Transcript
So, Zach Seymour, I'm from the Beaumont Health System. This is a talk about our initial experience with the Brainlab system, with elements and the clinical advantages with that system. Just for an overview of this talk, we're going to talk about my clinical practice patterns, as well as the practice patterns at Beaumont, and then also our pre-launch comparative planning which we did.
And then we'll sort of work through the workflow of the elements software treating a brain metastasis patient. So just going through the relative clinical advantages of each. And just because of the length of this talk, I don't have time to go into patient selection, but if you catch me afterwards, I can talk a little bit about that because we have a little bit of a unique setup.
At Beaumont Health, we have three radiation oncology centers, we treat over 230 patients a day. We have a history of a very robust Gamma Knife program where we've treated over 330 patients per year. I'm based out of the Dearborn branch and we treat over 90 patients a day. We installed a VersaHD with ExacTrac in 2018 and we launched the element system in later part of that year. Planning for to get that system up running when our Gamma Knife went down, before we put in our Icon.
Currently, we're treating about two patients with the cranial SRS system at Dearborn campus through all the multiple metastasis element, the Cranial VMAT, and we also have a Cones application. For my clinical experience, just to get an idea of where I'm coming from, I've pretty much practiced with every single stereotactic platform possible.
Currently, I'm with the Elekta Versa HD with ExacTrac of five millimeter leaves. And then also we have a Gamma Knife Icon. Before we launched, we wanted to get just an idea of what we could do and we basically export to the last 10 patients which I treated with Gamma Knife. Just for a comparison plan to get an idea of what we were going to be able to accomplish and what we were comfortable with moving forward.
Not surprisingly, once you're moving to a gantry system, you expect good conformity regardless. And that's what we found regardless of size excellent conformity index. When we look at gradient, no matter what platform you're working with, you should expect your gradient to go up right when you're two times the width leaf. So right around a centimeter is when we saw our gradients go up.
Even though clinical relevance of that is highly questionable in the vast majority of locations. But that did provide us a strong enough argument to convince my health system to get them to acquire Cones for me. This is an example of just sort of go through a spectrum of an example cases. The first case was at 23 CC target, and we treated to 15 gray with Gamma Knife.
When we compare that to the Cranial VMAT application, similar conformity, gradient was better. And just to get an idea as we look through these comparative plans, these were the first iteration effectively of plans that basically all I asked them to do, my physicist is just to make a conformal and get the gradient as low as possible. They had no real experience before with elements or Brainlab.
So in the comparative plan is based off of treatments that were planned by myself and Anne Mates, who was the original Pittsburgh physicist, and she was there for the first, almost 20 years of their Gamma Knife program. So that gives you an idea of just the quality of the comparative plan. You're not going to find a better planner than Anne. Yet still on that with this case with minimal experience, our Cranial VMAT plan was better as far as V10 goes to the whole brain. We go to a case where we have two targets treated with the multiple metastasis application, we see very similar plan quality with regards to conformity, gradient index, obviously for the smaller target in the superior frontal lobe, the gradient is higher.
However, when we actually look at whole brain because of the quality of the conformity, which I think often gets when we start to perseverate over this gradient index, the quality of the conformity increase actually lowered our whole brain V10 substantially from 45 to 36 CCs. And then we take a plan at the sort of the extreme, where we take five targets, all small, that were treated at 20 gray one fraction with Gamma Knife. And what we see here is obviously, we would expect the gradient to go up and we have gradients anywhere from 3.6 to 10.89 with the multiple metastasis application for the Gamma Knife application. What we see is gradients that were reaching 2.6 and 3.18.
So for this, what we're actually seeing is that the general workflow that we established... If you're not familiar with a Gamma Knife treatment unit, this is pretty standard. So we basically recapitulated that when we did our frameless plan. As soon as the patient is selected, we have a work group that essentially an email is sent that then gets everything and everyone's plate as far as working with. Both administrators to make sure MRI slots, CT Sim slots are all done, that we have time set aside on the machine exactly when we would want it. And also, for the biller to obtain authorization because we don't want to have any delays between the MRI for treatment planning and delivery. So if you actually look at basically our plan of the red, would signify patient one.
