Following a departmental expansion, an isocentric cobalt-60 external beam teletheraphy unit was modified to produce a large fixed field for total body irradiation. The sourcehead was separated from the gantry and installed at a distance of 251.2 cm from the floor. The collimator was removed and replaced with a custom built secondary collimator projecting a 277 x 132.6 cm 2 radiation field at floor level. The work presented in this thesis describes the measurements performed to bring the unit into clinical use for total body irradiation. A custom flattening filter was placed below the secondary collimator to flatten the beam to within +/-3% of the central axis dose as measured at 10 cm in water. Percent depth dose, tissue-phantom-ratios, surface dose and absolute output were measured in the radiation field. The effects of inhomogeneities were studied and the thickness of lead used for lung attenuators was determined. Verification of treatment planning and delivery was performed with an Alderson-Rando anthropomorphic phantom and showed dose uniformity within +/-10% of the prescribed dose when a lead attenuator was used over the lung.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.79026 |
| Date | January 2002 |
| Creators | Larouche, Renée-Xavière |
| Contributors | Evans, M. D. C. (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: 001976452, proquestno: AAIMQ88241, Theses scanned by UMI/ProQuest. |
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