Dr. John is a Professor of Radiology and Pediatrics,
Department of Radiology, University of Texas Houston Medical
School, and Chief of Pediatric Radiology, Memorial Hermann
Children's Hospital, and Chief of Diagnostic Radiology,
Memorial Hermann Hospital, Houston, TX.
It is a familiar scene in medicine: the thrill of discovering
new, more elegant ways to diagnose and treat disease, followed by
the recognition that the new capabilities are accompanied by the
potential for harm. Radiologists understand that the responsibility
for monitoring and controlling radiation exposure to patients is a
primary role of the specialty and have long attended to that task
with minimal fanfare. In our enthusiasm for developing more
accurate and sophisticated diagnostic imaging techniques, however,
patient safety may be relegated to a secondary consideration. This
is especially true for pediatric patients, who are physiologically
different from adults and comprise a relatively small proportion of
the patient population in many radiology practices.
Earlier this year, the association of radiation-induced cancer
with radiation exposure to children undergoing diagnostic computed
tomography (CT) captured the attention of the public, due to
several important publications on this issue
1,2
and a sudden blitz of dramatic media coverage. The negative
publicity had the positive effect of raising awareness within the
medical community about the potential for high radiation exposure
to patients undergoing helical CT. Medicine responded with a call
for renewed commitment to finding ways to better manage this safety
issue.
Recently, the Society of Pediatric Radiology sponsored a
conference addressing the concept of ALARA (As Low As Reasonably
Allowable) in CT of pediatric patients. Participants included a
diverse constellation of professionals, including radiologists,
radiobiologists, technologists, physicists, engineers, oncologists,
vendors, and government officials. Many of the speakers were
leaders in science and medicine with long-standing experience in
the effects of radiation and radiation control. The conference
provided an exceptional opportunity for communication and
discussion of what is already known about the issue and for
brainstorming about available remedies and areas where future
research is needed.
Although many questions and controversies remain regarding
radiation and cancer in children, consensus is evident on several
points. The increased risk of radiation-induced cancer in children
caused by exposure during CT remains very small for any given
patient, and the benefits for most indications are relatively
large. Nevertheless, the overall risks to children of this country
become significant when multiplied by the large number of studies
performed, estimated to be more than 2.5 million exams per year and
growing. Research on A-bomb survivors who received lower doses of
radiation exposure now provide risks estimates for
radiation-induced cancer in the population exposed to doses similar
to those occurring with CT. Children are 10 times more sensitive to
radiation-induced cancer than adults, presumably because of the
presence of a larger number of actively producing cells in infants
and children. Studies of fetal exposures due to in utero
radiographs suggest that risk of cancer increases with a dose of
approximately 1 rad to the fetus. If radiographic techniques are
not reduced properly for children, the dose to individual organs is
much larger in infants and children than in adults, and the close
proximity of the organs in a smaller body makes scatter more
important. Radiation doses can be decreased significantly by simple
adjustments of the imaging parameters during CT.
All participants of the conference agreed that action is needed
urgently to ensure the safety of children undergoing CT, and many
helpful ideas were proposed. Several of the large children's
hospitals have already implemented creative and successful programs
to decrease radiation dose during CT. One of the articles in this
issue of
Applied Radiology
presents one institution's experience with improving CT in
children, including radiation exposure. Many radiology practices in
the United States face special challenges in establishing effective
low-dose CT policies, because children are seen much less commonly
than adults. The answer to the challenges involves awareness,
education, and constant vigilance on the part of all who are
involved in pediatric imaging. Radiologists must impress upon the
manufacturers and designers of imaging equipment the importance of
making it easier to monitor and limit exposure to radiation and
other potentially harmful by-products of imaging modalities.
Technologists must be educated about the importance of minimizing
radiation dose in pediatric patients and should be involved
actively in planning strategies for decreasing exposure to children
during CT. Physicians referring children for CT must be counseled
about safer imaging alternatives when appropriate. The primary
responsibility lies with the radiologist to ensure that infants and
children receive the minimum necessary dose of radiation to provide
the information needed from CT.
The recent surge of interest in radiation exposure during CT
provides an excellent opportunity to examine potentially harmful
effects of other common forms of imaging in pediatric patients.
Although modalities such as ultrasound and magnetic resonance
imaging are considered safer than those that use ionizing
radiation, the energies used for these imaging modalities can also
have undesired effects. The American Institute of Ultrasound in
Medicine has published guidelines for the safe use of diagnostic
ultrasound, which can have potentially harmful thermal and
mechanical effects on fetal tissues and in the brain and
gastrointestinal tract of infants. Recent reports of accidents in
magnetic resonance scanners due to flying metal projectiles reminds
us of the need for constant surveillance of personnel and patients
near strong magnetic fields. All of these technologies provide
unquestioned benefits to the health of children, but our
responsibility for protecting these young patients from harm during
imaging endures. Vigilance pays.