The Role of SGRT for Online Adaptive SBRT Treatments Using AlignRT InBore on Ethos Linacs

George (Guang) Li (00:04):

It is my pleasure to share the experience with you today about our adaptive treatment using AlignRT as a system. So basically, we try to use the AlignRT to maximize the reproducibility for the SIM position, so therefore, the adaptation needs is reduced. So that’s number one thing. The second thing is we try to monitoring the patients throughout, even though from outside, so we can control the patient. It doesn’t move with out of the tolerance.

George (Guang) Li (00:51):

Okay, so a little bit background, so many of you already knows ISO system. ISO system is AI based adaptive treatment platform. So this system equipped with the AlignRT InBore system. So InBore system is a it’s different from a regular AlignRT advanced system. So they have external camera system is very much the same as AlignRT advanced system. But they aim at so-called SIM simulation ISO. So where is a user origin when you do the simulation? And then the camera, of course, gave you a 60 degree freedom. However, the ISO couch at least right now is only provided three degree freedom motion. Therefore, the AlignRT has advantage to offer us to control the patient rotation before we load the patient into the bore.

George (Guang) Li (02:03):

Also, the second part of the AlignRT InBore system is ring system, which is mounted on the cover of the board inside. So it contains two camera systems. So basically external, they have a three camera, but InBore they have a two. Because of this attachment to the Bore cover is very throughout. And so we set not robust. It’s like a spring-loaded over system. So at the New York state, we have a regulation to do the collision check every day before treatment. Therefore it is a very difficult to pass AlignRT daily QA and do the collision, because collision, you need to move the board cover about a cm or more. Therefore they will kick off the tolerance. We reported this approach last meeting in Phoenix. So we have developed a way to deal with this kind of thing. Now, we are successfully use AlignRT and then pass the data QE without any problem. So if you are interested, you can look back to the last year’s plantation.

George (Guang) Li (03:33):

Okay. So at MSK, we are treating the adaptive patient first on the prostate patient with nose involvements. So these are the prescription the either treated with post brachy or without brachy. So for the adaptive approach, we use AlignRT because we simul with first go through regular simulation process. We have a simulation city, and then we do the adaptive planning on the Ethos system. And then we use the sim city external counter as a reference to set up patient. And then we use extended CBE city using the acro reconstruction algorithm, which provides very high quality images. So later on, you can see we can not only build the adaptive plant on this CBE city, but also later on when we do the data analysis, we can use our AI based auto segmentation to do all this planning city online adaptive planning city and also intro fraction city. So, and then we can compare how the internal organ moves during the treatment delivery. Of course, we’re using AlignRT real-time margin monitoring at the PTB margin with a three millimeter safety margin. So this is relatively tight, and then later on we can show you how we can get this margin, and then the data will show that this is the truly optimal date margins we can use. And then do, I said during the treatment, we acquire intra fractional CBCT just to monitoring not only from external, but also internal.

George (Guang) Li (06:08):

So the detailed workflow is such. And then we haveinitial planning and then we using the AlignRT to set up patient, so therefore the maximize the reproducibility of the patient position. And then we achieve rotation correction, so on the 3D couch. And then, of course, we’re using the ICBCT, extended ICBCT to do the planning. And then we do the online with the physician. So we have to do the counter adjustment and then approve the plan through the QA and so on, and motion monitoring throughout. And then there’s three CBCT intra fractionally. And then after treatment, we will do the patient basically QA for every fraction, because for the new procedure at MSK, we always does this. So just make sure everything is as expected.

George (Guang) Li (07:21):

Okay, here is summary. What’s the stage? So they’re basically initial planning, adaptive planning, and then adaptive delivery. It,

George (Guang) Li (07:32):

So to prepare AlignRT. So, Ethos system does not provide a direct export filter to AlignRT system. However, it does provide a channel to export to eclipse system. So that’s we go through eclipse system, and then in the eclipse system, we recreated the simulation ISO with the BBs on the patient. And then also apply the third culture shift, which is required. I mean, in one instance, if one planner forgot about apply this, and then we got really in trouble at treatment because later on, you can see a simulation ISO and treatment iso, they’re far apart. If there’s more than two cm EO system cannot handle it. They just, no matter what you do, they just don’t create a reasonable map for planning. Therefore for that particular fraction, we have to use the original plan to deliver that actionable treatment. And then later on, we figure out what’s wrong with that. So yeah, so like I said, the DCS is required. Otherwise, you can have a lot of problem. So AlignRT’s function is just try to reproduce the patient position at least from external. Therefore, everything should be minimized and also overcome this 3D OF culture limitation. And then we monitor during the adaptive planning, and then we monitoring throughout the treatment.

George (Guang) Li (09:37):

Okay. Here is what withdrawal look like. Basically, they cover the thigh and also the hip part, and then the, the belly part will draw very low, just avoid the breathing motion. But even that, you can see later on with the video that we can still see the breathing motion there. And then hopefully, yeah, so you can see that middle, the right part means the patient breathing higher than the reference. The green means they’re within plus or minus three millimeter tolerance. So you can see this happens periodically. And then we set a tolerance of pretty small for therapies to set up patient. However, we still push them to get almost zero difference between the reference and the onsite. The reason is, so if you don’t align from outside well enough internally, you’re going to see a lot of more differences. So that’s a driver because we did another study on the head and neck, and then we, we found the near zero shift in all 6 DOF is a must to infer what happened internally. So this is what we were asking our therapists to do.

