SGRT Forum

Hi there,

I'm just wondering if people are checking the isocentre values displayed in Align RT against their planning system isocentre values as part of their checks. We are using Eclipse (Varian) and it's unfortunately not as straight forward as I would have hoped.

Thanks,
Conor

I check the isocenter for every plan. If the User Origin in the Eclipse plan was not moved by dosimetry, the numbers should match exactly. If the User Origin was moved (i.e. it is not coincident with the DICOM origin), you must either add or subtract the DICOM offset from the isocenter values to reconcile them. Care must be taken when patient is prone, since the X-coordinate switches sign.

Jose C Pichardo, Ph.D., DABR

Thanks for your response Jose!Our user origin is always moved as we import from ProSoma and this is where our problem lies. Hopefully we can find a more straight forward way of adding/subtracting the DICOM offset to make the workflow more efficient.

Possibly you could copy the plan, then reset to Dicom origin and write the isocenter value down.  It may or may not mess with the approved plan.  You will want to test it first.