Cancer - Prostate(구연) International Session I (I-12) Rm. 202 10월 31일(목) 15:00-16:00 Usefulness of bi-parametric magnetic resonance imaging with b = 1800 s/mm² diffusion-weighted imaging for diagnosing clinically significant prostate cancer Department of Urology, Pusan National University Yangsan Hospital Song Won Hoon, Baek Seung Ryong, Lee Seung Soo, Han Ji Yeon, Nam Jong Kil, Park Sung-Woo Purpose: This study was conducted to compare the accuracy of bi-parametric magnetic resonance imaging (bpMRI) with high b-value (b = 1000 s/mm2, b1000) diffusion-weighted imaging (DWI) to that of bpMRI with ultra-high b-value (b = 1800 s/mm2, b1800) DWI to detect clinically significant prostate cancer (csPCa). Materials and Methods: A total of 408 patients with suspected PCa were evaluated by bpMRI prior to biopsy. One reader retrospectively reviewed all images for confirmation of Prostate Imaging–Reporting and Data System (PI-RADS) score. Cognitive MR/ultrasound fusion target biopsy was done for all visible lesions (PI-RADS 3-5). Systematic biopsy was done for all cases. The csPCa detection rates were compared according to the bpMRI protocol (with/without b1800 DWI) or PI-RADS score. The accuracy of PI-RADS score was estimated using receiver operating characteristics curve. The signal intensity (SI) ratio (visible lesion/surrounding background) was evaluated. Results: Among 164 men confirmed having PCa, 102 had csPCa (Gleason score ≥ 7). Proportions of PI-RADS score 1-2/3/4/5 without b1800 DWI (n = 133) and with b1800 DWI (n = 275) were 19.5%/57.9%/15.8%/6.8% and 21.1%/48.7%/22.2%/8.0%, respectively. csPCa detection rates with/without b1800 DWI were 27.6%/19.5% (p = 0.048), respectively. Areas under the curve of PI-RADS grading with/without b1800 DWI for csPCa detection were 0.885 and 0.705, respectively. The SI ratio in b1800 DWI was higher than that in b1000 DWI (p < 0.001). Conclusions: Adding b1800 DWI to bpMRI protocol improved the diagnostic accuracy and detection rate of csPCa. The higher SI ratio (lesion/background) in b1800 DWI enabled clearer identification of lesions. keywords : image-guided biopsy, magnetic resonance imaging, prostatic neoplasms