Surface Guided Respiratory Gating with AlignRT’s Respiratory Module and DIBH for SABR lung

Kyle Noyce (00:04):

At Poole, we have four TrueBeam’s. There are three at the Poole site and one at the satellite center. And we got the Respiratory Module sort of at the beginning of this year and we’ve been sort of using it to try to find another avenue for patients that don’t fit our sort of existing motion management. So at the moment we can only, we don’t have any other motion management options other than essentially breath hold or an ITV to include the motion. So I think it might be and so we were sort of looking at what options we had for alternatives. And so for our existing pathway for the SABR breath hold for SRE breath hold patient for lungs, we used the MRT for doing the 4D CBCT. And it has a very similar sort of interface as the Respiratory Module for placing a sort of virtual patch on the patient and monitoring their trace to make sure that they’re happy that it’s an appropriate one.

Kyle Noyce (01:18):

And as you can see, we for breath holds patients. We do a 3D, CBCT breath hold, CBCT and 4D CBCT. So, and that’s just in case, you know, the patient can’t, isn’t able to do, you know, we do a lot of checks when they’re at the CT scan to make sure they’re appropriate for breath hold, but it might be that they come for treatment and there’s some issue and we need to switch them back. So we do the four D and the 3D as well just in case. So, currently we’ve treated eight SRE patients in breath hold. Well, we scanned eight patients in breath hold. Six of them were managed to treat and two of them we weren’t. And that’s because they breath hold doesn’t seem to work with everyone. So we got the PTB here and then this is where the tumor was when they were in breath hold and their diaphragm is obviously wildly different.

Kyle Noyce (02:18):

And we found that basically what the issue we were having was certain patients, if they don’t, there’s not a large amount of chest movement when they take their breath. If there’s, it’s mostly diaphragm movement, then the SRT can’t you know, if there’s only one or two mils of chest rise with that breath. The SRT essentially isn’t, can’t give you the information between the difference between what their free breath and what their breath hold is because all the motion is in their diaphragm. And so with this patient, you, you switch to the breath-hold surface, get the patient to breathe up, and nothing’s in the right place. So, so we, so for those patients that aren’t able to achieve the breath hold or can achieve a breath hold, but we couldn’t get it in a consistent place, we thought, well, the next stage is obviously gating to find the next solution for it.

Kyle Noyce (03:20):

So so what we were doing, we were looking at different solutions for that, and what are the options we have for gating? So at the moment, we just use the backup gating. So we just set certain tolerances on the altitude. After we’ve killed the patient’s trace, we only do a 3D cone beam and we just do this as a check to make sure that the patient is breathing larger than they’re supposed to be. But we want to move towards a phase or amplitude-based gating where we do a 4D CBCT and we can move in a specific part of the patient’s breathing phase. So the options we had when we were looking at it were either using the variant solution, but you know, it has its issues with, you know, you have to have the physical block and depending on the size or shape or position of the patient, where you position it, it can cause an issue with that. And it’s not the most user-friendly UI that we’ve seen. So instead we decided and colleague Josh, who’s been working on the commissioning of the Respiratory Module. So we thought, well, we’ll give that a go and see, see how we find it. And, as you can see, it’s very similar to the current SGRT system. And now I’m going to pass on to Chloe, who has been using it and give us some examples.

Chloe Westlake-Allen (04:53):

Hello everyone. I’m going to talk about how we go through the Respiratory Module on the machine that we are currently using. So as you see, it is the same as what you would normally see with using AlignRT. And this is the Respiratory Module just here. And what we do to begin with is that we set the patient up like normal in what we do in Poole. So we get the patient in position and then we go forward with making sure that they’re all intolerant. And then once we’re happy, we leave the room, and we do everything out in the control room. First of all we might put the gantry to 180 so it doesn’t block any of the cameras when we’re doing the capture for the gating. And then once that happens, we have the sign with editing the patch and usually it likes to be below this. I think it likes a bit of stability with the breathing and also it likes the breathing as well. So I feel like that’s a good sort of reference mark. And also it should be placed where the breathing was captured at CT as well.

Chloe Westlake-Allen (06:29):

We then click on the patch just here and that will start learning the trace, which is the dotted line. And then once it learns the breathing cycle of the patient, it will become a solid line like this. And then once that happens, we will set the threshold parameters of the amplitude just here, which will be shown on the next slide. And then we will go forward with

Chloe Westlake-Allen (07:03):

So that what does it look like in real time. So you can see here is that it’s learning it and then it’s just happy with the breathing. And as you can see it’s all intolerance here. And then that will set the parameters. So we, at the moment, we’ll do above the breathing cycle and then below and this will be adjusted to what you would like it to be. So we are doing the amplitude of the breathing rather than the phase. And then once that happens, we will then click on beam control and then carry on with the CBCT. Down here you will see the different colors. This is just within, so if you go back, go

Chloe Westlake-Allen (08:06):

Back, there we go.

Chloe Westlake-Allen (08:09):

So if you see here, this is when the, within the thresholds and then the other one is when it’s a little bit lighter with the yellow color and that is when the beam is on. And that would be the same principle. Once we do the CBCT, it’ll be once that’s learned that patch, you don’t have to do it again, it can go straight towards treatment and you don’t have to do the patch. It’ll just have learned where the patch is and you’ll have to retrace and relearn that breathing pattern before you do the treatment. At the moment, we are not doing the abnormal breathing, so it’s just this little lung button here and we just turn that off and that will be for the future, sort of next thing that we’re going to be doing. And so the considerations of doing this Respiratory Module are that the SGRT does not interlock with the CBCT on TrueBeam. So whilst we do the CBCT, it would just carry on. So even when that happens, as long as you’re looking at the video function and saying that they’re not com moved completely I think that’s kind of roughly as okay. And then when we go onto the treatment side of things, that will stop the beam. It’s not compatible with the 4D CBCT on TrueBeam as well. So

Chloe Westlake-Allen (09:48):

This will just be the next thing we’ll be doing in the future. And as I said before, you have to re relearn the trace every single day so it’s not a one-and-done thing. For us in the LINAC that we’re using it on, it doesn’t actually take, take too much time of the day within the treatment times that we have for patients. And then we also have to consider the patch position as well. This can change, you can change the patch wherever you think the patient is best for the patient. Sometimes that can be a little bit difficult with body size and the wrong position as well. So if people have a bigger stomach and it might be a slope or something that can change the position, and it might pop up with a sign saying it’s not really happy with it, so we just have to trial and error with the patch.

Chloe Westlake-Allen (10:49):

The camera that we use for the Respiratory Module is the central one, so that is just learning from the, from that one. And so again, with the patch and the camera, it has to be visible where the patch can see it, so then it can trace the breathing cycle. So it has to be in the correct position. What’s next? As I said previously, we’ll be using 4D CBCT and then we’ll be able to use more of it, with the Respiratory Module and hopefully get more patients with that and begin exploring further uses of the abdominal breathing at function because we’ve turned that off at the moment so we’re not using that one. And then we are going to use the phased gating Respiratory Module as well. Any questions.