[Utility of diffusion-weighted magnetic resonance imaging and apparent diffusion coefficient in detection of prostate cancer and prediction of pathologic Gleason score].

Thirty patients with histologically proven prostate cancer whose prostate specific antigen values were under 20 ng/ml received magnetic resonance imaging (MRI) at 1.5 T before transrectal ultrasound-guided systematic transrectal 10-core needle biopsy. Diffusion-weighted imaging (DWI) and apparent diffusion coefficient (ADC) on MRI were retrospectively analyzed by a single radiologist without any information of the results of the biopsy. The locations of cancer, indicated by the results of biopsy, coincided with the findings of MRI in 25 patients (83.3%). The characteristics of DWI and ADC in the lesion with a cancer focus could be analyzed in 21 patients. The mean ADC of cancer lesions was 0.96 ± 0.36 × 10⁻³ mm²/sec (± SD). The mean ADC of cancer lesions with a Gleason score of 6 was 1.14 ± 0.40 × 10⁻³ mm²/sec, while that of lesions with Gleason scores of 7 and 8 was 0.77 ± 0.20 × 10⁻³ mm²/s (p = 0.008, unpaired t test). DWI and ADC would be useful parameters in the diagnosis of prostate cancer. ADC of a cancer lesion may indicate the malignant potential of cancer cells represented by the Gleason score.