System for epidural needle guidance enabled by fiber-optics distributed shape sensing

A single-mode fiber (SMF) may be transformed into a distributed sensor using optical backscatter 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 signatures' changes in terms of wavelength shift. The OBR operation is confined to a single sensing fiber. Using multiple fibers simultaneously on OBR leads to detection difficulties since the parallel backscattered power cannot be distinguished. One of the solutions is using an optical switch. However, it 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 randomly with MgO nanoparticles that enlarge the backscattering power of the fiber by 40dB. In other words, NPDF's backscattering power is 40 dB higher than ordinary single-mode fiber (SMF)' s power. A pair of NPDF and SMF can be used to build multiple fiber configurations with discrimination of each sensor in 2mm at NPDF's 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% failure rate. The technique can be improved by adding a guidance system with optical fibers. In this article, we present a setup of four NPDF fibers along the epidural needle and evaluate performance on a 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, and the reach of ES can be guided.