Diffusion-weighted MRI of urinary bladder and prostate cancers.

P rostate cancer is the third leading cause of death and is the most common genitourinary malignancy in men. Cancer of the urinary bladder is the second most common malignancy of the genitourinary system (1, 2). For the radiological evaluation of the urinary bladder and prostate gland, magnetic resonance imaging (MRI) is a valuable imaging modality due to high tissue contrast, multiplanar imaging capabilities, and the possibility of tissue characterization (3). In addition, many new techniques in bladder imaging, and especially prostate gland MRI, are under development and refinement (1, 4). Recently, diffusion-weighted imaging (DWI) has emerged as a diagnostic technique in the evaluation of various abdominal lesions. DWI reveals micro-molecular diffusion, which is the Brownian motion of the spins in biologic tissues. This technique can delineate pathologic lesions with high tissue contrast against generally suppressed background signal. The apparent diffusion coefficent (ADC) value has been reported to be useful for quantitatively distinguishing malignancy from benign lesions (5, 6). We sought to present DWI features of bladder and prostate carcinomas, and to evaluate its ability to detect malignancy.