Radiation exposure during computed tomography-guided cryoablation of renal masses.

Abstract

e15116 Background: Despite heightened awareness of risks from ionizing radiation, the use of image-guided therapy is rising. Our goal was to calculate the radiation effective dose (ED) received during computed tomography (CT)-guided percutaneous cryoablation (PC) of renal masses. Methods: A retrospective chart review from January 2008 to June 2009 found 21 patients had undergone CT-guided PC. Using radiation dose estimates from the procedures based on a standard anthropomorphic phantom, mean radiation ED was estimated. Fluoroscopy time and total ED were used to compute the learning curve which was assessed with correlation testing. Results: We performed PC on 24 masses ranging from 0.9-8.0cm. Mean patient age, body mass index, and lesion size were 65.8 years, 28.3, and 2.9 cm, respectively. For each mass ablated, mean fluoroscopy time was 46.4 seconds (range 11.4-143.4 sec), mean fluoroscopy ED was 8.2 mSv (range 1.9-28.0 mSv), and mean total ED was 21.6 mSv (range 10.1-37.5 mSv). We estimated the learning curve by dividing the 24 masses into quartiles and calculated the mean mass size, fluoroscopy time, and total ED per quartile. There was a 59.3% decrease in fluoroscopy time and a 39.4% decrease in total ED between the 1st and 4th quartile despite a 17.7% increase in mass size. Fluoroscopy time was moderately correlated with case number (R2=0.32). When plotting fluoroscopy time utilized per individual mass versus case number a decline was seen (R2=0.35). Fluoroscopy time alone was minimally correlated with mass size (R2=0.19) and not at all with BMI (R2=0.05). Conclusions: Fluoroscopy time declined as operator experience increased, subjecting patients to less radiation exposure. Mean total radiation ED was 21.6 mSv for all cases. For comparison, three-phase renal CT ED on our scanner was 23.7 mSv. While the greatest decline in fluoroscopy time (51.0%) occurred between the 1st and 2nd quartile, there was still an 11.0% time decrease between the 3rd and 4th quartile suggesting continued improvement in the learning curve. No significant financial relationships to disclose.