Intensity modulated radiotherapy (IMRT) can potentially increase the dose delivered to liver tumours while sparing normal tissues from dose. More complex IMRT, with more modulation of the radiation beam is more susceptible to geometric and dosimetric uncertainties than simpler radiotherapy plans. Simple breath-hold liver IMRT using few radiation beam segments (<30) was investigated in 27 patients to determine the quality of treatment in terms of tumour dose coverage and normal tissue sparing as compared to index IMRT using >30 segments. In all 27 plans number of segments was reduced to <30 without compromising tumour coverage or normal tissue dose constraints, at the expense of dose conformity. Delivered tumour and normal tissue dose did not differ statistically between IMRT plans when accounting for treatment residual geometric error. This research supports considering the use of simple IMRT for treatment of liver cancer, except when loss of dose conformation is undesirable (i.e. very high doses).

From one treatment to the next, considerable effort is made to accurately position radiotherapy patients according to their treatment plans. However, some variation is unavoidable. The target volume and the organs at risk may also move within the patient and/or change shape during the treatment. Thus, it is important to be able to verify the success of the treatment by determining the position of patient and the dose deposited in the patient at each fraction. One possibility to achieve this, particularly when equipment, time and budgets are limited, would be to collect limited information while the patient is on the treatment couch. This research was aimed to develop a method for optimum beam position determination, for each patient-specific case. The optimized beam positions would balance the both treatment planning and image reconstruction, so that the patient???s image can be obtained during the treatment delivery using the information collected from the same angles as used for treatment. This will allow verification of the dose deposited in the patient for every fraction. Using a limited number of angles for image reconstruction, the dose to the patient can be minimized. This work has two major parts, beam position optimization for image reconstruction and beam position optimization for treatment planning. These two optimizations are then combined to obtain the optimum beam position for both image reconstruction and treatment planning. An objective function, projection correlation, was developed to investigate the image reconstruction method using limited information. Another objective function, the average optimization quality factor, was also introduced to optimize beam positions for treatment planning. Two optimization methods, the gradient descent method and the simulated annealing based on these objective functions were used to determine the beam angles. The results show that the projection correlation presents several advantages. It can be applied without any iterations, and it produces a fast algorithm. The present research will allow selection of the optimum beam positions without excessive computational cost for treatment planning and imaging. By combining the projection correlation and the average optimization quality factor together with more advanced image reconstruction software this could potentially be used in a clinical environment.

The measurement of productivity in health care is difficult. Studies in various specialty disciplines of medicine have identified that the variation in complexities (casemix) between departments or hospitals will vary and therefore will affect any basic productivity statistics that are produced. Radiation oncology is a discipline of medicine where no such studies into radiotherapy casemix variations and the effect that these may have on productivity measures have been performed, despite the high capital expenditure involved in the delivery of radiotherapy. Radiation oncology productivity on linear accelerators is currently measured by the number of patients treated or number of treatment fields treated per unit time (usually per hour). These statistics have been collected for many years and productivity assessments were made on the variations in these statistics that exist between departments. However, these statistics do not consider the variations in casemix that occur between departments. These complexity differences may be quite marked and therefore may strongly influence the ability of a department to achieve a high patient or treatment field throughput. This may be seen as 'reduced productivity' with no consideration of the complexity of the caseload seen in the department. In addition, future technological changes that improve patient outcome may be introduced. These changes may make treatment more complex. Using older measures of productivity such as fields per hour or patients per hour will not consider these technological changes and the subsequent changes in complexity and hence departments may be seen as less productive in the future using current methods of analysis unless a more valid measure of productivity that considers complexity variations is introduced. There have only been 3 previous attempts at developing measures of linear accelerator productivity. Each of these models have been developed empirically and have not been clinically validated. No previous attempts have been made in determining a scientifically-derived complexity model that considers the variations in treatment technique. This thesis describes research performed between 1995 and 2001. This research study???s primary aims were to study the factors that affect radiotherapy treatment time and treatment complexity and to develop a model of linear accelerator productivity that does consider complexity variations in radiotherapy treatment delivery. This model is called the Basic Treatment Equivalent (B.T.E.). This series of trials examines the old models of linear accelerator productivity, describes the derivation and validation of the BTE model both in Australasia and the United Kingdom, identifies the factors that contribute to treatment time and treatment complexity, describes the development of a pilot model of productivity of gynaecological brachytherapy and outpatient chemotherapy using similar BTE methodology, discusses the potential uses of the BTE model, recent independent reviews of BTE by other groups, and the advantages and disadvantages of using such a model. This research has shown that it is possible to identify the various factors that contribute to treatment time and treatment complexity and to derive a model of linear accelerator productivity that considers the variations in complexity. The BTE model has been clinically validated in Australia, New Zealand and a couple of departments in the United Kingdom and Canada and has been adopted as a new measure by various groups. It requires regular updating to maintain currency particularly as there are frequent improvements in radiation treatment technology. Future studies should identify the differences these technological enhancements make to productivity. The BTE derived from outpatient chemotherapy delivery and gynaecological brachytherapy delivery shows promise although these models require further research with the assistance of other departments.

