SU-E-I-55: Cumulative Radiation Exposure and Cancer Risk Estimates in Pediatric Hydrocephalus Patients Undergoing Repeat Or Multiple CT.

PURPOSE

Children with a shunt for hydrocephalus often undergo multiple follow-up head CT scans, increasing the risk for long-term effects of ionizing radiation. The study is to define a conservative estimate of frequent CT head scans for pediatric patients with a shunt for hydrocephalus and to quantify their cumulative CT radiation doses and lifetime attributable risk of developing cancer.

METHODS

All children at age of less than 17 years with a shunt for hydrocephalus who underwent non-enhanced head CT at a tertiary hospital between 2007 and 2011 were identified and categorized by total number of scans per study period as non-frequently (<3), or frequently (>=3) scanned. We retrospectively identified the number of CT head scans, dose length product (DLP) and the applied scan parameters according to age, gender and study time. Effective doses were estimated using age- specific DLP to effective dose conversion coefficients. Lifetime attributable cancer risk was then estimated based on the BEIR VII.

RESULTS

During the 5-year study period, a total of 264 children (mean age, 5.5 years; range less than one month to 17 years; 146 boys and 118 girls) underwent 747 CT head scans, of whom 100 patients (41.7%) were frequently scanned. The median and mean of frequently scans are 4 and 5.33, with the most frequently scanned patient underwent 34 CT head scans from birth to 4 years and 1 month age. The average effective dose was 15.71 mSv, ranging from 3.65 mSv to 64.70 mSv. The estimated lifetime attributable cancer risk is one in 637, ranging from one in 2739 to one in 155, based on the standardized BEIR VII conversion of 0.0001/mSv.

CONCLUSIONS

The children with shunts have a substantially increased risk of developing cancer from cumulative CT radiation exposure.