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A single-mode fiber (SMF) may be transformed into a distributed sensor using optical backscattering reflectometry (OBR). OBR interrogates Rayleigh scattering appearing in each section of optical fibers by tracking reflections and generating spectral signatures. When fiber experiences temperature and strain variations, OBR shows changes in terms of wavelength shift. The OBR operation works for single sensing fiber. Using multiple fibers on OBR leads to detection difficulties since the parallel backscattering cannot be distinguished. The use of optical switch increases the time of the scanning that is problematic in real-time clinical operations. Our solution is high scattering nanoparticles doped fiber (NPDF). The core of the fiber is doped with MgO nanoparticles that significantly increases the backscattering power of the fiber. In other words, NPDF backscattering power is 40 dB higher than ordinary single-mode fiber (SMF). A pair of NPDF and SMF can be used to build multiple fiber configurations with discrimination of each sensor in 2mm at NPDF location. This setup is suitable in a medical shape sensing environment, especially in epidural anesthesia. In epidural anesthesia, the needle is inserted through the spine of the patient till it reaches the epidural space and then the anesthetic fluid is delivered. The method is based on a doctor’s perception of strain and has a 12-13% failure rate. The technique can be improved by adding a guidance system with optical fibers. In this article, we present a system of four NPDF fibers along the epidural needle and evaluate performance on a medical phantom. The fibers are glued perpendicular to each other at 90 degrees on all four sides of the needle. These four distributed strain values enable the formation of the 3D shape of the needle. The shape information can be monitored so that the needle can be guided to achieve the epidural space.
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