SGRT Forum

We are getting Align RT installed in May and I have a couple questions.  Will Align RT work on extended distance treatments?  Also does anyone use Align RT for comprehensive breast or chest wall treatments and utilize two iso-centers?  If so, how does it work for your site and what tips or tricks do you have for these treatments.

Thanks,

Chad Tueller

You should have no problem using it for any distance.  We  use align RT on all of chestwall and sclav pt's.  We are one iso for Tx.  We have 2 ROI's when setting these pt's up.  Super easy to use and makes porting not a necessary entity even though we still do them.  Training will be easy.

Hi Chad

There can also be challenging situations with two -isocenters. I can give you one new example of challenging treatment and bolus cases with AlignRT. There is a VMAT mastectomy DIBH patient with two isocenters with bolus on the chest wall. Bolus is not used at the CT. We setup the patient to FB and BH reference surfaces normally inside treatment room without bolus. Then, daily, at the time patient is in BH and inside 1mm/1° accuracy in the “good” BH- surface (DICOM/VRT), we press pause, set bolus (covered with the paper) onto patient skin, quickly switch to an other AlignRT “bolus+treatment BH” field and acquire new reference surface for the treatment there and let the patient breath again. Then we ask the patient to take a breath to that same BH surface that we just acquired and once the values are again ok, we press pause, apply manually the planned shift laterally (18 cm or whatever it is in the plan), choose the other isocenter on AlignRT monitor, choose the “bolus+treatment BH field”, acquire new reference surface there and let the patient breath again. Then we do manually that LAT- shift back to first isocenter (to the couch LAT value that we had at the time we acquired BH- reference surface in first isocenter) and acquire first isocenter images there. (If there is a need for the couch shifts based on IGRT, we can do that and acquire new reference surface for treatment. After those possible small shifts we have to again ask the patient to take BH to that new BH surface and manually do planned LAT shift inside treatment room once patient is in BH and again acquire new reference surface to another isocenter.) Othervice we can use that same BH- field to the other isocenter, which has created before images, (still with calculated - planned couch shifts in LAT) which usually is the case. Then the imaging is performed to second isocenter (usually only tangential image to second isocenter). Then the first isocenter is treted and after that LAT shift to other isocentrer is again based on plan and it goes well to existing BH reference surface. Surprisingly well patients can hold their position in BH while we do not monitor them in BH during 1) bolus setup and during  2) couch shifts between isocenters in the setup. Also surprisingly often the errors in the images (if there is one) are systematical with this workflow, so corrections to setup FB/BH reference surfaces (without bolus) seems effective. Not any easy workflow for user to learn anyway, but on the other hand we have not had any flickering deltas with this and intrafractional control is better than with (for this kind of case easier) RPM.

BR Marko

I continue this VMAT DIBH bolus case with one more reply. One possibility is to setup the patient inside treatment room as said earlier that is to create "bolus+treatment" BH reference surfaces for treatment, but acquire only CBCT with TrueBeam. For that we need once again additional field at AlignRT, so finally we have four fields for 1-2)FB+BH setup without bolus, 3) for treatment with bolus and 4) for CBCT. Full arc CBCT is for example taken accordingly: once the patient is in BH (with 1mm/1° accuracy) in first isocenter BH reference surface (we name it "bolus+treatment" field in AlignRT), we perform center couch, acquire new reference surface under AlignRTs "CBCT field "and let the patient breath again. ROI must draw on the fly. CBCT is performed to that reference surface. If there is not need for small couch shifts based on that CBCT, we can (relax), restore couch and treat the patients with BH- reference surfaces that we created before imaging with bolus.

If there is need for couch shifts which exceed IGRT tolerances based on that CBCT, we are in the middle of challenges again. We need to acquire new BH reference surface in "CBCT field" after those small isocenter shifts. Then we should ask patient again to BH to that acquired BH reference surface and restore couch, patient in BH, and acquire new reference surface for the treatment in "bolus+treatment" field and let patient breath again. For the second isocenter we perform planned LAT shift, patient in BH and acquire new reference surface for the treatment, with the workflow as written in the previous reply, since the reference surface which was created before CBCT for that isocenter was not ok. Tangential image before treatment may be recommendable before treatment now from that side. Now we have updated BH reference surfaces for the treatment on both sides after isocenter corrections which exceeded IGRT tolerances based on CBCT.

Since the reference surface is taken under "bolus+treatment" field daily, there is a need to modify that ROI weekly to keep its original size and shape.

There may be other ways to do this two-isocenter VMAT DIBH with bolus, but as you assumed in some cases there is challenges and you may need to consider several things.