M Westermark et al.pointed out that the penumbral width for diameter of photon beams ³ 4 mm measured with a liquid ionization chamber and a plastic scintillator were slightly broadened due to their finite size. The measured with a double diode (designed to reduce a directional dependence) obtained smaller penumbral width due to its smaller size and higher density material.
Lárraga-Gutiérrez M. José et al accepted SFD diode as a standard measurement for narrow photon beams to evaluate EBT2 radiochromic film. They found that the film could be considered competent for measuring penumbral width but it still has somewhat inherent energy dependence.
In brief summary, CC01,Scanditronix p-type photon silicon diode and RK chamber are not suitable detector because they have volume-averaging effects which lead to overestimate penumbra width. The liquid ionization chamber and a plastic scintillator are slightly broadened due to the finite size. Moreover, the Kodak XV film has large energy dependence and also film scanner effect. The diamond detector has dose rate dependence and great expense.
EDGE detector is a new device that is designed for small fields in the scanning beam measurement. It is a diode encapsulated in a rectangular housing made of thin brass sheet. Its active dimension is 0.8 mm. It is intended to use for small field beam data collection modeling for intensity modulated radiation technique.
Therefore this study will evaluate the new designed diode called EDGE detector for penumbral width measurement at small field sizes (defined only by jaws). The stereotactic diode detector (SFD)is one of the diode detectors constructed for small filed measurement due to its high resolution and high sensitivity therefore it will also be assessed to compare with the EDGE detector. The photon diode detector (PFD) was clearly not suitable for penumbral width measurement in small field (M Heydarian et al therefore it will be employed to demonstrate as a poor result. The EDR2 radiographic film and EBT2 radiochromic film will be served as a reference for comparison.