So we actually even send them the week before they get treated. We get the MRI, we have set aside MRI slots. Our first MRI slot is for the evening of Sunday. So Monday when we come in, we're planning that case, and then we're delivering that patient on Wednesday. And then you work through the next patient, that would be green. We have a Sim slot, MRI slot same day, we're treatment planning in the afternoon. And then we're looking at delivering also probably Wednesday afternoon.
And then the next thing for patient three which we have patient in blue. Basically, what we're wanting is we want 48 to 72 hours between MRI and first treatment. There's a lot of data or I guess not a lot, that's probably an overstatement. There's three publications effectively that have looked at treatment time between MRI and delivery.
In one way or another, often it's been MRI to MRI comparisons, which seem to suggest between three and five days you might have a millimeter of difference. That could be simply due to distortion between two MRIs. So it's a little hard to extrapolate a clinically relevant difference. However, my data on evaluating actual workflow with clinically relevant end points, that time gets pushed all the way back to 14 days.
This was with a CyberKnife delivery system. When we looked at that, that was the only driving factor really with tumor failure was basically poor workflow management. So at 14 days, patients were more likely to recur and even there was an association with death with delays. So obviously there's probably some confounding variable there with patients who would delay treatment. However, again, you don't want to basically have a treatment that's going to provide 80% plus control and then have it dropped to 50% just because you delayed your treatment delivery.
As with regards to the actual workflow, once you obtain your MRI in Sim, this is basically a breakdown, we do our co-registration followed by image fusion. This is pretty fast, it takes 5 to 10 minutes, then we moved to contouring, your organ's at risk, as well as your target and then your object manipulation. Unless it's a very complex case, this really takes 10 to 15 minutes. And then when you're actual planning, unless you do have a complex plan that requires a nurse because we do have cones sometimes we're evaluating cross plans, what is the value of a cone, added plan versus not, that takes a little bit more time, but otherwise it's 10 to 15 minutes.
Starting with image fusion, what I really like about the element software is with regards to image fusion, the best way for me to assess, is there actual distortion in the MRI? With this it allows you to actually tilt and basically shrink in your region of interest, unlike any other fusion software which actually allows you to minimize sampling in areas of high distortion that are just inherent in your MRI.
And then if you basically do your fusion based off of that, then you can actually evaluate at the margins how much distortion you have and whether or not this is worthwhile to actually pursue. When we go to distortion correction, if you go talk to your radiologists, this is the list of everything they're going to give you. Basically, the main thing is the more systematic types of distortion, which you're going to get, which is the bottom one versus the non-linearities across a gradient field. Basically, the barrel of aberration, bow tie effect, potato chip effect, all those things basically you can summarize them by saying, you're going to have increased distortion at the edges of your field of view.
When we actually go to specific cases where we found this to be specifically a value, what we see is this was a patient that was a 62-year-old female. She had a solitary cerebellar recurrence after...it's actually a pretty complicated case. Essentially, we biopsy, she hemorrhaged. Question was, was the hemorrhage from actually the approach? Because the neurosurgeon apparently approached, withdrew and then actually got the tumor on the second stab, according to him.
So then we had hemorrhage on the post-op CT scan. How are we going to address the hemorrhage? Hemorrhage went away. We treated the residual nodule. She then recurred in the hemorrhage pattern about a year and a half later. And then we followed her for about another year and a half. And then there was some question on profusion of whether or not it was just adverse radiation effect from a second radio surgical delivery or whether or not this was really a growing nodule.
What it was is that there was only about 10% of active tumor in the specimen and what we actually decided after reviewed it with everybody and tumor board was to not proceed any additional adjuvant radiation. Three months after her surgery, she has a two-centimeter nodule sitting right in the resection cavity. So that being said, then on the MRI, we have one and a half millimeters of distortion. So that's pretty high. When we actually go and compare what does that mean for our plan? The green basically is our original MRI and distortion corrected. I'm sorry, the green is a distortion corrected. The light orange is the original MRI GTV.
And then we look at the dark orange on the PTV, which would be our one-millimeter expansion. So our one millimeter expansion seems to accommodate the degree of distortion, even though it was read as a little high. We still had good coverage of our GTV, but if you really want to make sure that you're really covering it. So we adjusted that and we actually planned for 27 gray in three fractions to the adjusted PTV.
