Laser Speckle Imaging Allows Real-Time Intraoperative Blood Flow Assessment During Neurosurgical Procedures

Abstract

Currently, there is no adequate technique for intraoperative monitoring of cerebral blood flow (CBF). To evaluate laser speckle imaging (LSI) for assessment of relative CBF, LSI was performed in 30 patients who underwent direct surgical revascularization for treatment of arteriosclerotic cerebrovascular disease (ACVD), Moyamoya disease (MMD), or giant aneurysms, and in 8 control patients who underwent intracranial surgery for reasons other than hemodynamic compromise. The applicability and sensitivity of LSI was investigated through baseline perfusion and CO2 reactivity testing. The dynamics of LSI were assessed during bypass test occlusion and flow initiation procedures. Laser speckle imaging permitted robust (pseudo-) quantitative assessment of relative microcirculatory flow and standard bypass grafting resulted in significantly higher postoperative baseline perfusion values in ACVD and MMD. The applicability and sensitivity of LSI was shown by a significantly reduced CO2 reactivity in ACVD (9.6±9%) and MMD (8.5±8%) compared with control (31.2±5%; P<0.0001). In high- and intermediate-flow bypass patients, LSI was characterized by a dynamic real-time response to acute perfusion changes and ultimately confirmed a sufficient flow substitution through the bypass graft. Thus, LSI can be used for sensitive and continuous, non-invasive real-time visualization and measurement of relative cortical CBF in excellent spatial-temporal resolution.

Infarct prediction by intraoperative laser speckle imaging in patients with malignant hemispheric stroke

“…16,17 CBF-Flux was recorded within an 18 Â 24 cm imaging field over the exposed cortical hemisphere with purpose designed data acquisition software (MoorFLPI measurement software, Version V3.0, Moor Instruments, Axminster, UK) at 25 Hz using a temporal filter of 100 frames per image resulting in a scan rate of 0.25 Hz to allow optimal spatial resolution (760 Â 568 pixel, exposure time 8.4 ms) and minimize potential motion artifacts due to spontaneous rapid blood flow fluctuations. Identical focal lens settings and exposure times were maintained during all measurements.…”

“…[9][10][11][12][13] More recently, intraoperative Laser Speckle Imaging (iLSI) was shown sensitive to blood flow changes in the human brain and feasible for non-invasive real-time monitoring of relative cerebral blood flow (CBF) within the cortical parenchyma. [14][15][16][17] Importantly, iLSI can also be smoothly integrated into surgical workflow without requiring demanding logistics. At present, however, clinical validation of iLSI remains challenging due to the complex physics that relate the measured cerebral perfusion values to the underlying absolute CBF 18 and because information on perfusion is only obtained on the surface of the brain.…”

Optimization of camera exposure durations for multi-exposure speckle imaging of the microcirculation

“…Beyond bench-side physiological research, there are direct implications for prognostic, diagnostic, and intraoperative imaging applications, as speckle imaging of microcirculatory flows is increasingly becoming applied for gauging local and systemic tissue health [8,9]. Consequently, laser speckle flowmetry studies are expanding in dermatological [10][11][12][13][14], ophthalmological [15][16][17], and neurosurgical settings [18][19][20].…”

A Registration Approach to Endoscopic Laser Speckle Contrast Imaging for Intrauterine Visualisation of Placental Vessels

“…LSCI is based on the principle that the rate of change of speckle intensity is a function of the average velocity of the tissue particles that reflect light [7]. Speckles depend on the movement of scatterers and the sensor exposure time; by measuring the statistics of speckle intensities, it is possible to obtain highresolution images of the vasculature and also relative estimates of blood flow [1]. Speckle contrast images are computed from raw images by taking the ratio of the standard deviation to the mean pixel intensity: K = σ/µ.…”

“…Laser speckle contrast imaging (LSCI) is emerging as an intraoperative tool for monitoring tissue perfusion and blood flow, particularly in neurosurgery where its clinical potential has been recently demonstrated [1]. Despite its potential for imaging perfusion and blood flow in minimally invasive procedures, relatively few applications of LSCI for endoscopic surgery have been described [2].…”