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0:05 So, I was asked by Brainlab about the role of the ExacTrac Dynamic System for stereotaxy, and so the topic was actually lung, liver, heart I also found a great mixture, actually just all the things I do, maybe that's why. I actually want to start with the picture, Ute has already shown it and also explained that actually on the bottom left you can see

0:34 If we use conventional fractionation and simply irradiate frequently, then you can't, I'll say, be so highly precise, because we simply have many fractions. But the higher the single dose and in our case we do a lot of one-time radiation, you really have to hit the right point and what we are most afraid of is just in the upper right that you just miss the mark.

1:01And you 've all come here to Munich today. You know, there is a fifth season in Munich, the Oktoberfest. Maybe one or the other has already been there, and what we actually like to do is that you go to the shooting range either after the marquee or before, and here also proof of very well-known stereotaxy experts.

1:29 Also with the kind company of Brainlab colleagues, here Philipp and at the shooting range, there are also, there are simple target volumes, I would say, and yet very complex ones, and if we want to make this comparison, then the simple, the so-called non-moving targets are. It's always the so-called rose shooting, you have to shoot at these white tubes or the stars, very popular when you come out of the tent and the

1:59 Image Guidance is no longer quite accurate. These goals are easier and so that you still get such a small prize or at least the roses. And if we transfer this to our stereotaxy world, then non-moving targets are primarily the brain and.

2:20 And I'll say not quite so strongly moving targets, including the spine or the prostate, where of course those, if you look at the maximum deviations, they are not so dramatic.

2:34 The supreme discipline are moving targets, so at the shooting range they are usually small rabbits or something, which then scurry past and you still have to hit them. And in fact, in stereotaxy, we also have such target volumes, and these are then mainly the lung and liver or generally the upper abdomen, which of course also includes adrenal glands or pancreas, and there we simply have the breathing movement.

3:03That means that our goal of hitting targets then becomes much more complex. And here we also have to use very, I would say, more elaborate techniques on how we can then apply the dose in the right place. There is tracking, which usually requires that markers are implanted so that it can then be tracked.

3:27And otherwise there is the possibility of a breath gating, which is usually combined with a combination, often with a Breath hold technique. Now I wanted to go through some points on the topic with you, the first question is why deep inspiration or “Breath hold” why does it make sense?

3:50As you all know, we usually do a 4D CT. That is, so that we can accurately track organ movement and thus also tumor movement. And from this we can then generate an ITV, with which we can then irradiate the entire area in which the tumor moves.

4:14And there is the point that sometimes these can simply be very, very large volumes. Here is an example from our clinic a lung metastasis and here we actually have almost 2 centimeters of craniocaudal tumor movement in this case, for example, what we can do is that we can do is a breath gating here, which means that we only ever irradiate when the tumour is in one position.

4:41 And this allows us to significantly reduce the margins and thus we can save more healthy volume.

4:53 How much is that in numbers and I found the study from Amsterdam very exciting. They compared it, they contoured GTV and then made a 10 millimeter margin just around it and compared it with an ITV concept and with a gating concept and with ITV you can halve the PTV volume, so it's 50% of this isotropic margin and with gating it's actually 33% from the PT volume.

5:23 That is, it is significantly smaller if we improve our technique of dose application and in breath gating we can take advantage of the fact that it is faster, because we can apply more dose in a shorter time, if we simply let the patient hold his breath and so that the tumor stays in a breathing position for a longer period of time and we apply the dose at the same time.

5:53 Here is an example. I was also asked  about the heart, a cardiac sarcoma a recurrence. You can see this black lump in the middle directly at the aortic outlet and here is our radiation plan: But we have a study on this, 5 * 7 Gray on the 80% isodose, and these are patients where we just want to have as little respiratory mobility as possible.

6:21 And here you can just apply a deep inspiration and then we only irradiate when the tumor is in a breathing position, when we are active in the abdomen, i.e. liver, pancreas, adrenal gland, then we often don't want to do this deep inspiration, but rather an expiration or simply we say intra Breath hold, i.e. one.

6:49 So not a very deep inspiration, but rather a lighter inspiration, which the patient can then keep as long and very stable as possible. What we do know is that no matter which technique we use, there can be great variability from day to day, i.e. from faction to faction, so that the Breath hold is not always hit accurately, so it is extremely important that we really do image guidance for each faction.

7:17 Here for liver an experience from Australia. You see here these bars of what motion management is done for liver stereotaxy and you see in blue, these are Breath hold techniques and that's exactly what goes on here until 2019, you see that.

7:34 Most of the centers here, for example, just use Breath hold and then others Free breathing with abdominal compression. But in fact, these Breath hold techniques that are used the most, here is an example from our clinic, it wasn't an adrenal gland, but adrenocortical carcinoma we also did a stereotaxy and these are patients where we just try whenever the patient can do it.

8:01 Of course, compliance must be right, then also carry out this in the Breath hold. A second and very important point is whether the surface actually correlates with our target volume, we know about breast irradiation and many know that I also have a lot of experience with SGRT, i.e. surface guidance.

8:23 There our target volume is directly on the surface and there we have an extremely good correlation and such systems work excellently there, of course. And here are the first experiences from Vienna published on the ExacTrac Dynamic System and there it is really, if you compare it to CBCT or to EPID, are they really

8:48 Very, very good results and you can probably choose the Service guidance as the sole IGRT method here. But if we are now in the lung and you have such a scan of a patient from the surface.

9:06 We don't even know how this correlates with the metastasis. It sits inside and is movable and that's of course a problem, which is with all these stereotaxis, lung, liver, all internal organs, prostate actually also counts there, and that's the way it is, there are many publications that really show, even if you do it with deep inspiration, with a method, which in the end usually only covers the surface.

9:36 Area of the patient and here, for example, pancreas SBRT, the patients were always within the gating window, for example, if you evaluate the marker position here, you can still see deviations of up to 8 millimeters comparable. There is also data from the lung.

9:56 Here was also a similar concept, they just did a before and after a CBCT and also here you saw that although the Breath hold was always reproducibly good, in 5% it was even the tumor outside of PTV, that means you have to look closely here and know exactly what to do or how to do it. And now I would like to briefly show how we do it at our clinic.

10:25 And then also what our wishes are for Brainlab and then Philipp will show what is in your roadmap at Brainlab and how we can do what might come in the future. So what is very important, we have seen before with the prostate that time is always very important. This means that the longer this takes, the more deviations you will see.

10:49 With these treatments, it's especially important because, of course, the more often the patient has to do these breath hold. They then also get tired and then it can drag on for a very long time and then you can also see more deviations, which means that it is very important that we really evaluate in the CT scan where the perfect breathing position is it reproducible for this patient and can he do it.

11:14

To do or not to do? And then you have to decide whether you can do it at all or not. And then you have to do all the imaging from planning, CT and then the CBCTs in the same breathing position. What we can already do very well

11:30

Is always before the radiation do a CBCT and see where our tumor is and adjust it. But where we don't have quite optimal tools yet is actually the intrafractional deviation, i.e. the surface is ok, but how can we check that the lung metastasis is also where I am irradiating?

11:52And that's where I think Brainlab has a big advantage, because we don't just have the surface, we also have the x-rays and that will definitely help us here in the future, so that we can also look at where our tumors are at the same time, while the patient is doing this breath hold here, for example. How do we do it now in Munich, we usually do 3 Deep Inspiration CTs on the CT

12:22In a breathing position that we, that the patient can reproduce. There are still these small deviations from Breath hold to Breath hold, we generate an ITV from it and have a bit of security with it and then we really try to make the plans in such a way that they are as effective as possible, that is, we use FFF.

12:50For the lungs especially. And just, so that we have as little MUs as possible, so that we don't need so many breath hold to apply the dose. Here is an example, this is a one-time stereotaxy, there we have with FFF it is just 590 seconds and otherwise it would be almost twice as much, so you can save a lot of time.

13:14What we do then is that we make a CBCT, of course also with breath holds. Different from what I learned today. With Varian there is an interlog to the device, with Elexta not, you have to stop it manually and continue. Most of the time you need 2 to 3 breath holds for us to do this CBCT, then we position the patient according to the tumor location and then comes the radiation.

13:43In Deep Inspiration Breath hold. Here is actually a video and you can see when the patients are very practiced, then we have patients especially those coming from the MR-linac, that's always excellent, they can hold their breath for a very, very long time, and what we're also doing now.

14:11 by the accelerator is that you do the CBCT for the repositioning beforehand and then we do an intrafractional CBCT during the irradiation, that is, we radiate and at the same time you can make a CBCT with the KV tube, which means you can look after each arc.

14:34 Whether you hit or not. But exactly, so to speak, only in retrospect. But of course you can then reposition again for the next act if you have seen that it is not optimal. In this case, this is now a real example from the clinic, we just had 3 millimeters, 1 millimeter, 0 millimeters deviation, and you could then readjust that again if you wanted.

15:04 We are shortly after Christmas. Then I brought another wish list to Brainlab while we're here, so that's exactly what I tried to summarize for myself, which would help us to really expand and optimize it in the near future. On the one hand, I don't know if it's already in planning -

15:29 Radiation in expiration. At the moment, we can only work in inspiration. I think that, especially for Abdomen, this is definitely a point that would be important for us and a very important one.

15:46 Where we would think it would be easy is that we also have the possibility, for example, that we can do marker tracking during the workflow with the deep inspiration, that you can also do marker tracking, especially if you have a gold marker in the liver, for example, then you could breath hold or just breath hold, then generate x-rays and could just see if the lesion is in the right place.

16:16 I have an example of a patient with ventricular tachycardia, we also do a one-time stereotaxy with 25 Grey.

16:28 And here is an example of positioning with ExacTrac Dynamic have also made a CBCT of course and you can see that the patients almost all have a pacemaker and that you can see the probes on the right side, for example, you can visualize it relatively well.

16:48 And here would be, for example, we did x-rays here, during the breath hold and it would be great if, for example, you could track that in the x-rays or say how much we deviate. With the heart, of course, there is also the heart movement, so it's an additional movement, which we don't usually have. Otherwise I think what will happen in the future.

17:18 Also on our wish list is that we don't need markers at all anymore and especially in the area of the lung, that while the patient is in Breath hold, for example, you can automatically see with soft tissue tracking. If it is stable, it stays where we want it to be or does the tumor go out and that you could then interact here. Summarizing here

17:45Can I say that we actually use the system a lot for very different things and that we just use intrafractional monitoring - I think that's the big advantage of the system, that we don't just have the surface, but that we will hopefully be able to see much more with the X-ray images in the future and that we can then really perform a safe stereotaxy in other parts of the body. Thank you very much.