Motility index measured by magnetic resonance enterography is associated with sex and mural thickness

BACKGROUND Recently,a technique has been developed to use magnetic resonance enterography(MRE)for the evaluation of small bowel motility.The hypothesis was that assessment of the motility index(MI)should reflect differences in motility between clinical conditions.AIM To aim of the present observational,cross-sectional study was to evaluate the use of the MI in daily clinical practice.METHODS All consecutive patients aged 18-70 years who were referred for MRE at the Department of Radiology during a 2-year period were asked to participate.Healthy volunteers were included as controls.MRE was prepared and conducted in accordance with clinical routines.On the day of examination,all the participants had to complete the visual analog scale for irritable bowel syndrome(IBS)and IBS-symptom severity scale.Maps of MI were calculated from dynamic MR images.ANOVA was used to evaluate differences in MI between groups,classified as healthy,Crohn’s disease,ulcerative colitis,IBS,other assorted disorders and dysmotility.Logistic and linear regression were applied to the MI values.All medical records were scrutinized for medical history.RESULTS In all,224 examinations were included(inclusion prevalence 76.3%),with 22 controls and 202 patients.There was a significant difference in the MI of the jejunum(P=0.021)and terminal ileum(P=0.007)between the different groups.The MI was inversely associated with the mural thickness of the terminal ileum in men(P<0.001)and women(P=0.063)after adjustments,and tended to be lower in men than in women(P=0.056).Subjectively observed reduction of motility on MRI was accomplished by reduced MI of terminal ileum in men(P<0.001)and women(P=0.030).In women,diarrhea was inversely associated with the MI of the jejunum(P=0.029),and constipation was positively associated with the MI of the terminal ileum(P=0.039).CONCLUSION Although MIs differ across diseases,a lower MI of the terminal ileum is mainly associated with male sex and an increased mural thickness.Symptoms are weakly associated with the MI.

Impact of Field Strength and Respiratory Motion Control on Diffusion-Weighted MR Imaging of the Liver

Purpose: To evaluate the impact of field strength and respiratory motion control on diffusion-weighted MR imaging (DWI) of the liver at 1.5 and 3 T. Material and Methods: Three DWI sequences using seven b-values from 20 - 400 s/mm2 were designed with identical parameters but with different handling of respiratory motion [respiratory triggered (RT), free breathing (FB), breath hold (BH)] on 3 T and 1.5 T. Thirteen volunteers were examined at a 3 T and six of them also at a 1.5 T magnet. DW images were analyzed quantitatively and qualitatively. Regions of interest were placed in cranial, middle and caudal parts of the right liver lobe (RLL) and ADC and SNR were calculated. Results: ADC in RLL tended to be lower at 3 T MRI. Least inter-subject ADC variability was found with RT in the middle RLL at 3 T. Highest ADCs were found caudally in the RLL. Significant differences in ADC between middle and caudal RLL were calculated in FB and RT at 3 T and FB and BH at 1.5 T, respectively. No significant difference in SNR was found between 3 T and 1.5 T. There were significantly more artifacts in the left liver lobe (LLL) compared to the RLL in all sequences and in the LLL at 3 T compared to 1.5 T. Conclusion: Our study suggests that longitudinal hepatic ADC measurements should be performed using equivalent field strength, b-values, and acquisition technique, given influence of these factors on ADC measurements.