This is another case where we had a lady who had previous whole brain radiation therapy. She had a pituitary stalk metastasis that was pushing up against her optic chiasm. When we did the MRI, this was a case that was done right after they changed the magnet and it turns out they didn't reset all the distortions. So this case sparked a conversation with our radiologists what lead to improvement in our subsequent MRIs. But what you see here clearly, right here is the optic nerve of the chiasm. That orange is actually where it was before.
So what it actually did is it pulled back into our field. So if we were going to treat that effectively, I was going to treat half of her chiasm, and potentially marginally missed the poster aspect. So we adjusted that and we actually developed a plan that met TG101 for both the corrected and uncorrected MRI. So we felt very safe delivering this treatment.
For a third case, we have extensive, or at least as I'm told by everyone who does Gamma Knife. And if that was the system, is we have extensive quality assurance on our MRI that we use for Gamma Knife plants. Turns out that we had a patient just when we were transitioning over that the frame was just too high to treat one targets, so we treated everything else with Gamma Knife. And then we're planning on moving her over to a frameless system, which we did with cranial VMAT to treat the one residual target.
Okay. What we see here is this residual target is even close to the bony surface. So even if you have any questions about the algorithm, that is real distortion. So she had 0.9 millimeters of distortion, right in the area, right where we were planning on delivering the dose. Question is how much does that matter? I mean, that's baked in the cake with all the Gamma Knife data, but it's always nice to know.
So we plan based off the distortion corrected, she is disease-free. As for contouring, I'm not going to belabor that. If you've been to any presentation with Brainlab before, they'll go through all the contouring and how easy it is, which I generally would agree with. It's great for metastasis. It's easy, you do it in the two dimension and then it generates the third dimension. It's a little bit more troublesome from irregular targets. It would be nice if there was an interpolation function. But other than that, I think the contouring application is very nice. For the auto contouring, to be honest, it gives you probably more data than you need. And really, you're ultimately usually only adjusting in worst case scenarios, one or two of the organs that they've generated for you.
Alternatively, you can import them, but again, as we've heard the other speaker, and if you're used to importing across platforms, that is something that you generally, like if you really pay attention, that happens, it's going to volumes, they're going to change it a little bit. As for treatment planning, particularly with, as we've gotten much more experienced with Cranial VMAT as we've sort of transitioned away from Gamma Knife. That's been probably one of the best systems that we've worked with, even I would say even more than the multiple metastasis element. Really the treatment planning, if you're not used to it, it just gives you what you asked for. If you're used to other planning systems where you have to do it and then you tinker, you don't really have that with this system.
And really what we have here is we initially planned... This is just based off of what I thought we could do. This is a case where there was a resection. The neurosurgeon said he got most of it. The MRI came back and there was a one and a half cm mass still sitting in there in the medial temporal lobe. So then you have to cover this like it's a resection cavity. You have to cover this like it's a tumor. So what we actually did was initially generated a plan as if we couldn't necessarily achieve everything, which is sort of what I've actually found when I've compared to other colleagues plans.
If you don't believe in the system, you're going to back away, but really what you should be doing is modulating things and making the system work. And when it does that, for instance in this case, we were able to generate a plan where were able to do 30 gray in five fractions to an SIB, to the actual residual, treat the rest of it to 25, still completely spare the optic nerve. And actually, if anything, the plan quality was just as good.
Okay. So you made it work. And this is when you're only adding a millimeter of margin, effectively, oftentimes you have a hard time increasing the actual dose within if you only have about a millimeter, if you're actually going to work and try to do SIB, but with this plan, I always want to say, you're not going to get more than 10% per millimeter. And for this plan, we were able to exceed that. So that was really nice. So if you think, well, let's say, okay, you can avoid an optic nerve, but what about if an optic nerve is nearly encased.
So this was a case of a patient where literally the tumor...this was a patient with small cell lung cancer, had whole brain radiation. Six months later, had bone only recurrence, and then she came in with optic nerve symptoms. The optic nerve was being compressed by the superior aspect that was extending outside the bone. So what we developed, actually this is a 10 fraction plan. And what we did is we integratively boost the actual gross disease to 30. We spare the optic nerve. You can actually see here that 25 dose just curves right around and just completely carves out that optic nerve. If you push it, particularly if you have a Monte Carlo, and you feel really comfortable trusting your plan, but again, excellent plan quality. And this is what sort of, if you talk to a physicist about how you adjust, those that are cranial VMAT cases with regards to the multiple metastasis planning.
