Resident Department of Neurosurgery, University Hospital Muenster, Muenster, Germany
Introduction: Intraoperative indocyanine green (ICG) video-angiography allows for real-time assessment of cerebral blood flow. Typically administered intravenously, ICG is diluted after passing through the lungs, which reduces sensitivity in detecting perfusion deficits. Intra-arterial ICG application may enable a more precise evaluation of cerebral blood flow. This study assesses the feasibility of intra-arterial ICG video angiography compared to the established intravenous method.
Methods: To perform ICG video-angiography, the abdominal aorta in n=20 eight-week-old female Wistar rats was exposed, chosen for its superior visibility and ease of manipulation. Surgery was performed while animals were under anesthesia and continuous monitoring. Measurements were conducted using an adapted Carl Zeiss Meditec Pico surgical microscope with an incorporated IR800. The Pico microscope was coupled with a highly sensitive infrared camera (150 frames/ second). Fluorescence angiography was performed after both intra-venous and intra-arterial ICG bolus. A micro clip was partially placed on the aorta to mimic clip-stenoses. All video data were analyzed using Fiji. Fluorescence intensities were calculated in predefined ROI in arbitrary intensity units. Rise time was evaluated in predefined ROIs. Rise times were compared between two modalities using unpaired t-tests.
Results: Rise time after inter-arterial was significantly shorter compared with the established gold standard. The average rise time after inter-arterial ICG application was 5.47 sec compared to 7.8 sec after i.v. application. As determined by arbitrary intensity units, fluorescence intensity was more robust after inter-arterial ICG application. Turbulent clip stenosis could be visualized in detail.
Conclusion : Our results show the feasibility of inter-arterial ICG application for neurovascular surgery. Fluorescence intensity after inter-arterial ICG application is more robust, and the time of rise is significantly shorter, which may allow more sensitive blood flow assessment. In particular, hemodynamic phenomena in stenoses can be excellently observed.
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