NIR spectroscopic imaging to map hemoglobin + myoglobin oxygenation, their concentration and optical pathlength across a beating pig heart during surgery

Noninvasive cardiac hemodynamics monitoring of acute myocardial ischemia in rats using near-infrared spectroscopy: A pilot study

Noninvasive and real-time optical detection of cardiac hemodynamics dysfunction during myocardial ischemia remains challenging. In this study, we developed a near-infrared spectroscopy device to monitor rats' myocardial hemodynamics. The well-designed system can accurately reflect the hemodynamics changes by the classic upper limb ischemia test. Systemic hypoxia by disconnecting to the ventilator and cardiac ischemia by coronary artery slipknot ligation was conducted to monitor myocardial hemodynamics. When systemic hypoxia occurred, ΔHbR and ΔtHb increased significantly, whereas ΔHbO decreased rapidly. When coronary blood flow was obstructed by slipknots, cardiothoracic ΔHbO immediately begins to decline, while ΔHbR also significantly increases. Simultaneously, SpO2 did not show any obvious changes during myocardial ischemia, while SpO2 decreased significantly during systemic hypoxia. These results demonstrated that cardiothoracic hemodynamics stemmed from myocardial ischemia. This pilot study demonstrated the practicality of noninvasive, low-cost optical monitoring for cardiac oxygenation dysfunction in rats.

Using near-infrared spectroscopy myocardial oximetry to monitor myocardial oxygen balance in a swine model of cardiac surgery: a descriptive study

Monitoring of the adequacy of myocardial protection with cardioplegia is nearly non-existent in clinical cardiac surgical practice and instead relies on well-defined protocols for delivery of cardioplegia often resulting in inadequate protection. We hypothesized that Near Infrared Spectroscopy technology could be useful in the monitoring of the myocardial oxygen state by attaching the monitors to the epicardium in a porcine model of cardiac surgery. The experiments were conducted with 3 different protocols of 2 pigs each for a total of 6 pigs. The objective was to induce episodic, oxygen supply-demand mismatch. Methods for decreased supply included decreasing coronary blood flow, coronary blood hypoxemia, coronary occlusion, hypovolemia, and hypotension. Methods for increase demand included rapid ventricular pacing and the administration of isoproterenol. Changes in myocardial tissue oximetry were measured and this measurement was then correlated with blood hemoglobin saturations of oxygen from coronary sinus blood samples. We found that decreases in myocardial oxygen supply or increases in demand due to any of the various experimental conditions led to decreases in both myocardial tissue oximetry and hemoglobin oxygen saturation of coronary sinus blood with recovery when the conditions were returned to baseline. Correlation between myocardial tissue oximetry and hemoglobin oxygen saturation of coronary sinus blood was moderate to strong under all tested conditions. This may have translational applications as a monitor of adequacy of myocardial protection and the detection of coronary occlusion.

In vivo photoacoustic tomography of myoglobin oxygen saturation

Myoglobin is an essential oxygen-binding hemoprotein in skeletal and cardiac muscles that buffers intracellular oxygen (O2) concentration in response to hypoxia or elevated muscle activities. We present a method that uses photoacoustic computed tomography to measure the distribution of myoglobin in tissue and the oxygen saturation of myoglobin (sO2-Mb ). From photoacoustic measurements of mice in different oxygenation states, we performed calibration-free quantification of the sO2-Mb change in the backbone muscle in vivo.

Near infrared image processing to quantitate and visualize oxygen saturation during vascular occlusion

The assessment of microcirculation spatial heterogeneity on the hand skin is the main objective of this work. Near-infrared spectroscopy based 2D imaging is a non-invasive technique for the assessment of tissue oxygenation. The haemoglobin oxygen saturation images were acquired by a dedicated camera (Kent Imaging) during baseline, ischaemia (brachial artery cuff occlusion) and reperfusion. Acquired images underwent a preliminary restoration process aimed at removing degradations occurring during signal capturing. Then, wavelet transform based multiscale analysis was applied to identify edges by detecting local maxima and minima across successive scales. Segmentation of test areas during different conditions was obtained by thresholding-based region growing approach. The method identifies the differences in microcirculatory control of blood flow in different regions of the hand skin. The obtained results demonstrate the potential use of NIRS images for the clinical evaluation of skin disease and microcirculatory dysfunction.