Abstract
PurposeEarly infarcts are hard to diagnose on non-contrast head CT. Dual-energy CT (DECT) may potentially increase infarct differentiation. The optimal DECT settings for differentiation were identified and evaluated.MethodsOne hundred and twenty-five consecutive patients who presented with suspected acute ischemic stroke (AIS) and underwent non-contrast DECT and subsequent DWI were retrospectively identified. The DWI was used as reference standard. First, virtual monochromatic images (VMI) of 25 patients were reconstructed from 40 to 140 keV and scored by two readers for acute infarct. Sensitivity, specificity, positive, and negative predictive values for infarct detection were compared and a subset of VMI energies were selected. Next, for a separate larger cohort of 100 suspected AIS patients, conventional non-contrast CT (NCT) and selected VMI were scored by two readers for the presence and location of infarct. The same statistics for infarct detection were calculated. Infarct location match was compared per vascular territory. Subgroup analyses were dichotomized by time from last-seen-well to CT imaging.ResultsA total of 80–90 keV VMI were marginally more sensitive (36.3–37.3%) than NCT (32.4%; p > 0.680), with marginally higher specificity (92.2–94.4 vs 91.1%; p > 0.509) for infarct detection. Location match was superior for VMI compared with NCT (28.7–27.4 vs 19.5%; p < 0.010). Within 4.5 h from last-seen-well, 80 keV VMI more accurately detected infarct (58.0 vs 54.0%) and localized infarcts (27.1 vs 11.9%; p = 0.004) than NCT, whereas after 4.5 h, 90 keV VMI was more accurate (69.3 vs 66.3%).ConclusionNon-contrast 80–90 keV VMI best differentiates normal from infarcted brain parenchyma.
Highlights
Materials and methods PatientsThis study was approved by the Stanford University Institutional Review Board which waived the need for informed consent, and data collection complied with the Health Insurance Portability and Accountability Act
Non-contrast CT is the mainstay in the initial evaluation of patients with suspicion of acute ischemic stroke (AIS) [1]
Location matching on virtual monochromatic images (VMI) at 80 keV was similar or better than non-contrast CT (NCT) in all regions (ACA, 0.0% vs. 0.0%, sub-MCA; 36.4% vs. 0.0%, sup-MCA; 43.8% vs. 25.0%, BG; 36.4% vs. 18.2% and posterior circulation (PCA); 5.9% vs. 5.9%)
Summary
This study was approved by the Stanford University Institutional Review Board which waived the need for informed consent, and data collection complied with the Health Insurance Portability and Accountability Act. We retrospectively enrolled consecutive patients between October 13, 2018, and April 18, 2019, with suspected AIS who underwent non-contrast DECT and subsequent MRI with DWI within 48 h. Baseline clinical data was collected, including age, sex, presentation National Institutes of Health Stroke Scale (NIHSS), time since last known well, time to initial DECT imaging, and time to subsequent MRI. Non-contrast CT is the mainstay in the initial evaluation of patients with suspicion of acute ischemic stroke (AIS) [1]. The sensitivity of non-contrast CT is limited for the detection of acute brain infarct [2]. DWI allows for detection of cytotoxic edema within infarcted tissue with high sensitivity, while CT is limited to detecting subtle changes in water content between infarcted and normal brain parenchyma
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