Laser speckle contrast imaging of the microcirculatory bed of the pancreas is performed, which allows its condition to be assessed and thereby is an additional valuable tool for making a diagnostic decision and dynamically monitoring the effectiveness of the treatment for pathology of the abdominal organs. Laparoscopic operations on the pancreas are low-traumatic and in most cases avoid open surgical interventions. For the first time an experimental system for recording speckle images, combined with a commercially available five-millimetre rigid laparoscope, is presented. The sensitivity of the system to the fluid motion in a capillary at different velocities is determined, and the possibility of finding areas of blood microcirculation disturbance in modelling pancreatic ischemia in an experiment on laboratory animals is revealed. The laparoscope illumination channel is verified by comparison with speckle dynamics under external illumination of the studied object.

Objective: Spectral analysis of laser Doppler flowmetry (LDF) signals has been widely used in studies of physiological vascular function regulation. An alternative to LDF is the laser speckle contrast imaging method (LSCI), which is based on the same physical principle. In contrast to LDF, LSCI provides non-scanning full-field imaging of a relatively wide skin area and offers high spatial and temporal resolutions, which allows visualization of microvascular structure. This circumstance, together with a large number of works which had shown the effectiveness of temporal LSCI analysis, gave impetus to experimental studies of the relation between LDF and LSCI used to monitor the temporal dynamics of blood flow. Methods: Continuous wavelet transform was applied to construct a time-frequency representation of a signal. Results: Analysis of 10 minute LDF and LSCI output signals recorded simultaneously revealed rather high correlation between oscillating components. It was demonstrated for the first time that the spectral energy of oscillations in the 0.01-2 Hz frequency range of temporal LSCI recordings carries the same information as the conventional LDF recordings and hence it reflects the same physiological vascular tone regulation mechanisms. Conclusion: The approach proposed can be used to investigate speckle pattern dynamics by LSCI in both normal and pathological conditions. Significance: The results of research on the influence of spatial binning and averaging on the spectral characteristics of perfusion monitored by LSCI are of considerable interest for the development of LSCI systems optimized to evaluate temporal dynamics.

In this article, we introduce a new method of signal processing and data analysis for the digital laser Doppler flowmetry. Our approach is based on the calculation of cumulative sums over the registered Doppler power spectra. The introduced new parameter represents an integral estimation for the redistribution of moving red blood cells over the range of speed. The prototype of the device implementing the technique is developed and tested in preliminary clinical trials. The methodology was verified with the involvement of two age groups of healthy volunteers and in a group of patients with type 2 diabetes mellitus. The main practical result of the study is the development of a set of binary linear classifiers that allow the method to identify typical patterns of the microcirculation for the healthy volunteers and diabetic patients based on the presented diagnostic algorithm.

Intraoperative assessment of cerebral hemodynamics is crucial for the success of neurosurgical interventions. This study evaluates the potential of laser speckle contrast imaging (LSCI) and imaging photoplethysmography (IPPG) for contactless perfusion monitoring during neurosurgery. Despite similarities in their hardware requirements, these techniques rely on fundamentally different principles: light scattering for LSCI and light absorption for IPPG. Comparative experiments were conducted using animals (rats) when assessing the reaction of cerebral hemodynamics to adenosine triphosphate infusion. The results show different spatial and temporal characteristics of the techniques: LSCI predominantly visualizes blood flow in large venous vessels, especially in the sagittal and transverse sinuses, showing a pronounced modulation associated with the heart that cannot be explained by venous blood flow alone. In contrast, IPPG quantifies the dynamics of perfusion changes in the parenchyma, showing minimal signal in large venous vessels. We propose that LSCI signal modulation is significantly influenced by the movement of vessel walls in response to mechanical pressure waves propagating through the parenchyma from nearby arteries. A novel algorithm for LSCI data processing was developed based on this interpretation, producing perfusion indices that align well with IPPG measurements. This study demonstrates that the complementary nature of these techniques (LSCI is sensitive to blood cells displacements, while IPPG detects a change in their density) makes their combined application particularly valuable for comprehensive assessment of cerebral hemodynamics during neurosurgery. Graphical Abstract