Arterial and venous phase evaluation in fast kV-switching dual-energy CT for detecting acute small bowel ischemia caused by small bowel obstruction.

Purpose: To compare the diagnostic performance of fast kV-switching dual-energy CT (DECT) parameters, including virtual monochromatic imaging (VMI) and iodine mapping, in the arterial and venous phases for detecting surgically confirmed acute small bowel ischemia (ASBI) in cases suspected as ASBI on conventional visual CT findings.

Materials and methods: Thirty-two patients with conventional visual CT findings suggesting possible or suspected ASBI caused by small bowel obstruction (SBO) were included. Two radiologists independently placed ten cursors on visually hypo-perfused bowel wall regions to measure CT values at 70 keV, 40 keV, and iodine quantity. Patients were categorized into surgically confirmed ASBI (n = 12) and non-confirmed ASBI (n = 20). ROC analysis assessed diagnostic performance, and inter-observer reliability was evaluated using intra-class correlation coefficients (ICC).

Results: For both observers, the CT value at 40 keV and iodine quantity in the arterial phase, as well as iodine quantity in the venous phase, was significantly different between surgically confirmed ASBI and non-confirmed ASBI groups (p < 0.05). Iodine quantity consistently yielded the highest AUC among the evaluated parameters in each phase although the differences compared to 70-keV VMI were not statistically significant. The parameters in the arterial phase tended to demonstrate higher AUCs than those in the venous phase. Inter-observer agreement was moderate to substantial (ICC 0.585-0.741), while intra-observer agreement was substantial to almost perfect (ICC 0.733-0.940).

Conclusions: DECT parameters, such as the CT value at 40-keV and the iodine quantity, were effective in differentiating surgically confirmed ASBI from non-confirmed ASBI in SBO cases with suspected ischemia. Iodine quantity showed the highest diagnostic performance among all evaluated parameters. Although the differences were not statistically significant, arterial phase parameters generally yielded higher AUCs than those in the venous phase, suggesting the potential utility of arterial phase DECT in the detection of ASBI.