the
upper ten thousand she would take her place, and an exalted place too,
among the great ones of the land; but—there was the rub!—there “pinched
the shoe,” and “galled the withers”—she was not and would not be, in the
course of nature, a peeress! Power—the power that wealth would give—
was hers, but precedence—that honour so dearly valued by her sex—was
sadly and, unless it were obtained by marriage, for ever wanting.
 When, after her parents’ decease, which occurred soon after she had
completed her twenty-third year, the orphaned heiress pondered regretfully
upon these things, the idea of purchasing with her valued thousands one of
the highest of England’s titles could scarcely fail to occur to one whose love
of rank—the well-imbibed prejudice of a dull and unsympathised-with
childhood—was only outdone by her passionate attachment to power. Well
did the Lady Millicent know—for her girlhood had not all been spent in the
seclusion of Gillingham, and at London balls and routs and dinner-parties
she had learned something of the level of gold—well did the heiress know
that, were she willing to barter her rent-roll for rank, the negotiation would
have been only too easily effected. But, all things considered, this young
woman was not so willing. Any superiority enjoyed by a husband, any
benefit conferred upon her through him, would—so singularly was she
constituted—have been as gall and wormwood to her taste. She was
overweeningly proud, besides, even as her parents had been before her, of
the name she bore; and, singular as it may at first seem, it was to that very
pride in, and attachment to the name of Vavasour that the tardy marriage of
this proud and impracticable lady was owing.
Late in the summer of the year following on her accession to wealth and
power, the Lady Millicent set forth in great state on a continental tour. As
companions on the way she had chosen Lord and Lady Merioneth: a good
simple-minded pair, ready and able to be amused, and withal tolerably slow
to comprehend (from the circumstance of their own entire want of foolish
family pride) the besetting sin of their young companion.
The delicate health of Lady Millicent Vavasour was, to the surprise of
the world in general, the alleged motive for her spending the winter abroad.
It had been suddenly discovered that the lungs of the heiress were delicate;
and although her breadth of chest and generally healthy appearance tended
to correct the assertion, public interest—no unusual occurrence when the
malade imaginaire, or otherwise, happens to be a millionaire—was
immediately enlisted in “poor dear” Lady Millicent’s behalf. “So young!”
“so gifted!” “so attractive!” It would, indeed, be hard (and a “liberty” was
implied, if not actually spoken) if Death should venture to approach within
hailing-distance the august person of the Lady of Gillingham. Happily,
however, as it soon became manifest, there was no immediate danger that
the wealth of the heiress would be turned into some obscure and probably
(to the public) uninteresting channel. Long before the money-scattering
English party had reached Florence the Lady Millicent had thrown off every
appearance of invalidness, and was ready for any amusement suitable to her
exalted position which chance might throw in her way. And ready, too, for
something more than amusement—ready to be softened into as much love
as her nature was capable of feeling, by one worthy of the best affections of
a far worthier woman than was the Lady Millicent Vavasour. Cecil
Vavasour was a cousin, many times removed, of that autocratic lady—the
descendant of a junior branch of the noble family whose name he bore; and,
moreover, in his branch of the family there existed the title of baron—a title
which there was every probability would eventually be borne by this poor
and comparatively obscure relation. Comparatively obscure, for in a world
of his own—a world that was not that of the Lady Millicent Vavasour—the
intellectual but retiring Cecil was known and honoured. She for that reason,
among others too insignificant to mention, had never till on the occasion of
this her first continental trip chanced to fall in with her kinsman; and when
at last she did make his acquaintance, the effect of even a first meeting was
marked and decisive. Not that there was much in Cecil Vavasour’s outward
man calculated to touch a woman’s fancy or to win her heart. He was some
years past thirty, and in person neither handsome nor the reverse; but there
was a something undefinably attractive even in the reserve of manner, that
spoke of latent power, and of an intelligence above that of ordinary and
unreflecting mortals. He was tall, too, and of a stately presence; one of
those men, in short, to whom, both physically and mentally, a woman, be
she ever so highly placed in her own estimation, would hardly have refused
to pay the tribute of tacitly acknowledging to her own self that he was her
master. Cecil’s father, a practical though not exactly a discerning man, had
intended his only son for the Bar; but circumstances, to say nothing of the
young man’s own individual tastes, decided against the realisation of the
old gentleman’s plans. A short sojourn in Italy, whither he had gone to
protect and comfort an invalid sister, whose days when she left the shores of
England were already well-nigh numbered, had completed the dislike to his
profession which before had been little more than a surmised distaste.
