Fiber Bragg Grating Sensors for Millimetric-Scale Temperature Monitoring of Cardiac Tissue Undergoing Radiofrequency Ablation: A Feasibility Assessment

Figures

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  Figure 1. Optical spectrum shown by one of the two nominally identical arrays. The seven peaks corresponding to the λB of each fiber Bragg grating (FBG) are clearly distinguishable.

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  Figure 2. (a) The thermal response of the FBG 1 embedded in Array 1 (red line) and the best linear fitting (black dash line); (b) the temperature calibration curves of the fourteen FBGs embedded in Array 1 and Array 2.

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  Figure 3. The experimental setup used to perform radiofrequency ablation (RFA) of the myocardial tissue. (a) Photo of the setup; (b) a zoom-in on the myocardial specimen showing the optical fibers and the RF ablator placement; (c) a graphic representation of the RF catheter showing the antenna tip, the thermocouple (located at 0.3 mm from the distal tip), and the lateral and punctiform irrigation holes.

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  Figure 4. Schematic of the FBG sensors and RF antenna positioning in the myocardial tissue during the RF ablation process: (a) setting for the ablation performed at 50 W (Trial 1); (b) setting for the ablation performed at 60 W (Trial 2).

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  Figure 5. Temperature variations in time recorded by Arrays 1 and 2 during Trial 1 (RFA performed at 50 W). In the upper image, the seven trends relative to the FBGs housed in the Array 1 are shown, while in the bottom image the seven trends relative to the FBGs housed in the Array 2 are reported. The pre-treatment phase (i.e., 0 s–30 s), the RFA phase (i.e., 30 s–90 s) and the cooling phase (i.e., 90 s–200 s) are clearly distinguishable.

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  Figure 6. Focus on the temperature variation recorded during Trial 1 by FBG 2 of Array 2: (a) temperature trend zoomed in on the pre-treatment and RFA phases; (b) optical spectra relative to the FBG 2 recorded during the three different steps of the procedure marked as (a): before (blue line), during (red line) and at the end of the RF treatment (yellow line).

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  Figure 7. Temperature variations in time recorded by the Arrays 1 and 2 during Trial 2 (RFA performed at 60 W). In the upper image, the seven trends relative to the FBGs housed in Array 1 are shown, while in the bottom image the seven trends relative to the FBGs housed in Array 2 are reported. The pre-treatment phase (i.e., 0 s–25 s), the RFA phase (i.e., 25 s–85 s) and the cooling phase (i.e., 85 s–200 s) are clearly distinguishable.

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  Figure 8. Focus on the temperature variation recorded during Trial 2 by FBG 2 of Array 2: (a) temperature trend zoomed on the pre-treatment and RFA phases; (b) optical spectra relative to the FBG 2 recorded during the three different steps of the procedure marked as (a): before (blue line), during (red line) and at the end of the RF treatment (yellow line).

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  Figure 9. (a) Temperature trend recorded by FBG 1 embedded in Array 1 during an RF procedure on myocardial tissue; (b) optical spectra relative to FBG 1 recorded during the three different steps of the procedure marked as (a). In the upper image, the spectra collected before (red line) and at the end of the RF procedure (blue line). In the bottom image, the spectra collected before the RFA (red line) and at the end of the cooling phase (green line).

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  Figure 10. Picture of the two half-sections of the treated tissues sliced in correspondence to the lesions and focused on the positioning of the sensors within the specimens: (a) section of myocardium subjected to RFA with power setting of 50 W (Trial 1) with a zoom-in on Lesion 1; (b) section of myocardium subjected to RFA with power setting of 60 W (Trial 2) with a zoom-in on Lesion 2.