Crohn's disease inflammation severity assessment with iodine density from photon counting CT enterography: comparison with endoscopic histopathology.

purposeTo determine optimal iodine density thresholds for active inflammation in CD patients with PCCT enterography and determine if iodine density can be used to stratify CD activity severity.

methodsA retrospective PACS search identified patients with CD imaged with PCCT enterography from 4/11/2022 to 10/30/2022 and with clinical notes, endoscopic/surgical pathology and available source PCCT data for iodine density analysis. Two abdominal radiologists with expertise in CD each drew two region of interest measurements within the visibly most affected region of terminal or neoterminal ileum wall on commercially available system (SyngoVia). Radiologists were blinded to clinical information and pathologic findings. Disease activity and severity were recorded from the pathology report. Harvey-Bradshaw Index, medications, and laboratory values were recorded. Receiver operating characteristic (ROC) curves were utilized to determine the optimum iodine density threshold for active inflammation and mild versus moderate-to-severe inflammation. Intra- and inter-reader agreement was assessed by intra-class correlation coefficient (ICC).

results23 CD patients (15 females; mean [SD] age: 52 [17] years) imaged with PCCT enterography were included. 15/23 had active inflammation: 9/15 mild, 4/15 moderate, and 2/15 severe active inflammation. The optimal iodine density threshold for active inflammation was 2.7 mg/mL, with 97% sensitivity, 100% specificity, and 98% accuracy (AUC = 1.00). The optimal iodine density threshold for distinguishing mild from moderate-to-severe inflammation was 3.4 mg/mL, with 83% sensitivity, 89% specificity, and 87% accuracy (AUC = 0.85). Intra-reader reliability (R1/R2) ICC was 0.81/0.86. Inter-reader reliability ICC was 0.94.

conclusionIodine density from PCCT enterography can distinguish mild from moderate-to-severe active inflammation.