Preliminary Evaluation Of Surgical Microscope-integrated Intraoperative Indocyanine Green Videoangiography With Flow 800 Technique During Neurovascular Surgery

Background:This study aimed to report our preliminary experience using FLOW 800 technique with indocyanine green (ICG) videoangiography in neurovascular surgery, to campare the validity of FLOW 800 with postoperative digital subtraction angiography (DSA) and microvascular Doppler sonography (mDs) in ancurysm surgeries and to evaluate the efficacy of FLOW 800 for quantitative assessment of flow dynamics and cortex perfusion in stepwise arteriovenous malformation (AVM) surgeries respectively. Methods:In the first part, we recorded all the intraoperative findings and details detected by FLOW 800 and mDs respectively. Results were compared with postoperative DSA. Discordance between FLOW 800 and DSA recorded. The validity of FLOW 800 was then evaluated by comparing with postoperative DSA. Discordance between FLOW 800 and DSA was used for further determining the predictive factors. To evaluate the quantitative assessment function, we measured FLOW 800-specific flow parameters. Results were compared with the value of mDs, and the correlation between the two data was further analyzed. In part two, FLOW 800 analyses were performed at pre-dissection, post clipping of feeders and post-resection phases. The color-coded map was used for high-resolution visualization of the vasculature and instant interpretation of the hemodynamic status. Changes in flow dynamics of AVM (feeders, nidus and draining veins), proximal and distal cortical components (artery and cortex) were evaluated using quantitative values of maximum intensity, delay time, transit time and brain flow index (BFI), and the FLOW 800-specific hemodynamic parameters were employed for real-time measurements of flow dynamics and cortex perfusion alterations.Results:In the first part,25 patients (31 aneurysms) underwent both FLOW 800 with ICG videoangiography and mDs. The overall agreement rate of FLOW 800 and postoperative DSA was 80.1%(25 of 31) and was 77.4%(24 of 31) of mDs and postoperative DSA. In comparison with postoperative DSA, FLOW 800 showed good correlation (p=0.0033) and non-significant difference (p=0.2888, correlated X2=1.1250). Discordance between FLOW 800 and DSA was analyzed and no predictive factors were found. In FLOW 800 quantitative assessment function test, the results of FLOW 800-specific parameters showed poor correlation with that of mDs (p>0.05). In part two, FLOW 800’s color-coded map aided the discrimination and complete resection of the AVM components in 10 cases, and the results were verified by postoperative DSA. One case with deep-seated nidus was complete resection in aid of intraoperative navigation which was failed to be detected by FLOW 800. In the FLOW 800-specific hemodynamic analyses, the parameter of transit time in proximal cortex was significantly shorter in the post-resection phase than in the pre-dissection phase (p< 0.01), while the parameter in distal cortex did not show the similarity (p>0.05). The parameters of the maximum intensity and BFI were not significantly different between these phases.Conclusion:Overall, FLOW 800 with ICG videoangiography is useful for intraoperative assessment of flow dynamics. This innovative technique facilitates safety and confidence in neurovascular surgery. The color-coded map allows high-resolution visualization of the vasculature and instant interpretation of the hemodynamic status which is particularly helpful in AVM surgery. The FLOW 800-specific hemodynamic analyses provided additional perfusion information that enabled real-time measurements of cortical perfusion alterations. But, it still shouldn’t be interpreted as stand-alone measures for quantitative flow.