Prostate cancer: body-array versus endorectal coil MR imaging at 3 T--comparison of image quality, localization, and staging performance

PURPOSE: To prospectively compare image quality and accuracy of prostate cancer localization and staging with body-array coil (BAC) versus endorectal coil (ERC) T2-weighted magnetic resonance (MR) imaging at 3 T, with histopathologic findings as the reference standard. MATERIALS AND METHODS: After institutional review board approval and written informed consent, 46 men underwent 3-T T2-weighted MR imaging with a BAC (voxel size, 0.43 x 0.43 x 4.00 mm) and an ERC (voxel size, 0.26 x 0.26 x 2.50 mm) before radical prostatectomy. Four radiologists independently evaluated data sets obtained with the BAC and ERC separately. Ten image quality characteristics related to prostate cancer localization and staging were assigned scores. Prostate cancer presence was recorded with a five-point probability scale in each of 14 segments that included the whole prostate. Disease stage was classified as organ-confined or locally advanced with a five-point probability scale. Whole-mount-section histopathologic examination was the reference standard. Areas under the receiver operating characteristic curve (AUCs) and diagnostic performance parameters were determined. A difference with a P value of less than .05 was considered significant. RESULTS: Forty-six patients (mean age, 61 years) were included for analysis. Significantly more motion artifacts were present with ERC imaging (P<.001). All other image quality characteristics improved significantly (P<.001) with ERC imaging. With ERC imaging, the AUC for localization of prostate cancer was significantly increased from 0.62 to 0.68 (P<.001). ERC imaging significantly increased the AUCs for staging, and sensitivity for detection of locally advanced disease by experienced readers was increased from 7\% (one of 15) to a range of 73\% (11 of 15) to 80\% (12 of 15) (P<.05), whereas a high specificity of 97\% (30 of 31) to 100\% (31 of 31) was maintained. Extracapsular extension as small as 0.5 mm at histopathologic examination could be accurately detected only with ERC imaging. CONCLUSION: Image quality and localization improved significantly with ERC imaging compared with BAC imaging. For experienced radiologists, the staging performance was significantly better with ERC imaging.