CT energy spectral parameters of creeping fat in Crohn's disease and correlation with inflammatory activity

Objectives Creeping fat is a kind of unique abnormal mesenteric tissue at the sites of diseased bowel of Crohn's disease. By using dual-energy CT enterography, this study aimed to evaluate the feasibility of spectral parameters in the quantitative analysis of mesenteric adipose tissue or creeping fat. Methods In this study, patients with known or suspected Crohn's disease who underwent dual-energy CT enterography from March 1, 2019, to March 31, 2021, were enrolled. Among them, 40 patients with surgery and pathology proven creeping fat were selected as the creeping fat Crohn's disease group, and 40 normal patients were selected as the control group. The quantitative spectral parameters including the slope of the Hounsfield unit curve, normalised fat-water concentration, normalised fat-iodine concentration, and normalised fat volume fraction at the enteric phases were obtained. Mann-Whitney U test, Kruskal-Wallis H test, and receiver operating characteristic curve analysis were applied to compare quantitative parameters among various groups. Results A significant difference was observed in the slope of the Hounsfield unit curve, normalised fat-water concentration, normalised fat-iodine concentration, and normalised fat volume fraction between mesenteric adipose tissue and creeping fat with Crohn's disease at the enteric phase (all p < 0.001). The slope of the Hounsfield unit curve of creeping fat at the enteric phase had a better capability to distinguish inactive and active Crohn's disease (AUC = 0.93, p < 0.001). Conclusion Dual-energy CT enterography with quantitative spectral parameters is a potentially novel noninvasive tool for evaluating creeping fat in Crohn's disease. Critical relevance statement Energy spectral parameters of creeping fat in Crohn's disease are significantly different from normal mesenteric adipose tissues and are correlated with inflammatory activity. Key points center dot Dual-energy CT enterography allows quantitatively assessing creeping fat with spectral parameters.center dot The creeping fat has distinct spectral parameters to normal mesenteric adipose.center dot The spectral parameters accurately differentiate active and inactive Crohn's disease.