Good question. I think this neck setup with SGRT is in the phase of progression and many hospitals are searching the best way to do it. The goal is to minimize the immobilization to make patient feel more comfortable inside the mask. Mike Tallhamer is having excellent presentation with the heading “Removing the Mask for H&N and Other Advancements in SGRT”. Please, check that video. As well, good new paper “Surface guided motion management in glottic larynx stereotactic body radiation therapy, Zhao et al 2020” handles this topic as well, from larynx RT point of view. Larynx is different target than large neck PTV and I am not handling it in my answer.
We have used AlignRT for neck patients only couple times, so my experience in practice is so far minor. We are planning to test neck setups with AlignRT in the near future anyway, after we have premeditatetly planned the entire workflow in the group.
My thoughts concerning the neck setup right now, at this point of the process, is that I would use 3 point open mask in neck RT with AlignRT, with proper support for chin and head in general (https://www.visionrt.com/technology/vision-rt-compatible/). ROI or monitoring area should not include mask material in any cases. I think it is important that patient bites the teeth naturally at the CT and treatment, to avoid from its part the displacement of the mandible, just like we do with the workflow of closed masks.
To setup the neck patient, I would go to planned couch values, which are typically acquired on the first fraction. Then I would switch AlignRT on, use faceROI (SRS brain ROI) to setup the head with AlignRT, and thereby eliminate the nodding effect of the head. This is supposed to have positive impact on mandible location accuracy in the images. Then I would use postural setup to adjust the shoulders and check the overall view of the patient around the treatment area. Then it is difficult at this point to say would I use both, either or neither cranial chestwallROI or neckROI (neck, clavicles, supsternal notch, laterally to the midcoronal plane). The latest one is suggested in the VisionRT ROI reference guide. At this point, to me it seems difficult idea to do corrections on the neck setup accurately, with the neckROI, even though it is the ROI around the isocenter. We can test this ROI with the colleaques with AlignRT, if you do not get any answers from the users that are following the VisionRT guidelines and use neckROI. In that practise, first we can acquire reference surface of our collaques head and neck, with AlignRT, and after that ask him/her to change the posture (move a little), and then try to re-setup our colleque to original posture with the aid of AlignRT with neckROI. After we are satisfied,the face ROI should be ok as well. Too difficult? May be I choose at this point 1) faceROI and 2) postural setup (shoulders and chest wall), 3) perhaps cranial chest wallROI, skip the neckROI and then go to acquire images.
During the fraction, we should typically monitor the area near isocenter, which in this case means neckROI. Still, only the location of the mandible exceeded the margin of 5 mm in the images taken after treatment in my data of closed 5 point mask patients. With neckROI mandible is not under control. With SGRT and in other hospitals with different workflows, situation can be of course different, if we can for example setup mandible to smaller residual error in the first place. Nevertheless, I would start to use faceROI for intrafractional monitoring with AlignRT and with video feature control the overall view of the patient. It would be great if we could monitor and see simultaneously two ROIs during the treatment with the AlignRT, in this case faceROI and neckROI.
One thing that you could do is to take contact on your local clinical application specialists. They can search some hospitals that are using the AlignRT system in neck treatments. Then you can discuss with the users, if they accept specialists request to discuss with you. Usually they/we do.
I hope I managed to bring something useful to you in my answer, with minimal practical experience concerning neck setup with AlignRT. I also hope that in year 2022 we have own data as an answer.
Best regards Marko