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org March 30, 2007

Radiation Exposure in X-ray Examinations

This information is reviewed by a physician with expertise in the area presented and is further reviewed by committees
from the American College of Radiology (ACR) and the Radiological Society of North America (RSNA), comprising
physicians with expertise in several radiologic areas.

What are x-rays and what do Naturally-occurring

they do? "background" radiation
X-rays are a form of radiant energy, like light or radio
exposure
waves. Unlike light, x-rays can penetrate the body, which We are exposed to radiation from natural sources all the
allows a radiologist to produce pictures of internal time. The average person in the U.S. receives an
structures. The radiologist can view these on effective dose of about 3 mSv per year from naturally
photographic film or on a TV or computer monitor. occurring radioactive materials and cosmic radiation
X-ray examinations provide valuable information about from outer space. These natural "background" doses vary
your health and play an important role in helping your throughout the country.
doctor make an accurate diagnosis. In some cases x-rays People living in the plateaus of Colorado or New Mexico
are used to assist with the placement of tubes or other receive about 1.5 mSv more per year than those living
devices in the body or with other therapeutic procedures. near sea level. The added dose from cosmic rays during a
coast-to-coast round trip flight in a commercial airplane
Measuring radiation dosage is about 0.03 mSv. Altitude plays a big role, but the
largest source of background radiation comes from radon
The scientific unit of measurement for radiation dose, gas in our homes (about 2 mSv per year). Like other
commonly referred to as effective dose, is the sources of background radiation, exposure to radon
millisievert (mSv). Other radiation dose measurement varies widely from one part of the country to another.
units include rad, rem, roentgen, and sievert.
To explain it in simple terms, we can compare the
Because different tissues and organs have varying radiation exposure from one chest x-ray as equivalent to
sensitivity to radiation exposure, the actual dose to the amount of radiation exposure one experiences from
different parts of the body from an x-ray procedure our natural surroundings in 10 days.
varies. The term effective dose is used when referring to
the dose averaged over the entire body. Following are comparisons of effective radiation dose
with background radiation exposure for several
The effective dose accounts for the relative sensitivities radiological procedures described within the
of the different tissues exposed. More importantly, it RadiologyInfo.org Web site:
allows for quantification of risk and comparison to more
familiar sources of exposure that range from natural
background radiation to radiographic medical
procedures.

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For this procedure: Your effective radiation Comparable to natural
dose is: background radiation for:

Abdominal region:

Computed Tomography (CT)-Abdomen 10 mSv 3 years

Computed Tomography (CT)-Body 10 mSv 3 years

Computed Tomography (CT)-Colonography 5 mSv 20 months

Intravenous Pyelogram (IVP) 1.6 mSv 6 months

Radiography-Lower GI Tract 4 mSv 16 months

Radiography-Upper GI Tract 2 mSv 8 months

Central nervous system:

Computed Tomography (CT)-Head 2 mSv 8 months

Computed Tomography (CT)-Spine 10 mSv 3 years

Myelography 4 mSv 16 months

Chest:

Computed Tomography (CT)-Chest 8 mSv 3 years

Radiography-Chest 0.1 mSv 10 days

Children's imaging:

Voiding Cystourethrogram 5-10 yr. old: 1.6 mSv 6 months

Infant: 0.8 mSv 3 months

Face and neck:

Computed Tomography (CT)-Sinuses 0.6 mSv 2 months

Heart:

Cardiac CT for Calcium Scoring 2 mSv 8 months

Men's imaging:

Bone Densitometry (DEXA) 0.01 mSv 1 day

Women's imaging:

