Influence of diffusion weighted imaging and contrast enhanced T1 sequences on the diagnostic accuracy of magnetic resonance enterography for Crohn’s disease Authors: Gauraang Bhatnagar, Sue Mallett, Richard Beable, Rebecca Greenhalgh, Rajapandian Ilangovan, Hannah Lambie, Evgenia Mainta, Uday Patel, François Porté, Harbir Sidhu, Arun Gupta, Anthony Higginson, Andrew Slater, Damian Tolan, Ian Zealley, Steve Halligan, Stuart A Taylor European Journal of Radiology 2024 Jun;175:111454. doi: 10.1016/j.ejrad.2024.111454. Epub 2024 Apr 5. Crohn's disease (CD) is a chronic inflammatory bowel disease that is characterised by transmural, segmental and, asymmetrical inflammation of the gastrointestinal tract, with a greater predilection for the terminal ileum and colon1. The disease manifests between the ages of 20 and 40, with a second peak occurring between the fifth and sixth decade of life1,2. The main symptoms are abdominal pain and diarrhea; however, they lack specificity and depend on the location of the disease3. Endoscopy is the gold standard for the diagnosis of CD, by allowing evaluation of the colon and terminal ileum mucosa, but it is unable to perform a complete examination of the entire intestine4. Consequently, cross-sectional imaging techniques have been employed to assess the degree of disease severity, extent, and presence of complications5. Among these techniques, Magnetic Resonance Enterography (MRE) allows the assessment of the severity, extent and complications of the disease by providing detailed images of submucosal edema and fluid without ionizing radiation6. The current protocol typically involves using T2-weighted sequences and steady-state free precession gradient echo (SSFP)7. T1-weighted images, enhanced by intravenous gadolinium, improve diagnostic accuracy but carry risks like adverse effects and potential renal failure7,8. Diffusion-weighted imaging (DWI) sequences are also an option for detecting disease, though their use is not mandatory7. This study aims to assess the added value of contrast-enhanced (CE) sequences and DWI in comparison to T2-weighted fast spin echo and SSFP in patients with Crohn's disease. The study was derived from a large multicenter prospective study investigating the sensitivity between MRE and small bowel ultrasound9. In this multi-centre prospective study, two cohorts of patients were included: those newly diagnosed and those with established disease and suspected relapse. The final population included in the study was 73 patients, comprising 28 newly diagnosed cases and 45 suspected relapses. The MRE protocol consists of T2-weighted, SSFP and DWI, unenhanced coronal T1-weighted fat-saturated sequences and contrast-enhanced coronal T1-weighted fat-saturated sequences, performed 60-70 seconds after injection. Thirteen radiologists from seven trial recruitment sites with at least one year of subspecialist training in gastrointestinal radiology were asked to evaluate three different datasets. These were: 1) SSFP and the fat-sat and non-fat-sat T2-weighted images alone; 2) the T2-weighted images with the addition of DWI; and 3) the entire examination, which comprised the T1 sequences after the administration of gadolinium. For each combination of sequences, the radiologists documented the presence of segmental disease, activity, extra-enteric manifestations, diagnostic confidence, and interpretation time of the three sets of sequences on a clinical research form (CRF). Each data set was read twice, resulting in a total of 146 reads, except for the third sequence block, for which seven missing information in the CRFs of contrast-enhanced T1-weighted images, leading to a final count of 139 reads. The results of the study demonstrate that the sensitivity and specificity for the presence of small bowel disease are highly comparable across the three sequence blocks. In particular, the sensitivity was 80% (95% CI 72-86%) for T2-weighted sequences alone, 81% (95% CI 73-87%) for T2-weighted and DWI, and 79% (95% CI 71-86%) for T2-weighted, DWI and CE sequences; while specificity was 82% (95% CI 64-92%) for all three sequence blocks. The three sequence blocks demonstrated comparable sensitivity and specificity in evaluating the extent of disease in the small intestine. Sensitivity was 56% (95% CI 47-65%) for both T2-weighted and T2-weighted + DWI, and 52% (95% CI 43-61%) for T2-weighted+DWI+CE - sequences. Regarding