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Diagnostic value of ultra-high b-value diffusion-weighted imaging in prostate cancer

Objective 
To explore the value of ultra-high b-value diffusion-weighted imaging (DWI) in diagnosis of prostate cancer. 
 
 
Methods 
According to inclusion and exclusion criteria, 73 consecutive examinees in Chinese PLA General Hospital from June 2014 to May 2015 were screened. Written informed consent was obtained from all patients. T2WI, conventional DWI with b-value of 1 000 s/mm2 and ultra-high b-value DWI with 2 000 s/mm2 and 3 000 s/mm2 were performed in each examinee. Images were interpreted and were corresponding to histological results conducted by ultrasound guided prostate systematic biopsy. Reference biopsy as the gold standard, the sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were calculated for each image. Sensitivity and specificity differences between ultra-high b-value DWI and conventional DWI were analyzed. The areas under the curves (AUCs) between ultra-high b-value DWI and other modalities were compared. 
 
 
Results 
The sensitivity and specificity for ultra-high b-value DWI were 92.5% and 68.8% with b-value of 3 000 s/mm2, and they were 88.1% and 53.1% for 2 000 s/mm2 in peripheral zone. The sensitivity and specificity for ultra-high b-value DWI were 88.0% and 88.2% with a b-value of 3 000 s/mm2, and they were 80.0% and 52.9% for 2 000 s/mm2 in transition zone. The values of sensitivity for ultra-high b-value DWI were significantly higher than those for conventional DWI both in peripheral zone and transition zone (all P 0.05), whereas the value of specificity for 3 000 s/mm2 were significantly higher than that for 2 000 s/mm2 in transition zone (P <0.000 1). PPV and NPV for 3 000 s/mm2 were significantly higher than those for the other three modalities both in peripheral zone (86.1% and 81.5%) and transition zone (91.7% and 83.3%). In peripheral zone, the AUCs were 0.591, 0.553, 0.698 and 0.806 in T2WI, conventional DWI and ultra-high b-value DWI at 2 000 s/mm2 and 3 000 s/mm2 respectively, for the diagnosis of transition zone cancer were 0.693, 0.506, 0.665 and 0.881 respectively, and the AUCs for the ultra-high b-value with 3 000 s/mm2 were the largest. 
 
 
Conclusion 
Ultra-high b-value DWI is an accurate and reliable method in the diagnosis of prostate cancer. 
 
 
Key words: 
Prostatic neoplasms; Magnetic resonance imaging; Ultra-high b-value diffusion-weighted imaging