Preliminary investigation of diagnostic value of ultra-high b-value based diffusion-weighted imaging in prostate central gland diagnosis

Abstract

Objective To explore the value of ultra- high b- value DWI in diagnosis of prostate cancer in central gland. Methods Seventy - one consecutive patients, who were scheduled for prostate biopsy, were prospectively screened. T2WI, conventional DWI with b-value of 1 000 s/mm2 and ultra-high b- value DWI with b-value of 2 000 s/mm2 and 3 000 s/mm2 were performed in each examination. Twelve-core ultrasound guided prostate systematic biopsy was operated within 3 weeks after MRI examination. Images were interpreted based on prostate MR guidelines (PI-RADS) and were corresponding to histological results conducted by ultrasound guided prostate systematic biopsy. Using biopsy as the gold standard, the sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were calculated for different imaging methods. Sensitivity and specificity differences between ultra- high b- value DWI and conventional DWI were analyzed using the McNemar test. The areas under the curves (AUCs) between ultra- high b- value DWI and other modalities were compared by using the Z test. Results Forty lesions were identified in the prostate central glands from the 33 sample patients in 71 examinees. Twenty two lesions were identified as prostate cancer in 15 patients and 18 lesions were identified as benign prostatic hyperplasia in 18 patients. MRI analysis of lesions in central gland, 27 (67.5%), 20 (50.0%), 32 (80.0%) and 35 (87.5%) were diagnosed accurately with the T2WI, conventional DWI and ultra- high b- value DWI (b= 2 000, 3 000 s/mm2) respectively. The sensitivity and specificity for ultra-high b-value DWI was 90.9% and 83.3% with a b-value of 3 000 s/mm2 and was 86.4% and 72.2% for 2 000 s/mm2. These values were significantly higher than conventional DWI with a b-value of 1 000 s/mm2 (59.1% and 38.9%, P 0.05). The AUCs were 0.674, 0.510, 0.793 and 0.871 in T2WI, conventional DWI and ultra-high b-value DWI at 2 000 s/mm2 and 3 000 s/mm2 respectively. ROC analysis showed greater AUCs for the ultra- high b value DWI, than for the T2WI and conventional DWI (P<0.05). Conclusion The ultra- high b- value DWI is a valuable MRI modality in the diagnosis of prostate cancer in central gland. Key words: Prostatic neoplasms; Magnetic resonance imaging; Comparative study