If you're going to talk to a physicist about how you can adjust, let's say we're off ISO, right? Because that's the issue for almost every target we treat when we do multiple metastasis treatments, how are you going to adjust for potential mild amounts of rotation when you're delivering treatment centimeters away from meiosis center. So they'll give you this, which you don't really need to look at. The crux of it is that for each additional centimeter from ISO, you can consider adding an additional 10th of a millimeter.
So by the time you get to 46 centimeters away from ISO, you may want to add another half millimeter of PTV margin. I'm happy to talk more at length about PTV margins, because we have pretty good data in a couple of institutions that they didn't really seem to matter with delivering with the frameless treatments. So, it's a little bit of a hot topic, but if you're going to do the belt and suspenders, there it is.
So in conclusion, the clinical advantages just from our initial review is the pros of the elements software. It's easy to use. There's very little learning curve here to develop optimal radiation plans, just distortion correction, auto-generated contouring, that's easy, speed and accurate planning. And then the nicest thing about the cranial VMAT is the direct plan quality that you get. Immediately spit out that's easy to evaluate and see whether or not you need to tweak a plan. And then also not only is the delivery fast, but it's a platform that allows you to treat a lot of different things. For the cons, workflow monitoring. But that's the same as we're moving a lot of towards more fractionated delivery. That's the same with any treatment platform that you're going to do frameless, you have to monitor the platform.
If you're not, just slapping a head frame on treating the same day, then you're going to have to monitor your workflow. For cross plan comparisons, that's getting better with new versions, but it's still a little cumbersome. And then the other thing about the multiple metastasis, if you're going to do that additional margin, in order to be able to measure the distance, you have to generate the plan and then you have to go back and then you measure all your distances to then see if you need to generate another plan to add an additional half a millimeter, which can be a little cumbersome, but again planning is fast. And finally, there's just no interpolation function on the targets. Okay. Thank you.
Speaker 1: Thank you very much.
And then we'll sort of work through the workflow of the elements software treating a brain metastasis patient. So just going through the relative clinical advantages of each. And just because of the length of this talk, I don't have time to go into patient selection, but if you catch me afterwards, I can talk a little bit about that because we have a little bit of a unique setup.
At Beaumont Health, we have three radiation oncology centers, we treat over 230 patients a day. We have a history of a very robust Gamma Knife program where we've treated over 330 patients per year. I'm based out of the Dearborn branch and we treat over 90 patients a day. We installed a VersaHD with ExacTrac in 2018 and we launched the element system in later part of that year. Planning for to get that system up running when our Gamma Knife went down, before we put in our Icon.
Currently, we're treating about two patients with the cranial SRS system at Dearborn campus through all the multiple metastasis element, the Cranial VMAT, and we also have a Cones application. For my clinical experience, just to get an idea of where I'm coming from, I've pretty much practiced with every single stereotactic platform possible.
Currently, I'm with the Elekta Versa HD with ExacTrac of five millimeter leaves. And then also we have a Gamma Knife Icon. Before we launched, we wanted to get just an idea of what we could do and we basically export to the last 10 patients which I treated with Gamma Knife. Just for a comparison plan to get an idea of what we were going to be able to accomplish and what we were comfortable with moving forward.
Not surprisingly, once you're moving to a gantry system, you expect good conformity regardless. And that's what we found regardless of size excellent conformity index. When we look at gradient, no matter what platform you're working with, you should expect your gradient to go up right when you're two times the width leaf. So right around a centimeter is when we saw our gradients go up.
Even though clinical relevance of that is highly questionable in the vast majority of locations. But that did provide us a strong enough argument to convince my health system to get them to acquire Cones for me. This is an example of just sort of go through a spectrum of an example cases. The first case was at 23 CC target, and we treated to 15 gray with Gamma Knife.
