Radiotherapy has been shown to increase the subsequent risk of heart disease among survivors of breast cancer, but little is known about factors, other than the dose of radiation delivered to the heart, which determine the magnitude of the risk. In addition, survivors of teenage and young adult cancer are internationally acknowledged as an understudied population, and limited information is available on their late health risks. This thesis sought to utilise the largest observational datasets available to date for these populations: the Collaborative Group on Observational Studies of Breast Cancer Survivors and the Teenage and Young Adult Cancer Survivor Study. These were used to firstly characterise the radiation-related risks of heart disease and lung cancer, and secondly to provide an overview of the long-term risk of heart disease for the entire spectrum of cancers diagnosed in teenagers and young adults aged 15 to 39. Initially, a methodology study and systematic review demonstrated that selection effects and other biases can be very problematic during analyses of observational cohorts, particularly when using a radiotherapy comparison. However, in the case of heart disease and lung cancer, one can take advantage of the breast being a paired organ and use a laterality comparison, particularly when laterality played little effect in treatment selection. This comparison was used throughout the analyses of breast cancer patients. This thesis demonstrated that adjuvant radiotherapy for breast cancer significantly increased the risk of heart disease among women with left-sided breast cancer and those patients with ipsilateral lung cancer. Interestingly, younger women were at the highest risk of heart disease, and a progressive proportional decrease in risk with increasing age at diagnosis was found, which has not been shown before. It also suggested that radiotherapy and chemotherapy combined may further increase the risk of heart disease among breast cancer patients. Survivors of teenage and young adult cancer, particularly Hodgkin lymphoma, were at a significantly raised cardiac mortality risk compared to the matched general population. The findings of this thesis provide evidence to support continued follow-up for cancer patients, as survivors were found to be at a substantial risk into the second or third decade after treatment. It has permitted the detection of groups of individuals at particularly increased risks, for example younger patients and survivors of Hodgkin lymphoma diagnosed in teenagers and young adults, for whom closer monitoring for late effects or measures to reduce the risk, such as adaptations to treatment, may be appropriate. Finally, evidence was also presented to support the development of clinical follow-up guidelines specifically for survivors of teenage and young adult cancer.

An improved method is introduced for prediction of local tumor control following lung stereotactic body radiation therapy (SBRT) for early stage non-small cell lung cancer (NSCLC) patients using 18F-fluorodeoxyglucose positron emission tomography (18F-FDG PET). A normalized background-corrected tumor maximum Standard Uptake Value (SUVcmax) is introduced using the mean uptake of adjacent aorta (SUVref), instead of the maximum uptake of lung tumor (SUVmax). This method minimizes the variations associated with SUVmax and objectively demonstrates a strong correlation between the low SUVcmax (< 2.5-3.0) and local control of post lung SBRT. The false positive rates of both SUVmax and SUVcmax increase with inclusion of early (<6 months) PET scans, therefore such inclusion is not recommended for assessing local tumor control of post lung SBRT. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2013.

The purpose of this study is to investigate the changes of the pericardial dose at different respiratory phases and statuses in accelerated partial breast irradiation (APBI) using Cyberknife M6™ multileaf collimators (CK-MLC). Anonymous 6 female patient files with respiration gated four-dimensional computed tomography (4DCT) sets, and 6 left breast cancer cases with CT images in free-breathing (FB) and deep inhalation breath-hold (BH) were selected. One CT image set from each patient was planned for APBI in Accuray Multiplan™ 5.2, and respectively compared its pericardial dose with those from CT sets of other respiratory phases. All the comparable CT images were fused in the planning system according to the left chest wall, among which the lung gap anterior to the pericardium varies by the lung expansion. For the purpose of this study, the tumor volume was outlined in the media-lower quadrant of the left breast where this lung gap is relatively small. All the plans in this study met the requirements set by the National Surgical Adjuvant Breast and Bowel Project/Radiation Therapy Oncology Group (NSABP/RTOG), specifically protocol B-39/RTOG 0413. From the comparisons in this investigation, the mean relative pericardial dose of the BH CT group showed significant or 45% (p < 0.01) lower value than that of FB CT group. However, in FB 4DCT group, 3 of 6 cases indicated a meaningful reduction (p < 0.05) in 100% inhalation phase when compared with the mean dose over other phases. The inconsistent pericardial doses were displayed in FB 4DCT group due to minimal changes in the anterior lung gap of the pericardium, when the diaphragmatic breathing was dominant in those patients. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2015. / FAU Electronic Theses and Dissertations Collection

