We demonstrated that BWIC measurements based on LA phase DECT scanning provide significantly higher diagnostic accuracy for the assessment of ABI compared to BWIC performed on PV phase or to conventional attenuation values. In addition, LA phase iodine maps received superior ratings regarding suitability of images for subjective evaluation of ABI compared to PV phase iodine maps, further emphasizing their potentially important role for the clinical use.

ABI clinical presentation is variable and early diagnosis is critical since delayed treatment may lead to worsening of patient outcome and higher mortality rate [5]. In particular, different studies have shown that early treatment (i.e., endovascular or surgical), performed within the first 12 h following the onset of AMI symptoms, has a significantly reduced mortality rate compared to those who underwent delayed surgical intervention (14% vs. 75%) (3).

CT angiography represents the current imaging method of choice for diagnosis of ABI, and it should be timely performed in patients presenting clinical symptoms [23]. Early CT findings in ABI consist of various morphologic changes such as reduction of visceral enhancement, mucosal hemorrhage, intestinal dilatation, and thickening of the bowel wall associated with perifocal ascites [7]. On the other hand, in terminal stage typical findings are mesenteric stranding, vascular engorgement, pneumatosis, portal venous gas, and free abdominal air [24].

While diagnosis of superior mesenteric artery occlusion or portal vein thrombosis causing ABI can be readily assessed, radiological diagnosis of ABI can often be particularly challenging in early-stage NOMI, due to a substantial overlap with early findings of differential diagnoses such as inflammatory and infectious bowel diseases [6, 25]. For this reason, reduced visceral enhancement is still considered the most specific findings for the diagnosis of NOMI.

With the advent of DECT, several studies have demonstrated improved tissue differentiation and lesion detection in a number of abdominal conditions [8,9,10,11,12,13,14,15,16,17]. Color-coded iodine maps may also facilitate the assessment of bowel wall vascularization compared to conventional single-energy CT attenuation measurements, since they show directly contrast material distribution without any superimposed anatomical structures that contribute to attenuation values.

A recent animal model study showed that DECT can significantly improve the conspicuity of the ischemic bowel loops compared with conventional CT [26].

Similarly, Lourenco et al. demonstrated higher sensitivity of DECT iodine maps for the assessment of ABI in comparison with conventional CT, with a reduction of false positive diagnosis [18]. However, in their study, the authors assessed IC measurements on PV phase scan only, and in a small cohort of true positive patients, in whose only seven out of sixteen total patients had a definitive diagnosis of NOMI.

Moreover, the iodinated contrast dose was not adjusted for the patient body weight, which may result in less homogenous and reproducible patterns of intestinal mural enhancement.

Our study cohort included 142 patients with definite diagnosis of NOMI who underwent DECT on both LA and PV phases.

Compared to the results from Lourenco et al., we found concordant mean BWIC on the PV phase and CT attenuation values on the LA phase, for both ischemic and non-ischemic bowel segments. However, our results show a better diagnostic accuracy when BWIC measurement is performed on LA phase iodine maps, which represents new knowledge compared to previous studies. In addition, we firstly identified optimal cutoff values for differentiation of ischemic and non-ischemic bowel segments. In this setting, a cutoff BWIC value of 1.34 mg/dl based on LA phase showed sensitivity and specificity of 100% and 96.50%, respectively, potentially representing an accurate method for the diagnosis of NOMI.

Patients may benefit from this diagnostic performance especially in case of early-stage NOMI, when clinical outcome may be improved due to earlier detection of reduced bowel wall perfusion, with subsequent accelerated therapy initiation. Moreover, this particular DECT algorithm may be most valuable in cases where intramural hemorrhage potentially mimics mural thickening and enhancement, or to help differentiate effective from ineffective reperfusion, which is a phenomenon often occurring in patients with NOMI [27, 28].

We believe that DECT LA phase iodine map and the corresponding BWIC measurements should be performed in the suspicion of ABI, especially when superior mesenteric artery occlusion or portal venous thrombosis is absent.

However, there are limitations in our study that need to be addressed. Firstly, all CT scans were performed on a third-generation dual-source DECT scanner. Because improved technical and computational material differentiation, soft-tissue contrast, and spatial resolution have improved significantly, results from former dual-source platforms or other DECT scanners may show different diagnostic accuracy and should be evaluated in further studies. Secondly, our study design was retrospective, which may have influenced the results. Thirdly, the ROI placement can be difficult in some cases due to the flexible anatomy of bowel segments, which may affect the measurement validity. In order to minimize this error, the ROI placement was performed by experienced radiologists, who were aware of the surgical report. Fourthly, BWIC remains dependent on patient-related factors, even when standardized contrast-medium protocols are adopted, as in this study. Particularly, in the case of severely obese patients, the peak arterial parenchyma enhancement could be affected by the injection duration, while the venous enhancement depends solely on the amount of iodine injected [29]. Additionally, the results of this study are only valid for the specific scan protocol applied; different diagnostic performances may result from using alternative scan or contrast injections protocols. Furthermore, reperfusion phenomena and intramural hemorrhage may have altered the mucosal enhancement, thus modifying BWIC values [28, 30]. Finally, in our study, we did not distinguish between normally collapsed and distended loops. The former may exhibit higher values compared to the latter [31]. Further research on this topic could benefit from making this distinction to enhance understanding and accuracy.

In conclusion, DECT iodine maps based on LA phase significantly improve the diagnostic accuracy for the diagnosis of NOMI compared to conventional CT series and PV phase iodine maps. Therefore, we believe that LA phase iodine map reconstruction should be performed in case of suspected ABI.