Radiation dose during CT-guided percutaneous cryoablation of renal tumors: Effect of a dose reduction protocol

• Potentially substantial radiation doses are received by patients during CT-guided percutaneous cryoablation of renal tumors.
• Radiation dose reductions are achievable by decreasing tube current and kilovoltage of targeting and monitoring scans and reducing the number of monitoring scans.
• Further dose reductions are possible through the use of CT fluoroscopy during the targeting phase so as to limit the number of helical CT scans acquired.
• The findings of this study have an important implication for patient care: the potential radiation doses received by patients during CT-guided percutaneous renal cryoablation procedures should alert interventional radiologists of the need for adopting procedural techniques and dose reduction protocols that limit radiation dose.

PurposeTo estimate and compare the radiation dose using a standard protocol and that of a dose reduction protocol in patients undergoing CT-guided percutaneous cryoablation of renal tumors.Materials and methodsAn IRB-approved, HIPAA-compliant retrospective study of 97 CT-guided cryoablation procedures to treat a solitary renal tumor in each of 97 patients (64M, 33F; range 31–84 yrs) was performed. Fifty patients were treated using a standard dose protocol (kVp = 120, mean mAs = 180, monitoring scans every 3 min during freezes), and an additional 47 patients were treated using a dose reduction protocol (kVp = 100, mean mAs = 100, monitoring scans less frequently than every 3 min during freezes). Multiple Wilcoxon Mann-Whitney (rank-sum) tests were used to compare dose-length product (DLP) between the two groups. Fisher’s exact test was used to compare technique effectiveness at 12 months post ablation between the two groups.ResultsMedian DLP for the standard protocol group was 4833.5 mGy*cm (range, 1667–8267 mGy*cm); median DLP for the dose reduction group was 2648 mGy*cm (range, 850–7169 mGy*cm), significantly less than that of the standard protocol group (p < 0.01). The technique effectiveness for the dose reduction group was not significantly different from that of the standard protocol group at 12 month follow up (p = 0.434).ConclusionThe radiation dose during percutaneous CT-guided cryoablation of renal tumors was substantial in both the standard and the dose reduction groups; however, it was significantly lower with the protocol change that reduced dose parameters and decreased the number of CT scans.