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Intravoxel Incoherent Motion Imaging for MR-Guided Cryoablation

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J Yung

J Yung*, K Ahrar , J Hazle , R Stafford , UT MD Anderson Cancer Center, Houston, TX


SU-E-QI-10 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

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 MR-guided cryoablation will be analyzed to determine the accuracy of these damage predictions.

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