Use computed tomography scans with caution

November 1, 2011

The author recalls the first time she ordered a CT scan in the mid-1970s.

I don't remember the reason we thought the CT would be helpful in this particular case, but I do remember that we were hoping that a CT of the head of a child would provide us with better information than any available alternative modality. Those included skull films, which didn't really image the brain at all; radionuclide brain scans, which were used to identify tumors and anything that might be associated with inflammation (eg, brain abscess); and pneumoencephalograms, which allowed visualization of ventricular size and identified shifts in brain structure.

The latter involved removing most of the cerebrospinal fluid before injecting air through a lumbar puncture so that the ventricles and the general shape and symmetry of the brain could be visualized using x-ray. The procedure was extremely painful and involved maneuvering the patient into a variety of uncomfortable positions so that the air would enter and distribute throughout the ventricles. (For a video describing the earliest use of the CT scan and an illustration of pneumoencephalography, see http://www.youtube.com/watch?v=u_R47LDdlZM/.)

As discussed by Karen Frush, MD, in this issue, availability of CT scans has allowed earlier and more accurate diagnosis of sometimes life-threatening conditions, and we would certainly not like to return to the pre-CT world.

Those benefits, however, must be weighed against the risks associated with ionizing radiation-risks that are enhanced when multiple studies are employed to follow a condition or for repeated screening. Potential risks include development of malignancy later in life and an increased risk for cataracts after head studies, as well as other problems not yet identified.

Experts from multiple disciplines, including urologists, radiologists, surgeons, neurologists, gastroenterologists, emergency medicine specialists, and general pediatricians, are engaged in determining methods to reduce exposure to ionizing radiation while preserving the diagnostic benefits of CT scans. The number of scans we order can be reduced by the use of clinical decision rules that identify patients at low risk.

It's been more than 35 years since we've had to rely on x-rays and radionuclide scans alone for diagnostic imaging. Ultrasound, magnetic resonance imaging, and CT scans have outstripped our physical examination skills so that techniques that were once relied on now seem clumsy and even useless. Perhaps it's time to give those skills a little more credit and use them to scan with caution.

DR MCMILLAN Editor-in-Chief Contemporary Pediatrics

REFERENCE

1. Dorfman AL, Fazel R, Einstein SJ, et al. Use of medical imaging procedures with ionizing radiation in children: a population-based study. Arch Pediatr Adolesc Med. 2011;165(5):458-464.