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Discuss best practices and workflow advice for Surface Guided Radiation Therapy on all treatment sites.
By nicola_snell
Hi All,
Just wondering if anyone has had any experience of having significant pitch on their pelvis patients that is not picked up on SGRT but CBCT's show it? We have looked at drawing our ROI's slightly higher on the hips and more post on the legs. But just wondering if anywhere else has experienced this and found a solution. We have not noticed it on our breast or thorax patients. Just out pelvis patients.
Many thanks,
By michelle_comer
Hi Nicola,
Yes on some pelvic patients we have this problem. Most it is fine.

Like you we try to ensure we start with good quality ROI. Not too anterior on thighs and upwards laterally to include hip and if possible protuberance of the iliac crest. We use a thin strip anteriorly on the lower pelvis if BMI not too large. But occasionally, despite ROI edits, pitch issues persist on CBCT.

For most patients we use 'CT sim' reference surface on AlignRT for set-up. If there are consistent tilt issues we will update our set up instructions to say 'Induce pitch of +4 on AlignRT'/ 'Induce pitch of approx -2.5' etc to try create a better starting point for CBCT. Ask them to tilt their pelvis up or down on set up to achieve this. We take new Reference SGRT for 'This Session Only' once happy with CBCT.

If very consistent on this new pitch value and no resets for ~3days we may take new SGRT surface on this 'This and Future Sessions' and update our set-up instructions accordingly.

If patients are consistently problematic in their pitch we may take a 2D KV lateral image (the reference DRR prepped with inf L-Spine, sacrum and pubic symph. contoured). This is to try achieve a good pelvic position prior to proceeding to CBCT in order to minimize dose from repeat CBCTs.

Hope this helps, and I'm also keen to hear feedback from other centers!