Native T1 Mapping and Magnetization Transfer Imaging in Grading Bowel Fibrosis in Crohn’s Disease: A Comparative Animal Study

Abstract

In this study, we investigated the utility of native <i>T</i>₁ mapping in differentiating between various grades of fibrosis and compared its diagnostic accuracy to magnetization transfer imaging (MTI) in a rat model of CD. Bowel specimens (64) from 46 CD model rats undergoing native <i>T</i>₁ mapping and MTI were enrolled. The longitudinal relaxation time (<i>T</i>₁ value) and normalized magnetization transfer ratio (MTR) were compared between none-to-mild and moderate-to-severe fibrotic bowel walls confirmed by pathological assessments. The results showed that the correlation between the <i>T</i>₁ value and fibrosis (<i>r</i> = 0.438, <i>p</i> < 0.001) was lower than that between the normalized MTR and fibrosis (<i>r</i> = 0.623, <i>p</i> < 0.001). Overall, the <i>T</i>₁ values (<i>t</i> = -3.066, <i>p</i> = 0.004) and normalized MTRs (<i>z</i> = 0.081, <i>p</i> < 0.001) in none-to-mild fibrotic bowel walls were lower than those in moderate-to-severe fibrotic bowel walls. The area under the curve (AUC) of the <i>T</i>₁ value (AUC = 0.716, <i>p</i> = 0.004) was significantly lower than that of the normalized MTR (AUC = 0.881, <i>p</i> < 0.001) in differentiating moderate-to-severe fibrosis from none-to-mild fibrosis (<i>z</i> = -2.037, <i>p</i> = 0.042). Our results support the view that the <i>T</i>₁ value could be a promising imaging biomarker in grading the fibrosis severity of CD. However, the diagnostic performance of native <i>T</i>₁ mapping was not superior to MTI.