Calculation of electron beam depth-dose curves and output factors for arbitrary field shapes. 1988

I A Bruinvis, and W A Mathol
Radiotherapy Department, The Netherlands Cancer Institute (Antoni van Leeuwenhoekhuis), Amsterdam.

A previously presented method to calculate depth-dose curves and output factors for arbitrarily shaped electron beams is evaluated. The method employs a Gaussian pencil model for direct incident and applicator scattered electrons; the parameter values are derived from measured central axis depth-dose distributions. In addition, an empirical model is used to compute the dose due to electrons scattered by field-defining frames. In this way, the properties of the clinical electron beams are taken into account. In this paper, calculations and measurements for electron beams with energies between 6 and 20 MeV, treatment field dimensions between 3 and 14 cm, and various applicator sizes are compared. The results demonstrate the importance of irregular field dose calculations and the scope of the present method. Agreement better than 3% in dose and 0.2 cm in depth is achieved. For electron beams without applicators, the calculations show the same accuracy. Another method in electron treatment planning that derives values for the radial width parameter of the pencil beam from measured broad beam profiles is also investigated. This method gives good results for dose calculations in beams without applicator scatter. It should be used with care, however, for beams that contain such a scatter component. When electrons scattered by the applicator walls and field-defining frames are neglected, differences between measured and calculated dose up to 8% are found.

UI MeSH Term Description Entries
D008961 Models, Structural A representation, generally small in scale, to show the structure, construction, or appearance of something. (From Random House Unabridged Dictionary, 2d ed) Model, Structural,Structural Model,Structural Models
D011879 Radiotherapy Dosage The total amount of radiation absorbed by tissues as a result of radiotherapy. Dosage, Radiotherapy,Dosages, Radiotherapy,Radiotherapy Dosages
D011882 Radiotherapy, High-Energy Radiotherapy using high-energy (megavolt or higher) ionizing radiation. Types of radiation include gamma rays, produced by a radioisotope within a teletherapy unit; x-rays, electrons, protons, alpha particles (helium ions) and heavy charged ions, produced by particle acceleration; and neutrons and pi-mesons (pions), produced as secondary particles following bombardment of a target with a primary particle. Megavolt Radiotherapy,High-Energy Radiotherapy,Radiotherapy, Megavolt,High Energy Radiotherapy,Radiotherapy, High Energy
D004583 Electrons Stable elementary particles having the smallest known negative charge, present in all elements; also called negatrons. Positively charged electrons are called positrons. The numbers, energies and arrangement of electrons around atomic nuclei determine the chemical identities of elements. Beams of electrons are called CATHODE RAYS. Fast Electrons,Negatrons,Positrons,Electron,Electron, Fast,Electrons, Fast,Fast Electron,Negatron,Positron
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D012542 Scattering, Radiation The diversion of RADIATION (thermal, electromagnetic, or nuclear) from its original path as a result of interactions or collisions with atoms, molecules, or larger particles in the atmosphere or other media. (McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed) Radiation Scattering,Radiation Scatterings,Scatterings, Radiation

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