Post implant dosimetric analysis for prostate brachytherapy

Annette Haworth

    Research output: ThesisDoctoral Thesis

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    Abstract

    [Truncated abstract] Purpose: Permanent prostate brachytherapy (PPB) as a treatment option for prostate cancer requires implantation of 80-150 radioactive iodine-125 (I-125) "seeds" into the prostate. Seed positions are carefully planned using ultrasound images of the prostate. The objective is to implant the seeds in a pattern that will deliver an integral radiation dose that is adequate for tumour sterilisation without significant toxicity. The post-implant dosimetry study facilitates the establishment of treatment planning guidelines to minimise toxicity with optimal tumour control. Multiple uncertainties associated with PPB can directly influence treatment decisions and treatment outcomes. Uncertainties can impact on: the selection of the optimal prescription dose, the selection of the optimal dose distribution, accuracy of pre and post-implant dosimetry methods, dosimetric and clinical factors that determine tumour control and normal-tissue toxicity interaction of complementary therapies. Consensus on these uncertainties and optimal treatment approaches are not readily derived from the literature. The purpose of this thesis was therefore to use data derived from the establishment of a PBB program, to determine dosimetric relationships for tumour response and induction of toxicities, and to examine these parameters in the context of other published series. Method and Materials: A post-implant dosimetry technique was developed to determine the dose distribution in a prostate implant. The technique registers stereo-shift (anteroposterior) radiographically defined seed positions with the ultrasound defined prostate anatomy. The dose distribution was correlated with treatment related toxicity and local tumour control. A bioeffect model was developed as a robust means of predicting for biochemical control. The model incorporates a distribution of cell densities that is related to the probability of finding cancer foci in select regions of the prostate
    Original languageEnglish
    QualificationDoctor of Philosophy
    Publication statusUnpublished - 2005

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