Diagnostic value of high b- value DWI relative signal intensity in prostate cancer

Abstract

Objective To investigate the value of lesion to obturator muscle signal intensity ratio during high b-value DWI in the diagnosis and differential diagnosis of prostate cancer, so as to determine the optimal b value and cutoff value. Methods A retrospective analysis was performed on data from patients undergoing multiple-b value DWI sequence scanning and confirmed by pathology to be with prostate cancer (n=27) or benign lesions (n=20, including benign prostatic hyperplasia in 16 and prostatitis in 4 patients). We measured and analyzed the original DWI signal intensity of prostate lesions, and the diagnostic efficacy of relative signal of lesion to obturator muscle on the same plane as related to the change of b value. Results In the low b-value interval (0 s/mm2 and 400 s/mm2) , the sensitivity of the relative signal was both 92.6% (25/27) , and the specificity was 30% (6/20) and 60% (12/20) , respectively, compared with the sensitivity of the original signal being 70.4% (19/27) and 44.4% (12/27) , and specificity being 70.0% (14/20) and 80.0% (16/20). In high b- value interval (1 000 s/mm2, 1 500 s/mm2, 2 000 s/mm2 and 3 000 s/mm2) , the sensitivity of the relative signal was, in the ascending order of b-value, 100% (27/27) , 100% (27/27) , 96.3% (26/27) , and 96.3% (26/27) , compared with that of the original signal being 74.1% (20/27) , 77.8% (21/27) , 85.2% (23/27) and 81.5% (22/27) ; the specificity of relative signal was 80% (16/20) , 90% (18/20) , 95% (19/20) , and 100% (20/20) , compared with that of the original signal being 90% (18/20) , 90% (18/20) , 90% (18/20) and 100% (20/20). Using the maximum sum of sensitivity and specificity as a reference, b=3 000 s/mm2 yielded highest performance in identifying prostate cancer, and the optimal cutoff value of relative signal was 1.98. Conclusion Compared with original DWI signal, relative signal results in higher sensitivity and specificity in high b-value interval. Within low b-value interval, relative signal yields high sensitivity but low specificity. 3 000 s/mm2 is the optimal b value, and the corresponding optimal cutoff value is 1.98. Key words: Prostate cancer; Benign prostatic hyperplasia; Diffusion magnetic resonance imaging; Signal intensity