Radiology: Pectus Innovations

with, uh, presenting, um, a case that may just sort of, uh, get us warmed up and get us, uh, on, on track to see how we sort of approach things, uh, as far as the preoperative assessment and workup of a child with a pectus excavatum, um. So, um, as a case presentation, this was a case of Doctor Garcia's. It's a 13-year-old male, uh, who presented with a, uh, pectus excavatum, uh, that was noted 2 years, uh, prior, uh, and he presented with significant exercise intolerance. Uh, the defect, as well as his symptoms were progressively worsening. He was a very tall, thin, you know, hyper flexible, uh, young man. And so, um, as part of the, uh, workup, uh, which is pretty what we would normally do, uh, we, uh, started with a cardiac MRI and, uh, Doctor Taylor's gonna talk about this as well as Doctor Crotty about, um, the significance of why we do cardiac MRI as opposed to other modalities. And, uh, this, uh, child's cardiac MRI showed a Haller index of 4.8, uh, with some cardiac compression but had normal anatomy and function. Um, he subsequently, uh, because of his body habitus and hyperflexibility, uh, was referred to genetics, uh, for further evaluation. Um, it's interesting he never actually did that, uh, and that'll come into play later as we look at how that can manifest as some chronic pain and issues after surgery. Uh, but he was referred to allergy for me allergy testing, which we do in every patient and was found to have allergies to nickel as well as vanadium. And therefore he underwent the Nest procedure. He had two titanium bars because of his nickel allergy, had a stabilizer on each bar, but he did have chronic pain postoperatively 2 years out. The bars are still in place, and he's been referred once again to genetics for workup for his connective tissue disorders, which may be contributing to some of his chronic pain. So just as a, a case presentation to sort of get us started and um I was gonna have Doctor uh Crotty now just uh start to comment on uh the MRI and uh radiology evaluation. Thank you, Becky. Um. So just want to get the first slide up here. Um, Right, so essentially, um, you know, People often ask you, how do we, uh, preoperative assess, uh, patients with pectus escovatum as regards, uh, candidates, uh, their candidacy for, um, operation, and, uh, I suppose bottom line is we've moved away from CT and now do MRI. Um, we find that obviously first of all, it's a, uh, uh, it's a more comprehensive examination and Doctor Taylor will talk a little bit about the. Uh, the cardiac function side of it, and I'll discuss more of the anatomical features that we, we evaluate these patients for, uh, during these studies, um, as a background, you know, why we changed to MR initially, uh, when, when we started thinking about it, we were, there was a heightened awareness, I think, in general on the, uh. Long term effects of CT dose and part of our training as radiologists is to try to adhere to the AAA principle, which is where you use as low as reasonably achievable as regards the amount of radiation that you use. So we're trying to get away from CT studies which use radiation to non-radiation studies, and MR seemed to be the most likely candidate for that. Just a background, we were using quite low doses for our CTs anyway. We were trying to use just one slice imaging at the lowest depression on the chest. Uh, but you know, depending on where you, you have your study done, uh, some places can use very, very high doses, including scanning the entirety of the chest. So, uh, we undertook a study initially to see whether we could replace MR with CT. There was an internal study, and we found that the, the measurements were, were very, very comparable or were exactly the same essentially between MR and CT. So we knew technically. could replace a CT, but we also looked at what when was the best time to image these patients. Was it at end inspiration, which is traditionally when we would perform a CT imaging, versus end expiration, or whether just just during quiet respiration, and that was prompted by the fact that we had a number of patients who Uh, I had obvious pectus deformities on clinical examination, but when they came to CT or imaging, they, their holler index was actually normal, and we couldn't quite understand why that was. And it turns out there are a couple of reasons. One was, uh, as we saw in the study that we did, that when you, uh, depending on the phase of respiration, you can actually alter. What your Haller index turns out to be, so we had quite a substantial or significant number of patients whose Haller indexes were abnormal at end exploration but were actually turned out to be normal even though they had a clinical. pectus excavatum when you did it at and inspiration. Um, so the, the indices now that we, um, obtain when we do our studies are the Haller index, which is the standard, uh, uh, measure, uh, that's, uh, kind of the, uh, the gold standard really for measurement of pectus excavatum. We also use a correct correction index, uh, depression index, and we also supply the sternal tilt or the, the angulation of the sternum relative to the horizontal plane, um. And so to get the Haller index, you've probably all done this. This is just the you take the The transverse diameter and divide that by the AP diameter, so from the posterior aspect of the sternum back to the anterior aspect of the vertebral body, divide that into the transverse diameter of the chest, and you know, Haller found that patients who had a Haller index of greater than 3.25 were ones that he operated on. Uh, however, as I said, we found a number of patients that did not quite fit those criteria. Uh, so we looked for other indices, and we now, we now also include the, the correction index. Was there, was there some reason that Alec Hauer came up with, is that just, was that an arbitrary number that he came up with, or was there a scientific reason that he came up with that number? Uh well, I don't think it was very scientific. I think it was more of an observational. thing he kind of looked at the number of the patients that he had performed in his surgery on and kind of came up with this number. It wasn't a rigorous scientific study, but I think, I don't think he ever claimed that it was either. It was kind of an observational study that he said needed further. Uh, assessment