Intrafraction motion has long been suspected of causing inaccuracies in the resultant dose delivered to the patient. This study attempts to determine how breathing motion affects intact-breast cancer patients for three different treatment techniques commonly used in the clinic: physical wedge compensators (PWs), enhanced dynamic wedges (EDWs), and step-and-shoot intensity modulated radiation therapy (ssIMRT). Some of the effects of intrafraction motion can be eliminated with Gating Therapy. In this study, we have also investigated the efficiency of a Real-Time Position Management Gating System.
In order to mimic patient breathing, equipment has been designed to simulate respiratory motion to a first order approximation. A breast phantom has also been designed to represent patient tissue and shape. Film was used as a dosimeter and static dosimetry data were used as a control for comparison. Three velocities of the breast phantom were studied, and Gating Therapy was introduced for each data set. Dose area histograms were calculated for a breast and lung planning target area (PTA), and Normalized Agreement Test (NAT) Indexes were calculated in reference to the static case.
Our study shows that the results are dependent on the respiratory rate and the wedge angle and that deviation from the static case is highest if the collimator speed is of the same magnitude as the speed of the target. Generally, there is a large overdosage to the lung PTA and a large underdosage to the breast PTA. However, with the implementation of Gating Therapy, these dose discrepancies are dramatically reduced. The areas of high and low dose within the treatment field observed in this study can be related to other treatment sites affected by respiratory motion. Based on these results, we highly recommend using Gating Therapy for all treatments that may be affected by intrafraction organ motion.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:SSU.etd-04112005-113609 |
| Date | 11 April 2005 |
| Creators | Sidhu, Sabeena |
| Contributors | Sidhu, Narinder, Pywell, Robert E., Mayer, Monique, Manson, Alan, Koustov, Alexandre V. (Sasha), Kendall, Edward J. |
| Publisher | University of Saskatchewan |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://library.usask.ca/theses/available/etd-04112005-113609/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University of Saskatchewan or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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