Pylinac WinstonLutz MultiTarget with SunNuclear Phanton Agility

[Giulia Faés]

Hello everyone,

I'm trying to analyze a multi-target Winston-Lutz test using Pylinac and I'm encountering a problem.

I irradiated a MultiMet-WL Cube phantom on an Elekta linear accelerator with MLC Agility. The treatment plans were provided by the manufacturer (Sun Nuclear). 

I exported all the DICOM images and loaded them into Pylinac using the library (from pylinac import WinstonLutzMultiTargetMultiField, BBArrangement) as a compressed folder:

wl = WinstonLutzMultiTargetMultiField.from_zip("/content/MultiMet 17-01-2025-20260304T164442Z-1-001.zip")

And I analyzed them using:

wl.analyze(bb_arrangement=BBArrangement.SNC_MULTIMET, is_open_field=True)

However, I get the following error:

ValueError: The number of detected fields and BBs does not match

Due to this error, I cannot complete the evaluation.

My questions:

1. What could cause the discrepancy between the detected fields and the BBs? 2. Are there any specific acquisition requirements (field size, collimator angle, number of images, etc.) that must strictly match the SNC_MULTIMET configuration?

3. Is there any way to debug which fields or BBs are not being detected correctly?

I would appreciate any guidance on how to correctly structure the dataset for this phantom.

Thank you very much!