VMAT DynDelivery

[Erik Kryck]

I'm trying to analyze halcyon Dynamic Delivery files with PyLinac. Varian provides 3 DICOM files for these tests: Variable Dose Rate, Variable Gantry Speed, Variable Leaf speed.

The default VMAT tests in PyLinac don't create the ROIs properly for these fields, so I'm trying to manually create them. Varian provides the Horizontal Offset (in mm) from the left side of the image for each ROI, while the PyLinac offset is from the calculated center of the image.

Is there a way to somehow implement the offsets from the left side of the image?

See attached for more information.

[tbe...@gmail.com]

Hi Erik,

you can customize the roi config (https://pylinac.readthedocs.io/en/latest/vmat_docs.html#customizing-the-analysis) but it is always referenced in relation to the center of the open field.

regards

Thomas

[Erik Kryck]

Thanks, 

I'm aware of the customize roi config and I'm able to come up with a workable solution with the assumption that the Varian center ROI offset is exactly at the center of the open field. Although I wanted to test PyLinac with ROIs placed "exactly" as per the Varian instructions (offset from the left side of the image). Clinically, I'm not too worried about the small potential differences; but as a benchmarking test, I'd like to have a 1:1 comparison with the manual method vs PyLinac.

I'm sure I can also come up with a custom workaround using pydicom, but didn't know if pylinac had any tools to help with this.

-Erik