Defense Date

2012

Document Type

Dissertation

Degree Name

Doctor of Philosophy

Department

Medical Physics

First Advisor

Jeffrey Siebers

Abstract

Dose verification is a critical component of adaptive radiotherapy, as it provides a measurement of treatment delivery success. Based on the measured outcome, the plan may be adapted to account for differences between the planned dose and the delivered dose. Although placement of an EPID behind the patient during treatment allows for exit dosimetry which may be used to reconstruct the delivered patient dose via backprojection of the fluence, there have not been any studies examining the basic assumption of backprojection-based dose verification: that deviations between the expected and delivered exit fluences are totally caused by errors in the delivered fluence, and not caused by patient geometry changes. In this dissertation, the validity of this assumption is tested. Exit fluence deviations caused by machine fluence delivery errors are measured as well as those caused by interfractional changes in the patient anatomy. Dose reconstruction errors resulting from the backprojection assumption are assessed. Correlations are examined between exit fluence deviations and patient dose reconstruction deviations. Based on these correlations, a decision tree is proposed detailing when caution should be taken in performing dose reconstruction to achieve delivery verification. Finally, a semi-automated dose verification tool is constructed for both clinical and research purposes.

Rights

© The Author

Is Part Of

VCU University Archives

Is Part Of

VCU Theses and Dissertations

Date of Submission

December 2012

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