SU‐EE‐A4‐05: Radiation Dose Reduction in CT Guided Cryoablation Using HYPR‐LR

Purpose: Patients under CT guided interventional procedures usually receive high radiation dose as multiple scans are performed. The purpose of this study is to investigate potential of dose reduction for CT‐guided renal tumor cryoablation using a newly developed image reconstruction technique: Local HYPR Reconstruction (HYPR‐LR). Method and Materials: Three patients, each with a renal tumor, underwent percutaneous cryoablation with CT monitoring. Original full dose projection data sets were saved and exported to a personal computer. Noise was inserted into the projection data to simulate low dose scans (50% of the original dose) using a novel noise insertion tool developed by our lab. Low dose images at different freezing time were then reconstructed from the simulated low dose projections using commercial reconstruction algorithm. HYPR‐LR was conducted using the average low dose images as a composite image. Image quality, focusing on target (ice ball) visibility and image noise, was compared among full dose images (FD), low dose images (LD) and low dose HYPR‐LR images. Results: Low dose images reconstructed with HYPR‐LR demonstrate similar image quality as the full dose scan images and superior to the low dose images reconstructed with commercial software. Image noise measured at three set of images were: 51.3 (LD), 38.3 (FD), and 31.8 HU (HYPR‐LR). The growing ice ball can be better visualized in the HYPR‐LR image series compared to the low dose images due to improved image quality. Conclusion: HYPR‐LR has been demonstrated to be useful for dose reduction in renal tumor cryoablation with CT monitoring. Our study shows that at least a factor of 2 dose reduction is achievable by reducing the tube mAs by 50%. Clinically, this translates into a factor of 2 reduction in radiation risk (deterministic or stochastic) for the increasing numbers of patients undergoing CT‐guided tumor cryoablation.