Unfocused Multielement and Tapered Phased Array Ultrasound Transducers for Hyperthermia Treatment (Heat, Perfusion, Tumor, Phantom, Cancer)
Benkeser, Paul Joseph
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https://hdl.handle.net/2142/69311
Description
Title
Unfocused Multielement and Tapered Phased Array Ultrasound Transducers for Hyperthermia Treatment (Heat, Perfusion, Tumor, Phantom, Cancer)
Author(s)
Benkeser, Paul Joseph
Issue Date
1985
Department of Study
Electrical Engineering
Discipline
Electrical Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Biomedical
Abstract
Currently used ultrasound clinical hyperthermia systems lack adequate control of the energy deposition used to heat tumors. This thesis discusses the development and testing of two different ultrasound hyperthermia transducers which allow improved control of the energy deposition.
An unfocused multielement transducer was developed to treat superficial tumors. The acoustical power outputs of the elements can be adjusted independently to control the temperature in the tumor and normal tissues. Acoustical power output measurements and temperature data from exposures of tissues in vitro indicated that the transducer is capable of providing intensities seven times greater than those required to produce therapeutic temperatures.
Two ultrasonic tapered phased array transducers were developed to study the feasability of using such transducers to treat deep seated tumors. A tapered phased array transducer consists of a linear phased array employing elements with a tapered thickness. The cylindrical focal region is generated and steered in two dimensions by controlling the phases of the driving signals on each element, and moved in the third dimension by controlling the driving frquency. A theoretical model of the field intensity distribution of a tapered phased array was developed which agreed well with the experimentally obtained data. Acoustical power output measurements indicated that tapered phased arrays are capable of providing the intensities necessary for producing therapeutic temperatures in tumors. However, an analysis of the intensity gain produced by a tapered phased array indicated that it could severely limit the size of tumors that can be preferentially heated.
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