SGRT Forum

Hi,

We use 2 linacs for intracranial SRS. Both have AlignRT and 6-DoF couch (Hexapod). On one of these linacs we have the VisionRT SRS cube calibration but not on the other. Testing AlignRT with a phantom and couch rotations we have found:

Both linacs show the same sensitivity and accuracy to small deviations.
Both linacs start to show unstable RTDs for couch rotation greater than 45degrees.
Both linacs lose monitoring completely at large couch rotations (>70degrees)

Thr ROI was drawn covering the anterior and both sides of the mask

Is there something we are missing in terms of the use of AlignRT for SRS with couch rotations?
Could someone explain the benefit (if any) of using the SRS cube calibration?

hi colin
we don't do SRS and don't have the cube for calibration - but from what i have heard the problem could well be the elekta couch! i think they are fairly poor for accuracy. also i would not be testing it with an ROI on a H&N shell - do it on an anthropomorphic phantom or a person.

how are your winston lutz results for different couch angles?