title: Temperature measurement artefacts of thermocouples and fluoroptic probes during laser irradiation at 810 nm.
abstract: This study examined the artefact induced in temperature measurements made with thermocouples and Luxtron fluoroptic probes in the presence of infrared radiation. Localized heating was created using a continuous-wave, 810 nm diode laser system emitting 2.0 W from a cylindrical diffusing optical fibre, in air, water and an agar-albumin phantom. The temperature was measured every 1.0 s for 10 to 150 s, with both a thermocouple and a Luxtron fluoroptic probe at distances of 2, 3, 4, 5, 6 and 7 mm from the cylindrical diffusing tip. In all cases, the fluoroptic probe recorded a higher temperature than the thermocouple during laser irradiation. The difference in measured temperatures between the Luxtron probe and the thermocouple ranged from 1.6 degrees C to 18.8 degrees C in air, from 0.3 degrees C to 10.2 degrees C in water, and from 1.4 degrees C to 10.1 degrees C in phantom, depending on the distance of the probe from the laser source. The results suggest that in the presence of laser irradiation, self-heating of the Luxtron probe induces a significant artefact in temperature measurements at distances less than 4 mm from the source fibre. As a result, fluoroptic probes may not be suitable for monitoring tissue temperature for treatments when laser irradiation is present if sensors are located close to the fibre tip (<4 mm).
authors: Medical Physics Division, Ontario Cancer Institute/Princess Margaret Hospital, University Health Network, Toronto, Canada.
authors: A D
authors: AD
authors: Reid
authors: M R
authors: MR
authors: Gertner
authors: M D
authors: MD
authors: Sherar
mesh_terms: D000388:Air; D006361:Heating; D007259:Infrared Rays; D007834:Lasers; D019047:Phantoms, Imaging; D013696:Temperature; D013997:Time Factors; D014867:Water
chemical_list: D014867:Water