title: Use of multiple layers of Gafchromic film to increase sensitivity.
abstract: This note investigates the increase of the sensitivity of radiochromic film by layering the film together. Investigations with up to five layers of radiochromic film placed together as a single dosimeter have allowed accurate two-dimensional dosimetry at low radiotherapy doses. The sensitivity of the response of the layered film increases with the number of layers, with the five-layer dosimeter increasing the change in optical density by 4.3 +/- 0.2 times that for a single layer film at 670 nm readout wavelength. Measurements in the penumbral region of a 6 MV x-ray beam show that the spatial resolution is slightly reduced with the layered film. The distance across the region from 20 to 80% of the maximum dose at the beam edge (20/80% penumbra) measured at 1.5 cm depth was measured as 3.1 +/- 0.3 and 3.5 +/- 0.3 mm for one and five layers, respectively. Thus no major reduction in spatial resolution was found by layering the film to five layers but the sensitivity was increased by 430% at 670 nm readout wavelength.
authors.affiliation: Department of Physics and Materials Science, City University of Hong Kong, Kowloon Tong, People's Republic of China.
authors.forename: T
authors.initials: T
authors.lastname: Cheung
authors.forename: M J
authors.initials: MJ
authors.lastname: Butso
authors.forename: P K
authors.initials: PK
authors.lastname: Yu
mesh_terms: D010315:Particle Accelerators / Q000295:instrumentation; D011874:Radiometry / Q000295:instrumentation* / Q000379:methods*; D012680:Sensitivity and Specificity; D014962:X-Ray Film; D014965:X-Rays