Prostate cancer vs. post-biopsy hemorrhage: diagnosis with T2- and diffusion-weighted imaging.

PURPOSE: To assess the value of quantitative T2 signal intensity (SI) and apparent diffusion coefficient (ADC) to differentiate prostate cancer from post-biopsy hemorrhage, using prostatectomy as the reference.
MATERIALS AND METHODS: Forty-five men with prostate cancer underwent prostate magnetic resonance imaging (MRI), including axial T1-weighted imaging (T1WI), T2WI, and single-shot echo-planar image (SS EPI) diffusion-weighted imaging. Two observers measured, in consensus, normalized T2 signal intensity (SI) (nT2, relative to muscle T2 SI), ADC, and normalized ADC (nADC, relative to urine ADC) on peripheral zone (PZ) tumors, benign PZ hemorrhage, and non-hemorrhagic benign PZ. Tumor maps from prostatectomy were used as the reference. Mixed model analysis of variance was performed to compare parameters among the three tissue classes, and Pearson's correlation coefficient was utilized to assess correlation between parameters and tumor size and Gleason score. Receiver-operating characteristic (ROC)-curve analysis was used to determine the performance of nT2, ADC, and nADC for diagnosis of prostate cancer.
RESULTS: nT2, ADC, and nADC were significantly lower in tumor compared with hemorrhagic and non-hemorrhagic benign PZ (P < 0.0001). There was a weak but significant correlation between ADC and Gleason score (r = -0.30, P = 0.0119), and between ADC and tumor size (r = -0.40, P = 0.0027), whereas there was no correlation between nT2 and Gleason score and tumor size. The areas under the curve to distinguish tumor from benign hemorrhagic and non-hemorrhagic PZ were 0.97, 0.96, and 0.933 for nT2, ADC, and nADC, respectively.
CONCLUSION: Quantitative T2 SI and ADC/nADC values may be used to reliably distinguish prostate cancer from post-biopsy hemorrhage.