1Royal Adelaide Hospital, Clinical Radiobiology Unit, Cancer Services, North Terrace, Adelaide, South Australia 5000
Tóm tắt
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.