Cecilia Vavasour died a tranquil death in the soft climate of Tuscany; and
her brother, throwing law study to the winds, and leaving Blackstone to
grow dusty on its shelves, remained to make the best of his three hundred a
year in the sunny land that he had learned so soon to love.
 Cecil Vavasour had been three years in Italy—a busy idler, devoted,
almost to idolatry, to the Beautiful that has survived the touch of Time; as
well as to the memories, the associations, and the soft sadness that cling
around the decaying ruins of the past. He had roved from place to place,
mixing little in society, but yet not actually shunning communion with his
fellows, when Lady Millicent arrived at Florence. It would have been
impossible, even had he felt the wish (which he did not) to avoid his cousin,
for the quondam barrister not to become intimate with the heiress of
Gillingham. At first he was very shy—as shy as a proud poor man was
almost certain to be under the peculiar circumstances in which he was
placed. Compared to the cousin, who called him Cecil, and treated him
from the first with marked kindness and consideration, he might well be
termed an impecunious relation. Had Lady Millicent’s conduct towards him
been different—had she behaved to him with anything approaching to her
usual rigid arrogance—his poverty would have troubled Cecil Vavasour but
little. It was his young kinswoman’s gentleness, her unwonted amiability,
her actual deference towards himself, that, while it rendered him ill at ease
in her society, both puzzled and touched him. He little guessed, while
gradually falling under the spell of a woman who in youth was not destitute
of personal attractions, and who could be agreeable when she chose, what
was the true mainspring of her conduct regarding him. He could form no
idea of the hidden demon of Pride lurking beneath that still exterior. To his
thinking, Lady Millicent Vavasour—young, courted, with tens of thousands
yearly at her command, with power to effect so vast an amount of good to
others, and (which we fear was almost equally enviable in Mr. Vavasour’s
sight) with wealth to indulge to the utmost every æsthetic taste—was
scarcely likely to ambition any extra or unpossessed advantage. And then
he was himself so utterly unassuming, so entirely unaware that he in his
own person owned, or was likely ever to own, gifts that the rich heiress of
Gillingham could covet, that, as I said before, he was at the beginning
almost more puzzled than gratified by her notice.
That this state of things should have occasioned at first a something of
distance in the relations between the cousins is not surprising, nor need it
afford subject for wonder that that very distance lent a piquancy to their
intercourse which was not, to the petted heiress at least, without its charm.
Lady Millicent had been so beset by flatterers, and so cloyed by adulation,
that the silence, the fits of absence, and the almost brusqueries of her cousin
Cecil were greeted by her as a very agreeable variety. She was sick to death
of oversweet confections, of butter and honey she had been positively
surfeited, so that the honest brown-bread diet, dry and husky though it was,
which was all that she appeared likely to obtain from Cecil Vavasour, tasted
fresh and wholesome to her fevered palate.
But there was, as I before said, another cause—the cause, in fact—for
Lady Millicent’s obvious appreciation of her cousin, and that motive power
was her cousin’s future rank; for Mr. Vavasour, simple as he stood before
her, quiet, unpretending, noticeable for his carelessness of outward
advantages, his simple manners, and his unfashionable dress, could
nevertheless, failing some very abnormal event, be the means of obtaining
for her in a mitigated degree the fulfilment of her long-cherished desire—
the hope of her heart, the insatiable craving, known only to herself, to wear,
while retaining the noble name of Vavasour, the coronet of a British peeress
on her brow.
The courtship, if courtship it could be called, between Lady Millicent
and the future Baron de Vavasour was somewhat singular and out of rule;
and if any distinct offer of marriage were made between the parties—not a
common occurrence, by the way, in set and deliberate phrase, between
acknowledged lovers—that offer was believed by those best acquainted
with the contracting parties to have emanated from the lady. That Cecil
believed—free from personal vanity though he was—in her attachment to
himself there could be no doubt; nothing, therefore, remained for the man
whose own nature was too noble for him to fear for himself the imputation
of mercenary motives, but to put his pride, and his scruples, if such he had,
into his comparatively empty pockets, and to accept the goods which his
millionaire kinswoman had provided for him.
