Distributed Sensing Network Enabled by High-Scattering MgO-Doped Optical Fibers for 3D Temperature Monitoring of Thermal Ablation in Liver Phantom

Abstract

Thermal ablation is achieved by delivering heat directly to tissue through a minimally invasive applicator. The therapy requires a temperature control between 50–100 °C since the mortality of the tumor is directly connected with the thermal dosimetry. Existing temperature monitoring techniques have limitations such as single-point monitoring, require costly equipment, and expose patients to X-ray radiation. Therefore, it is important to explore an alternative sensing solution, which can accurately monitor temperature over the whole ablated region. The work aims to propose a distributed fiber optic sensor as a potential candidate for this application due to the small size, high resolution, bio-compatibility, and temperature sensitivity of the optical fibers. The working principle is based on spatial multiplexing of optical fibers to achieve 3D temperature monitoring. The multiplexing is achieved by high-scattering, nanoparticle-doped fibers as sensing fibers, which are spatially separated by lower-scattering level of single-mode fibers. The setup, consisting of twelve sensing fibers, monitors tissue of 16 mm × 16 mm × 25 mm in size exposed to a gold nanoparticle-mediated microwave ablation. The results provide real-time 3D thermal maps of the whole ablated region with a high resolution. The setup allows for identification of the asymmetry in the temperature distribution over the tissue and adjustment of the applicator to follow the allowed temperature limits.

Optical Fiber Distributed Sensing Network for Thermal Mapping in Radiofrequency Ablation Neighboring a Blood Vessel

“…The increment of the temperature during RFA can be affected by several parameters such as the location of the blood vessel and its distance from the tumor [ 31 ]. The thermal maps presented in Figure 6 show that the vessel located in a parallel position at a distance of 1 cm has a higher impact on the temperature cooling compared to the perpendicularly located vessel at a distance of 1.5 cm, indicating that the distance of the vessel from the tumor is an important parameter that can affect the heating performance.…”

“…This system achieves the best thermal rendering when using the scattering-level multiplexing (SLMux) configuration: in this case, the sensing elements are replaced by high-scattering fibers, having the core doped with Mg-silicate nanoparticles [ 30 ]. Such fibers are designed to match the size and compound of single-mode fibers, but yield a scattering increment of >30 dB; the SLMux enables the simultaneous and distributed detection of each fiber with sub-centimeter resolution, and can provide 2D [ 27 ] and 3D [ 31 ] temperature sensing in thermotherapies.…”

Green-Synthesized Silver Nanoparticle–Assisted Radiofrequency Ablation for Improved Thermal Treatment Distribution

“…The non-metallic composition of fiber-optic sensors prevents the sensors from electromagnetic interference and corrosion [ 21 ]. Recent achievements in the field of fiber-optic sensors made it possible to implement multi-point temperature-sensing opportunities in space by integrating the sensing elements into a single optical fiber [ 24 , 25 , 26 ]. Two approaches utilize multiplexed sensing with a high spatial resolution that is vital in biomedical applications.…”

Spatial-Division Multiplexing Approach for Simultaneous Detection of Fiber-Optic Ball Resonator Sensors: Applications for Refractometers and Biosensors

“…Optical-fiber sensors are inherently suitable for multiplexing (sensing networks that can encompass hundreds of sensors) [ 8 ] and distributed sensing (sensing networks that enable continuous, real-time measurements along the entire length of a fiber-optic cable) [ 9 ]. Several methods have been proposed for physical sensors based on multiplexed sensing.…”

“…Because of their inherent weak reflectivity and low finesse, BR sensors are suitable for being detected only by interrogators operating in reflection mode and capable of resolving very low power levels, such as the optical backscatter reflectometer (OBR) [ 39 ]. Thanks to the spatial distribution features [ 9 ], we design an SDM method that allows for connecting and simultaneously scanning an arbitrary number of BR sensors. The SDM approach solves the problem of enabling multiplexing specifically for BR sensors, since they appear as wideband shallow sensors, and, therefore, neither wavelength-based methods nor cepstrum- or other transform-based methods would work, since BRs share the same bandwidth and have a non-periodical spectral envelope.…”