Brachytherapy 2

Brachytherapy Planning and
Quality Assurance
Classical implant systems
 Most common clinical
applications and modern
dosimetry methods
Quality assurance
Classical implant systems
 Manchester (Paterson-Parker)
 Quimby
 Paris
 With the advent of computerized
treatment planning these are little used
today with the possible exception of the
Manchester System for cervix cancer
treatments
The Manchester System
 Aims at producing as uniform a dose as
possible within the treatment volume
 Sources of variable strength used
 Rules provided for placement of sources of
different strengths
 Tables provided to determine treatment time
 Originally devised for Ra-226 but later
extended to Cs-137
The Quimby System
 Developed by Edith Quimby at Memorial
Hospital, New York
 Required uniform distribution of same strength
sources
 Produced non-uniform dose distributions
 Tables provided to determine treatment times
 Originally devised for Ra-226 and Rn-222
seeds but later extended to Ir-192 and I-125
The Paris System
 Designed for Ir-192 wires but later extended
to Ir-192 seeds in strands
 The sources should be equidistant arranged
in patterns (squares or triangles)
 The dose (called the “basal dose”) is the
arithmetic mean of the minimum dose rates
located half-way between the sources in the
well defined patterns
 Tables provided to determine treatment times
Most common clinical
applications
Gynecological
treatments
Prostate implants
Breast implants
Gynecological
brachytherapy
Uterine cervix
Vagina
Endometrium
Cervix cancer: Manchester System
Fletcher-Suit tandem and ovoids
Tandems
Caps
Ovoids
Tandem and ovoids are inserted into the uterine

canal and vagina, respectively
Some newer cervix
cancer applicators
Manchester System: doses were
calculated at two points, A and B
Off-axis tandem
Meigooni, 2005
The American Brachytherapy Society recommended
Point A doses with HDR for early disease
The American Brachytherapy Society recommended
Point A doses with HDR for advanced disease
ICRU Report 89
Tissues imaged and
planned in 3-D
ICRU 89 recommended prescribing,
recording, and reporting levels
 Level 1: minimum requirements that should
be followed by all centers, for all patients, and
represents the minimum standard of
treatment
 Level 2: advanced standards of dose
planning and treatment that allows a more
comprehensive and standardized exchange
of information between centers and based on
a more complete set of parameters
Example: Level 1 dose and delivery
reporting for cervix brachytherapy
Level 2: additional dose and
delivery reporting
Vaginal brachytherapy
 Can be treated low dose rate although,
nowadays, most commonly, high dose
rate
 Usually use cylindrical applicator of
appropriate diameter
 Stepping pattern designed to give
uniform dose around the applicator at
selected depth in tissue, typically 0.5 cm
Intracavitary applicators used
for vaginal brachytherapy
Use the largest diameter applicator that is comfortable

for the patient so as to produce the best depth dose
Endometrial brachytherapy
 Can be treated low dose rate although,
nowadays, most commonly, high dose rate
 For post-hysterectomy patients
• treat the vagina (vaginal cuff brachytherapy)
 For other patients
• treat the vagina plus the uterine cavity with
special applicator
Endometrial brachytherapy
Typical dose distribution
IJROBP October 1, 2000 Volume 48, Issue 3, Pages 779–790

ABS HDR dose guidelines
(if no added external beam)
HDR doses are specified at 2 cm from the

midpoint of intrauterine sources
IJROBP October 1, 2000 Volume 48, Issue 3, Pages 779–790
Prostate brachytherapy
There are two major alternatives:
Permanent implants with either
I-125 or Pd-103 seeds
Temporary high dose rate
implants with Ir-192 or electronic
brachytherapy
Ultrasound-Guided Transperineal
Prostate Brachytherapy
Series of transrectal
ultrasound (TRUS) images
TRUS images used for planning
Schematic of the planning and treatment
process for permanent implants
Moorrees et al. Radiation Oncology 2012, 7:196

Sources used for permanent
prostate implants
 With I-125 (half life 60 days) the dose is
delivered over many months
 With Pd-103 (half life 17 days) the dose is
delivered over many weeks
 The total dose delivered to infinity is
calculated by the formula:
Total dose = (initial dose rate) x (mean life)
Examples
1. If the initial dose rate for an I-125 implant is 7
cGy/h, then the total dose to complete decay is:
7 x 1.44 x 60 x 24 = 14,515 cGy
i.e. about 145 Gy
2. If the initial dose rate for a Pd-103 implant is 21
cGy/h, then the total dose to complete decay is:
21 x 1.44 x 17 x 24 = 12,338 cGy
i.e. about 123 Gy
American Brachytherapy Society recommended
total doses for prostate treatments
ABS Prostate TG suggested doses
for HDR prostate treatments
For monotherapy either
10.5 Gy x 3 fractions
or 8.5-9.5 Gy x 4 fractions
ABS Prostate TG suggested doses
for HDR prostate treatments
As a boost in combination with 36-40 Gy EBRT
15 Gy x 1 fraction
or, with 40-50 Gy EBRT either

