Picket Fence: Skipped Leaf Pair Label?


I’ve been adapting the pylinac Picket Fence module into some of our analysis scripts but noticed that for our HDMLC unit that one of the leaves is being skipped when I was plotting the max errors for each leaf (see picket_fence_max_offsets.PNG). Looking at the normal pylinac analysis plot, there didn’t seem to be any obvious gaps in the leaf analysis. I was looking through the picket fence documentation and code for any clues but haven’t come up with anything. I thought I’d compare the picket’s leaf numbers and center positions to the center positions in the picket settings just to double check whether a leaf was being skipped for some reason but the centers appear to match even though one of the leaf pair labels is skipped: [14,107].

I haven’t seen this behaviour with our Millennium 120 MLC units. Any ideas what might be happening?


Hey Brandon, unsure why it would skip a leaf, but often it’s a matter of noise. Have you tried applying a filter first? As mentioned on github, the MLC handling will change in v2.5, moving from an empirical detection process to a configurable a priori MLC configuration which should deprecate problems like these.

Hi James,

I tried a fairly wide range of filters but none seemed to label any of the leaf pairs with [14,107]. I’ll check in with v2.5 to see if that resolves this!