Abstract Background Magnetic resonance imaging (MRI) is the gold standard for diagnosing, classifying, and monitoring perianal Crohn’s disease (pCD). Fistula T2 signal intensity and volume/complexity are predictive of treatment response. We developed pTRACK, an interactive tool that enables radiologists to measure fistula volume, normalised average T2 signal intensity, and anatomical relationships to generate 3D digital models of pCD within minutes. This study aimed to evaluate pTRACK-generated MRI metrics against MAGNIFI-CD and assess their predictive value for clinical outcomes. Methods We retrospectively included consecutive adult patients (>18 years) with pCD who underwent pelvic MRI and clinical assessment. Two independent, blinded abdominal radiologists scored MAGNIFI-CD and pTRACK metrics (figure 1) on axial T2 STIR TSE sequences. Clinical outcomes (remission, response, non-response) were scored using the fistula drainage assessment (FDA). Correlations, unpaired two-tailed t-tests, and leave-one-patient-out cross-validation (LOPOCV) performance metrics were used to compare MRI metrics (fistula volume, normalised average T2 signal intensity, MAGNIFI-CD score) and predict FDA categories. T2 signal intensity was normalised using an ROI in adjacent pelvic muscles. Results 36 patients having 77 MRI scans were included. Mean C-reactive protein at the time of assessment was 12.9 ± 22 mg/L. 38.2% of patients had class 1 disease, 42.7% had class 2a disease with a minority having more complex disease. 58.4% of patients experienced non-response, with 14.3% experiencing response and 27.3% experiencing remission. Significant differences were observed across metrics when dichotomized into remission and active groups (responding and non-responding): normalised T2 signal (1.65 ± 1.10 vs. 2.98 ± 1.52, p<0.001), fistula volume (1.58 ± 3.08 mL vs. 4.55 ± 8.66 mL, p=0.03), and MAGNIFI-CD scores (5.86 ± 4.70 vs. 12.41 ± 5.80, p<0.001). Fistula volume and average T2 signal intensity showed moderate correlation to MAGNIFI-CD (r=0.72, p<0.001; r=0.49, p<0.001 respectively). LOPOCV AUC for normalised average T2 and fistula volume were 0.77 and 0.74, respectively, with sensitivities of 87% and 95%, and specificities of 62% and 52%. For MAGNIGI-CD, LOPOCV AUC was 0.84, with a sensitivity of 77% and specificity of 81%. Conclusion pTRACK’s normalised T2 signal and fistula volume demonstrated comparable accuracy to MAGNIFI-CD, with higher sensitivity for predicting pCD activity and distinguishing active from non-active disease. These findings underscore pTRACK’s potential utility, warranting prospective validation in cohorts with more severe disease.
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