In situ temperature measurements with thermocouple probes during laser interstitial thermotherapy (LITT): Quantification and correction of a measurement artifact

Fabrice Manns, Peter J. Milne, Xochitl Gonzalez-Cirre, David B. Denham, Jean Marie Parel, David S. Robinson

Research output: Contribution to journalArticle

74 Scopus citations

Abstract

Background and Objective: 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. Results: Direct absorption of Nd:YAG laser radiation by the thermocouple probes induced an overestimation of the temperature, ranging from 1.8°C to 118.6°C in air, 2.2°C to 9.9°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. Conclusion: 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.

Original languageEnglish (US)
Pages (from-to)94-103
Number of pages10
JournalLasers in Surgery and Medicine
Volume23
Issue number2
DOIs
StatePublished - Sep 17 1998

Keywords

  • Breast cancer
  • Hyperthermia
  • Laser-tissue interaction
  • Tissue temperature measurements

ASJC Scopus subject areas

  • Surgery

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