Abstract：
:It is shown that in narrow monoenergetic photon beams under conditions of lateral electron disequilibrium, primary absorbed dose P(r) is a simple function of beam radius r: P(r) = P lambda.(1 - e(-gamma.r)), where P lambda is the primary dose in broad beams for which complete lateral electron equilibrium exists, and gamma depends on photon energy and absorbing medium. This formula was evaluated using Monte-Carlo-generated data for the primary dose in water from monoenergetic photons in the energy range from 2 to 8 MeV. The primary dose was studied in beams of radii 0.006 cm less than r less than 5.0 cm and within the depth interval 0.5 cm less than or equal to d less than or equal to 24 cm. It was concluded that the saturation equation above provides an accurate description of the primary dose from monoenergetic photon beams, as judged by comparison with Monte Carlo results.
journal_name
Med Physjournal_title
Medical physicsauthors
Nizin PS,Chang XSdoi
10.1118/1.596741subject
Has Abstractpub_date
1991-07-01 00:00:00pages
744-8issue
4eissn
0094-2405issn
2473-4209journal_volume
18pub_type
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