Volume 27, Issue 11, November 2000
Index of content:
- PH. D. THESES ABSTRACTS
27(2000); http://dx.doi.org/10.1118/1.1320061View Description Hide Description
The main purpose of this thesis is to encourage the development of bioeffect planning as an experimental tool by which means bioeffect plans may be compared with standard isodose plans. The limitations of isodose planning become apparent in many common clinical circumstances when such comparisons can be made. Most of this thesis addresses the fundamental problems of the derivation of useful biological models for clinical application and the description of tumor and normal tissue parameter values and their variability. Particular emphasis has been placed on comparing the predictive value of the models and parameters against clinical results of fractionated and continuous irradiation. A bioeffect planning system has been developed using an IGE Target computer and this permits testing the sensitivity of the models to changes in parameter values as applied to an actual patient with or without CT based plans. As a clinician the author is painfully aware of the tantalizing challenge of attempting to perceive the operation of biological systems as a whole when so many variables need to be considered simultaneously. Bioeffect planning provides a means of demonstrating some of these complicated interactions. There are many reasons why bioeffect planning has not been adequately developed. These include concerns about the clinical applications of theoretical models, the uncertainty of normal tissue and tumor parameter values and the nonavailability of suitable computer systems capable of bioeffect planning. These concerns are fully justified and isodose planning must remain the gold standard for clinical treatment. Yet these hazards must be judged against the certainties that isodose planning, in which the only variable usually considered is the total dose, can be substantially misleading.
27(2000); http://dx.doi.org/10.1118/1.1320062View Description Hide Description
Diffuse coronary artery disease (DCAD), a common form of atherosclerosis, may be responsible for the failure of improved coronary flow reserve after successful PTCA (percutaneous transluminal coronary angioplasty). However, DCAD is especially difficult to diagnose because the lumen cross-sectional area is diffusely diseased along multiple vessels. In this study, the normal coronary arterial tree was defined from a supply and demand perspective through the establishment of a hemodynamic model. The definition is embodied by the following correlations between different morphometric and hemodynamic parameters. For any supplying segment in a normal coronary artery tree, the coronary blood flow is proportional to its dependent distal cumulative arterial length. Furthermore, the cross-sectional area of any supplying segment and its cumulative distal arterial volume relate to its distal cumulative arterial length in forms of fractal power law. The power law indices were found to observe certain constraints. The proposed correlations were validated using flow simulation on a complete set of anatomical data of a normal pig’s coronary arterial tree. Validations of morphometric and hemodynamic parameters were also performed on angiographic data from a swine animal model using techniques of 3-D reconstruction of the arterial tree and videodensitometry. The detectability of DCAD was evaluated by simulating a moderate level of DCAD and propagation of measurement error for morphometric and hemodynamic parameters. In conclusion, the proposed methodology can be used for detection and quantification of DCAD.