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Hello
I have a problem with writing/finding a macro/plugin which calculates gamma index based on dose differential image (difference between dosemap calculated in treatment planning system and measured with matrix of detectors or film).For those who are not familiar with it a gamma index is a parameter commonly used in verification of IMRT treatment plans and it is defined as the minimum radial distance between the measured point of interest and calculation points, which are expressed as a surface in the dose-distance space.
To lighten up the issue ill quote the part of the instruction of Doselab program describing calculation method of gamma index :
"The best way to illustrate gamma calculations is through a simplified example. For this example, we will use 3%/3 mm criteria and a reference dose of 200 cGy. A pixel of the measured image has a dose of 100 cGy. The same pixel of the calculated image is 90 cGy (+5% relative difference, 0 mm DTA), and a calculated pixel 2 mm away has a dose of 96 cGy (+2%, 2 mm). The gamma distribution is obtained by adding the relative dose difference divided by the dose criterion in quadrature with the DTA divided by the DTA criterion (DTA means Distance to agreement). To find the gamma value for one measured pixel, this number must be computed for all surrounding calculated pixels. The surrounding pixel with the lowest value is set as the gamma value of the reference pixel. The values for our two surrounding pixels are shown below.
sqrt((5%/3%)^2(0mm/3mm)^2)= 1.67
sqrt((2%/3%)^2(2mm/3mm)^2)= 0.94
The gamma value is the lowest value found: 0.94 for these two pixels. The 0.94 value would be assigned to the measured pixel, as it is the reference image. The measured pixel would “pass” the gamma evaluation test because it is 1 or less."
My question is how to implement these calculations in imagej macro/plugin language? or maybe there is already a plugin that solves this problem ....then please send me.
Thanks a lot
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