Browsing by Subject "Fiber Optic Technology"
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Item Developing a Real-Time, Axially Resolving Optical Monitor of Spinal Cord Blood Flow(2019-01-22) Gao, Feng; Busch, David R.; Goh, Chia Chieh; Lin, Wei; Yodh, Arjun G.; Floyd, Thomas F.BACKGROUND: Spinal cord ischemia is a disease of high morbidity and mortality often caused by surgeries repairing the thoracic and abdominal aorta. Current methods to monitor spinal cord hemodynamics such as electrophysiology methods, MR arterial spin labeling, and laser Doppler either have a slow response time or are unfeasible intra-operatively. In this study, we developed an optical probe to monitor spinal cord blood flow and oxygenation in real-time at multiple sites along the spine. METHODS: Experiments were conducted on 8 adult domestic pigs. Probes were inserted into the epidural space through a laminotomy prior to asphyxia and local ischemia via catheter balloon inflation. Vital signs, anesthetic parameters, and spinal hemodynamics were measured continuously prior to intervention, throughout asphyxia, and during inflation/deflation of the balloon catheter. Optical blood flow measurements were compared against microspheres. Optical hemoglobin saturation of spinal cord was compared to mixed venous blood gases. RESULTS: The fiber optic probe detected changes in flow and oxygenation in all asphyxia and balloon inflation trials across multiple sites along the spine. We observed significant changes in spinal cord blood flow during balloon inflation in the epidural space. We also observed a significant correlation between optically measured hemoglobin saturation and mixed venous blood gases. CONCLUSION: We developed an intra-operative tool that provides continuous, real-time monitoring of spinal cord hemodynamics at multiple sites along the spine. We hope this tool can more safely guide surgeons in reducing the incidence of spinal cord ischemia.Item Quality Assessment of Fiber Optic Pressure Sensors(2014-02-04) Rosenblatt, Anna; Purdy, Phillip D.; King, KevinBACKGROUND: Since the functional features of an artery can correlate to the risk of cardiovascular events, intra-arterial pressures can be utilized as a tool to gain more information about the condition of a vessel or even downstream structural features in the vasculature. Pressure waveforms contain information regarding peak systolic and diastolic pressures, as well as the elasticity and possibly sites of reflection. Similarly, the pulse wave velocity can be indicative of the mechanical properties of the arterial system. Intravascular fiber optic pressure sensors are one tool that can be used to record continuous pressure readings. OBJECTIVE: In order to effectively maximize the capabilities of the RJC fiber optic pressure sensors, they must be tested to fully understand the magnitude of their capabilities. Specific tests were performed to analyze the behavior, precision, and accuracy in different scenarios. METHOD: In vitro, four RJC fiber optic pressure sensors were immersed into known depths of water systematically. The pressures ranged from 0 mm H2O to 500 mmH2O. The pressure measurements included 6 measurements at low pressures (under 100 mmH2O) and 1 measurement at 500 mmH2O. Each pressure reading was approximately 10 seconds and the sensor recorded pressure measurements at a frequency of 1000 Hz. At each pressure reading, the variation and behavior of each individual sensor, the discrepancies between two sensors, as well as the accuracy compared to the theoretical pressure value were evaluated. In addition, the pressure receiver box and various methods of calibration were tested to ensure that there were not other factors causing a bias on the sensors' measurements. RESULTS: The sensors were found to have the capability of giving instantaneous pressure values with a precision of 0.03 mm Hg. The standard deviation of one pressure sensor at a constant pressure for 10 seconds was 0.15mmHg. The average difference between two sensors' pressure values that were calibrated simultaneously was 0.66 mmHg. Lastly, the accuracy of the sensors decreased at higher pressures. Specifically, at a pressure of 37 mmHg, the accuracy of the sensors was approximately 1.9%. CONCLUSION: This data will be important for all future experiments and measurements that involve the RJC fiber optic pressure sensors. With a complete understanding of quantitatively how the sensors behave, it will be feasible to analyze results of future pressure measurements.