574 underwent MRI before biopsy (group 1), and 103 patients underwent MRI after biopsy (group 2). 　The mean age of group 1 was 67.16±6.38 years, the mean PSA value was 14.16±17.66 ng/ml, the mean prostate size was 42.98±22.70 ml, and the mean number of prostate bi- opsy cores was 10.24±0.65. The mean age of group 2 was 69.09±7.55 years, the mean PSA value was 16.60±23.07 ng/ml, the mean prostate size was 37.28±16.28 ml, and the mean number of prostate biopsy cores was 10.08±0.38 (Table 1). 　In group 1, 36 patients were diagnosed as having pros- tate cancer by prostate biopsy, and the remaining 15 pa- tients were diagnosed as having benign prostatic hyperplasia. Of 37 patients who were diagnosed as having prostate cancer by MRI, 31 patients were definitely diag- nosed as having prostate cancer by prostate biopsy. The re- maining patients were found to have benign prostatic hy- perplasia or chronic inflammation. Of 31 patients who were definitely diagnosed as having prostate cancer, the site of the MRI lesion matched in 28 patients. Of 14 patients who were diagnosed as having a low possibility of prostate can- cer by MRI, 5 patients were diagnosed as having prostate Choi et al cancer and the remaining 9 patients were diagnosed as having benign prostatic hyperplasia or chronic in- flammation by biopsy (Fig. 1). 　In group 2, 93 patients were diagnosed as having pros- tate cancer by prostate biopsy, and the remaining 10 pa- tients were diagnosed as having benign prostatic hyper- plasia. Of 93 patients who were diagnosed as having pros- tate cancer by MRI, 86 patients were definitely diagnosed as having prostate cancer by prostate biopsy. The remain- ing 7 patients were found to have benign prostatic hyper- plasia or chronic inflammation. Of 86 patients who were definitely diagnosed as having prostate cancer, the site of the MRI lesion matched in 81 patients. Of 10 patients who were diagnosed as having a low possibility of prostate can- cer by MRI, 7 patients were diagnosed as having prostate cancer and the remaining 3 patients were diagnosed as having benign prostatic hyperplasia or chronic in- flammation by biopsy (Fig. 2). 　Cases in which the location of the primary lesions match- ed were limited to the cases whose ADC map and the loca- tion confirmed by the pathologic results were identical (Fig. 3). Korean J Urol 2011;52:572-577 FIG. 1. Study design and schematic flow of group 1. FIG. 2. Study design and schematic flow of group 2.