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Film dosimetry of small electron beams for routine radiotherapy planning
Author(s) -
NiroomandRad Azam,
Gillin Michael T.,
Kline Robert W.,
Grimm Daniel F.
Publication year - 1986
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 - 10.1118/1.595887
Subject(s) - dosimetry , flatness (cosmology) , densitometer , ionization chamber , electron , materials science , optics , percentage depth dose curve , radiation , field (mathematics) , ion , atomic physics , nuclear medicine , physics , nuclear physics , mathematics , medicine , cosmology , quantum mechanics , pure mathematics , ionization
The characteristics of very small fields, 1×1 and 2×2 cm, of electron beams of nominal energies, 5, 7, 10, 12, 15, and 18 MeV have been studied and compared to a 10×10 cm field. A parallel‐plate ion chamber and film have been used to obtain various dose parameters. The central axis depth dose measurements, field flatness, uniformity index, and relative output factors are presented. It was found that satisfactory results for determining the relative output factor can be obtained from film data using a scanning densitometer. It is our conclusion that film dosimetry is acceptable in determining the necessary clinical parameters needed to treat patients with fields as small as 2×2 cm. For the 1×1 cm field size and for the electron energies greater than 10 MeV, there was substantial disagreement between the ion chamber and film data in the buildup region as well as the regions beyond the depth of maximum dose to the depth of 90% dose.