MR Elastography of the Pancreas: Bowel Preparation and Repeatability Assessment in Pancreatic Cancer Patients and Healthy Controls

Abstract

BackgroundPancreatic ductal adenocarcinoma (PDAC) stromal viscoelasticity can be measured using MR elastography (MRE). Bowel preparation regimens could affect MRE quality and knowledge on repeatability is crucial for clinical implementation.PurposeTo assess effects of four bowel preparation regimens on MRE quality and to evaluate repeatability and differentiate patients from healthy controls.Study TypeProspective.Population15 controls (41 ± 16 years; 47% female), 16 PDAC patients (one excluded, 66 ± 12 years; 40% female) with 15 age‐/sex‐matched controls (65 ± 11 years; 40% female). Final sample size was 25 controls and 15 PDAC.Field Strength/Sequence3‐T, spin‐echo echo‐planar‐imaging, turbo spin‐echo, and fast field echo gradient‐echo.AssessmentFour different regimens were used: fasting; scopolaminebutyl; drinking 0.5 L water; combination of 0.5 L water and scopolaminebutyl. MRE signal‐to‐noise ratio (SNR) was compared between all regimens. MRE repeatability (test–retest) and differences in shear wave speed (SWS) and phase angle (ϕ) were assessed in PDAC and controls. Regions‐of‐interest were defined for tumor, nontumorous (n = 8) tissue in PDAC, and whole pancreas in controls. Two radiologists delineated tumors twice for evaluation of intraobserver and interobserver variability.Statistical TestsRepeated measures analysis of variance, coefficients of variation (CoVs), Bland–Altman analysis, (un)paired t‐test, Mann–Whitney U‐test, and Wilcoxon signed‐rank test. P‐value<0.05 was considered statistically significant.ResultsPreparation regimens did not significantly influence MRE‐SNR. Therefore, the least burdensome preparation (fasting only) was continued. CoVs for tumor SWS were: intrasession (12.8%) and intersession (21.7%), and intraobserver (7.9%) and interobserver (10.3%) comparisons. For controls, CoVs were intrasession (4.6%) and intersession (6.4%). Average SWS for tumor, nontumor, and healthy tissue were: 1.74 ± 0.58, 1.38 ± 0.27, and 1.18 ± 0.16 m/sec (ϕ: 1.02 ± 0.17, 0.91 ± 0.07, and 0.85 ± 0.08 rad), respectively. Significant differences were found between all groups, except for ϕ between healthy–nontumor (P = 0.094).Data ConclusionThe proposed bowel preparation regimens may not influence MRE quality. MRE may be able to differentiate between healthy tissue–tumor and tumor–nontumor.Level of Evidence2Technical Efficacy Stage2