The accuracy of conventional dose calculation algorithms employed in external photonbeam treatment planning is limited by their inability to fully model the radiation source andaccount for the electron fluence perturbations which occur in regions of non-uniform density.In this work, we evaluated the dosimetric accuracy of the PEREGRINE Monte Carlo dosecalculation code for 6 MV photons. Dose profiles calculated by PEREGRINE werecompared with measurements in homogeneous and heterogeneous phantoms. A comparisonof dose profiles calculated by PEREGRINE and the EGSnrc Monte Carlo code was alsoperformed. To fully model the Varian Millennium 120 leaf collimator, a new MLCcomponent module was developed for BEAMnrc.Overall, the agreement between PEREGRINE and measurements and EGSnrc is within1% with the exception of the buildup region, where the accuracy of the beam model isaffected by an artificially increased electron subsource weight, and for 30x30 cm2 fieldswhere the beam model does not accurately predict the off-axis fluence. A clinical comparisonof IMRT dose distributions calculated by PEREGRINE and the CORVUS pencil beamalgorithm indicates that the heterogeneity correction implemented in CORVUSunderestimates the dose received by sensitive structures, receiving up to 20% of theprescribed dose, which lie in the vicinity of low density tissues.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.19418 |
| Date | January 2003 |
| Creators | Heath, Emily C. |
| 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: 002009947, Theses scanned by McGill Library. |
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