User manual

57
bottom of the Image Window when the Image movement tool is active. For translational
movement click the arrows on the large square button or turn the circular knob for
rotation. Alternatively the motions can be controlled by clicking either of the large
buttons and using the keyboard arrows. For relative dosimetry the maximum dose value
in the treatment plan can be scale up or down. Use the spin arrows to
increase/decrease the maximum reference dose or type in a value and press enter to
accept the value.
FilmQA
Pro provides for various quantitative comparisons of the
measured dose distribution with the Treatment Plan. Click on the
Comparison map selector icon to choose between the gamma,
distance-to-agreement and differential delta functions.
This example focuses on the gamma analysis test - Low, et al, Med. Phys. 25, 656
(1998) and FilmQA
Pro calculates the gamma value for each pixel in one of two
ways (% relative error):
1. as √( DD
2
+ DTA
2
. tolerance/distance) where DD = dose difference in %;
DTA is distance to agreement, tolerance is the dose threshold and distance is
the distance threshold; or
2. as √( DD
2
/tolerance
2
+ DTA
2
/distance
2
).
The passing criterion in the first case is gamma value ≤ tolerance value and gamma
value ≤1 for the second case.
The test criteria are set by entering the tolerance and distance values into the cells near
the bottom of the Film Evaluation Panel. The default values are 3% at 3 mm with the
minimum threshold set at 0% (i.e. 0% of the maximum value in the Treatment Plan).