Radiosurgery is characterized by high radiation doses, delivered via small diameter radiation beams in a single session, placing stringent requirements on the numerical and spatial accuracy of dose delivery to the target volume within the brain. In this thesis, physical and clinical aspects of radiosurgery are discussed, including a method for the production of cylindrical dose distributions with rectangular beams using cylindrical dynamic rotation. / The measurements of radiosurgical x-ray beam parameters are presented. Monte Carlo simulations determine that a measured increase depth of dose maximum with increasing field size is a result of primary dose deposition in phantom for small diameter beams. / An analytical representation based on a curve-fitting process is developed to parametrize radiosurgical x-ray beam percentage depth doses as a function of depth in phantom, field diameter and beam energy using bi-exponential and polynomial functions. / Measurements of dose in the build-up region of x-ray beams ranging from 1 x 1 cm$ sp2$ to 30 x 30 cm$ sp2$ show that the depth of dose maximum increases rapidly with increasing field size at small fields, reaches a maximum around 5 x 5 cm$ sp2$ and then gradually decreases with increasing field size for large fields. Monte Carlo simulations attribute effect observed at large fields to the scatter contamination of the primary beam from the linac head. This scatter contamination is measured by a half-block technique and further experiments show that it consists of electrons originating in the flattening filter of the linac.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.41242 |
| Date | January 1993 |
| Creators | Sixel, Katharina E. (Katharina Elisabeth) |
| Contributors | Podgorsak, E. B. (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 | Doctor of Philosophy (Department of Physics.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001357775, proquestno: NN91715, Theses scanned by UMI/ProQuest. |
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