Thin Slices and Maximum Intensity Projection Reconstructions Increase Sensitivity to Hyperdense Middle Cerebral Artery Sign in Acute Ischemic Stroke

Abstract

Introduction: Cranial nonenhanced CT (NECT) imaging in hyperacute ischemic stroke is rarely used for assessing arterial obstruction of middle cerebral artery by identifying hyperdense artery sign (HAS). Considering, however, its growing importance due to its impact on the decision-making process of thrombolysis with or without mechanical thrombectomy improved sensitivity to HAS is necessary, particularly in the group of less experienced clinicians being frequently the first one assessing the presence of HAS on NECT. Objective: The present study aimed to investigate the effect of different NECT image reconstructions on the correct detection of hyperdense middle cerebral artery sign in a cohort of observers with lower experience level on NECT. Particularly, MIP image reconstructions were expected to be useful for less experienced observers due to both strengthening of the hyperdensity of HAS and streamlining to less image slices. Methods: Twenty-five of 100 patients’ NECT image data presented with HAS. Sixteen observers with lower practice level on NECT (10 radiologists and 6 neurologists) evaluated independently the 3 image reconstructions of each data set with thin slice 1.5 mm, thick slab 5 mm, and 6-mm maximum intensity projection (MIP) and rated the presence of HAS in middle cerebral artery. A GEE model with random observer effect was used to examine the influence of the 3 image reconstructions on sensitivity to HAS. A linear mixed effects regression model was used to investigate the ranking of detectability of HAS. Interrater reliability was determined by Fleiss’ kappa coefficient (κ). Results: Recognition of HAS and sensitivity to HAS significantly differed between the 3 image reconstructions (p = 0.0106). MIP and thin slice reconstructions yielded each on average the highest sensitivities with 73% compared to thick slab reconstruction with 45% sensitivity. The interobserver reliability was fair (κ, 0.3–0.4). Detectability of HAS was significantly easier and better visible ranked on MIP and thin slice reconstructions compared to thick slab (p < 0.05). Conclusion: MIP and thin slice reconstructions increased the sensitivity to HAS (73%), whereas thick slab reconstructions seemed to be less appropriate (45%).

Hyperdense Artery Sign in Patients With Acute Ischemic Stroke–Automated Detection With Artificial Intelligence-Driven Software

“…Using exclusively slices at a thickness of 1 mm in the present study, sensitivity and specificity of two blinded neuroradiologists were 80 and 97%, as well as 93 and 71%, respectively. This is in keeping with results from another study comparing performances of human readers with different slice thicknesses ( 34 ) where sensitivity (73%) and specificity (83%) were best with 1 mm slices and worsened with increasing slices thickness. Comparing AI and human readers, very similar results were presented in 2019 by a group using another commercial application (Nico.lab®) in 59 patients with proven LVO out of 107 ( 29 ).…”

Visualization of thrombus using iterative reconstruction and maximum intensity projection of thin-slice CT images

“…In addition, the continuity of the blood vessel is lost, resulting in a point-like appearance that is difficult to verify as a thrombus. However, thrombus detection by thin-slice noncontrast CT and MIP is effective [4,7]. Using MIP, blood vessels, which are visualized as dots in a single slice, can be visualized as a single vascular structure when multiple slices are combined.…”

“…Two neurosurgeons and one neurologist with expertise in endovascular and cerebral infarction treatment evaluated the results independently. Studies show that MIP without IR is effective in detecting thrombus [4,7]. The aim of this study was not to detect, but to visualize the entire thrombus.…”

“…In patients with stroke, thrombus diagnosis using CT has been widely investigated. Several studies focused on thrombus detection using non-contrast CT with MIP [4,7]. We hypothesize that CT evaluation using IR and MIP is more useful for evaluating thrombus in patients with stroke.…”

Usefulness of maximum intensity projection images of non-enhanced CT for detection of hyperdense middle cerebral artery sign in acute thromboembolic ischemic stroke

“…Many attempts have been made to improve the sensitivity of the hyperdense MCA sign [ 8 , 9 , 12 , 13 ]. Previous reports showed that an acute thromboembolus could be detected with higher sensitivity on 1 or 1.5 mm thin-section non-enhanced CT than on 5 mm non-enhanced CT [ 8 , 9 , 13 , 14 ]. However, the increased number of images and the low signal-to-noise ratio have been reported as drawbacks of thin-section images [ 9 ].…”