Can I transfer the RAS coordinate system back to LPS

I know that patient data has been converted to values in the RAS coordinate system after being imported into 3Dslicer. For example, I have a DICOM metadata with Origin [-202, -33,100]. But the Origin obtained from the vtkMRMLVolumeNode and vtkMRMLSegmentationNode types is [202,33,100]. I would like to know if there is a method to convert or obtain the original Origin: [-202, -33,100].
Thanks :–)

Can you please describe why you need this conversion within Slicer? Normally all operations in Slicer happen in RAS, and then one can export the results in LPS. Would that work for you?


I agree that it should not be necessary to convert the internal coordinate values when you are in Slicer, as all coordinate values are stored as RAS.

You can of course display coordinate values in any coordinate system; or use positive values and add the direction code (L/R, A/P, I/S) - as we do it in the Data Probe (in the lower-left corner). Conversion is trivial: invert the sign of the first two coordinates.

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Thank you for your answer. I know that doing so in 3Dslicer looks a bit like taking off your pants and farting. It’s unnecessary. It’s a long story. The representation I encountered earlier can only store one context, which means that no matter how many segments I annotate on a SegmentationNode. These segments have their own attributes. But in the end, these attributes will only correspond to a large annotation area in the end. Similar to the feeling of many to one. So I made other attempts. In fact, after observing, I also found that the conversion between LPS and RAS only requires adjusting the xy axis.

That’s it. Thank you again