Calculate angular displacement of rotated DICOM data

Development
1

Hey there,

I would need to know the procedure (mathematical calculations) how to calculate the angular displacement (axis x, y and z) of rotated DICOM data. I already know that it is possible to access the image axis directions in RAS coordinate system from the volume, but I would need the direct calculation only out of the DICOM attributes. I also already know that the attribute (0020, 0037) “ImageOrientationPatient” includes the x and y vectors of the image and z can be calculated with the cross product of x and y. Is there also another attribute necessary to calculate the angles?

Thank you in advanced for any help.
Manuel

2

ImageOrientationPatient tag everything you need to compute image axis angles relative to patient axes. There are several parametrizations available for computing angles between coordinate systems. Euler angles wikipedia page gives a nice summary and also formulae that you can use to compute rotation angles from axis vectors.

1 Like
3

Perfect. It’s good to know that only the attribute is needed to calculate the angles. Then I’m not too far off with my approach.
Thank you very much for your help.

1 Like