Intensity Modulated Radiation Therapy (IMRT) is a modern radiotherapy treatment technique used to obtain highly conformal dose distributions. The delivery of IMRT is commonly achieved through the use of a multileaf collimator (MLC). One of the hindrances at present to the widespread use of IMRT is the increased time required for its planning, delivery and verification. In this thesis one particular method of MLC based IMRT, known as Static Multileaf Collimator based IMRT (SMLC-IMRT), has been studied along with methods for improving it???s delivery efficiency. The properties of an MLC commonly used in SMLC-IMRT have been characterised. The potential ramifications of these properties on the dosimetric accuracy of the delivered IMRT field were also investigated. An Interactive Leaf Sequencing (ILS) program was developed that allowed for the manipulation and processing of intensity maps using a variety of methods. The objective of each method was to improve the delivery efficiency whilst maintaining the dosimetric quality of the IMRT treatment. The different methods investigated were collimator angle optimisation, filtration, and intensity level optimisation. The collimator was optimised by identifying the angle at which the minimum monitor unit???s (MU???s) were required when using a sliding-window delivery method. A Savitzky-Golay filter was applied to random intensity maps and suitable filtration parameters identified for filtering clinical IMRT fields, and the intensity levels were optimised based on a deviation threshold. The deviation threshold identified the acceptable level of difference tolerable between the original and modified intensity map. Several IMRT cases were investigated and the impact of each the methods on MU???s, segments and dose distribution observed. As the complexity of IMRT fields increases the dosimetric impact of the MLC properties increases. Complex SMLC-IMRT fields require longer delivery times due to the increased number of MU???s and segments. Collimator optimisation was shown to be a fast and effective means of improving delivery efficiency with negligible dosimetric change to the optimised plan. Modifying intensity maps by applying a filter and optimising the intensity levels did reduce the complexity and improve the delivery efficiency, but also required a dosimetric compromise of the optimised plan.

Bibliography: leaves 241-250. / xviii, 250 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / A multileaf collimator for radiation therapy has been designed that splits each leaf bank into two vertically displaced assemblies or levels with each level consisting of alternate leaves and leaf spaces. The radiation profiles transmitted for image formation through the collimator design were investigated to examine their dependence on the collimator design features. / Thesis (Ph.D.)--University of Adelaide, Dept. of Physics and Mathematical Physics, 2000

Bibliography: leaves 241-250. / xviii, 250 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / A multileaf collimator for radiation therapy has been designed that splits each leaf bank into two vertically displaced assemblies or levels with each level consisting of alternate leaves and leaf spaces. The radiation profiles transmitted for image formation through the collimator design were investigated to examine their dependence on the collimator design features. / Thesis (Ph.D.)--University of Adelaide, Dept. of Physics and Mathematical Physics, 2000

A system for visual guidance in patient set-up for external-beam radiotherapy procedures was developed using augmented reality. The system uses video cameras to obtain views of the linear accelerator, and the live images are displayed on a monitor in the treatment room. A 3D model of the patient's external surface, obtained from planning CT data, is superimposed onto the treatment couch in the camera images. The augmented monitor can then be viewed, and alignment performed against the virtual contour. The system provides an intuitive method for set-up guidance, and allows non-rigid deformations to patient pose to be visualised. It also allows changes to patient geometry between treatment fractions to become observable, and can remain in operation throughout the treatment procedure, so that patient motion becomes apparent. Coordinate registration between the camera view and the linac is performed using a cube which is aligned with the linac isocentre using room lasers or cone-beam CT. The AR tracking software detects planar fiducial tracking markers attached to the cube faces, and determines their positions in order to perform pose estimation of the 3D model on-screen. Experimental results with an anthropomorphic phantom in a clinical environment have shown that the system can be used to position a rigid-body with a translational error of 3 mm, and a rotational error of 0.19 degrees, 0.06 degrees and 0.27 degrees, corresponding to pitch, roll and yaw respectively. With further developments to optimise the system accuracy and its interface, it could be made into a valuable tool for radiotherapy clinics. The outcome of the project has been encouraging, and has shown that augmented reality for patient set-up guidance has great potential.

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

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

Thesis (Ph.D.)--University of Wollongong, 2005. / Typescript. Includes bibliographical references.