Bone Densitometry (DEXA) 0.01 mSv 1 day

Galactography 0.7 mSv 3 months

Hysterosalpingography 1 mSv 4 months

Mammography 0.7 mSv 3 months

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X-ray safety to order a different type of exam for a pregnant patient or
reduce the number of x-rays from that which are
As with other medical procedures, x-rays are safe when normally acquired. Therefore it is important that you
used with care. Radiologists and x-ray technologists have inform your physician or the x-ray technologist about
been trained to use the minimum amount of radiation your reproductive status before the x-ray study is
necessary to obtain the needed results. The amount of performed.
radiation used in most examinations is very small and the
Most standard x-ray examinations of the abdomen are
benefits greatly outweigh the risk of harm.
not likely to pose a serious risk to the child. Some
X-rays are produced only when a switch is momentarily abdominal and pelvic studies such as CT deliver greater
turned on. As with visible light, no radiation remains amounts of radiation to a developing pregnancy.
after the switch is turned off. Informing the radiologist that you are or might be
pregnant is important so that your medical care can be
planned with both you and your baby in mind.
X-rays over your lifetime Remember, this is done to optimize medical care by
reducing any potential risk.
The decision to have an x-ray exam is a medical one,
based on the likelihood of benefit from the exam and the Radionuclide exams, also known as nuclear medicine,
potential risk from radiation. For low dose examinations, also use x-ray-like radiation. But the method of use is
usually those that involve only films taken by a quite different from x-rays and they produce very
technologist, this is generally an easy decision. For different looking images. The same advice for informing
higher dose exams such as computed tomography (CT) your physician or the nuclear medicine technologist
scans and those involving the use of contrast materials about any possible pregnancy before the examination
(dyes) such as barium or iodine, the radiologist may want begins is important.
to consider your past history of exposure to x-rays. If you
have had frequent x-ray exams and change healthcare However, in nuclear medicine another precaution is
providers, it is a good idea to keep a record of your x-ray advised for women who are breast-feeding a child. Some
history for yourself. This can help your doctor make an of the pharmaceuticals that are used for the study can
informed decision. It is also very important to tell your pass into the mother's milk and subsequently the child
doctor if you are pregnant before having an exam that will consume them. To avoid this possibility, it is
involves the abdomen or pelvic region. important that a nursing mother inform her physician and
the nuclear medicine technologist about this before the
examination begins. Usually, you will be asked to
Pregnancy and x-rays discontinue breast-feeding for a short while, pump your
breasts in the interim and discard the milk. Breast-
As with any aspect of medical care, knowing that a feeding can often resume shortly afterwards.
patient is or could be pregnant is important information.
Pregnancy, for example, might explain certain symptoms
or medical findings. When a pregnant patient is ill or Radiation dose from
injured, the physician will carefully select medications to interventional radiology
avoid potential risks to the developing child. This is also
true of x-rays. procedures
While the vast majority of medical x-rays do not pose a Interventional radiologic procedures use diagnostic-type
critical risk to a developing child, there may be a small imaging equipment to assist a physician in the treatment
likelihood of causing a serious illness or other of a patient's condition. These procedures frequently
complication. The actual risk depends on how far along provide favorable medical results with minimal recovery
the pregnancy is and on the type of x-ray. Ultrasound time. In some cases these procedures avoid the need for
studies, for example, don't use x-rays and have never conventional surgery or improve the prospects for a
demonstrated any potential for risk to a pregnancy. X-ray favorable outcome from surgery. As with any medical
studies of the head, arms, legs and chest do not usually procedure, there are associated risks and the nature of
expose the baby directly to x-rays and typically the these risks depend on the procedure.
technologist who takes the x-rays will implement special
Ultrasound imaging is sometimes used for interventional
precautions to ensure that the baby of a pregnant patient
radiology procedures. Ultrasound uses acoustic radiation
is not directly exposed.
and, at current intensities, no risk is known to exist for
Sometimes patients need examinations of the abdomen this type of imaging procedure. Magnetic resonance
or pelvis while they are pregnant. When studies of the imaging is used for other interventional radiology
abdomen or pelvis are required, the physician may prefer procedures. For these procedures, a careful screening is

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performed prior to admission to the scanner room. This Disclaimer:
screening is to make sure that you have not had previous
medical or cosmetic procedures that might make the This information is copied from the RadiologyInfo Web
procedure hazardous. site (http://www.radiologyinfo.org) which is dedicated to
providing the highest quality information. To ensure
With interventional radiology procedures using x-rays,
that, each section is reviewed by a physician with
the level of risk depends on the type of procedure
because some use very little radiation, while complex expertise in the area presented. All information
procedures use much more. In general, the risk of contained in the Web site is further reviewed by an ACR
developing a cancer from the exposure is not a major (American College of Radiology) - RSNA (Radiological
concern when compared to the benefits of the procedure. Society of North America) committee, comprising
Many of the complex procedures, such as are used to physicians with expertise in several radiologic areas.
open a partially blocked blood vessel, repair a weak area
of a bulging vessel, or to redirect blood flow through However, it is not possible to assure that this Web site
malformed vessels, use extensive radiation. But such contains complete, up-to-date information on any
complex procedures are also frequently lifesaving in particular subject. Therefore, ACR and RSNA make no
their benefit and the risks associated with the radiation representations or warranties about the suitability of this
are a secondary consideration. In very rare cases, some information for use for any particular purpose. All
patients develop skin damage as a result of the information is provided "as is" without express or
procedure. As with any surgical procedure, these rare implied warranty.
events are an important possibility when procedures are
difficult and extensive. Since the risk for such Please visit the RadiologyInfo Web site at
complications depends on the individual circumstances, http://www.radiologyinfo.org to view or download the
the physician should discuss these possibilities with the latest information.
patient as is appropriate.

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