Characterization of an amorphous silicon electronic portal imaging device for use as a relative dosimeter in radiation therapy

Cancer is the second leading cause of death in Canada and in the United States. Over 50% of cancer patients will receive radiation therapy as a part of or all of their treatment. In order to ensure proper tumour coverage and normal tissue avoidance, accurate dose verification is vital. Increased use of advanced techniques such as Intensity Modulated Radiation Therapy (IMRT) has accelerated the need for real-time digital dose verification of patient fields.; Dosimetric properties of the EPID were studied and results were compared to methods of dosimetry currently used at Princess Margaret Hospital (PMH). The EPID displayed a linear response to dose, good short-term reproducibility and was not significantly affected by changes in dose rate. Comparisons of the EPID with current relative dosimetry methods have shown that its dose profiles closely match those of film and water phantom for static, dynamic wedge-shaped, and IMRT fields.; There is an energy response with the EPID, which is due to the high atomic number content of its detector material. The long-term stability trend of the EPID is somewhat uncertain and further investigation is recommended. Overall, the amorphous silicon electronic portal imaging device (EPID) not only shows promise as relative dosimeter, but also as an efficient tool for IMRT quality assurance.