Perhaps, had the autocratic mistress of Gillingham and its dependencies
been better acquainted with the character of Cecil Vavasour, she might have
hesitated longer ere she selected him as the partner of her life. With all her
ambition, she yet required a husband who would understand her character
and enter into her views; and of this Mr. Vavasour soon showed himself to
be incapable. Misled by the natural faith which we all are apt to place in our
own individual judgment, Lady Millicent had discovered imaginary
qualities in the man whom she had honoured with her choice. Deceived by
the extreme composure of manner and the gentle reserve which were among
her kinsman’s outward characteristics, she had given him credit for an
indolence of disposition which she rather approved of than regretted, and
for an inborn pride of race calculated to assimilate satisfactorily with her
own. They were married, and the Lady Millicent was not long in
discovering to her annoyance—for hers was not a character to take a
disappointment to heart—that she had made a fatal mistake. A better man,
nor one possessed of a more conscientious spirit than that which dwelt in
Cecil Vavasour, never walked the earth. That this was so, no one who
boasted the slightest knowledge of character would long doubt. It might be,
though that fact had yet to be decided, that the lawyer manqué was not
likely to be a distinguished man; but the most casual observer would have
decided at once upon the impossibility of his being otherwise than an
upright and a straightforward one. But for all this, and though Mr. Vavasour
proved to be, in the broad and usual acceptation of the term, an excellent
husband, Lady Millicent was, and withal showed herself to be, bitterly and
hopelessly disappointed. It was terrible to find that, instead of sympathising
in her ambitious desires, Cecil was content to devote himself to the
cultivation of his understanding, the care of his wife’s extensive property,
the amelioration of the condition of the poor, and later, as the—to him—
exceeding blessing of children was granted to his hopes, to the education
and moral training of his sons and daughters. At every time and season, and
to all the occupations and interests of her husband, Lady Millicent took
marked exception. She had expected to find him an amiable nonentity, and
instead, there was ever at her side an earnest and highly intelligent
companion; one too who, although he was no rival power ready to edge her
off the throne she so dearly prized, was nevertheless a man who,
entertaining both stern and exalted notions of the responsibilities of the rich,
was not easily to be diverted from the line of duty—often narrow and
difficult—which he had marked out for himself to follow. Under the
vexatiousness of this tardy discovery, Lady Millicent daily fumed and
fretted—fumed and fretted till her temper, never one of the best, grew
peevish and easy of irritation, and till the chafing of the crumpled rose-leaf
against the sensitive skin of the proud woman’s self-esteem grew to be a
painful, and in process of time a never-to-be-cicatrised sore.
Nor was Cecil Vavasour long behindhand in awaking from the one
delusion that had so effectually changed for him the cherished habits of a
life. The conviction that the love in which he had believed had been but a
passing fancy, and the certainty that he was solely valued by her as a
stepping-stone on which to rise to rank, were not subjects for agreeable
reflection. But though Vavasour was capable of feeling keenly the wrong—
for wrong it was—that had been done him, he was the last man in the world
either to complain of, or to grow silently morbid under, its infliction; only
by his deeds could it be surmised that he was an unwilling sharer in the
good things procurable by the Lady Millicent’s gold; and as, previously to
his marriage, he had steadfastly resisted the making of any settlement by
which he could in his own person benefit, so did he, after becoming
convinced of his wife’s indifference, keep with rigid economy his private
expenses within the scope of his own limited means to defray, while he
abstained as much as lay in his power from indulgence in luxuries which
those means would, unassisted, have been inadequate to procure for him.
Setting aside this glaring instance (which it clearly was) of eccentricity,
Cecil Vavasour, as was universally allowed, acted well up to the obligations
imposed upon the rich and powerful. There was no lordly house throughout
the length and breadth of the land in which the rights of hospitality were
exercised with a more liberal hand than at the various residences owned and
occupied by the Vavasour family. At Gillingham Castle especially, where
the establishment was on an almost princely scale, the grand old house was
twice a year brimming over with guests, and far and wide spread the
reputation for “good entertaining” of the Lady Millicent and her consort.
But for all that this was so, and although Cecil Vavasour was loved and
appreciated by the poor, whose invaluable friend and adviser he ever proved
himself to be, he was not generally popular either with his equals or his
superiors in social position. To anyone accustomed to look inquiringly into
human motives, and to those who have gained knowledge of mankind by
enlarged association with their fellows, the fact that Cecil Vavasour, with all
his excellence, his gentleness and his hospitality, was not generally a
favourite, will excite but little surprise. As a rule, the silent and apparently
self-conceited man rarely meets with favour, for silence is too often taken
for a diagnostic of pride, and pride is of all human qualities the one which
both men and women find the most difficult to pardon. But there was yet
another quality, and it was the one to which his taciturnity was mainly to be
attributed, that interfered greatly with the comfort of Cecil Vavasour’s
existence—he was constitutionally, and therefore incurably, shy. Now the
shyness of a middle-aged gentleman who has lived much in society, and
whose intellect is above the average, is one of those “facts” to believe in