User manual

115
The benefit of using the type of rational function described above is that you can
actually reduce the number of dose points required for calibration. Figure 3 shows the
fit when four of the data points were removed. It is almost identical to the fit in Figure 1
with seven data points. The function has three constants a, b and c and is fully defined
with three data points – two films exposed to known doses plus one unexposed film.
Figure 3
IV. EQUIPMENT AND MATERIALS
 Gafchromic
™
EBT2 or EBT3 radiochromic films
 Adhesive tape
 Radiation source – usually a linear accelerator, but it could be a source delivering
photons between about 10kV and 25MV
 48-bit RGB Epson
®
flatbed scanner, preferably model 10000XL or 11000XL with
transparency adapter
 Epson
®
Scanner Software
 FilmQA
™
Pro Software
 The use of a phantom to provide electron equilibrium (e.g. water equivalent
plastic blocks) is optional.