Intraoperative laser speckle contrast imaging to visualize blood flow dynamics in neurosurgery

Laser Speckle Contrast Imaging (LSCI) has emerged as a promising imaging modality that offers full field, real time, continuous and agent free monitoring of cerebral blood flow during neurosurgery. Since LSCI does not require the injection of a contrast agent, it has the potential to complement fluorescence-based modalities by providing continuous and dynamic changes in blood flow during critical moments of neurosurgery. We performed a clinical study with LSCI to investigate the clinical utility of the technique intraoperatively. A commercially available Zeiss Pentero 900 (R) microscope was equipped with lambda=785nm laser diode attached to a customized mount. The backscattered laser light was collected by the microscope, producing a laser speckle image on the external camera which was mounted on the microscope side-port. Custom software collected laser speckle images, computed, and then displayed the speckle contrast images in real time throughout the surgery onto the operating room monitors. The images were displayed with custom color maps and thresholding. The robust integration in the surgical workflow of the technology enabled the investigation of the need for dynamic vessel-flow characterization in 20-patients at the Inselspital in Bern, Switzerland. We assessed vessel flow during key time points in the surgery and provided real time and continuous measurements to the surgeon.