Abstract 028: Intraoperative Time‐Resolved Spectroscopy During Mechanical Thrombectomy Can Predict the Extent of Infarct
Authors: Rafi M. , Khachatryan T. , Rivera R. , Khachatryan E. , Zhang A. , Mansooridara S. , Huynh A. , Abdel‐Hadi S. , Hason S. , Hsu F. , Golshani K. , Yuki I. , Xu J. , Suzuki S. , Akbari Y. 
Published: January 2025

Introduction
The Thrombolysis in Cerebral Infarction (TICI) score is a predictor ofclinical outcomes following thrombectomy. However, leptomeningeal collateral circulation inlarge vessel occlusion (LVO) also influences the infarct size on postoperative magnetic resonanceimaging (MRI). Near‐infrared spectroscopy (NIRS) offers potential for evaluating collateralmicrocirculation in LVO patients. Time‐resolved spectroscopy (TRS), an advanced NIRStechnology, provides absolute optical properties with greater spatial resolution and deeperpenetration compared to conventional NIRS. This study compares intraoperative TRSmeasurements with infarct size observed on post‐thrombectomy MRI.

Methods
Nine patients with acute ischemic stroke underwent endovascular therapy (EVT) for LVO involving the superior division of the middle cerebral artery (MCA). Intraoperative TRSmeasurements, including oxy‐/deoxy‐/total‐hemoglobin (HbO2, HHb, HbTot) and oxygensaturation (StO2), were taken in the MCA superior division territory on affected and unaffectedsides. Post‐thrombectomy reperfusion was assessed using TICI score. MRI was performed toevaluate stroke extent following thrombectomy. Recanalization was marked when the guidingcatheter was withdrawn from the internal carotid artery and full reperfusion was restored.Hemodynamic parameters, medications, and relevant interventions were recorded and time‐lockedwith corresponding TRS data.Patients were assigned to 2 groups based on postoperative MRI findings. Group 1 had a corticalinfarct in the TRS detection region. Group 2 had no infarct in the TRS detection region. To evaluate immediate changes in cerebral perfusion on the affected side, we conducted the Wilcoxon signed‐rank test to compare average 5‐minute TRS values before and afterrecanalization. Using said averages, we performed Welch's t test to assess the difference in the HbO2/HHb ratio pre‐ vs post‐recanalization between patients with and without cortical infarct inthe TRS detection region.

Results
Successful reperfusion (TICI 2b/3) was achieved in all patients. On the affected side, differences between average pre‐ and post‐recanalization HbO2, HbTot, and StO2 werestatistically significant (p‐value: 0.0078, 0.0078, 0.0156, respectively). In contrast, differenceswere not statistically significant on the unaffected side. These findings align with reperfusionoutcomes graded by TICI scores. Additionally, there was a statistically significant difference inthe HbO2/HHb ratio pre‐ vs post‐recanalization between patients with and without infarct (p‐value: 0.0208, 95% CI: ‐0.5514 ‐ 0.06268). Moreover, larger difference in the HbO2/HHb ratiocorrelates with a higher likelihood of developing post‐thrombectomy cortical infarct, regardless of TICI scores. This difference may be due to a perfusion‐metabolism mismatch during reperfusion, which may be strongly associated with the extent of brain tissue infarction, particularly in patients
with limited or absent collateral circulation. Patients without substantial cortical stroke onpostoperative MRI had relatively stable TRS readings on both sides throughout the procedure, likely reflecting robust collateral circulation.

Conclusions
These results suggest that TRS can be used as a non‐invasive tool to monitorchanges in cerebral microvascular perfusion during EVT, including quantifying reperfusionoutcomes and evaluating the extent of collateral circulation. Additionally, TRS may play a crucialrole in assessing brain tissue viability and guiding post‐EVT clinical decision‐making. Validationof these findings requires a larger cohort and further consideration of patient‐specific factors.(Funding: HP‐5568330; Akbari/Milner).