OBJECTIVE. Diagnosis of anterior prostate cancer is challenging. The purpose of this study was to evaluate the diagnostic performance of T2-weighted imaging and an apparent diffusion coefficient (ADC) map in the detection of anterior prostate cancer and to compare that with the diagnostic performance in the detection of posterior prostate cancer. MATERIALS AND METHODS. We retrospectively reviewed the records of 87 patients who underwent 3-T MRI that included T2-weighted imaging and diffusion-weighted imaging before radical prostatectomy. The prostate gland was divided into anterior and posterior segments, and the radiologists interpreted two protocols (T2-weighted imaging alone vs T2-weighted imaging and an ADC map) and sorted the confidence levels for the presence of prostate cancer into five grades. ROC analysis was performed to evaluate the diagnostic performance of each protocol for the detection of anterior and posterior prostate cancers. We also assessed the relative fractions of sensitivity and specificity between anterior and posterior prostate cancers. Additionally, the ADCs of noncancerous anterior fibromuscular stroma were measured and compared with the ADCs of anterior prostate cancers. RESULTS. The AUCs with T2-weighted imaging alone and with T2-weighted imaging and an ADC map were 0.75 and 0.88 for anterior prostate cancer, respectively, and were 0.70 and 0.81 for posterior prostate cancer. The sensitivity for detecting anterior prostate cancer was 90% and was significantly higher than that for detecting posterior prostate cancer in the protocol using T2-weighted imaging and an ADC map (p = 0.003) when scores of 3-5 were considered as positive for prostate cancer. The ADC was significantly lower in anterior prostate cancer (mean, 0.80 × 10-3 mm2/s) than in noncancerous anterior fibromuscular stroma (1.13 × 10-3 mm2/s) (p < 0.001). CONCLUSION. The protocol using T2-weighted imaging and an ADC map showed higher accuracy for the detection of anterior prostate cancer than for the detection of posterior prostate cancer.
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