Usefulness of apparent diffusion coefficient map in diagnosing prostate carcinoma: Correlation with stepwise histopathology

Purpose: To elucidate the performance of apparent diffusion coefficient (ADC) map in localizing prostate carcinoma (PC) using stepwise histopathology as a reference. Materials and Methods: Preoperative MR images of 37 patients with PC who had undergone radical prostatectomy were retrospectively evaluated. First, T2-weighted images (T2WI) alone were interpreted (T2WI reading), and then T2WI along with ADC map were interpreted (T2WI/ ADC map reading). Sextant-based sensitivity and speci- ficity, and the ratio of the detected volume to the whole tumor volume (% tumor volume) were compared between the two interpretations, and results were also correlated to Gleason's scores (GS). ADC values were correlated to histological grades. Results: Sensitivity was significantly higher in T2WI/ ADC map reading than in T2WI reading (71% vs. 51%), but specificity was similar (61% vs. 60%). By adding ADC map to T2WI, % tumor volume detected increased significantly in transitional zone (TZ) lesions, but not in peripheral zone (PZ) lesions. % tumor volume detected with T2WI/ADC map reading showed a positive correlation with GS of the specimens. Less differentiated PC were associated with lower ADC values and higher detectability. Conclusion: T2WI/ADC map reading was better than T2WI reading in PC detection and localization. This approach may be particularly useful for detecting TZ lesions and biologically aggressive lesions.