User manual

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reference film, one reference film exposed to a known dose of radiation in addition to
the exposed application film. Note: All films used for the One Scan Protocol must be
from the same production lot and from the same production lot as the films used
for the primary calibration. The illustration shows an application film is shown with two
reference strips above it. The upper strip is the unexposed film and the lower strip is the
one exposed to a known dose. As a rule the exposed reference strip should receive a
dose close to the maximum dose expected in the application film.
To demonstrate the One Scan Protocol, we will use the images in the EBT3 Rapid Arc
example included with the FilmQA
Pro installation package. The root is Program
Files/Ashland Advanced Materials/FilmQAPro/Images/Example EBT3 Rapid Arc.
Click "Add new case object" at the bottom of the case tree and select 'Film
calibration (ordinary)' from the list. Navigate to the Example EBT3 Rapid Arc folder
and open the file 0__69_2__138_3__368_8.tif. The file name embeds the calibration
dose values. The dose values are also available in the file Exposures.txt in the same
folder. The technique of having all calibration films in a single image is called an
OneScan calibration. It minimizes the number of calibration images and uses film and
your time efficiently. Because FilmQA
Pro uses asymptotic fitting functions that
behave like film, i.e. the responses approach constant values at high dose just as the
darkening of the film gets progressively smaller with each dose increment, fewer points
are needed to correlate the response of a specific film to dose. One of the most useful
fitting functions is X(D) = A + B/(D-C) where X(D) is the response at dose D and A, B
and C are coefficients to be determined. Responses are fitted separately for each color
channel.
Since only three coefficients per channel need to be defined, as few as three dose
points are needed for the correlation. However, it is preferable to add one or two more
points to provide statistics showing the goodness of the fit, to eliminate bad dose points
and to select the best fitting function. To fit all the calibration films in a single scan cut
1½”x8” strips from an 8”x10” sheet of film. Not only does this provide an easy reference