title: Thermal conduction effects associated with temperature measurements in proximity to radiofrequency electrodes and microwave antennas.
abstract: The smearing effects due to thermal conduction along various, nonenergized, interstitial devices were quantified in a flow cell-thermal step gradient. An insulated cylindrical flow cell with a high (ca 45 degrees C, 1.12 cm i.d., 1.6 cm o.d.) temperature region surrounded by a low (ca 37 degrees C) temperature region was used to compare temperature profiles measured with a thermocouple sensor inside a Stanford radiofrequency (RF) hyperthermia/brachytherapy catheter, a BSD instrumented microwave (MW) antenna (i.e., thermistor integrated into a dipole antenna) and a Dartmouth MW antenna with a juxtaposed optical sensor. Two parameters were used to quantify the thermal smearing of each interstitial device in the flow cell: (a) the maximum temperature difference (MTD) and (b) the full- width- half-maximum (FWHM) of the high temperature region. The "true" temperature maximum (45.4 degrees C) and distribution (FWHM = 1.65 +/- 0.06 cm) were measured with an optical sensor. These data indicate that the BSD instrumented MW antenna significantly smeared the true temperature profile (MTD = 2.7 degrees C, FWHM = 2.1 cm), as did the Dartmouth MW antenna (MTD = 1.5 degrees C, FWHM = 1.7 cm). The Stanford RF catheter, when insulated, resulted in minimal smearing (MTD = 0.3 degrees C, FWHM = 1.9 cm). Moreover, when the insulation was removed so the RF electrode was exposed to the thermal step gradient, smearing was again minimal (MTD = 0.3 degrees C, FWHM = 1.9 cm).
authors.affiliation: Dartmouth Medical Center, Dartmouth College, Hanover, NH 03755.
authors.forename: T P
authors.initials: TP
authors.lastname: Ryan
authors.forename: T V
authors.initials: TV
authors.lastname: Samulski
authors.forename: B E
authors.initials: BE
authors.lastname: Lyons
authors.forename: E
authors.initials: E
authors.lastname: Lee
authors.forename: D
authors.initials: D
authors.lastname: Holdren
authors.forename: P
authors.initials: P
authors.lastname: Fessenden
authors.forename: J W
authors.initials: JW
authors.lastname: Strohbehn
mesh_terms: D001918:Brachytherapy / Q000295:instrumentation* / Q000379:methods; D006979:Hyperthermia, Induced / Q000295:instrumentation* / Q000379:methods; D008872:Microwaves; D011846:Radio Waves; D013814:Thermal Conductivity; D013821:Thermometers