Abstract:

Objective ·To evaluate the enhancement of thrombi in patients with different subtypes of hyperacute ischemic stroke using pre-interventional non-contrast computed tomography (NCCT) and dual-phase computed tomography angiography (CTA). Methods ·From January 2018 to October 2020, the clinical data of patients with hyperacute ischemic stroke who presented to the Emergency Department of Neurology, Shanghai Sixth People's Hospital, Shanghai Jiao Tong University School of Medicine were retrospectively analyzed and the patients with hyperacute ischemic stroke caused by occlusion of the M1 or M2 segment of the middle cerebral artery were included. All patients were classified according to the TOAST (Trial of Org 10172 in Acute Stroke Treatment) classification criteria for acute ischemic stroke. The clinical and imaging data of these patients obtained at admission and during subsequent follow-up were analyzed, with particular emphasis on the initial NCCT and CTA images (n=113). Additionally, histological examinations of the retrieved thrombi were performed following mechanical thrombectomy (n=53). Differences in CT values were calculated between NCCT and conventional arterial-phase CTA (Δ₁), as well as between NCCT and late arterial-phase CTA (Δ₂). Percentages of each component on hematoxylin-eosin-stained sections were measured by ImageJ. The differences in thrombus composition among the groups and the correlation between CT value changes and thrombus composition were analyzed. Results ·The Δ₁ value in the large-artery atherosclerosis (LAA) group was lower than that in the cardioembolic group (P=0.001). No significant difference was found in the Δ₁ value between the cardioembolic group and the cryptogenic group (P=0.840). The Δ₂ value in the LAA group was higher than that in the cryptogenic group (P=0.035). No significant difference was found in the Δ₂ value between the cardioembolic group and the cryptogenic group (P=0.691). The Δ₂ value was significantly higher than the Δ₁ value in the LAA group (P<0.001). No significant differences were found between Δ₁ and Δ₂ values in the cardioembolic group or the cryptogenic group (both P>0.05). The percentage of red blood cells in the thrombi from patients with LAA stroke was significantly higher than that in the cardioembolic group and the cryptogenic group (both P<0.05). The Δ₁ value was negatively correlated with the percentage of red blood cells (r=-0.511, P<0.001) and positively with the percentage of fibrin/platelet aggregates (r=0.502, P<0.001). Conclusion ·Thrombus enhancement on admission NCCT and dual-phase CTA can help identify the origin of thrombi in patients with hyperacute ischemic stroke. In the patients with LAA stroke, thrombi show enhancement in the conventional arterial phase with more prominent enhancement in the late arterial phase. In the patients with cardioembolic or cryptogenic stroke, thrombi also manifest enhancement in the conventional arterial phase, while the enhancement degree in the late arterial phase shows no difference from that in the conventional arterial phase.

Key words: acute ischemic stroke, computed tomography angiography (CTA), large-artery atherosclerosis (LAA), middle cerebral artery, non-contrast computed tomography (NCCT)