Fiber bragg grating sensors for temperature monitoring during thermal ablation procedure: Experimental assessment of artefact caused by respiratory movements

Temperature monitoring inside tissue undergoing minimally invasive thermal ablation is a primary goal to improve the clinical outcomes. Existing techniques for temperature measurements, classified as invasive or contactless, have limited clinical practice applications due to several practical issues. Fiber Bragg grating sensors (FBG) can be a valid solution since they can perform accurate and multi-point temperature measurements by inserting a single and small fiber optic within the tissue. Notwithstanding, their cross-sensitivity to strain may cause measurement errors during thermal procedures. Indeed, several organs (e.g., lungs, liver, pancreas) can strain gratings due to movements caused by breathing. To date, only a few studies have specifically addressed this concern, despite the wide use of FBGs in this field. To overcome this lack, we estimated the artefact of the FBGs output in response to lungs' movements induced by breathing. This investigation was carried out by inserting FBGs within a manually ventilated lung model (ex vivo swine lungs). We measured both the lungs' movements during breathing by a Motion Capture system and the related fluctuations of the FBGs' output. Moreover, we performed the same experiments during thermal ablation of lungs to assess the mentioned artefact's influence. In this study, we demonstrated the relevance of the respiratory artefact on FBGs, and also the possibility to correct this error during thermal ablation.