UBC Theses and Dissertations

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UBC Theses and Dissertations

Dose verification of a stereotactic IMRT treatment planning system Xian, Zheng


In this project, ion chamber measurement and film dosimetry were used to verify dose distributions for a new stereotactic IMRT (Intensity Modulated Radiation Therapy) treatment planning system. This technique combines the principles of stereotactic radiosurgery and IMRT to significantly increase the positioning accuracy compared with conventional IMRT . Ion chamber measurements reveal that the discrepancy between the measured and the calculated dose at the isocenter can be up to 2%. Angular dependence of ion chamber sensitivity and the tissue equivalence of the phantom material were determined to be the main sources of this discrepancy. Radiochromic film was used as the film dosimeter in the project. A set of performance tests of Gafchromic EBT film indicated that the uncertainty in Gafchromic EBT film dosimety was expected to be 2.5%. However, the discrepancies we found in measurements of clinical cases using the film were much larger than this. And further investigation into this discrepancy was beyond the scope of this thesis.

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