Performance assessment of FBG temperature sensors for laser ablation of tumors

Abstract

The paper presents the characterization results of temperature sensors designed to be employed during thermal treatments of tumors, such as in the laser ablation of malignant cells. The developed sensors are based on Fiber Bragg Gratings, a sensing element able to measure the temperature in proximity of the laser beam without significantly modifying the radiation pattern or perturb the temperature at the sensor site. Different sensor embodiments are analyzed and compared in term of linearity and dynamic response; then a preliminary test during an emulated ablation using a phantom is also presented.

A Fiber Optic Probe for Tumor Laser Ablation With Integrated Temperature Measurement Capability

“…The FBG interrogator is made by a Super-luminescent Light Emitting Diode (SLED) coupled to a handheld spectrometer through a circulator and allows estimating the temperature changes in different locations by measuring the shift of the peak positions in the spectrum reflected by wavelength multiplexed FBGs acting as temperature transducers. Since the resolution provided by the spectrometer is about 100 pm, which is too coarse to meet the application requirements, specific signal processing real-time routines are used to improve it, down to few picometers, corresponding to approximately 0.2 • to 0.5 • depending on the grating spectrum profile and working conditions [12]. As already mentioned, the probe is made out of a dual cladding fiber, similar to those of high power fiber lasers [22], but in which the inner cladding is used to guide the laser ablation beam and the core the sensing signal (Fig.…”

“…Particularly interesting are the sensors based on Fiber Bragg Gratings (FBGs) [13] because already extensively investigated as temperature sensors both in biomedical [14] [15] and non-biomedical [16] [17] applications; moreover they are able to measure temperatures with uncertainty below 1 • C [18], exhibit good stability [19] and have reduced dimensions [20]. Temperature measurement requirements can be indeed rather demanding, as accuracy better than few degrees, with spatial resolution better than 1 cm and time response below 1 s are typically requested to precisely monitor the temperature distribution over the area under ablation, especially during the fast tissue heating phase [11], [12].…”

Characterization of fiber optic distributed temperature sensors for tissue laser ablation

“…The grating has been interrogated using a home-made instrument that uses a broadband SLED source and a spectrometer. A specific signal processing software has been implemented [4] to improve the performance provided by spectrometer: with a suitable gaussian fitting and signal filtering the wavelength resolution of spectrometer of 100 pm, which corresponds to about 10…”

“…In these case optical technologies -in particular fiber optics, whose remarkable advancement in the last decades has been mainly driven by the development of components for telecommunications -provide an excellent alternative for sensing temperatures: indeed, fiber optic sensors (FOSs) are known not only to outperform their metallic counterparts in terms of invasive impact and sensitivity, but also for their intrinsic safety, immunity to electromagnetic interference and possibility operate without degradation in harsh environments [1], [2]. Moreover, some of the working principles exploited in FOSs simplify the realization of so-called distributed or quasi-distributed sensors, which are measurement systems that allow evaluating the entire profile of the quantity of interest (i.e., temperature in the considered case, but also strain) along a certain length [3], [4] [5]. These distributed sensors provide a key advantage in applications where large temperature gradients are involved, like in tumor laser ablation, because in these cases localized sensors can introduce non negligible errors in the reading due to their finite dimension [5].…”

Theoretical and Experimental Study of Structural Elements’ Influence of Fiber-Optic Strain Sensor on Its Readings and Correction Procedure for Transfer Function

“…Например, волоконная брэгговская решетка (ВБР) представляет собой модифицированный участок оптического волокна. На сегодняш-ний день ВБР -один из самых используемых чувствительных элементов ВОД, встречаю-щийся во многих типах датчиков: температуры [3][4][5], деформации [6][7][8], давления [9][10][11] и т.д. В российской и зарубежной литературе широко освещены вопросы исследования и практического применения ВОД в биомеханике [12][13][14], химии [15][16][17], композиционных материалах [18][19][20][21][22], инженерных сооружениях [23][24][25][26][27][28], медицине [29][30][31] и других облас-тях.…”