Gamma calculation in Dose Comparison

HI, I’m able to calculate the gamma pass rate for 3%//3mm for two dose volumes and get ~ 99% pass rate. If I click calculate gamma again, my pass rate falls dramatically to like 7% with the same 3%/3mm criteria. After calculating gamma, do I need to Clear Scene and reload my dose volumes? The gamma pass rate only seem accurate the first time I calculate or after I clear Scene.


No, it shouldn’t be necessary to clear the scene. I just tried and was not able to reproduce the problem. Please do double check that both of your dose volumes are correct. What version of Slicer are you using?

Hi Greg,

I’m using 5.2.2. Here are couple screenshots illustrating what I’m seeing.

  1. Initial gamma at 2%.2mm pass rate 98%

  2. Click ‘Calculate Gamma’ a second time without changing parameters. Pass rate falls to 8%


Ah, ok, I see what happened. In the top image, your output gamma volume is set to “43: RTDOSE: Eclipse Doses” which is also your input reference dose. In other words, the first calculation overwrote one of your input volumes.

If you instead set the Gamma volume to “Create new volume” and it will work as expected.

1 Like

Thanks for the help Greg!