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Ultrasound is a very good power source for doing the
hyperthermia treatment since it owns the properties such as
penetration, scan, focus, flexibility, and so on. Several
investigators have been studying the ultrasound hyperthermia
using the external heating method through one or several
ultrasound transducers. Very good treatment results for the
superficial tumors have been obtained during the clinical
patient trials. In contrast to the superficial heating method,
a deep heating method must be employed to obtain good heating
patterns when tumors are located in the deep-seated regions.
Thus for the first portion of this thesis we study the
relationship between the heating depth and the transducer
parameters (frequency, diameter and radius of curvature) based
on the bioheat transfer equation. Secondly, we have chosen a
single , fixed (frequency, diameter and radius of curvature)
transducer, scanning a single circle or double circles, around
a given tumor with fixed blood perfusion. The following five
system parameters can be varied: acoustic output power
magnitude, the depth of focus of the ultrasonic beam in the
tissue, the size of the scan circle, and the transducer
rotation and tilt angles. The steady- state bioheat transfer
equation is used to determine that set of these five scan
parameters which can result in suitable steady- state tissue
temperature distributions under a variety of tumor and normal
tissue conditions. These results are then extended to form a
stationary multiple-transducer system which can be employed to
heat different types of tumors. This simulation study can be
used as the guideline for designing a new external heating
system and for the further treatment planning.
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