Reliability of Laser Speckle Flow Imaging for Intraoperative Monitoring of Cerebral Blood Flow During Cerebrovascular Surgery: Comparison with Cerebral Blood Flow Measurement by Single Photon Emission Computed Tomography

OBJECTIVE: To determine the clinical utility of laser speckle flow imaging ( LSFI) and its comparability to I-123-iodoamphetamine single photon emission computed tomography ( IMP-SPECT), we used LSFI to monitor cerebral blood flow ( CBF) during extracranial-intracranial ( EC-IC) bypass surgery. METHODS: Intraoperative intensity of CBF ( iCBF) by LSFI and preoperative and postoperative CBF by IMP-SPECT were measured in 3 patients with internal carotid artery ( ICA) aneurysms who were undergoing ICA trapping surgery and in 16 patients with major cerebral artery occlusion who were undergoing EC-IC bypass surgery. RESULTS: The decrease in iCBF ( 16.9% +/- 2.3%) with ICA interruption was equivalent to the decrease in CBF during the preoperative balloon test occlusion, as measured by IMP-SPECT ( 12.2% +/- 4.4%). Whether preserved iCBF in LSFI promised postoperative intact CBF was not determined, as no patient showed ischemic tolerance by ICA occlusion. The increase in iCBF resulting from EC-IC bypass correlated moderately with the increase in postoperative CBF as measured by IMP-SPECT. However, the increase in iCBF was too small to be recognized intraoperatively by visual inspection. CONCLUSIONS: Although LSFI clearly demonstrated a decrease in CBF, the information is taken only from the surface of the brain. Combined use of LFSI with an electrophysiologic examination is required for intraoperative diagnosis of ischemia. LSFI was not sensitive enough to detect increased CBF by superficial temporal artery-to-middle cerebral artery anastomosis, because CBF changes are minimized during anesthesia, probably owing to low metabolic activity.