Non-invasive optical blood flow monitoring systems for disease diagnosis and healthcare monitoring have been studied. Diffuse Speckle Contrast Analysis (DSCA) system can measure deep-tissue blood flow with a relatively simple system configuration, high speed, and high sensitivity. However, the relative blood flow index (BFI) is acquired with the system, and it changes with every acquisition. In this study, we adopt machine learning to overcome this limitation. DSCA system was established with a micro-size camera, and the correlation between conventional BFI and ML-based BFI was analyzed. This work will be the first step toward a quantitative Diffuse Speckle Contrast Velocimetry (DSCV).
Many studies on diagnosing adult chronic diseases such as diabetes have been achieved by analyzing blood data. Here, we present machine learning algorithm-based diagnostic methods for diabetes by analyzing blood flow oscillations. We used diffuse speckle contrast analysis(DSCA) to measure the blood flow of rats. It can non-invasively measure changes in the relative blood flow of the tissue. Blood flow data acquired from Streptozotocin-induced and control rats were preprocessed by wavelet transform and then classified from machine learning algorithms. In conclusion, the machine learning method can successfully classify two blood flow oscillations in diabetic and control rats.
Various end-effectors of microsurgical instruments have been developed and studied. Also, many approaches to stabilize the tool-tip using robotics have been studied such as the steady hand robot system, Micron, and SMART system. In our previous study, the horizontal SMART micro-scissors with a common path swept source OCT distance and one linear piezoelectric (PZT) motor was demonstrated as a microsurgical system. Because the outer needle is connected with a mechanical handle and moved to engage the tool tip manually, the tool tip position is instantaneously changed during the engaging. The undesirable motion can make unexpected tissue damages and low surgical accuracy. In this study, we suggest a prototype horizontal SMART micro-scissors which has dual OCT sensors and two motors to improve the tremor cancellation. Dual OCT sensors provide two distance information. Front OCT sensor detects a distance from the sample surface to the tool tip. Rear OCT sensors gives current PZT motor movement, acting like a motor encoder. The PZT motor can compensate the hand tremor with a feedback loop control. The manual engaging of tool tip in previous SMART system is replaced by electrical engaging using a squiggle motor. Compared with previous study, this study showed better performance in the hand tremor reduction. From the result, the SMART with automatic engaging may become increasingly valuable in microsurgical instruments.
KEYWORDS: Blood circulation, Cameras, Speckle, Sensors, Tissues, Motion measurement, In vivo imaging, Laser sources, Arteries, Cerebral blood flow, Simulation of CCA and DLA aggregates, Surgery, Brain
To date, various blood flow measurement systems have been presented. Recently we demonstrated multi-channel diffuse speckle contrast analysis (DSCA) to monitor in-vivo relative blood flow in deep tissues noninvasively. It has a limitation in a long-term use due to camera contamination. Here, we present a novel fiber-lens combined DSCA which can solve it. Also it has been applied to cerebral blood flow monitoring of rats during middle cerebral artery occlusion surgery. As a result, the system showed relative changes of the flow during the arterial perfusion periods. It secures novel applications of the DSCA in in-vivo blood flow measurement.
A combined diffuse speckle contrast analysis (DSCA)–near-infrared spectroscopy (NIRS) system is proposed to simultaneously measure qualitative blood flow and blood oxygenation changes in human tissue. The system employs an optical switch to alternate two laser sources at two different wavelengths and a CCD camera to capture the speckle image. Therefore, an optical density can be measured from two wavelengths for NIRS measurements and a speckle contrast can be calculated for DSCA measurements. In order to validate the system, a flow phantom test and an arm occlusion protocol for arterial and venous occlusion were performed. Shorter exposure times (<1 ms) show a higher drop (between 50% and 66%) and recovery of 1/KS2 values after occlusion (approximately 150%), but longer exposure time (3 ms) shows more consistent hemodynamic changes. For four subjects, the 1/KS2 values dropped to an average of 82.1±4.0% during the occlusion period and the average recovery of 1/KS2 values after occlusion was 109.1±0.8%. There was also an approximately equivalent amplitude change in oxyhemoglobin (OHb) and deoxyhemoglobin (RHb) during arterial occlusion (max RHb=0.0085±0.0024 mM/DPF, min OHb=−0.0057±0.0044 mM/DPF). The sensitivity of the system makes it a suitable modality to observe qualitative hemodynamic trends during induced physiological changes.
Appropriate oxygen supply and blood flow are important in coordination of body functions and maintaining a life. To measure both oxygen supply and blood flow simultaneously, we developed a system that combined near-infrared spectroscopy (NIRS) and diffuse speckle contrast analysis (DSCA). Our system is more cost effective and compact than such combined systems as diffuse correlation spectroscopy(DCS)-NIRS or DCS flow oximeter, and also offers the same quantitative information. In this article, we present the configuration of DSCA-NIRS and preliminary data from an arm cuff occlusion and a repeated gripping exercise. With further investigation, we believe that DSCA-NIRS can be a useful tool for the field of neuroscience, muscle physiology and metabolic diseases such as diabetes.
Hand tremor reduction is important to achieve stable micro manipulation of the tool tip. A micro-scissors can be used for cutting delicate tissues safely. Here, we implement an OCT distance sensor guided SMART micro-scissors which could incise micro-surgical targets precisely and horizontally. Compared to freehand incision, it demonstrates enhanced incision performance on dry phantoms with great tremor suppression.
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