LOCALIZING PROSTATE-CANCER IN THE PRESENCE OF POSTBIOPSY CHANGES ON MR-IMAGES - ROLE OF PROTON MR SPECTROSCOPIC IMAGING

PURPOSE: To assess whether magnetic resonance (MR) spectroscopic imagi ng with MR imaging can improve prostate cancer localization in postbio psy hemorrhage cases. MATERIALS AND METHODS: Records of 175 patients w ith prostate cancer were retrospectively reviewed; 42 patients (135 he morrhagic sites) had spatially correlated biopsy data. Patients underw ent both phased-array coil-endorectal coil MR imaging and three-dimens ional MR spectroscopic imaging within 180 days after transrectal ultra sound (US)-guided biopsy. High-signal-intensity hemorrhage on T1-weigh ted images and corresponding high- or low-signal-intensity areas on T2 -weighted images and the metabolic ratio (choline + creatine)/citrate were recorded. Cancer was identified as a low-signal-intensity area at T2-weighted MR imaging or a metabolite ratio greater than 3 standard deviations above normal at MR spectroscopic imaging. MR imaging, spect roscopic, and biopsy findings were compared. RESULTS: Forty-nine patie nts had postbiopsy hemorrhage. On T2-weighted images, a higher (P < .0 1) percentage of hemorrhagic sites demonstrated low signal intensity ( 80% [108 of 135 sites]), which is similar to the signal intensity seen with cancer. The addition of MR spectroscopic imaging to MR imaging r esulted in a significant increase (P < .01) in the accuracy (52% to 75 %) and specificity (26% to 66%) of tumor detection. CONCLUSION: The ad dition of MR spectroscopic imaging to MR imaging significantly improve s the ability to determine the presence of prostate cancer and spatial extent when postbiopsy changes hinder interpretation with MR imaging alone.