title: A recommended revision in the RTOG thermometry guidelines for hyperthermia administered by ultrasound.
abstract: RTOG thermometry guidelines for clinical trials of hyperthermia using planar ultrasound recommended that temperatures be mapped in polyurethane catheters by use of single-junction copper-constantan thermocouples. These guidelines were based on an assumption that the error in temperature measurement due to thermal conduction would generally not exceed +/- 0.3 degrees C. The validity of this assumption was tested with a commercially available single-junction copper-constantan thermocouple. The width of the point spread function, an indicator of the relative magnitude of the conduction error, was five times greater than expected. As a result, the conduction error is projected to exceed 0.3 degrees C in a temperature gradient of only 1.5 degrees C/cm. This projection was confirmed by mapping a thermal peak which simulates a typical clinical temperature profile. This peak had an amplitude of 6 degrees C, a full-width at half-maximum of 3.5 cm, and a maximum gradient of approximately 3 degrees C/cm. Temperatures measured at 0.5-cm intervals over the span of this peak were in error by a mean of +/- 0.6 degrees C. It is strongly recommended that the RTOG guidelines be revised to replace copper-constantan thermocouples with manganin-constantan single- or multi-junction thermocouples which will assure that the conduction error will be < +/- 0.3 degrees C.
authors.affiliation: Department of Radiation Oncology and Nuclear Medicine, Thomas Jefferson University Hospital, Philadelphia, PA 19107.
authors.forename: F M
authors.initials: FM
authors.lastname: Waterman
authors.forename: L L
authors.initials: LL
authors.lastname: Hoh
mesh_terms: D001831:Body Temperature; D006801:Humans; D006979:Hyperthermia, Induced / Q000295:instrumentation / Q000592:standards*; D017410:Practice Guidelines as Topic; D013821:Thermometers; D014465:Ultrasonics