Cappelli S, Saccomandi P, Massaroni C, Polimadei A, Silvestri S, Caponero M A, Frauenfelder G, Schena E
Annu Int Conf IEEE Eng Med Biol Soc. 2015 Aug;2015:1287-90. doi: 10.1109/EMBC.2015.7318603.
Temperature monitoring in tissue undergone Laser Ablation (LA) may be particularly beneficial to optimize treatment outcome. Among many techniques, fiber Bragg grating (FBG) sensors show valuable characteristics for temperature monitoring in this medical scenario: good sensitivity and accuracy, and immunity from electromagnetic interferences. Their main drawback is the sensitivity to strain, which can entail measurement error for respiratory and patient movements. The aims of this work are the design, the manufacturing and the characterization of a needle-like probe which houses 4 FBGs. Three FBGs have sensitive length of 1 mm and are used as temperature sensors; one FBG with length of 10 mm is used as reference and to sense eventual strain. The optical fiber housing the FBGs was encapsulated within a needle routinely used in clinical practice to perform MRI-guided biopsy. Two materials were used for the encapsulation: i) thermal paste for the 3 FBGs used for temperature monitoring, to maximize the thermal exchange with the needle; ii) epoxy resin for the reference FBG, to improve its sensitivity to strain. The static calibration of the needle-like probe was performed to estimate the thermal sensitivity of each FBG; the step response was investigated to estimate the response time. FBGs 1 mm long have thermal sensitivity of 0.01 nm·°C(-1), whereas the reference FBG presents 0.02 nm·°C(-1). For all FBGs, the response time was in the order of 100 ms. Lastly, experiments were performed on ex vivo swine liver undergoing LA to i) evaluate the possible presence of measurement artifact, due to the direct absorption of laser light by the needle and ii) assess the feasibility of the probe in a quasi clinical scenario.
对接受激光消融（LA）的组织进行温度监测可能对优化治疗效果特别有益。在众多技术中，光纤布拉格光栅（FBG）传感器在这种医疗场景下的温度监测中表现出有价值的特性：灵敏度和准确性高，且不受电磁干扰。其主要缺点是对应变敏感，这可能会导致呼吸和患者移动时的测量误差。这项工作的目的是设计、制造和表征一种容纳4个FBG的针状探头。三个FBG的敏感长度为1毫米，用作温度传感器；一个长度为10毫米的FBG用作参考并检测最终应变。容纳FBG的光纤被封装在临床实践中常规用于进行磁共振成像引导活检的针内。使用了两种材料进行封装：i）用于温度监测的3个FBG的导热膏，以最大化与针的热交换；ii）用于参考FBG的环氧树脂，以提高其对应变的灵敏度。对针状探头进行了静态校准以估计每个FBG的热灵敏度；研究了阶跃响应以估计响应时间。1毫米长的FBG的热灵敏度为0.01 nm·°C⁻¹，而参考FBG的热灵敏度为0.02 nm·°C⁻¹。对于所有FBG，响应时间约为100毫秒。最后，对接受LA的离体猪肝进行了实验，以i）评估由于针直接吸收激光光而可能出现的测量伪影，以及ii）评估该探头在准临床场景中的可行性。