When we compare that to the Cranial VMAT application, similar conformity, gradient was better. And just to get an idea as we look through these comparative plans, these were the first iteration effectively of plans that basically all I asked them to do, my physicist is just to make a conformal and get the gradient as low as possible. They had no real experience before with elements or Brainlab.
So in the comparative plan is based off of treatments that were planned by myself and Anne Mates, who was the original Pittsburgh physicist, and she was there for the first, almost 20 years of their Gamma Knife program. So that gives you an idea of just the quality of the comparative plan. You're not going to find a better planner than Anne. Yet still on that with this case with minimal experience, our Cranial VMAT plan was better as far as V10 goes to the whole brain. We go to a case where we have two targets treated with the multiple metastasis application, we see very similar plan quality with regards to conformity, gradient index, obviously for the smaller target in the superior frontal lobe, the gradient is higher.
However, when we actually look at whole brain because of the quality of the conformity, which I think often gets when we start to perseverate over this gradient index, the quality of the conformity increase actually lowered our whole brain V10 substantially from 45 to 36 CCs. And then we take a plan at the sort of the extreme, where we take five targets, all small, that were treated at 20 gray one fraction with Gamma Knife. And what we see here is obviously, we would expect the gradient to go up and we have gradients anywhere from 3.6 to 10.89 with the multiple metastasis application for the Gamma Knife application. What we see is gradients that were reaching 2.6 and 3.18.
So for this, what we're actually seeing is that the general workflow that we established... If you're not familiar with a Gamma Knife treatment unit, this is pretty standard. So we basically recapitulated that when we did our frameless plan. As soon as the patient is selected, we have a work group that essentially an email is sent that then gets everything and everyone's plate as far as working with. Both administrators to make sure MRI slots, CT Sim slots are all done, that we have time set aside on the machine exactly when we would want it. And also, for the biller to obtain authorization because we don't want to have any delays between the MRI for treatment planning and delivery. So if you actually look at basically our plan of the red, would signify patient one.
So we actually even send them the week before they get treated. We get the MRI, we have set aside MRI slots. Our first MRI slot is for the evening of Sunday. So Monday when we come in, we're planning that case, and then we're delivering that patient on Wednesday. And then you work through the next patient, that would be green. We have a Sim slot, MRI slot same day, we're treatment planning in the afternoon. And then we're looking at delivering also probably Wednesday afternoon.
And then the next thing for patient three which we have patient in blue. Basically, what we're wanting is we want 48 to 72 hours between MRI and first treatment. There's a lot of data or I guess not a lot, that's probably an overstatement. There's three publications effectively that have looked at treatment time between MRI and delivery.
In one way or another, often it's been MRI to MRI comparisons, which seem to suggest between three and five days you might have a millimeter of difference. That could be simply due to distortion between two MRIs. So it's a little hard to extrapolate a clinically relevant difference. However, my data on evaluating actual workflow with clinically relevant end points, that time gets pushed all the way back to 14 days.
This was with a CyberKnife delivery system. When we looked at that, that was the only driving factor really with tumor failure was basically poor workflow management. So at 14 days, patients were more likely to recur and even there was an association with death with delays. So obviously there's probably some confounding variable there with patients who would delay treatment. However, again, you don't want to basically have a treatment that's going to provide 80% plus control and then have it dropped to 50% just because you delayed your treatment delivery.
As with regards to the actual workflow, once you obtain your MRI in Sim, this is basically a breakdown, we do our co-registration followed by image fusion. This is pretty fast, it takes 5 to 10 minutes, then we moved to contouring, your organ's at risk, as well as your target and then your object manipulation. Unless it's a very complex case, this really takes 10 to 15 minutes. And then when you're actual planning, unless you do have a complex plan that requires a nurse because we do have cones sometimes we're evaluating cross plans, what is the value of a cone, added plan versus not, that takes a little bit more time, but otherwise it's 10 to 15 minutes.
Starting with image fusion, what I really like about the element software is with regards to image fusion, the best way for me to assess, is there actual distortion in the MRI? With this it allows you to actually tilt and basically shrink in your region of interest, unlike any other fusion software which actually allows you to minimize sampling in areas of high distortion that are just inherent in your MRI.
