Inaccurate dose calculation in radiotherapy can lead to errors in treatment delivery and evaluation of treatment efficacy. Respiration can cause of intra-fractional motions, leading to uncertainties in tumor targeting. These motions should therefore be included in dose calculation. The finite element method-based deformable registration platform MORFEUS is able to accurately quantify organ deformations. The dose accumulation algorithm included in MORFEUS takes organ deformation and tumor movement into account. This study has experimentally validated this dose accumulation algorithm by combining 3D gel dosimetry, respiratory motion-mimicking actuation mechanism, and finite element analysis. Results have shown that within the intrinsic measurement uncertainties of gel dosimetry, under normal conformal dose distribution conditions, more than 90% of the voxels in MORFEUS generated dose grids have met the criterion analogous to the gamma test. The average (SD) distance between selected pairs of isodose surfaces on the gel and MORFEUS dose distributions is 0.12 (0.08) cm.

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. This thesis also addresses the fundamental problems of the derivation of useful biological models for clinical application and the description of tumour 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 either alone or combined.

Bibliography: leaves 148-155. / xiv, 210 leaves : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / This thesis provides several methods for assessment of total machine dependent distortion which allows the clinical significance of that distortion to be established. A method for removal of machine dependent distortions is also presented and shown to work for a locally produced, large field of view spatial linearity phantom. Finally, a possible method is developed which is suitable for application of the distortion correction method to actual patients. / Thesis (Ph.D.)--University of Adelaide, Dept. of Physics and Mathematical Physics, 1997?

The EPID (electronic portal imaging device) was designed for in vivo imaging of patients during radiotherapy treatment. The ability of EPIDs to promptly acquire two dimensional data, lends them to be considered for use in quality assurance of the linac. This thesis set out to investigate the possibility of using a radionuclide, technetium 99 m (Tc99m), to produce a flood field for the calibration of an EPID, because using a beam calibrated EPID to measure the beam is self-referential. The difference in relative response between the energy spectrum of a 6MV beam and the Tc99m was investigated using EGSNRC DoseXYZ Monte Carlo Modelling. The relative output ratio was calculated to be less than 1.6%. The dose response of the EPID with respect to dose rate was checked using different activities of Tc99m and found to be linear. The flatness from a phantom was calculated, with a model in MATLAB, for a range of heights, overlaps, thickness, and deformations, to find the optimum balances between signal strength and flatness. This model was checked for accuracy using diagnostic radiographic film. The culmination of the energy response, linearity and the calculated flatness is a flood field taken with a flood phantom on the EPID with low signal strength. To get a signal to noise ratio of 3% the mean of over 2000 flood field images were used. This accuracy was not adequate for clinical use but the averaging of pixels it is accurate enough for QA.

Doctor of Health Science / It is well documented that for prostate cancer patients undergoing radiation therapy there is a correlation between target volume displacement and changes in bladder and rectal volumes. However, these studies have used a methodology that has captured only a subset of all treatment positions. This research used daily Computer Tomography (CT) imaging to comprehensively assess organ volumes, organ motion and their effect on dose, something that has never been performed previously, thus adding considerably to the understanding of the topic. Daily CT images were obtained using a Siemens Primus Linear Accelerator equipped with an in-room Somatom CT unit in the accelerator suite, marketed as ‘Primatom’, to accurately position the patient prior to treatment delivery. The internal structures of interest were contoured on the planning workstation by the investigator. The daily volume and location of the organs were derived from the computer to assess and analyse internal organ motion. The planned dose distribution was then imported onto the treatment CT datasets and used to compare the planned dose to i) the actual isocentre, where the isocentre was actually placed for that fraction, ii) the uncorrected isocentre, by un-doing any on-line corrections performed by the treatment staff prior to treatment delivery, and iii) the future isocentre, by placing the isocentre relative to internal organ motion on a daily basis. The results of this study did not confirm a statistically significant decrease in rectum volumes over time (hypothesis 1), however large fluctuations in bladder volume were confirmed (hypothesis 2). Internal organ motion for the rectum and bladder was demonstrated to be related to organ filling. Ideal planning volumes for these organs have been reported to minimise systematic and random uncertainty in the treatment volumes. An observed decrease in prostate volume over time, a systematic uncertainty in the location of the prostate at the time of the planning CT scan and a significant relationship between prostate centre of volume and rectum and bladder volumes has resulted in a recommendation that patients should be re-scanned during treatment to ensure appropriate clinical target volume coverage. A significant relationship between rectal and bladder volumes and the dose delivered to these organs was found (hypothesis 3). The dose delivered to the planning target volume was not related to the rectal or bladder volumes, although it was related to the motion of these organs. Despite these results only minimal effects on the dose delivered to any of the three isocentres occurred, indicating that the planned dose was accurately delivered using the methodology presented here (hypothesis 4). However the results do indicate that the patient preparation instructions need to be improved if margins are to be reduced in the future. It is unrealistic to assume that Image Guided Radiation Therapy will ever become routine practice due to infrastructure costs and time limitations. This research will inform radiation therapy centres of the variables associated with prostate cancer treatment on a daily basis, something that has never before been realistically achievable. As a result centres will be able to devise protocols to improve treatment outcomes.

[Truncated abstract] Purpose: Permanent prostate brachytherapy (PPB) as a treatment option for prostate cancer requires implantation of 80-150 radioactive iodine-125 (I-125)

Diss. (sammanfattning) Göteborg : Göteborgs universitet, 2007. / Härtill 4 uppsatser.

Thesis (M.Sc.(Hons.))--University of Western Sydney, Nepean, 1995. / "A thesis submitted in fulfilment of the requirements for the degree of Master of Science (Honours) in Physics at the University of Western Sydney, Nepean" -- T.p. Bibliography: leaves 123-128.

Dissertation (Ph.D.).--University of Texas Graduate School of Biomedical Sciences at San Antonio, 2006. / Vita. Includes bibliographical references.

Thesis (M.Sc. (Hons.))--University of Western Sydney, Nepean. / Bibliography: leaves 104-108.