Dual-energy CT iodine mapping and 40-keV monoenergetic applications in the diagnosis of acute bowel ischemia

Abstract

OBJECTIVE. Sensitivity of CT of the abdomen for detection of acute bowel ischemia (ABI) can be as low as 60%. In this study, we assessed the diagnostic performance of iodine-map and monoenergetic (40-keV) images in patients with suspected ABI. MATERIALS AND METHODS. This retrospective study included 60 consecutive patients with suspected ABI who underwent a standardized imaging protocol dual-source dual-energy CT (DECT) over a 26-month period. Clinical and operative outcomes were recorded as the reference standard. Two abdominal radiologists who were unaware of clinical and surgical information independently assessed conventional CT images for ABI. After a time interval designed to reduce recall, readers reassessed conventional images with supplementary iodine-map and 40-keV postprocessed images. Quantitative ROI analysis was also performed. RESULTS. ABI was observed in 11 patients. For reader A, sensitivity was 63.6% (95% CI, 30.8–89.1%) when interpreting conventional images alone. Sensitivity for detection of ABI increased to 81.8% (95% CI, 48.2–97.7%) and 100% (95% CI, 71.5–100%) when iodine-map and 40-keV images were assessed, respectively. For reader B, no change in sensitivity was seen with either technique, but the number of false-positives were reduced with supplementary iodine-map and 40-keV postprocessed images. Interobserver agreement was fair with conventional images (κ = 0.29) but improved to moderate (κ = 0.45) and substantial (κ = 0.63) with iodine-map and 40-keV images, respectively. Quantitative assessment found significant differences in iodine uptake (1.01 ± 0.55 mg/mL vs 3.04 ± 1.19 mg/mL) and mean attenuation (75.2 ± 38.4 HU vs 163.5 ± 48.9 HU) between nonischemic and ischemic segments, respectively. CONCLUSION. Iodine-map and 40-keV monoenergetic images increase conspicuity of ABI, resulting in improved diagnostic accuracy compared with review of conventional CT images alone.