Doctoral Dissertations

Date of Award


Degree Type


Degree Name

Doctor of Philosophy


Nuclear Engineering

Major Professor

Lawrence Townsend


In order to increase the effectiveness of radiotherapy in lung cancer treatment, a method must be developed to further increase tumor dose while further minimizing the dose to healthy lung tissue. In this work, a respiratory gated radiation therapy program is established at the Thompson Cancer Survival Center for the treatment lung cancer. A commercially available gating system is used to selectively deliver absorbed dose to moving target volumes during time intervals when the target volume is within the intended region. Although respiratory gating has been used in other applications, such as MRI and CT, free breathing gating has never before been applied to conventional radiotherapy. In this work, techniques are developed for the first time for the implementation of free breathing respiratory gated radiation therapy. In the first phase of this study, the clinical efficacy of the procedure is justified for the treatment of lung, liver, and pancreatic cancers. In the second phase, the stability and reproducibility of the gating hardware are evaluated. This includes an evaluation of the dosimetric stability of the linear accelerator. The consistency of the gating circuit is tested for rapid beam on and off conditions. In addition, a dynamic test phantom is designed and built that simulates respiration in order to test the gating system. In the third phase, monthly and annual quality assurance programs are developed for the respiratory gating system to insure that the entire system is operating correctly. In the final phase, the clinical efficiency and practicality of this respiratory gating is addressed. In addition, patient specific quality assurance (QA) procedures are developed to ensure that the correct dose is delivered safely.

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