Catheter induced temperature artifacts in ultrasound hyperthermia.
Temperature artifacts were evaluated at 72 different sensor locations in 10 different tumour sites heated by use of planar ultrasound transducers operated at 1 and 3 MHz. Thermometry was carried out by single- and multisensor thermocouple probes inserted into 19- and 16-gauge polyurethane catheters, respectively. Nearly all catheters were oriented approximately perpendicular to the ultrasound beam. The artifacts were determined by backward extrapolation of the thermal decay 30-60s after the power was turned off. The effective blood flow and specific absorption rate (SAR) at the sensor locations were determined from the rate of decay and the steady-state temperature. The sample mean steady-state temperature, effective blood flow, and SAR were 41.4 degrees C, 17.5 ml/100 g/min, and 46.3 W/kg, respectively. The most frequent artifact was in the range 0-0.2 degrees C and the mean artifact was 0.6 degrees C. Less than 15% of the artifacts were above 1 degree C. The magnitude of the artifact correlates with the SAR of ultrasonic power, the effective blood flow rate, and the steady-state temperature. These results indicate that the artifact produced at 1 MHz by a multisensor, Teflon-sheathed thermocouple inserted into a 16-gauge polyurethane catheter is 1.7 +/- 0.4 degrees at an SAR of 100 W/kg.
Waterman
F M
FM
Department of Radiation Oncology and Nuclear Medicine, Thomas Jefferson University Hospital, Philadelphia, PA 19107.
Nerlinger
R E
RE
Leeper
J B
JB
D001831:Body Temperature; D002404:Catheterization; D006358:Hot Temperature / Q000627:therapeutic use*; D006801:Humans; D009369:Neoplasms / Q000098:blood supply / Q000503:physiopathology / Q000628:therapy*; D012039:Regional Blood Flow; D013814:Thermal Conductivity; D013821:Thermometers; D014159:Transducers; D014464:Ultrasonic Therapy / Q000295:instrumentation*