Manns F, Milne P J, Gonzalez-Cirre X, Denham D B, Parel J M, Robinson D S
Department of Biomedical Engineering, University of Miami College of Engineering, Coral Gables, Florida 33146, USA.
Lasers Surg Med. 1998;23(2):94-103. doi: 10.1002/(sici)1096-9101(1998)23:2<94::aid-lsm7>3.0.co;2-q.
The purpose of this work was to quantify the magnitude of an artifact induced by stainless steel thermocouple probes in temperature measurements made in situ during experimental laser interstitial thermo-therapy (LITT). A procedure for correction of this observational error is outlined.
STUDY DESIGN/MATERIALS AND METHODS: A CW Nd:YAG laser system emitting 20W for 25-30 s delivered through a fiber-optic probe was used to create localized heating. The temperature field around the fiber-optic probe during laser irradiation was measured every 0.3 s in air, water, 0.4% intralipid solution, and fatty cadaver pig tissue, with a field of up to fifteen needle thermocouple probes.
Direct absorption of Nd:YAG laser radiation by the thermocouple probes induced an overestimation of the temperature, ranging from 1.8 degrees C to 118.6 degrees C in air, 2.2 degrees C to 9.9 degrees C in water, 0.7 C to 4.7 C in intralipid and 0.3 C to 17.9 C in porcine tissue after irradiation at 20W for 30 s and depending on the thermocouple location. The artifact in porcine tissue was removed by applying exponential and linear fits to the measured temperature curves.
Light absorption by thermocouple probes can induce a significant artifact in the measurement of laser-induced temperature increases. When the time constant of the thermocouple effect is much smaller than the thermal relaxation time of the surrounding tissue, the artifact can be accurately quantified. During LITT experiments where temperature differences of a few degrees are significant, the thermocouple artifact must be removed in order to be able accurately to predict the treatment outcome.
本研究旨在量化在实验性激光间质热疗（LITT）过程中，不锈钢热电偶探头在原位温度测量时所产生伪影的大小。概述了一种校正此观测误差的方法。
研究设计/材料与方法：使用通过光纤探头发射20W功率、持续25 - 30秒的连续波Nd:YAG激光系统产生局部加热。在空气、水、0.4%脂质体溶液和猪脂肪尸体组织中，每隔0.3秒测量一次光纤探头周围的温度场，测量区域最多包含15个针状热电偶探头。
热电偶探头对Nd:YAG激光辐射的直接吸收导致温度高估，在20W照射30秒后，空气中高估范围为1.8℃至118.6℃，水中为2.2℃至9.9℃，脂质体中为0.7℃至4.7℃，猪组织中为0.3℃至17.9℃，且取决于热电偶的位置。通过对测量温度曲线进行指数和线性拟合，消除了猪组织中的伪影。
热电偶探头对光的吸收会在激光诱导的温度升高测量中引起显著伪影。当热电偶效应的时间常数远小于周围组织的热弛豫时间时，可准确量化该伪影。在LITT实验中，几度的温度差异就很显著，因此必须消除热电偶伪影，以便准确预测治疗结果。