Advanced-stage nasopharyngeal carcinoma (NPC) presents very difficult scenarios for radiation therapy (RT) planning. The infiltration of tumor to the skull base and beyond means that the tumor is very close to critical normal organs (organs at risk, OARs). Despite the advent of intensity-modulated radiotherapy (IMRT) treatment technique---the state-of-art RT technique, conflicting requirements between organ protection and target dose conformity is still problematic. The objectives of the present research are (1) to investigate the dosimetry properties of IMRT treatment in advanced-stage NPC in respect of its dosimetric limitations and planning problems, (2) to develop new methods and tools to resolve such problems, in particular to improve the quality of treatment plans and efficiency of the dose planning and optimization process. A series of four inter-linked studies were conducted to address these issues. / In conclusion, the solutions to several major problems in IMRT planning for advanced-stage NPC were investigated and established. It has been demonstrated in this research that, by applying these methods and tools, significant improvement in the dosimetry and efficiency of IMRT treatment planning can be accomplished as compared with conventional IMRT planning techniques. It is expected that such would translate into an improvement in treatment throughput, better tumor control and reduction in normal tissues complications. The methods developed have potential to be applied to all stages of NPC and to other tumor sites. / The first study was to improve the efficacy in target coverage and organs sparing using an "organ-splitting" approach. The OARs which overlapped with targets were split into target-overlapping and non-overlapping segments and each segment was assigned with different constraints parameters to increase the degree of flexibility during optimization. As a result, a steep gradient in the dose distribution at the regions of interface between the targets and normal critical organs could be achieved and treatment quality was improved. In the second study, a thorough dosimetric comparison between conventional 2-dimensional (2D) RT and IMRT plans was conducted to determine, with reference to outcome of 2D treatments, the extended tolerance dose limits for the critical organs, especially that of the brainstem and spinal cord, and their planning organ at risk volume. Such data could then serve as reference in IMRT planning when the dose of critical organs need be exceeded in order to allow adequate dose to a very close by target. In the third study, the feasibility of using interpolated contours for segmentation of targets and OARs in IMRT planning was investigated. The result indicated that the use of interpolated contours in IMRT planning could significantly reduce the contouring time by about 50% without degrading the target coverage and OARS sparing. In the final study, an array of dose constraint templates that could accommodate different degrees of overlap between the targets and OARs, together with a template selection program, were developed to improve the efficiency of IMRT planning. By applying the methods and tools developed, IMRT treatment planning of advanced NPC could become more efficient and less dependent on planner's experience. / Chau, Ming Chun. / Adviser: Anthony Chan Tak Cheung. / Source: Dissertation Abstracts International, Volume: 69-02, Section: B, page: 0948. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (leaves 118-128). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese. / School code: 1307.

The purpose of this study is to verify and validate the dose at various points of interest in accelerated partial breast irradiation (APBI) treated with the Strut Adjusted Volume Implant (SAVI) applicator using Thermoluminescent Dosimeters (TLDs). A set of CT images were selected from a patient’s data who had received APBI using the SAVI applicator. The images were used to make 3D models. TLDs were calibrated for Brachytherapy. Various points of interest were marked out and slots were carved in the 3D models to fit the TLDs. CT scans were taken of the 3D models with expanded SAVI applicator inserted. A plan was made following B-39 protocol. The TLDs were read and the absorbed doses were calculated and compared to the delivered doses. The results of this study show that the overall average reading of the TLDs is within expected value. The TPS shows overestimated dose calculations for brachytherapy. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2017. / FAU Electronic Theses and Dissertations Collection

No description available.

