Primary Care Corner with Geoffrey Modest MD: CT scanning in kids and radiation exposure

By: Dr. Geoffrey Modest

I will post an old blog:

The use of CT scans is increasing dramatically in kids. Data collected from 7 large HMOs in the US over 10 years (2001-2011) in kids <15yo, with 4.9M child-years of observation. One advance in this study is that they collected the actual technical parameters (radiation dose) used in diverse facilities.

Major findings:

— a doubling of CT scans done in kids –large variability of radiation dose per scan at different sites. highest dosages overall with abd/pelvic CTs (40% done for pain, 11% for r/o appendicitis, 6% for infection)
–Head CT was the most commonly done CT and increased 50%, though the % increase was highest in abd CT for children 5-14yo.
–using risk models (some based on the Japanese atomic bomb survivors, with those numbers of cancers being similar in a recent CT study), they calculated that:
–in kids under 5yo, those getting head scans (the most common) assoc with one solid cancer developing per 570 CTs in girls and 1350 CTs in boys, and one case of leukemia in 5000 scans (less in older kids);
–for abd/pelvic CT: 300 scans in girls and 670 scans in boys assoc with likely development of one solid tumor (not much difference by age)

So, not huge increased risk for an individual getting a scan (i.e., get one if really necessary), but in population overall, the annual pedi CT scan rate of about 4-9 million CTs/year leads to a large projected increase in cancer, on the order of 5000 cancers/yr. Some studies suggest that 1/3 of CT scans in kids are unnecessary, though changing this is sometimes difficult (we recently had a kid where we suggested doing an ultrasound as initial w/u for possible appendicitis, but the ER/surgeon insisted on CT scan). Also, the great variability in radiation dosage per test (which seems in part due to radiology techs not scaling down radiation exposure sufficiently in kids) needs to be reduced. the potential reduction in cancer by eliminating the unnecessary CTs and decreasing the radiation dosage per CT could decrease the cancer rate by more than 60%. Behavior change for us guys ain’t easy, but the good news is that after repeated battering, we are really doing better at not prescribing antibiotics for likely viral bronchitis, etc.

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