Detection of Hyperdense Arterial Sign in Acute Ischemic Stroke with Dual-Energy Computed Tomography: Optimal Combination with X-ray Energy and Slice Thickness.

BACKGROUND: The hyperdense artery sign (HAS) in acute ischemic stroke (AIS) is considered an important marker of a thrombus on computed tomography (CT). An advantage of scanning with dual-energy CT (DECT) is its ability to reconstruct CT images with various energies using the virtual monochromatic imaging (VMI) technique. The aim of this study was to investigate the optimal combination of X-ray energy and slice thickness to detect HASs on DECT. METHODS: A total of 32 patients with confirmed occlusion of the horizontal (M1) portion of the middle cerebral artery were included in this study. Modified contrast-to-noise ratio (modified CNR) analysis was used as a method for evaluating HASs in AIS. A region of interest (ROI) was set as an HAS, the M1 portion, and an approximately 2 cm diameter ROI was set as the background including the HAS and measured. CT images with X-ray energies from 40 to 190 keV, with increments of 10 keV, were reconstructed based on VMI with 1, 2, and 3 mm slice thicknesses. RESULTS: The top five combinations of X-ray energy and slice thickness in descending order of the mean HAS-modified CNR were as follows: Rank 1, 60 keV-1 mm; Rank 2, 70 keV-1 mm; Rank 3, 60 keV-2 mm; Rank 4, 80 keV-2 mm; Rank 5, 60 keV-3 mm. CONCLUSIONS: Our study showed that the optimal combination to detect an HAS was 60 keV and a 1 mm slice thickness on DECT.

The CT-Defined Hyperdense Arterial Sign as a Marker for Acute Intracerebral Large Vessel Occlusion.

BACKGROUND AND PURPOSE: To determine the sensitivity and specificity of the hyperdense artery sign (HAS) on thin-slice non-contrast computed tomography (NCCT), combined with brief clinical history, as an indicator for large vessel occlusion (LVO) in the setting of acute ischemic stroke. METHODS: Ninety-nine LVO and 102 non-LVO acute ischemic stroke patients were retrospectively identified from a prospective database at a single institution. After reviewing each patient's neurologic presentation based on his or her initial National Institute of Health Stroke Scale (NIHSS) and neurologic evaluation, all thin (1 mm) and thick (5 mm) NCCT scans were reviewed for the HAS. Analysis of sensitivity and specificity was conducted to determine the utility of the HAS sign as a reliable marker for LVO in acute ischemic stroke patients. RESULTS: Of the 99 LVO stroke patients, 66 HASs were identified on NCCT. Of the 102 non-LVO patients, 18 false-positive HASs were identified. The sensitivity and specificity of the HAS, respectively, was 67% and 82%. By anatomic distribution, the sensitivity of identifying basilar artery occlusions was 75%, and the sensitivity of identifying middle cerebral artery (MCA) M1 branch occlusions was 76%. Among patients with an NIHSS > 10, the sensitivity was 79%; whereas sensitivity was 50% if NIHSS was ≤ 10. CONCLUSIONS: The HAS on thin-slice NCCT has a reasonably high sensitivity and specificity for identifying LVO in acute ischemic stroke patients presenting with an NIHSS > 10 and suspected MCA M1 or basilar artery occlusion.