title: Relevance of a new impedance matching, or subtrap, method for the reduction of pain during hyperthermia.
abstract: Capacitive heating is widely used in hyperthermic treatment of human malignancies. However, the pain on the body surface or thermoesthesia in the subcutaneous fatty layer may prevent an elevation of temperature in the tumors. Impedance matching is improved by a subtrap method entailing the application of two copper plates (10 x 850 x 0.06 mm) as a subtrap circuit to each of two capacitive electrodes. In a clinical trial the Tmax, Tave, Tmin for the subtrap method were all higher in comparison with those for the conventional technique (42.5 +/- 0.7 degrees C, 41.9 +/- 1.0 degrees C, 41.3 +/- 1.1 degrees C vs. 41.1 +/- 1.5 degrees C, 40.6 +/- 1.3 degrees C, 40.0 +/- 1.3 degrees C). Although the maximal radiofrequency (RF) power applied to patients was higher with the subtrap method (875 +/- 189 W vs. 763 +/- 200 W), the incidence of surface pain was reduced dramatically. It is concluded that the subtrap method substantially improves the RF capacitive heating of deep-seated tumors.
authors.affiliation: Department of Radiology, Kansai Medical University, Osaka, Japan. akagi@takii.kmu.ac.jp
authors.forename: T
authors.initials: T
authors.lastname: Murata
authors.forename: K
authors.initials: K
authors.lastname: Akagi
authors.forename: V V
authors.initials: VV
authors.lastname: Ostapenko
authors.forename: H
authors.initials: H
authors.lastname: Isoda
authors.forename: K
authors.initials: K
authors.lastname: Nagata
authors.forename: R
authors.initials: R
authors.lastname: Nasu
authors.forename: T
authors.initials: T
authors.lastname: Shiga
authors.forename: Y
authors.initials: Y
authors.lastname: Tanaka
authors.forename: I
authors.initials: I
authors.lastname: Yamamoto
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D017097:Electric Impedance; D005260:Female; D006801:Humans; D006979:Hyperthermia, Induced / Q000009:adverse effects* / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009369:Neoplasms / Q000628:therapy*; D010146:Pain / Q000209:etiology / Q000517:prevention & control*; D017288:Pain Threshold; D013696:Temperature