RESUMO
INTRODUCTION: Upgrading computerized tomography (CT) scanners to iterative reconstruction techniques (IRT) decreases radiation dose. This reduction, combined with changes in surveillance protocols in clinical stage I testicular cancer (CS1TC) measurably decrease the lifetime attributable risk (LAR) of dying of radiation-associated cancer. MATERIALS AND METHODS: This IRB-approved study enrolled 24 CS1TC patients who had CT scans on the same Toshiba Aquilion 64 CT before and after IRT software installation. Dose-length product and CT dose index volume were recorded. A physicist calculated effective doses. Radiation doses were compared using the Wilcoxon signed rank test. Median effective dose per scan was multiplied by scan number based on 16 versus 7 scans in 5-year AS protocols to calculate estimated cumulative dose (ECD). LAR of dying of radiation-associated solid tumor was estimated using ECD for a single exposure at age 35 with the excess absolute risk transport model from the BEIR VII analysis of long-term atomic bomb survivors. RESULTS: Median preupgrade and postupgrade effective doses were 12.5 and 7.7 mSv, respectively (P<0.0001). A linear regression model with a constrained zero intercept fit to the data found that IRT dose was estimated as 61% of filtered back projection dose (95% confidence interval, 0.56-0.66). The IRT upgrade reduced the LAR of the 16-scan protocol 35%. Combination of IRT upgrade and 7-scan protocol reduced surveillance LAR 72%. CONCLUSIONS: Modern CT technology combined with reduced scanning strategies can markedly decrease lifetime radiation exposure, further lowering the already small potential mortality of imaging-associated cancers.
