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Measurement of high energy x‐ray beam penumbra with Gafchromic™ EBT radiochromic film
Author(s) -
Cheung Tsang,
Butson Martin J.,
Yu Peter K. N.
Publication year - 2006
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 - 10.1118/1.2218318
Subject(s) - penumbra , materials science , x ray , optics , beam (structure) , nuclear medicine , medical physics , physics , medicine , ischemia , cardiology
High energy x‐ray beam penumbra are measured using Gafchromic™ EBT film. Gafchromic™ EBT, due to its limited energy dependence and high spatial resolution provide a high level of accuracy for dose assessment in penumbral regions. The spatial resolution of film detector systems is normally limited by the scanning resolution of the densitometer. Penumbral widths (80%/20%) measured atD maxwere found to be 2.8, 3.0, 3.2, and 3.4 mm ( ± 0.2 mm ) using 5, 10, 20, and 30 cm square field sizes, respectively, for a 6 MV linear accelerator produced x‐ray beam. This is compared to 3.2 mm ± 0.2 mm (Kodak EDR2) and 3.6 mm ± 0.2 mm (Kodak X‐Omat V) at 10 cm × 10 cm measured using radiographic film. Using a zero volume extrapolation technique for ionization chamber measurements, the 10 cm × 10 cm field penumbra atD maxwas measured to be 3.1 mm , a close match to Gafchromic™ EBT results. Penumbral measurements can also be made at other depths, including the surface, as the film does not suffer significantly from dosimetric variations caused by changing x‐ray energy spectra. Gafchromic™ EBT film provides an adequate measure of penumbral dose for high energy x‐ray beams.