Optical Fiber Pressure Sensor

About

Background Currently in cardiology cases, the angiogram is the only practical method to find the location of blockages in patients and to determine their severity. It uses guide-wire to inject contract materials such as dyes to the arteries followed by taking x-ray pictures. However, 2-D imaging method may not be sufficient to determine the extent of blockages and it may underestimate the severity without accounting for some collateral flow. Moreover, it is risky to some patients who may be allergic to the dyes and those who have kidney or liver problem. Also, it exposes patients to harmful x-ray radiation. Therefore, an alternatively tool is sought in the market. Fractional flow reserve (FFR) directly measures blood pressure drop across blockage to determine the extent of the problem. It’s increasingly becoming acceptable among doctors for this use. However, the blood pressure cannot be determined accurately. Technology UMass Lowell researcher Dr. Xingwei Wang has developed a miniature pressure sensor, which can provide high fidelity blood pressure measurements in the Cathlab. The sensor is half the diameter of the guidewire tube inside diameter, and can be inserted into the standard guidewire, and be guided to the arteries. The sensor is based on Fabry-Pérot (FP) principle. On the sensor tip, there is a gap between the fiber core and the diaphragm. The optical light is launched into the optical fiber. Part of the light will be reflected back by the fiber end face. The other part of the light will transmit to diaphragm and reflected back. These two reflected beams will interfere with each other and form the fringe. When the blood pressure is applied on the diaphragm, the gap distance will change and the fringe will shift accordingly. By demodulation of the spectrum, the applied blood pressure can be accurately measured. In animal model, this optical sensor accurately reflects invasive arterial hemodynamics. It also identified coronary stenosis –induced arterial pressure gradient Applications Extremely useful during Initial diagnosis of the blockage Location/extent/severity of stenosis. Medication option? Monitor pressure during angioplasty Pinpoint the location of narrowing. Reporting possible lesion in real-time. Post evaluation of performance (artery opening) Being fluidic pressure sensor, it can also be embedded in other catheters for brain/bladder/lung pressure management and monitoring Advantages Compared to currently available electrical fiber, UML sensor is based on optical fiber. It has inherent merit of immunity to EMI. This is very important in the cathlab or surgery room. UML sensor is made of silica which is reported as biocompatible material and safe to human body. UML sensor is disposable due to simple design and MEMS fabrication technology, which is expected to be 1/10 of the sensors available in the market. The 1st test of UML sensor has demonstrated ten times better resolution than currently available sensors and very good hysteresis and repeatability performance. References [1] Wenhui Wang, Nan Wu, Ye Tian, Christopher Niezrecki, and Xingwei Wang, "Miniature all-silica optical fiber pressure sensor with an ultrathin uniform diaphragm", Optics Express, 18(9), 9006-9014, 2010. [2] Nan Wu, Wenhui Wang, Ye Tian, Xiaotian Zou, Michael Maffeo, Christopher Niezrecki, Julie Chen, and Xingwei Wang, "Low-cost rapid miniature optical pressure sensors for blast wave measurements", Optics Express, 19(11), 10797–10804, 2011.  [3] Ye Tian, Wenhui Wang, Nan Wu, Xiaotian Zou, and Xingwei Wang, "Tapered Optical Fiber Sensor for Label-Free Detection of Biomolecules", Sensors, 11(4), 3780-3790, 2011.  [4] Ye Tian, Wenhui Wang, Nan Wu, Xiaotian Zou, Charles Guthy and Xingwei Wang, "A Miniature Fiber Optic Refractive Index Sensor Built in a MEMS-Based Microchannel", Sensors, 11(1), 1078-1087, 2011.