RTOG quality assurance guidelines for clinical trials using hyperthermia administered by ultrasound

Clinical quality assurance guidelines are established for RTOG hyperthermia protocols in which unfocused planar ultrasound may be used to administer hyperthermia. Measurement of temperature at a few fixed points is no longer considered to be adequate. Thermal mapping is required to obtain profiles of the temperature across the tumor dimensions, including margins of normal tissue. The thermometry strategies established for microwaves are to be adhered to with oblique insertion of the probes recommended. Two types of errors arise which are generally not present with microwaves. A measurement error, commonly referred to as a temperature artifact, arises because of absorption and/or viscous heating of the probe. Another error arises when thermocouples are used due to the conduction of heat along the wire leads, especially the copper wire. Several thermometry systems are evaluated with regard to the expected artifact and conduction errors. Acceptable systems include: a) indexing a polyurethane sheathed single sensor thermocouple in a polyurethane catheter, b) indexing a fiberoptic probe in a steel needle, c) indexing a single sensor thermocouple in a steel needle, and d) use of manganin-constantan multisensor thermocouples. Unacceptable systems include: a) fixed or static probes that do not provide profiles of the temperature across the tumor dimensions, b) copper-constantan multisensor thermocouples, and c) teflon sheathed thermocouples inserted into a teflon catheter.