Imaging gently: kids and CT
The last sessions of the day today looked at pediatrics and CT. The discussion began, appropriately, with a few presentations on dosing and radiation in pediatric patients -- a hot topic in recent years with the advent of the ACR's Image Gently campaign, a push to spread the word about "child-sizing" pediatric imaging dose. Frandics Chan, MD, PhD, presented on the topic "Radiation in Pediatric Cardiac CTA: Myth and Reality." His view of the issue at hand was sobering. "Does radiation at the diagnostic dose of CT cause cancer?" he asked the audience. "We don't know, but the likelihood is probably high." Chan went on to urge conference-goers to "get over the hump" and assume that CT does cause cancer, saying the only real question now is how much cancer does it cause? We know that young children exposed to radiation are three times more likely to get cancer than adults exposed to the same dosage. And we know that since the year 2000 or so, significant decreases in radiation dose have resulted from adoption of weight-based mAs and kVp adjustment. Good to know, because, as subsequent presenters pointed out, there are situations involving pediatric patients as young as newborns where CT is simply necessary. "There are a lot of challenges to doing CT in infants," noted Bruce Greenberg, MD, of Arkansas Children's Hospital, "but there are also advantages." These include the universal availability of the modality -- as Greenberg put it, "Most places have folks who are comfortable using it, unlike MR" -- as well as its speed and high-res images. In fact, Greenberg looked at some ACH data and found that 32% of the CT studies performed at his hospital last year were in children under a year of age. Nine percent were under a month. Greenberg observed that CT is more useful than other modalities for surgical planning. He was alluding to planning for surgery to correct complex congenital heart disease, but his point was reiterated by Beverley Newman, BSc, regarding intrapulmonary neoplasms, and by Richard Barth, MD, regarding prenatally diagnosed lung malformations. "Why do we image them with CT?" Barth said. "To confirm the presence of a lesion before sending a surgeon in; to determine the nature of the lesion; and to create a roadmap for any necessary surgery." That's where dose metrics come in handy. Like those described by Donald Frush, MD, in his presentation on effective dose in pediatric CT. "We need to have some measure of risk stratification, but right now effective dose is the best thing we have," he said. "Lookup tables seem to be the easiest method for clinical practice -- but be aware of their limitations." What would be better than lookup tables? How about a full-body computer model that can be used to prospectively calculate organ dose? "Most of the call from the scientific community is to evolve toward that," Frush noted. "But we're probably years away."