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A model to generate beam profiles of the Varian Clinac 4 for three‐dimensional dose calculation: Open fields
Author(s) -
Lam KamShing,
Lam WingChee
Publication year - 1984
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.595453
Subject(s) - dosimetry , beam (structure) , physics , source model , medical imaging , medical physics , nuclear medicine , computer science , optics , computational physics , medicine , artificial intelligence
For the Clinac 4, open field profiles measured in the principal plane have higher intensity “horns” than those in off‐axis planes. The maximum deviation occurs at 1‐cm depth, where in the worst case of large field sizes and off‐axis distances the deviation can be as high as 16% in the region near the horns. A model is proposed to generate open field beam profiles in off‐axis planes, based on measured profiles in the transverse principal plane and in the largest field size diagonal plane of the machine. Within the central 90% portion of the field, the maximum deviation of the generated profiles from the measured ones at the same off‐axis distance varies from about 3% at 1‐cm depth to about 2% at 13‐cm depth and then increases to less than 5% at 25‐cm depth, even for very large field sizes and off‐axis distances. Very little additional computer time and data storage are required for this procedure. Using these profiles, the Milan and Bentley method can be extended to three‐dimensional treatment planning with good accuracy.