George (Guang) Li (11:23):

This is picture pictures borrowed from AlignRT website. So basically, in the SGRT setup process, we are using this poster video mode to guide the align the body parts. So yesterday, many speaker already talk about these wonderful features. I think this is very useful and to, especially while you are far away from the treatment position, this will provide guidance because at that time, the two, the current position and the treatment position are too far away. Registration doesn’t kick in yet, so this is only guidance you can use to move the patient to the treatment position. So this is step number one. And then, like I said, once we close, we correct the rotation first and then apply the culture shift to deal with the translation. And this point, we ask the therapist to get almost zero shift.

George (Guang) Li (12:35):

And then we turn on the defamation view because the body part we’re dealing with is deformable, especially with the side in there. So the top graph shows the leg is too high. So why we bother to look at the leg, because even though that is not part of a treatment, because the leg position difference will affect the spine curvature. So if you lower the leg, the spine will be in a different shape, and then that’s where the prostate nose located. Okay, so after correct the leg, then we can get the defamation under control. And then basically we ask for like a three quarter of surface or in the green zone. So that means plasma minus three millimeters. We don’t want to see the systematic red or blue showing on the surface displacement. So if that does, that means they have still have something to improve before they move on. And then after all this done, they can load the patient into the bore.

George (Guang) Li (14:00):

Yeah, so this is just controlling the deformation with the first to control the body rotation. And this pretty much a summarize what I just described for the three steps of for the procedure. And this is two instance. Just give you an example of what actual patient set up on the AlignRT display look like. And, as I said, which we asked them to achieve like three quarter ring. I think this AlignRT system offer this deformation control is very unique and very useful features for many sites. We have done this for the prostate, we have done for the extremity, and also for head and neck. So many parts deformation view could help the therapist to adjust the patient’s position. They know where to adjust, and then they give you real time feedback in the room. So everything can be done within seconds. So basically, this is wonderful together with the Postural video view they can pretty much control all kinds of deformation you may encounter.

George (Guang) Li (15:32):

Okay. So this will give you two examples. One is the first patient we treated is fracture number two, and then the fifth patient we treated fracture number four. So this is RTT process monitoring the entire treatment process. At the very beginning, we’re using SGRT setup to just to adjust the patient rotation and correction, all those kind of things. And after we load the patient into, and then we acquire the extended city because extended Cone Beam CT require culture movement. So that’s why you see the square plateau on the longitudinal directions. And then after the planning the later on time is adapt the planning process. At the beginning it take about half hour and now reduce to like two third of that. And then during this both time planning time and delivery time, we do motion monitoring. Of course we also acquire cone beam every three beam. And then we will, so this is a zoom for the treatment delivery time. So you can see there’s some periodic motion. So that’s because the breathing motion, the on the belly part so we don’t worry about that because that’s it’s a periodic. That doesn’t mean the patient move out tolerance. As long as the baseline of the curve remains steady. We’re okay with this. The patient. Number five, hypo more involved was the bracing motion.

George (Guang) Li (17:30):

So last time when we studied the internal fractional int fractional Cone Beam CT, we, we tried to check the organ motion during treatment. So based here, we’re using AI-based contouring. The reason we do this is ai, it doesn’t give you the bias from the inter or intra observer variation the pretty robust. And then in fact, this AI algorithm is applied in our clinic in the routine. And then we count toward a bladder rectum, and the prostate on the nose. You can see the, the bladder keep growing during treatment. Fortunately, they’re moving in the anterior and then superior direction and also a little bit laterally. They don’t change the process shape and then doesn’t affect the nose. And then we did a contour for all infraction Cone Beam CT. And then there the contour overlay to each other. You can see there the bandwidth for the overlay contour on the interface between the bladder and the prostate is about three millimeter. So that’s is very consistent with the planning margin we used.

George (Guang) Li (19:26):

Lastly, we did aN analysis about these kors to see how much agree each other. So first is mean distance agreements are MDA. So this shows on the left side of the table, it’s about a roughly two millimeter and so on. And then also we did a INE index. They are about 0.8 for prostate and 0.9 for the dose. The more sensitive for the prostate because the smaller, you know, the dice index is sensitive to the size of the organ you are evaluating. So

George (Guang) Li (20:22):

In conclusion, the SGRT is necessary for online adaptive treatment, especially for the SBRT case. So we have a few fraction only five fractions. So there’s ensure the PDV margin of three millimeter is secure during treatment delivery because the motion monitoring and then so on, they tell you whether we’re out of tolerance. And then the SGRT workflow is very useful. And then we have a 1, 2, 3 steps. SoI think this is a good start for many sites. We will follow the anxiety procedure for deformation control. Basically, I think this is one of the new direction using AlignRT guided patient set up to control the body deformation. And so far we’re treated about a dozen such patients. And then we’ll keep using this for this and other sites.