disease activity in the small bowel, the authors found similar sensitivity between the three blocks: 97% (95% CI 90-99%) for T2-weighted, 97% (95% CI 91-99%) for T2-weighted and DWI, and 98% (95% CI 92-99%) for T2-weighted+DWI+CE sequences. The specificity was comparable between the three samples. Regarding colonic disease, both sensitivity and specificity were lower than in the small bowel, but no significant difference was found between the 3 sequence blocks. Abscesses and fistulas were diagnosed based on T2-weighted sequences in 75% and 90% of cases, respectively. However, post-contrast T1-weighted sequences led to the identification of a single abscess. The median time for interpreting T2 alone was 7 minutes, while the addition of DWI images required an additional 3 minutes, and post-contrast T1 images necessitated an additional 3 minutes. Consequently, the time for interpreting T2+DWI+CE was 6 minutes longer than for T2 alone. According to previous studies, the use of a short MRE protocol based on the use of T2-weighted and SSFP sequences has a diagnostic impact that is not inferior to the use of gadolinium-enhanced or DWI sequences. This allows the implementation of an MR protocol that is cost-effective, time-efficient, and minimizes patient discomfort. However, as present in previous studies, some complications were better diagnosed with the use of gadolinium, suggesting a customised use of gadolinium administration in selected patients with suspected complications. Despite the encouraging results, the study is not without limitations. These include the small number of participants enrolled, the involvement of radiologists with experience in the gastrointestinal tract, the use of a specific order for sequence detection, and finally the inability to draw conclusions in case of subtle disease. Further, larger cohorts are encouraged to confirm the results obtained. In conclusion, the examination of MRE can be performed with a reduced sequence protocol without impacting diagnostic accuracy. | References: 1. Torres J, Mehandru S, Colombel JF, Peyrin-Biroulet L. Crohn's disease. Lancet. Apr 29 2017;389(10080):1741-1755. doi:10.1016/S0140-6736(16)31711-1 2. Loftus EV. Clinical epidemiology of inflammatory bowel disease: Incidence, prevalence, and environmental influences. Gastroenterology. May 2004;126(6):1504-17. doi:10.1053/j.gastro.2004.01.063 3. Roda G, Chien Ng S, Kotze PG, et al. Crohn's disease. Nat Rev Dis Primers. Apr 02 2020;6(1):22. doi:10.1038/s41572-020-0156-2 4. Puylaert CA, Tielbeek JA, Bipat S, Stoker J. Grading of Crohn's disease activity using CT, MRI, US and scintigraphy: a meta-analysis. Eur Radiol. Nov 2015;25(11):3295-313. doi:10.1007/s00330-015-3737-9 5. Deepak P, Park SH, Ehman EC, et al. Crohn's disease diagnosis, treatment approach, and management paradigm: what the radiologist needs to know. Abdom Radiol (NY). Apr 2017;42(4):1068-1086. doi:10.1007/s00261-017-1068-9 6. Mantarro A, Scalise P, Guidi E, Neri E. Magnetic resonance enterography in Crohn's disease: How we do it and common imaging findings. World J Radiol. Feb 28 2017;9(2):46-54. doi:10.4329/wjr.v9.i2.46 7. Sturm A, Maaser C, Calabrese E, et al. ECCO-ESGAR Guideline for Diagnostic Assessment in IBD Part 2: IBD scores and general principles and technical aspects. J Crohns Colitis. Mar 26 2019;13(3):273-284. doi:10.1093/ecco-jcc/jjy114 8. Seo N, Park SH, Kim KJ, et al. MR Enterography for the Evaluation of Small-Bowel Inflammation in Crohn Disease by Using Diffusion-weighted Imaging without Intravenous Contrast Material: A Prospective Noninferiority Study. Radiology. Mar 2016;278(3):762-72. doi:10.1148/radiol.2015150809 9. Taylor SA, Mallett S, Bhatnagar G, et al. Diagnostic accuracy of magnetic resonance enterography and small bowel ultrasound for the extent and activity of newly diagnosed and relapsed Crohn's disease (METRIC): a multicentre trial. Lancet Gastroenterol Hepatol. Aug 2018;3(8):548-558. doi:10.1016/S2468-1253(18)30161-4 Dr. Stefano Nardacci is a radiology resident at the Sant'Andrea University Hospital of the “Sapienza” University of Rome and he is in his third year of residency. He has a wide range of interests in abdominal radiology, focusing on gastrointestinal MRI and quantitative hepatic MRI. He has also been actively involved in clinical imaging research and has co-authored some publications. Comments may be sent to stefano.nardacci(at)uniroma1.it |