Equispaced beam arrangements are typically used for IMRT plans. This beam arrangement provides adequate dose coverage to the target while sparing dose to other structures. However, an equispaced beam arrangement may not provide the best dose coverage to the target while sparing dose to the other structures. Beam angle optimization attempts to optimize the beam directions to produce a better IMRT plan; this is achieved by increasing dose to the target while minimizing dose to the remaining structures. Most methods of beam angle optimization attempt to optimize the beam angles and the beam intensity profiles to find an optimal set of beam angles. This thesis attempts to optimize the beam angles without determining the beam intensity profiles. An MCNP simulation is run to score the beam directions; the simulation is run as an adjoint problem to reduce simulation time, with the target as the source and the detectors scoring the dose for the gantry angles of the beam. Then, an optimization algorithm is run to select a set of beam angles for an optimized IMRT plan. The optimized IMRT plan is compared to an equispaced IMRT plan on a commercial treatment planning system to determine if this method of beam angle optimization is better than using an equispaced beam arrangement. The results of this thesis indicate that the coupling of an MCNP simulation for scoring with an optimization algorithm to select beam angles will produce a better IMRT plan than an equispaced IMRT plan. Three different geometries were used and for all geometries, the optimized IMRT plan had a higher average dose to the target while maintaining or increasing dose sparing to the critical structure and normal tissue.

published_or_final_version / Dentistry / Doctoral / Doctor of Philosophy

Thesis (M.Tech.: Radiography) - Dept. of Radiography, Durban Institute of Technology, 2003 1 v. (various pagings) / Cancer is an inexorably progressive disease and a favourable outcome in its management often depends on early intervention (Mackillop, Zhou and Quirt, 1995: 532). Early detection of the disease is therefore important for a favourable outcome to be achieved. When the disease is diagnosed at a late stage, the treatment that is offered is only palliative. Palliative treatment is only offered with the aim to relieve the local symptoms of advanced disease. The treatment intent is therefore not curative but only to give the patient a better quality of life, which sometimes is not possible especially for very advanced disease. In KwaZulu-Natal the incidence of Zulu speaking patients presenting with a late stage disease to the major cancer treatment centres is very high with the result that the majority of these patients can only be offered palliative treatment (Pervan, Cohen and Jaftha, 1995 : 162). Aim of the study is to investigate the factors that contribute to the late presentation of rural Zulu patients with cancer to the two major provincial cancer treatment centers in KwaZulu-Natal (prior to December 2002).

The goal of conformal radiation techniques is to improve local tumour control through dose escalation to target volumes while at the same time sparing surrounding healthy tissue. Respiratory motion is known to be the largest intra-fractional organ motion and the most significant source of uncertainty in treatment planning for chest lesions. A method to account for the effects of respiratory motion is to use four-dimensional radiotherapy. While analytical models are useful, it is essential that the motion problem in radiotherapy is addressed by both modeling as well as experimentally studies so that different obstacles can be overcome before clinical implementation of a motion compensation method. Validation of techniques aimed at measuring and minimizing the effects of respiratory motion require a realistic dynamic deformable phantom for use as a gold standard. In this work we present the design, construction, performance and deformable image registration of a novel breathing, tissue equivalent phantom with a deformable lung that can reproducibly emulate 3D non-isotropic lung deformations according to any real lung-like breathing pattern. The phantom consists of a Lucite cylinder filled with water containing a latex balloon stuffed with dampened natural sponges. The balloon is attached to a piston that mimics the human diaphragm. Nylon wires and Lucite beads, emulating vascular and bronchial bifurcations, were glued at various locations, uniformly throughout the sponges. The phantom is capable of simulating programmed irregular breathing patterns with varying periods and amplitudes. A deformable, tissue equivalent tumour, suitable for holding radiochromic film for dose measurements was embedded in the sponge. Experiments for 3D motion assessment, motion reproducibility as well as deformable image registration and validation are presented using the deformable phantom.