Monitoring prostate thermal therapy with diffusion-weighted MRI

For MR‐guided minimally invasive therapies, it is important to have a repeatable and reliable tissue viability evaluation method. The use of diffusion‐weighted MRI (DWI) to evaluate tissue damage was assessed in 19 canine prostates with cryoablation or high‐intensity ultrasound (HIU) ablation. The apparent diffusion coefficient (ADC) trace value was measured in the treated tissue immediately upon the procedure and on the posttreatment follow‐up. For the acute lesions, the ADC value decreased to (1.05 ± 0.25) × 10–3 mm2/s, as compared to (1.64 ± 0.24) × 10–3 mm2/s before the treatment. There was no statistical difference between previously frozen or previously ultrasound‐heated lesions in terms of the 36% ADC reduction (P = 0.66). The ADC decrease occurred early during the course of the treatment, which appears to complicate DWI‐based thermometry. Over time, the ADC value increased as the tissue recovered and regenerated. This study shows that DWI could be a promising method to monitor prostate thermal therapies and to provide insight on tissue damage and tissue remodeling after injury. Magn Reson Med 59:1365–1372, 2008. © 2008 Wiley‐Liss, Inc.