Scan parameter optimization and a temperature controller for scanned focussed ultrasound hyperthermia: A theoretical and experimental study.

Persistent Link:
http://hdl.handle.net/10150/185181
Title:
Scan parameter optimization and a temperature controller for scanned focussed ultrasound hyperthermia: A theoretical and experimental study.
Author:
Lin, Win-Li.
Issue Date:
1990
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:
Maintenance of the treatment temperatures at their target levels in the face of disturbances, a uniform temperature distribution within the treatment region, an acceptable temperature rise outside that volume, a fast temperature rise, and stability are desirable characteristics of an optimal hyperthermia treatment control system. Since scanned, focussed ultrasound systems (SFUS) have a great deal of flexibility it is necessary to use such a feedback system in shaping the power field during hyperthermia treatments. For best use of such a system many complicated, interacting decisions must be made to obtain an optimal hyperthermia treatment. This dissertation studies this optimization problem using a simulation program which searches for the optimal scan parameters, and presents a PID plus bang-bang feedback control system which gives a suitable power distribution to meet the above requirements for this hyperthermia system. Several objective functions were studied and compared based on temperature criteria. An extensive objective function study has been done in order to determine; the best formulation for that objection function, the characteristics of that objective function near the optimal operating point, the effects of the scan parameters on that objective function, and the domain of acceptable initial guess points for obtaining a globally optimal solution. A further comprehensive study of the optimal temperature distributions attainable with single and multiple circular scans of a tumor was done. The results show that the optimal scan parameter configuration will allow this SFUS to produce a close to ideal treatment temperature distribution for a wide variety of clinically relevant conditions. To further study the variation of the temporal and spatial blood perfusion, a controller was used to obtain a more suitable power to meet the treatment needs. Both the simulation results and experimental animal results show that the controlled region can be rapidly heated to the target temperature with a small overshoot and maintained at that level in the face of disturbances. In vitro dog kidney model and in vivo dog thigh experiments show that the controller works well in practice, and verify that it can compensate for spatial and temporal blood perfusion variations. As shown in both these experiments and in simulations, the controller can be used for controlling a single temperature or multiple temperature points simultaneously, thus allowing relatively uniform temperature fields to be created.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Engineering
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Aerospace and Mechanical Engineering; Graduate College
Degree Grantor:
University of Arizona
Advisor:
Roemer, Robert B.

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titleScan parameter optimization and a temperature controller for scanned focussed ultrasound hyperthermia: A theoretical and experimental study.en_US
dc.creatorLin, Win-Li.en_US
dc.contributor.authorLin, Win-Li.en_US
dc.date.issued1990en_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.abstractMaintenance of the treatment temperatures at their target levels in the face of disturbances, a uniform temperature distribution within the treatment region, an acceptable temperature rise outside that volume, a fast temperature rise, and stability are desirable characteristics of an optimal hyperthermia treatment control system. Since scanned, focussed ultrasound systems (SFUS) have a great deal of flexibility it is necessary to use such a feedback system in shaping the power field during hyperthermia treatments. For best use of such a system many complicated, interacting decisions must be made to obtain an optimal hyperthermia treatment. This dissertation studies this optimization problem using a simulation program which searches for the optimal scan parameters, and presents a PID plus bang-bang feedback control system which gives a suitable power distribution to meet the above requirements for this hyperthermia system. Several objective functions were studied and compared based on temperature criteria. An extensive objective function study has been done in order to determine; the best formulation for that objection function, the characteristics of that objective function near the optimal operating point, the effects of the scan parameters on that objective function, and the domain of acceptable initial guess points for obtaining a globally optimal solution. A further comprehensive study of the optimal temperature distributions attainable with single and multiple circular scans of a tumor was done. The results show that the optimal scan parameter configuration will allow this SFUS to produce a close to ideal treatment temperature distribution for a wide variety of clinically relevant conditions. To further study the variation of the temporal and spatial blood perfusion, a controller was used to obtain a more suitable power to meet the treatment needs. Both the simulation results and experimental animal results show that the controlled region can be rapidly heated to the target temperature with a small overshoot and maintained at that level in the face of disturbances. In vitro dog kidney model and in vivo dog thigh experiments show that the controller works well in practice, and verify that it can compensate for spatial and temporal blood perfusion variations. As shown in both these experiments and in simulations, the controller can be used for controlling a single temperature or multiple temperature points simultaneously, thus allowing relatively uniform temperature fields to be created.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectEngineeringen_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineAerospace and Mechanical Engineeringen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorRoemer, Robert B.en_US
dc.contributor.committeememberHynynen, Kullervoen_US
dc.contributor.committeememberOrtega, Alfonsoen_US
dc.contributor.committeememberTharp, Hal S.en_US
dc.identifier.proquest9103043en_US
dc.identifier.oclc709777258en_US
All Items in UA Campus Repository are protected by copyright, with all rights reserved, unless otherwise indicated.