Endorectal diffusion‐weighted imaging in prostate cancer to differentiate malignant and benign peripheral zone tissue

Abstract

Purpose To determine if the apparent diffusion coefficient (ADC) can discriminate benign from malignant peripheral zone (PZ) tissue in patients with biopsy‐proven prostate cancer that have undergone endorectal diffusion‐weighted imaging (DWI) of the prostate. Materials and Methods Ten patients with prostate cancer underwent endorectal magnetic resonance imaging (MRI) in addition to DWI. A two‐dimensional grid was placed over the axial images, and each voxel was graded by a 4‐point rating scale to discriminate nonmalignant from malignant PZ tissue based on MR images alone. ADC was then determined for each voxel and plotted for nonmalignant and malignant voxels for the entire patient set. Second, with the radiologist aware of biopsy locations, any previously assigned voxel grade that was inconsistent with biopsy data was regrouped and ADCs were replotted. Results For the entire patient set, without and with knowledge of the biopsy data, the mean ADCs for nonmalignant and malignant tissue were 1.61 ± 0.27 and 1.34 ± 0.38 × 10⁻³ mm²/second (P = 0.002) and 1.61 ± 0.26 and 1.27 ± 0.37 × 10⁻³ mm²/second (P = 0.0005), respectively. Conclusion DWI of the prostate is possible with an endorectal coil. The mean ADC for malignant PZ tissue is less than nonmalignant tissue, although there is overlap in individual values. J. Magn. Reson. Imaging 2004;20:654–661.