User manual

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Once the IMRT image has loaded, FilmQA
Pro by default, uses triple-channel
dosimetry and automatically builds a dose map and a consistency map. When the
calculations are complete the dose map and consistency map are displayed as
thumbnail images under the dose map object branch. Triple-channel dosimetry
involves the solution of a non-linear optimization problem for each pixel in an image.
Since many images contain >500,000 pixels the creation of triple-channel dose map
may take more than 10 seconds depending on the computer resources available. In the
bottom right hand corner of the screen is a little star icon. When the star is colored blue
- - it indicates the application is busy with calculations. The number beside the star
is the number of calculation processes under way.
The consistency map displays a representation of dose uncertainty defined as
√ ((D
R
- D
B
)
2
+ (D
B
- D
G
)
2
+ (D
G
- D
R
)
2
) where D
R
, D
G
and D
B
are the calculated doses
in the red, green and blue channels respectively. The optimization problem used to
calculate doses in multi-channel dosimetry involves
minimizing the consistency function for each pixel in
the image. Full frame images on an A3 scanner can
involve the solution of a million optimization
problems, or more. Using triple channel dosimetry
and the One Scan Protocol see Lewis, et al., Med.
Phys., 39(10), 2012, pp 6339 - consistency values
better than 1% of the maximum dose to the
application film are the standard.
In addition to triple-channel dosimetry other dose
mapping methods and options are available. By right-clicking on the “Dose-map
(single scan)” line, a menu of options appears.
Rebuild: Recalculates dose and consistency maps using the selected method
Dose mapping method: Allows the following options to be specified: