SU‐E‐QI‐10: Intravoxel Incoherent Motion Imaging for MR‐Guided Cryoablation

Abstract

Purpose:Percutaneous renal cryoablation for renal tumors has been shown to be nephron sparing and have low morbidity. Post‐treatment verification of the ablated tissue often utilizes contrast‐enhanced MR imaging (ce‐MRI) to assess the region of altered perfusion. However, particularly within this population, some patients are contraindicated for contrast injection. Intravoxel incoherent motion (IVIM) MRI is a technique that measures diffusion and perfusion characteristics from the measured diffusion signals of multiple b values. In this study, IVIM MRI is evaluated versus ce‐MRI to assess its feasibility for differentiating normal and ablated tissue.Methods:Under real‐time MR guidance, 3 cryoprobes were introduced to a patient with renal cell carcinoma in the right kidney. Two cycles of cryoablation were performed with each cycle consisting of 12 minutes and a thaw cycle of 10 minutes. Dynamic ce‐MRI was performed following the last thaw cycle and diffusion‐weighted imaging. IVIM MRI was obtained using a respiratory navigator triggered single‐shot echo planar imaging sequence on a 1.5T clinical scanner. The diffusion coefficient D and the perfusion f parameters were estimated by fitting the diffusion for b values higher and lower than 200 sec/mm2 signal, respectively, using the IVIM model. Regions of interest (ROI) were manually placed in non‐enhancing and enhancing regions according to the post‐treatment contrast‐enhanced images and compared to one another.Results:The perfusion fraction and diffusion coefficient values decreased in the ablated tissue (5.51 ± 7.28 and 0.94 ± .30) compared to the normal kidney tissue (13.13 ± 10.37 and 1.68 ± 0.22). The perfusion fraction and diffusion coefficient maps demonstrate good agreement with the contrast‐enhanced images.Conclusion:In these preliminary results, the use of IVIM parameters could help verify treatment without the use of contrast. In the future, more patients undergoing MRguided cryoablation will be analyzed to determine the accuracy of these damage predictions.