And then if you basically do your fusion based off of that, then you can actually evaluate at the margins how much distortion you have and whether or not this is worthwhile to actually pursue. When we go to distortion correction, if you go talk to your radiologists, this is the list of everything they're going to give you. Basically, the main thing is the more systematic types of distortion, which you're going to get, which is the bottom one versus the non-linearities across a gradient field. Basically, the barrel of aberration, bow tie effect, potato chip effect, all those things basically you can summarize them by saying, you're going to have increased distortion at the edges of your field of view.
When we actually go to specific cases where we found this to be specifically a value, what we see is this was a patient that was a 62-year-old female. She had a solitary cerebellar recurrence after...it's actually a pretty complicated case. Essentially, we biopsy, she hemorrhaged. Question was, was the hemorrhage from actually the approach? Because the neurosurgeon apparently approached, withdrew and then actually got the tumor on the second stab, according to him.
So then we had hemorrhage on the post-op CT scan. How are we going to address the hemorrhage? Hemorrhage went away. We treated the residual nodule. She then recurred in the hemorrhage pattern about a year and a half later. And then we followed her for about another year and a half. And then there was some question on profusion of whether or not it was just adverse radiation effect from a second radio surgical delivery or whether or not this was really a growing nodule.
What it was is that there was only about 10% of active tumor in the specimen and what we actually decided after reviewed it with everybody and tumor board was to not proceed any additional adjuvant radiation. Three months after her surgery, she has a two-centimeter nodule sitting right in the resection cavity. So that being said, then on the MRI, we have one and a half millimeters of distortion. So that's pretty high. When we actually go and compare what does that mean for our plan? The green basically is our original MRI and distortion corrected. I'm sorry, the green is a distortion corrected. The light orange is the original MRI GTV.
And then we look at the dark orange on the PTV, which would be our one-millimeter expansion. So our one millimeter expansion seems to accommodate the degree of distortion, even though it was read as a little high. We still had good coverage of our GTV, but if you really want to make sure that you're really covering it. So we adjusted that and we actually planned for 27 gray in three fractions to the adjusted PTV.
This is another case where we had a lady who had previous whole brain radiation therapy. She had a pituitary stalk metastasis that was pushing up against her optic chiasm. When we did the MRI, this was a case that was done right after they changed the magnet and it turns out they didn't reset all the distortions. So this case sparked a conversation with our radiologists what lead to improvement in our subsequent MRIs. But what you see here clearly, right here is the optic nerve of the chiasm. That orange is actually where it was before.
So what it actually did is it pulled back into our field. So if we were going to treat that effectively, I was going to treat half of her chiasm, and potentially marginally missed the poster aspect. So we adjusted that and we actually developed a plan that met TG101 for both the corrected and uncorrected MRI. So we felt very safe delivering this treatment.
For a third case, we have extensive, or at least as I'm told by everyone who does Gamma Knife. And if that was the system, is we have extensive quality assurance on our MRI that we use for Gamma Knife plants. Turns out that we had a patient just when we were transitioning over that the frame was just too high to treat one targets, so we treated everything else with Gamma Knife. And then we're planning on moving her over to a frameless system, which we did with cranial VMAT to treat the one residual target.
Okay. What we see here is this residual target is even close to the bony surface. So even if you have any questions about the algorithm, that is real distortion. So she had 0.9 millimeters of distortion, right in the area, right where we were planning on delivering the dose. Question is how much does that matter? I mean, that's baked in the cake with all the Gamma Knife data, but it's always nice to know.
So we plan based off the distortion corrected, she is disease-free. As for contouring, I'm not going to belabor that. If you've been to any presentation with Brainlab before, they'll go through all the contouring and how easy it is, which I generally would agree with. It's great for metastasis. It's easy, you do it in the two dimension and then it generates the third dimension. It's a little bit more troublesome from irregular targets. It would be nice if there was an interpolation function. But other than that, I think the contouring application is very nice. For the auto contouring, to be honest, it gives you probably more data than you need. And really, you're ultimately usually only adjusting in worst case scenarios, one or two of the organs that they've generated for you.
