Value of Dual-Energy Dual-Layer CT After Mechanical Recanalization for the Quantification of Ischemic Brain Edema

Abstract

Background and Purpose: Ischemic brain edema can be measured in computed tomography (CT) using quantitative net water uptake (NWU), a recently established imaging biomarker. NWU determined in follow-up CT after mechanical thrombectomy (MT) has shown to be a strong predictor of functional outcome. However, disruption of the blood–brain barrier after MT may also lead to contrast staining, increasing the density on CT scans, and hence, directly impairing measurements of NWU. The purpose of this study was to determine whether dual-energy dual-layer CT (DDCT) after MT can improve the quantification of NWU by measuring NWU in conventional polychromatic CT images (CP-I) and virtual non-contrast images (VNC-I). We hypothesized that VNC-based NWU (vNWU) differs from NWU in conventional CT (cNWU).Methods: Ten patients with middle cerebral artery occlusion who received a DDCT follow-up scan after MT were included. NWU was quantified in conventional and VNC images as previously published and was compared using paired sample t-tests.Results: The mean cNWU was 3.3% (95%CI: 0–0.41%), and vNWU was 11% (95%CI: 1.3–23.4), which was not statistically different (p = 0.09). Two patients showed significant differences between cNWU and vNWU (Δ = 24% and Δ = 36%), while the agreement of cNWU/vNWU in 8/10 patients was high (difference 2.3%, p = 0.23).Conclusion: NWU may be quantified precisely on conventional CT images, as the underestimation of ischemic edema due to contrast staining was low. However, a proportion of patients after MT might show significant contrast leakage resulting in edema underestimation. Further research is needed to validate these findings and investigate clinical implications.

Occult contrast retention post-thrombectomy on 24-h follow-up dual-energy CT: Associations and impact on imaging analysis

“…26,29–31 Blood–brain barrier disruption occurs through endothelial injury and basement membrane degradation mediated through ischemia-related inflammation, iatrogenic toxicity and reperfusion injury, impairment of microcirculation by tissue edema, and direct mechanical vessel injury via procedural instrument manipulation during EVT. 2,3,26,28,32,33 Concordantly, we found larger infarct volumes to be independently associated with contrast leakage, in keeping with more severe ischemic injury leading to greater area of infarct and more intense intralesional injury with blood-brain-barrier disruption. 34…”

“…Our findings contrast with the results of a recent small pilot retrospective single center study of 10 patients with follow-up conventional CT and DECT after middle cerebral artery territory infarcts. 3 However, this study applied statistical analyses designed for larger normally distributed sample size and therefore may have been underpowered as it did not detect a statistically significant difference despite 2 of 10 patients demonstrating more than 20% differences in NWU values between conventional CT and DECT. Furthermore, the timing of the DECT, which will directly influence contrast retained and eliminated, was not specified in this study, which limits direct comparison with our findings.…”

“…Residual iodine contrast retention is a phenomenon specific to follow-up CT that is increasingly seen in the modern era of thrombectomy for ischemic stroke. Iodine extravasation is most commonly recognized immediately after endovascular thrombectomy (EVT), and may account for 27-84% of hyperdense lesions on CT at 24 h. [1][2][3][4] As iodine contrast media is known to be incrementally eliminated in a two-compartment model based on early pharmacokinetic studies, the high prevalence of visible contrast staining suggests smaller amounts of iodine contrast that may not be qualitatively detectible by visual inspection may also be present in tissue (i.e. occult contrast retention), on early follow-up imaging at 24 h. 5 Visible contrast extravasation mimics hyperdense blood products and complicates accurate identification of hemorrhagic transformation, with implications for prognostication and clinical decisions regarding post-stroke antithrombotic use.…”

Correlation Between Computed Tomography-Based Tissue Net Water Uptake and Volumetric Measures of Cerebral Edema After Reperfusion Therapy

“…Postthrombectomy hyperdensity from hemorrhagic transformations and contrast staining occur in up to 84% of follow-up CT. 18 Even in the absence of obvious hyperdensity, visually inapparent iodine contrast staining after thrombectomy has been shown to substantially alter NWU measurements. 19 Although NWU has not been validated in the postreperfusion setting to account for these phenomena, this metric has been increasingly applied to post-thrombectomy follow-up CT without accounting for patients with postthrombectomy hemorrhage or contrast staining. [14][15][16] We aimed to investigate the accuracy of NWU on follow-up CT after treatment with or without hemorrhagic transformation and the use of thrombectomy by examining its correlation with conventional volumetric-orientated measures of cerebral edema.…”

Post-ASPECTS based on hyperdensity in NCCT immediately after thrombectomy is an ultra-early predictor of hemorrhagic transformation and prognosis

“…Non-contrast computed tomography is a routine examination after thrombectomy, and brain parenchymal hyperdensity is a common imaging manifestation. The incidence of brain parenchymal hyperdensity after thrombectomy has been reported to vary from 60.8 to 84.2%, which is related to whether the artery is successfully recanalized as well as the time of CT examinations ( 17 , 19 , 29 , 30 ). In this study, we restricted our research objects to successful recanalization, and NCCT was completed immediately (within 1 h) after thrombectomy.…”