Native T ₁ mapping of the terminal ileum in Crohn's disease: an exploratory study

Background Native T1 mapping can quantitatively depict small variations in tissue T1 values. Purpose To evaluate T1 value distribution and differences within affected ileum, in active Crohn’s disease (CD) patients, using native T1-maps derived from axial Modified Look-Locker inversion recovery (MOLLI) sequences. Material and Methods MOLLI sequences were added to the magnetic resonance enterography (MRE) standard protocol. The mid-point of the ileum with the most significant wall thickening was selected. The T1 values were first measured on a single region of interest (ROI), then divided into two, and further into six equal segments (mesenteric: posterior [P], medial posterior [MP], lateral posterior [LP]; anti-mesenteric: anterior [A], medial anterior [MA], lateral anterior [LA]). The Wilcoxon signed-rank test was used to compare T1 values. Results In total, 40 patients with active CD (sMARIA ≥2) were retrospectively included (22 men, 18 women; mean age = 51.1 ± 14.3 years). The cohort was stratified into two groups: mild-to-moderate (wall thickness = 4–8 mm, n = 20) and moderate-to-severe (>8 mm, n = 20). In the mild-to-moderate group, significant differences were found in anti-mesenteric side segments, between MA vs. A (z = 2.606; p = 0.008) and MA vs. LA (z = 2.014; p = 0.038); and comparing opposite segments, between P vs. A (z = 2.014; p = 0.038); P vs. LA (z = 2.132; p = 0.028) and MP vs. A segments (z = 2.014; p = 0.038). In the moderate-to-severe group, significant differences were found between A vs. LP (z = 2.014; p = 0.038) and LA vs. LP (z = 2.606; p = 0.008). Conclusion Native T1 maps can display heterogeneous T1 value distribution within active severe CD ileal segments, particularly in mild-to-moderate wall thickness patients. The T1 value could be a promising imaging biomarker for patient phenotyping.