Characterizing clot composition and stroke etiology through hounsfield units.

PURPOSE: We aimed to analyze clot composition using Hounsfield Units (HU) in non-enhanced computed tomography (NECT). METHODS: Thrombi retrieved from mechanical thrombectomy (MT) were imaged on micro-computed tomography (micro-CT) and histologically analyzed. Micro-CT slides were matched to histological sections. Spearman's rank correlation was performed to correlate micro-CT HU with red blood cells (RBCs) and fibrin composition. A sensitivity analysis was conducted between micro-CT HU and histological slides with > 70% of these components. The same clots were then localized in the pre-MT NECT, and NECT HU values were obtained. Micro-CT HU and NECT HU were correlated for histologically informed interpretation. Receiver operating characteristic analysis was performed to retrieve NECT HU thresholds. A dataset of patients who presented with large vessel occlusion of cardioembolic, large artery atherosclerosis (LAA), and cryptogenic strokes were then assessed through NECT HU. RESULTS: Ten thrombi were analyzed. Micro-CT HU were strongly correlated with histological sections with > 70% of RBCs (Rho 0.675) but not to sections with > 70% of fibrin (Rho 0.325). Micro-CT HU and NECT HU of clots that had > 70% of RBCs were strongly correlated (Rho 0.774). NECT HU of 44 had a sensitivity of 67% and specificity of 86% to determine clots with > 70% of RBCs. A total of 240 NECT images were analyzed including 80 cardioembolic, 80 LAA and 80 cryptogenic strokes. NECT HU assessment showed that 75% of cardioembolic, 40% of LAA and 55% of cryptogenic clots are composed of RBCs. CONCLUSION: NECT HU is a promising tool to assess clot RBCs composition and infer stroke etiology.