Review of cumulative diagnostic radiation exposure during childhood in patients with spina bifida
Authors: Gregory Smookler
Background
Diagnostic imaging using ionizing radiation is a crucial tool in
the management of patients with spina bifida, starting almost
directly from birth. During childhood, a patient with spina bifida
will have multiple CT scans of the head, voiding
cysto-urethrograms, and X-rays of the limbs and spine. Hence, the
patient with spina bifida will have a much greater exposure to
radiation than the average person throughout their lifetime. For a
child, the radiation exposure to their immature and developing body
can have significant consequences. Experts such as the
International Commission on Radiation Protection have described a
risk of cancer due to imaging studies that increases with
increasing radiation dose. This study describes the magnitude
of the exposure to diagnostic radiation in children with spina
bifida. Understanding this should help the clinician caring for
children with spina bifida to be prudent with the ordering of
radiologic studies. It will also help clinicians caring for
children and adults with spina bifida to be cognisant that their
patients have a significant risk factor for the development of
malignancies, especially those known to be related to radiation
exposure such as leukaemia and lymphoma. They then can provide
timely screening for early detection for these
conditions.
Materials and Methods
The spina bifida program at Children's Hospital of Los Angeles
cares for well over 600 patients. Out of the portion of the clinic
population that is presently 18 years old or older, 30 were chosen
randomly as subjects for the study. Inclusion criteria were that
they had myelomenigocele and hydrocephalus, and had been receiving
their care at CHLA since at least one year of age. Exclusion
criteria included any other significant chronic illness not related
to myelomeningocele and hydrocephalus, e.g. cystic fibrosis,
cancer, congenital heart disease, chronic lung disease, etc.
The radiologic records for each of the 30 subjects were reviewed
and the total number of imaging studies involving ionizing
radiation was noted. Using standard values for the amount of
radiation involved in each study, each recorded study was converted
into a radiation dose, e.g. one CT of the head equals a dose of
4mSv of radiation. Then the total radiation dose for a patient's
childhood is determined by adding up all of the individual doses.
The total dose per patient is then averaged among the 30 subjects,
determining the average total dose of ionizing radiation during
childhood for a patient with myelomenigocele and
hydrocephalus.
Results
Children with myelomeningocele and hydrocephalus are exposed to
significantly high amounts of ionizing diagnostic radiation,
averaging about 50 mSv over 18 years.
Conclusions
Children with myelomenigocele and hydrocephalus are exposed to
large amounts of radiation as part of their medical care and
management. Ionizing radiation has been identified as a risk factor
for the development of cancer. Children are especially vulnerable
due to increased sensitivity of growing tissues, possible long
latency period, and smaller cross-sectional areas are
exposed. Clinicians should be aware of the magnitude of
radiation exposure during childhood for their patients with spina
bifida so that they can exercise prudence in ordering studies and
screen for possible malignancies.
Children's Hospital of Los Angeles, MS#76, 4650 Sunset
Blvd., Los Angeles, CA 90027
USA
E-Mail: gsmookler@chla.usc.edu
