We investigated the feasibility of constructing compensators for intensity modulated beams. The average uncertainty in the constructed compensator thickness was +/-0.3 mm. It was found that the beam hardening effect was significant, and can lead to an error of 6.2% in the transmission, for 6 cm of lead alloy in the beam. The maximum scatter contribution to the measured fluence was 19.8% for a 20 x 20 cm2 field size, and 6 cm of lead alloy in the beam. The compensators were constructed using a simple attenuation model. For a simple wedge-step compensator there was a maximum deviation of 6% between the measured and our predicted fluence profile. For simple compensators this deviation can be attributed to scatter according to the scatter analysis introduced. The maximum deviation between the measured and predicted fluence, for fluence files derived from a commercial inverse treatment planning system was slightly higher at 7%. This is because other factors such as penumbra and scatter from neighboring modulations must be considered for each compensator individually.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.30367 |
| Date | January 2000 |
| Creators | Dimitriadis, Doris M. |
| Contributors | Fallone, B. G. (advisor) |
| Publisher | McGill University |
| 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 | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Master of Science (Department of Medical Radiation Physics.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001740639, proquestno: MQ64343, Theses scanned by UMI/ProQuest. |
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