9.5-10.5 Gy x 2 fractions
Accelerated Partial Breast
Irradiation (APBI)
 Brachytherapy for breast cancer can be used after
lumpectomy either as a boost to external beam
therapy or as monotherapy
 Two major techniques are applied
1. needles are inserted interstitially into the breast
using a template with either LDR or HDR, or
2. an applicator is inserted at the time of surgery
into the cavity and expanded so as to make the
cavity roughly spherical and an HDR is source is
stepped through the applicator
Template for interstitial
needle technique
Interstitial needle technique
APBI applicators available
MammoSite: Hologic
Contura: SenoRX
Savi: Cianna Medical
ClearPath: North America Scientific
Double Balloon: Best
Axxent Balloon: iCAD (electronic
brachytherapy)
Example: the MammoSite
There are two types: a single lumen (shown) and multiple lumens
Njeh et al. Radiation Oncology 2010 5:90
Typical APBI brachytherapy doses
when used as monotherapy
LDR: 45-50 Gy at about

0.5 Gy/h
HDR: 34 Gy at 1.0 cm
outside the cavity wall in
10 fractions
Imaging for brachytherapy
Gerbaulet et al, 2002

General flow scheme for a brachytherapy
procedure: preparation and application
ESTRO Booklet No. 8

Flow scheme for brachytherapy
imaging for treatment planning
ESTRO Booklet No. 8

General flow scheme for a brachytherapy
procedure: planning and treatment
ESTRO Booklet No. 8

Brachytherapy quality assurance
 Quality assurance program is needed
to assure:
• safety of the patient, the public, and the
staff
• positional accuracy
• temporal accuracy
• dose delivery accuracy
ESTRO Brachytherapy QA Guidelines
AAPM Report No. 59:
Code of practice for brachytherapy physics
Safety of the patient, the
public, and the staff
 Error avoidance
• clear prescriptions, equipment testing,
patient identification, etc.
 Emergency procedures
• training staff, availability of equipment, etc.
 Radiation safety
• room shielding, control of sources,
monitoring devices, interlocks, etc.
Positional accuracy
 Machine programming parameters
• accurate transfer of positional data from
treatment planning system to treatment machine
• correct lengths, positions, channel numbers
 Correct location of applicators, catheters, etc.
• for each patient treatment
 Correct location of sources
• for each patient treatment
Typical source positioning
accuracy QA phantom
Temporal accuracy
 LDR
• need to assure that treatment is terminated once
the prescribed dose is delivered
 Remote afterloading (LDR, PDR and HDR)
 timer and dwell time accuracy
 magnitude of transit dose
 accurate transfer of temporal data from
treatment planning system to treatment machine
Dose delivery accuracy
 Physical aspects
• source strength calibration, accurate data in
treatment planning computer, accurate decay
correction, account for effect of applicator
attenuation, etc.
 Clinical aspects
• accuracy of anatomical data and transfer of
that data to the treatment planning system
• accuracy of planning system, optimization, etc.
Source strength calibration
Primary standards laboratories
have developed advanced methods
to calibrate different sources
 These are typically well beyond the
scope of most users who need to
check source strengths in-house
Source strength
verification by the user
This is typically done using a
well-type ionization chamber
that has been calibrated by the
primary standards laboratory or
at a secondary standards lab
using a method traceable to that
at the primary lab
Typical well-type ionization
chambers
Standard Imaging Nucletron PTW

Data supplied by the
calibration lab
Sweet spot location
Air kerma strength calibration factor
for the chamber
Source used for the calibration
Irradiation conditions
Traceability to national calibration lab
Sweet spot location
The location of
the sweet spot on
the central axis
of the chamber is
determined by
moving a single
source and
taking multiple
readings
Pre-treatment brachytherapy QA
for each patient
 Check for completeness of printed information
 Check for consistency of plan with treatment
prescription
 Double check of data by independent second
person
 If possible perform (simple) manual calculation of
treatment time
 Signing of document before treatment starts by
physician and physicist
ESTRO Booklet No. 8
Summary
 Classical systems little used today
except for the Manchester System for
cervix cancer
 Computerized planning now used with
advanced imaging
 QA program for delivery and planning
equipment, input and output data,
essential to assure safety and accuracy

Brachytherapy 2

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Brachytherapy Planning and

Tandem and ovoids are inserted into the uterine

Use the largest diameter applicator that is comfortable

IJROBP October 1, 2000 Volume 48, Issue 3, Pages 779–790

HDR doses are specified at 2 cm from the

Moorrees et al. Radiation Oncology 2012, 7:196

or, with 40-50 Gy EBRT either

LDR: 45-50 Gy at about

Gerbaulet et al, 2002

ESTRO Booklet No. 8

ESTRO Booklet No. 8

ESTRO Booklet No. 8

Standard Imaging Nucletron PTW

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