Optimal b value of diffusion-weighted imaging on a 3.0T magnetic resonance scanner in Crohn's disease

摘要

AIM:To determine the optimal b value of diffusionweighted imaging for detecting active inflammation in Crohn's disease.METHODS:Thirty-one patients clinically diagnosed with active Crohn’s disease were referred for magnetic resonance examination.All patients were scanned on a3.0T magnetic resonance scanner using the same protocol involving four different b values(800,1500,2000and 2500 s/mm2).The diagnostic effect of diffusionweighted imaging was evaluated and compared with endoscopic findings.The diffusion-weighted image quality of four b value groups was evaluated and apparent diffusion coefficient was measured for both nor-mal and inflammatory intestinal segments.RESULTS:The contrast-to-noise ratio and signal-tonoise ratio were not satisfied when b value 2000 or2500 s/mm2 was adopted(36.52±14.95 vs 34.78±24.83,P>0.05;53.58±23.45 vs 47.58±29.67,P>0.05).The qualitative image quality was not enough to meet diagnostic requirement.No matter which b value was chosen,the apparent diffusion coefficient of inflammatory intestinal segments was significantly lower than that of normal intestinal segments(1.38±0.28 vs 2.00±0.38,P<0.01;1.09±0.20 vs 1.50±0.28,P<0.01;0.95±0.19 vs 1.34±0.28,P<0.01;0.88±0.14 vs 1.20±0.21,P<0.01).The lesion detection rate(90.32%),diagnostic sensitivity(81.18%)and specificity(95.10%)would be appropriate when b value 1500 s/mm2 was adopted.CONCLUSION:High b value is suitable for intestinal DW examination on a high field MR scanner.