title: Feasibility of ultrasound hyperthermia with waveguide interstitial applicator.
abstract: Interstitial and intracavitary ultrasonic hyperthermia applicators facilitate well-controlled power deposition in tissues. In this paper, analysis of temperature elevation and experimental results in tissue phantom, animal tissue in vivo and animal tissue in vitro are presented for a waveguide applicator intended for treatment of brain tumors. It consisted of a G18 hypodermic needle attached via a conical velocity transformer to a 12.7-mm-diameter piezoelectric disk operated at 1.0 MHz. The axial acoustic pressure distribution had a standing-wave pattern with the four cycles/cm spatial periodicity. This periodicity was absent in the temperature distribution in tissue phantoms. The simulations based on a solution to the effective heat conductivity equation indicated that the hyperthermic range can be reached within a 4- and a 10-mm radius around the applicator for a 21- and a 60-mm sample diameters, respectively, with reasonable input power. The first number corresponded closely to the 5-mm radius observed in porcine brain in vivo and the second one came close to the 9-mm radius in porcine brain in vitro. The presented results demonstrate the potential of the ultrasound waveguide interstitial applicator for hyperthermia of small volume tumors.
authors.affiliation: Ottawa-Carleton Institute for Physics, Department of Physics, Carleton University, Canada. jarosz@physics.carleton.ca
authors.forename: B J
authors.initials: BJ
authors.lastname: Jarosz
mesh_terms: D000818:Animals; D001833:Body Temperature Regulation / Q000502:physiology; D001921:Brain / Q000503:physiopathology*; D001932:Brain Neoplasms / Q000556:secondary / Q000628:therapy; D002560:Cerebrovascular Circulation; D004867:Equipment Design; D005240:Feasibility Studies; D005583:Fourier Analysis; D066298:In Vitro Techniques; D008838:Microcomputers; D009339:Needles; D010507:Periodicity; D019047:Phantoms, Imaging; D011312:Pressure; D011897:Random Allocation; D012016:Reference Values; D013552:Swine; D013696:Temperature; D014159:Transducers; D014464:Ultrasonic Therapy / Q000295:instrumentation*