MR Imaging of Prostate after Treatment with High-Intensity Focused Ultrasound

PURPOSE: To prospectively evaluate magnetic resonance (MR) imaging findings after high-intensity focused ultrasound (HIFU) treatment of the prostate and to correlate them with clinical and histologic findings. MATERIALS AND METHODS: Local ethics committee approval and informed consent were obtained. Fifteen consecutive men aged 46-70 years with organ-confined prostate cancer underwent ultrasonographically guided ablation of the whole prostate. Postoperative MR images were obtained within 1 month (12 patients), at 1-3 months (five patients), and in all patients at 6 months. Prostate volume was measured on T2-weighted images, and enhancing tissue was measured on dynamic images after intravenous administration of gadopentetate dimeglumine. Prostate-specific antigen (PSA) level was measured at regular intervals, and transrectal biopsy was performed in each patient at 6 months after treatment. RESULTS: Initial post-HIFU images showed a central nonenhancing area, surrounded by an enhancing rim. At 6 months, the prostate was small (median volume reduction, 61%) and was of predominantly low signal intensity on T2-weighted images. The volume of prostate enhancing on the initial posttreatment image correlated well with serum PSA level nadir (Spearman r = 0.90, P < .001) and with volume at 6 months (Pearson r = 0.80, P = .001). The three patients with the highest volume of enhancing prostate at the initial posttreatment acquisition had persistent cancer at 6-month biopsy. CONCLUSION: MR imaging results of the prostate show a consistent sequence of changes after treatment with HIFU and can provide information to the operator about completeness of treatment.