Theoretical and experimental evaluation of high-temperature ultrasound in cancer therapy.

Persistent Link:
http://hdl.handle.net/10150/186466
Title:
Theoretical and experimental evaluation of high-temperature ultrasound in cancer therapy.
Author:
Damianou, Christakis Andrea.
Issue Date:
1993
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
The purpose of this study was to use the concept of calculated thermal dose to predict the necrosed tissue volume, and to evaluate the near-field heating due to application of multiple pulses to cover a large volume. In addition, overlaying tissue damage caused by sonicating a highly-perfused tissue seated only a few cms deep was evaluated. The thermal dose distribution during focused ultrasound exposure was calculated based on numerical models used for calculating ultrasound power distributions and the resulting temperature distributions in tissue. In vivo experiments in dogs and rabbits were conducted to obtain the reliability of the predictions. It was found that the lesion intensity threshold was almost independent of the frequency for transducers with an F-number of 1. It was found that the lesion size was practically perfusion independent for pulses 5 s or shorter. The lesion size increased with increasing pulse duration, acoustical power, and F-number, but decreased with increasing frequency at a constant focal intensity. The results shown in this dissertation can be used as a guide for selection of transducer parameters for ultrasonic surgery. The temperature elevation in the near-field was elevated. It was found that significant delays (20 s or longer) between the pulses must be introduced in order to avoid unwanted tissue damage in front of the focal zone. In addition, decreasing the pulse duration and F-number reduced the temperature elevation in front of the focus. It was shown that the damage to surrounding tissues when sonicating a highly-perfused tissue (such as kidney) seated a few cms deep, can be avoided by using transducer with an F-number of 0.8 and a frequency of about 1 MHz. The heating of the surrounding tissues can be reduced more by correct selection of the pulse duration and power. The tissue necrosis due to ultrasound was monitored using MRI imaging. A study of MR signal intensity charge with temperature of dog and rabbit tissues in vitro showed that MRI has the potential to monitor temperature non-invasively. The signal sensitivity with temperature was found to be about 1.2-1.7 %/°C.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Biomedical engineering.; Electrical engineering.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Electrical and Computer Engineering; Graduate College
Degree Grantor:
University of Arizona
Committee Chair:
Tharp, Hal S.

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titleTheoretical and experimental evaluation of high-temperature ultrasound in cancer therapy.en_US
dc.creatorDamianou, Christakis Andrea.en_US
dc.contributor.authorDamianou, Christakis Andrea.en_US
dc.date.issued1993en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractThe purpose of this study was to use the concept of calculated thermal dose to predict the necrosed tissue volume, and to evaluate the near-field heating due to application of multiple pulses to cover a large volume. In addition, overlaying tissue damage caused by sonicating a highly-perfused tissue seated only a few cms deep was evaluated. The thermal dose distribution during focused ultrasound exposure was calculated based on numerical models used for calculating ultrasound power distributions and the resulting temperature distributions in tissue. In vivo experiments in dogs and rabbits were conducted to obtain the reliability of the predictions. It was found that the lesion intensity threshold was almost independent of the frequency for transducers with an F-number of 1. It was found that the lesion size was practically perfusion independent for pulses 5 s or shorter. The lesion size increased with increasing pulse duration, acoustical power, and F-number, but decreased with increasing frequency at a constant focal intensity. The results shown in this dissertation can be used as a guide for selection of transducer parameters for ultrasonic surgery. The temperature elevation in the near-field was elevated. It was found that significant delays (20 s or longer) between the pulses must be introduced in order to avoid unwanted tissue damage in front of the focal zone. In addition, decreasing the pulse duration and F-number reduced the temperature elevation in front of the focus. It was shown that the damage to surrounding tissues when sonicating a highly-perfused tissue (such as kidney) seated a few cms deep, can be avoided by using transducer with an F-number of 0.8 and a frequency of about 1 MHz. The heating of the surrounding tissues can be reduced more by correct selection of the pulse duration and power. The tissue necrosis due to ultrasound was monitored using MRI imaging. A study of MR signal intensity charge with temperature of dog and rabbit tissues in vitro showed that MRI has the potential to monitor temperature non-invasively. The signal sensitivity with temperature was found to be about 1.2-1.7 %/°C.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectBiomedical engineering.en_US
dc.subjectElectrical engineering.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineElectrical and Computer Engineeringen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.chairTharp, Hal S.en_US
dc.contributor.committeememberCangellaris, Andreas C.en_US
dc.contributor.committeememberGerhard, Glen C.en_US
dc.identifier.proquest9410667en_US
dc.identifier.oclc702683737en_US
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