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Application Menu > MLCQA continued
Section 2 - Using PIPSpro
Fiducial #1
The first fiducial needs to be placed over the spherical marker in the
phantom that is aligned with isocenter. Click anywhere near the marker
on the image and the software will perform a search for the marker and
automatically place the fiducial over the center of the sphere.
This first fiducial tells the software that this is isocenter and all
measurements will be made from this point. This allows the software
to correctly determine the position of each of the MLC’s and accurately
determine the distance from isocenter the edge of the MLC is positioned at.
Choose the linear accelerator that the image was acquired on and then
click ‘Select’ in the dialog.
The image will be shown in the right hand panel of the screen. The linear
accelerator data will be shown in the left hand panel along with the settings
(default) for performing the analysis.
The default settings should work for most images. If adjustments are
needed the following explanation of each setting parameter should assist
with making them.
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Edge Strength – The 50% default value describes the grayscale pixel
intensity between the area of irradiation and the non-irradiated area.
For example if the irradiated area has a pixel intensity of 20 and the
non-irradiated area had a pixel intensity of 240, and the edge strength
is set to 50% the edge will be considered where the pixel intensity
is 110 ([240-20]*.5). If the intensity is set to 40% then the edge will
be found where the pixel intensity is 88 ([240-20]*.4). For the Leaf
Transmission module this value is used for the software to correctly
determine the area of the openings around the fiducials so these
areas can be ignored in the analysis
Fiducial #2
The second fiducial needs to be placed over the spherical marker that is
furthest from the center marker in the direction of the opening of the MLC’s.
Click anywhere near the marker on the image and the software will perform
a search for the marker and automatically place the fiducial over the center
of the sphere.
The second fiducial tells the software the scale for the image and also
which direction the collimator and MLC’s are turned.
Pixel Size – This value will automatically be determined from the
image once the calibration marks have been placed.
A Window/Level bar on the left of the image can be used to adjust the
brightness and contrast.
Click on the ‘Leaf Transmission’ button to perform the analysis.
Two fiducial marks need to be placed on the image.
The software will place profiles at 5 cm from isocenter in either direction
to measure a background value for the image. Two profiles will then be
placed 2 cm from isocenter to measure the amount of inter-leaf leakage. A
single profile will be placed at isocenter to measure the inter-bank leakage
(ignoring the open areas).
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