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.
Highlights
Randomized control trials demonstrated that mechanical thrombectomy (MT) of anterior large vessel occlusion (LVO) in acute stroke patients improves the clinical outcome compared to standard therapy [1]
It has been observed that the degree of edema formation in early follow-up imaging captured by net water uptake (NWU), a quantitative imaging biomarker, is an indicator of the response to MT [4]
Considering the clinical relevance of cerebral edema as an indicator for malignant infarction as well as for outcome prediction, we aim to investigate the potential underestimation of edema on conventional computed tomography (CT) images due to contrast staining by using dual-energy dual-layer CT (DDCT) scans for VNC-based NWU quantification
Summary
Randomized control trials demonstrated that mechanical thrombectomy (MT) of anterior large vessel occlusion (LVO) in acute stroke patients improves the clinical outcome compared to standard therapy [1]. Different parameters influence the outcome, for example, the time from clinical onset to reperfusion, patient age, the National Institutes of Health Stroke Scale (NIHSS) at admission, the Alberta stroke program early computed tomography (ASPECT) score at admission, and the baseline functional status [3]. NWU is an accurate predictor of functional outcome and outperforms clinical variables, for example, age, NIHSS, and/or ASPECTS [4]. These results are in accordance with other studies describing a strong correlation between NWU quantified in CT and the final infarct volume [5, 6]. 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)
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