Penumbral width measurement by film
Tsang Cheung et al. studied the GafchromicTMEBT film to measure the penumbra region of high energy of 6 MV photon beams by measuring at depth of 0.12, 1.5, 5 and 10 cm for field size of 5×5 to 30×30 cm2. The results were compared with Kodak EDR 2 and Kodak X-Omat V films. The extrapolation method among various sizes of ionization chambers was used for measuring reference penumbral widths. Table 1 shows that the penumbra widths using X-Omat V radiographic film had the largest values compared with other detectors due to its large energy dependence. The penumbra width measured with Kodak EDR 2 and the GafchromicTMEBT film were closely to the values obtained from the extrapolation method so the Kodak EDR 2 and the GafchromicTMEBT were adequate dosimetry for penumbra measurement. However, Kodak EDR 2 had disadvantages such as energy dependence at low energy photon and film processor required which the GafchromicTMEBT was superior to the Kodak EDR 2 for example near- tissue equivalence, less energy dependence as well as self-developing film.