Publication Date


Document Type


Committee Members

Brent Foy (Advisor), Michael Gossman (Committee Member), Amit Sharma (Committee Member)

Degree Name

Master of Science (MS)


During radiation treatment, the patient commonly lies on a horizontal treatment table called a couch. The material used for the couch is chosen during the manufacturing process so as to minimize the effect of the couch on dose delivery, but it still has an effect. In addition to couch attenuation on the beam, the modern approach of using multiple beam angles for dose delivery makes treatment planning in the presence of the couch more challenging. However, the effect of the couch is not always considered when creating treatment plans, generally due to treatment planning software limitations. In this evaluation, the effects of the Varian Medical Systems, Inc® (Palo Alto, CA) Model IGRT Couch Top® on the dose distribution of head and neck cancer treatment was determined for a linear accelerator operating at 6 MV. Four head and neck cancer patients were selected for the study. Varian Model Eclipse®; treatment planning software was used to create two Volumetric Modulated Arc Therapy (VMAT) plans. One plan assumed the couch was not present, and one assumed it was present. Both plans were optimized to achieve the same physician directed dose objectives. Comparisons were then made using the planning system's Dose Volume Histogram (DVH) statistical and volumetric data. Dose changes to the tumor volumes along with normal tissue structures around the target area were clinically assessed. The mean dose to the tumor was reduced by 0.5 to 0.65 Gy as a consequence of including the couch during planning. Doses to surrounding normal tissues showed variable, yet significant effects.

Page Count


Department or Program

Department of Physics

Year Degree Awarded


Creative Commons License

Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License.

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