Test procedures for verification of an electron pencil beam algorithm implemented for treatment planning
1996 (English)In: Radiotherapy and Oncology, ISSN 0167-8140, E-ISSN 1879-0887, Vol. 39, no 3, 271-286 p.Article in journal (Refereed) Published
The calculation of an electron dose distribution in a patient is a difficult problem because of the presence of tissue and surface inhomogeneities. Verification of the dose planning system is therefore essential. In this investigation, a novel method is used to evaluate a commercially available system (Helax-TMS), at electron energies between 10 and 50 MeV, both for a conventional treatment unit and an MLC-collimated scanned beam unit with a helium-filled treatment head. First, the experiments were designed to verify the local beam database and some fundamental characteristics of the electron beam calculations. Secondly, a number of generalised situations that would be encountered in the clinical treatment planning were evaluated: oblique incidence, field shaping with multi-leaf collimator, bolus edges, and air cavities. Dose distributions in two generalised anatomical phantoms simulating a neck and a nose were also analysed. The results have, when so possible, been presented as the dose ratio within the 'flattened area' for dose profiles and down to the 'treatment depth' (80% dose level) for depth doses. In the penumbra region and in the dose fall-off region, the comparison has been represented by the distance deviation between calculated and measured dose profiles or depth doses. A new tool, 'volume integration', was used to evaluate the deviations from a more clinical point of view. Most results were within +/-2% in dose for volumes larger than a sphere with a diameter of 15 mm, or +/-2 mm in position. Dose deviations were generally found for oblique incidences and below heterogeneities such as small air cavities and bolus edges in limited volumes.
Place, publisher, year, edition, pages
1996. Vol. 39, no 3, 271-286 p.
Electron beams; Algorithm verification; Treatment planning; Inhomogeneities
IdentifiersURN: urn:nbn:se:umu:diva-39958DOI: 10.1016/0167-8140(96)01742-2ISI: A1996UP29200009OAI: oai:DiVA.org:umu-39958DiVA: diva2:396925