Alternatively, you can import them, but again, as we've heard the other speaker, and if you're used to importing across platforms, that is something that you generally, like if you really pay attention, that happens, it's going to volumes, they're going to change it a little bit. As for treatment planning, particularly with, as we've gotten much more experienced with Cranial VMAT as we've sort of transitioned away from Gamma Knife. That's been probably one of the best systems that we've worked with, even I would say even more than the multiple metastasis element. Really the treatment planning, if you're not used to it, it just gives you what you asked for. If you're used to other planning systems where you have to do it and then you tinker, you don't really have that with this system.
And really what we have here is we initially planned... This is just based off of what I thought we could do. This is a case where there was a resection. The neurosurgeon said he got most of it. The MRI came back and there was a one and a half cm mass still sitting in there in the medial temporal lobe. So then you have to cover this like it's a resection cavity. You have to cover this like it's a tumor. So what we actually did was initially generated a plan as if we couldn't necessarily achieve everything, which is sort of what I've actually found when I've compared to other colleagues plans.
If you don't believe in the system, you're going to back away, but really what you should be doing is modulating things and making the system work. And when it does that, for instance in this case, we were able to generate a plan where were able to do 30 gray in five fractions to an SIB, to the actual residual, treat the rest of it to 25, still completely spare the optic nerve. And actually, if anything, the plan quality was just as good.
Okay. So you made it work. And this is when you're only adding a millimeter of margin, effectively, oftentimes you have a hard time increasing the actual dose within if you only have about a millimeter, if you're actually going to work and try to do SIB, but with this plan, I always want to say, you're not going to get more than 10% per millimeter. And for this plan, we were able to exceed that. So that was really nice. So if you think, well, let's say, okay, you can avoid an optic nerve, but what about if an optic nerve is nearly encased.
So this was a case of a patient where literally the tumor...this was a patient with small cell lung cancer, had whole brain radiation. Six months later, had bone only recurrence, and then she came in with optic nerve symptoms. The optic nerve was being compressed by the superior aspect that was extending outside the bone. So what we developed, actually this is a 10 fraction plan. And what we did is we integratively boost the actual gross disease to 30. We spare the optic nerve. You can actually see here that 25 dose just curves right around and just completely carves out that optic nerve. If you push it, particularly if you have a Monte Carlo, and you feel really comfortable trusting your plan, but again, excellent plan quality. And this is what sort of, if you talk to a physicist about how you adjust, those that are cranial VMAT cases with regards to the multiple metastasis planning.
If you're going to talk to a physicist about how you can adjust, let's say we're off ISO, right? Because that's the issue for almost every target we treat when we do multiple metastasis treatments, how are you going to adjust for potential mild amounts of rotation when you're delivering treatment centimeters away from meiosis center. So they'll give you this, which you don't really need to look at. The crux of it is that for each additional centimeter from ISO, you can consider adding an additional 10th of a millimeter.
So by the time you get to 46 centimeters away from ISO, you may want to add another half millimeter of PTV margin. I'm happy to talk more at length about PTV margins, because we have pretty good data in a couple of institutions that they didn't really seem to matter with delivering with the frameless treatments. So, it's a little bit of a hot topic, but if you're going to do the belt and suspenders, there it is.
So in conclusion, the clinical advantages just from our initial review is the pros of the elements software. It's easy to use. There's very little learning curve here to develop optimal radiation plans, just distortion correction, auto-generated contouring, that's easy, speed and accurate planning. And then the nicest thing about the cranial VMAT is the direct plan quality that you get. Immediately spit out that's easy to evaluate and see whether or not you need to tweak a plan. And then also not only is the delivery fast, but it's a platform that allows you to treat a lot of different things. For the cons, workflow monitoring. But that's the same as we're moving a lot of towards more fractionated delivery. That's the same with any treatment platform that you're going to do frameless, you have to monitor the platform.
If you're not, just slapping a head frame on treating the same day, then you're going to have to monitor your workflow. For cross plan comparisons, that's getting better with new versions, but it's still a little cumbersome. And then the other thing about the multiple metastasis, if you're going to do that additional margin, in order to be able to measure the distance, you have to generate the plan and then you have to go back and then you measure all your distances to then see if you need to generate another plan to add an additional half a millimeter, which can be a little cumbersome, but again planning is fast. And finally, there's just no interpolation function on the targets. Okay. Thank you.
Speaker 1: Thank you very much.