Adjunctive Flat-panel CT-based Reperfusion Grading after Endovascular Therapy: Enhanced Detection of Residual Distal Vessel Occlusion

The detection of residual distal vessel occlusion is crucial for the evolution of endovascular therapy outcomes. This study evaluated whether distal occlusion tracker signs on immediate postprocedural flat-panel CT could assist in the detection of residual distal vessel occlusion in patients with acute ischemic stroke due to large vessel occlusion after thrombectomy. A single-center retrospective analysis was conducted on patients with anterior circulation large-vessel occlusion who achieved successful reperfusion, defined as a modified TICI score of ≥2b, following endovascular therapy and underwent immediate postprocedural flat-panel CT and perfusion MRI. Two reviewers, blinded to the clinical data and perfusion findings, independently assessed the presence, number, and location of distal occlusion tracker signs on flat-panel CT and the final reperfusion state on cerebral DSA. Distal occlusion tracker signs were defined as dot-like, round, or tubular hyperdensities along the course of the distal intracranial arteries on immediate postprocedural flat-panel CT. Two datasets were compared: (I) using DSA alone, and (II) using DSA combined with flat-panel CT. A core laboratory determined the TICI grading and residual distal occlusion using both DSA and postprocedural perfusion MRI as reference standards. The distal occlusion tracker sign was present in 65/156 patients (41.7%), with excellent inter-rater agreement (weighted kappa = 0.91; 95%CI, 0.85-0.96). Distal occlusion tracker signs demonstrated a sensitivity and specificity of 81.5 and 96.2%, respectively. The diagnostic accuracy in detecting residual distal occlusion was greater with the addition of flat-panel CT findings to DSA than with DSA alone (the area under the curve increased from 0.884 to 0.955, P=0.009). Reperfusion grading overestimation decreased from 17.9% with DSA alone to 3.8% with the addition of flat-panel CT to DSA. Distal occlusion tracker signs are common findings on immediate postprocedural flat-panel CT, indicating residual distal vessel occlusion. The addition of flat-panel CT findings to DSA may enhance the detection of residual distal vessel occlusion after endovascular therapy. EVT = endovascular therapy; DVO = distal vessel occlusion; FPCT = flat-panel computed tomography; DOT = distal occlusion tracker; FPCT+DSA_TICI = TICI grading performed using FPCT and DSA; DSA_TICI = TICI grading performed using DSA alone; Core_TICI = TICI grading performed by the Core laboratory.