and read that further assessments never really has never really occurred and we still use, we still use it so it was not a prospective study, it was just a retrospective as I mentioned and the insurance companies just latched onto it, right, uh, which is one of the reasons why we're sort of looking at that prospectively here, OK. Thank you. And so actually the people who did the study for the correction index found that there was a very, very large overlap between patients who had normal uh uh. Uh, chests and also patients with pectus excavatums as regards the Haller indices Haller index. So, you know, essentially you could have normal patients who had technically an abnormal Haller index, even though they did not have pectus excavatum and vice versa. You could also have patients with a uh with a pectus excavatum who turned out to have Haller in normal Haar indices as we had seen ourselves. Uh, so the, the correction index, essentially what it does is tries to um. Give you a percentage of the depth of the stern sternal depression and how much it needs to be elevated to make the chest more of a normal configuration, and that study found that there was no overlap between normal and abnormal patients when if you use a measurement of greater than 10%. And the third index that we use is the depression index, which tries to take away the shape, the variable shape of the patient. So whether you have a barrel-shaped chest or you have a more of an elliptical type chest, your depression index should be abnormal if you have if you have a pectus excavatum, and they found that a greater than 0.2 was their cutoff between normal and abnormal patients. And just from their paper actually they had a very nice example here of a of a person, a patient on the left has a circular chest and the patient on the right has more of an elliptical type chest, and you can see there the holler index actually turns out to be normal on the patient on the left hand side of the screen, even though they obviously have a pretty significant pectus deformity and that's simply because of their. The shape of their chest, they have a relatively barrels shaped chest, I suppose, whereas the patient on the right has more of an elliptical shaped chest and has a has a grossly abnormal hallar index. And you can see there on those other two patients, even though, the patient on the left hand side, even though the Haller index is normal, both their correction index and their depression index are abnormal. Kind of demonstrating, I think again what we've seen in our observation that the shape of the chest can affect your Haller index. So Haller index may not be the most reliable or the most accurate way of determining whether somebody has a pectus deformity or not. So, Eric, I mean, I think, um, one of the implications of this is, is that you could have a patient who you as a surgeon feel has a pectus index, and if you just simply look, I mean, it has a pectus at the bottom, but if you simply rely on the calorie index or the pectus index, your insurance companies that rely on just that number would deny it. Correct, and unfortunately we've, we have seen that ourselves, that uh I think that's kind of started the ball rolling that you came down to me a few times and said, listen, this patient has an obvious, but I was kind and gentle. That's right, right, it's most unlike you, but yeah, OK, thanks. Thank you. OK. And uh then, uh, Doctor Taylor, uh, we work very closely with cardiology as well, obviously with our cardio cardiac MRIs and if you wanna go ahead and, uh, comment on, um, some of your findings as far as, you know, the cardiology and the importance of the cardiac MRI and how we can use that. Sure, so I'll expound a little on what Eric said, and we'll just, uh, I, I have a few, uh, slides to show. The, the advantage of cardiac MR for us is that we can get the same information, like Eric said, from CT in addition to getting what is a very nice, uh, functional evaluation, all without contrast in the course of about 25 minutes maybe. So we think, uh, it's this, it's a perfect application of cardiac MR. So this is just in review of what we know about pectus and its effect on the heart and the cardiac effects of the what I'm calling sternal geometry for lack of a better term. Certainly the direct mechanical compression which we can see. And we know that there are effects on ventricular function. Occasionally these patients have conduction abnormalities, so it's likely that screening ECGs are indicated. Very rarely you can get arrhythmias. And then associated cardiac findings, which are extremely important to screen for, include valve disease and aortopathy, both of which are part of the connective tissue spectrum. But the cardiac MR allows us to screen for all of these things at the same time. So you can actually get these things from echocardiograms, but there's one really good reason why we don't do echocardiograms, uh, well, uh we don't, we don't rely on them in Pectus patients. And I will show you what that is. So can you hit play for, can you play that movie from there for me? You just click it, click the video, yeah. I All right, well, I will describe what it is that I was trying to show here. So basically that the uh hover over the video and then. The, the image quality in most Pus patients is atrocious. So most people who don't, who don't look at echoes could tell you that you can't see at all. So this is actually supposed to be all four chambers of the heart with the aortic valve, and you can see that you can't really see much of anything. As opposed to when we look at some cardiac MRI pictures, uh, they're quite easy to look at. So again, it's one modality that gives you cardiac structure and function, allows you to look at aortopathy. So I'm just gonna start this playing way so you can look at it as I'm talking, thoracic geometry and then relationship of the sternum to the right ventricle, which we found to be quite important. So if you actually see up in this top right-hand corner, top left-hand corner, sorry. That you can actually see the pectus compressing or pushing on the anterior surface of the right ventricle. It's a finding that's nearly impossible to see with echo because in echo, the actual right ventricle and the sternum is in the very, very near field of the transducer and impossible to see. And as Eric said, it replaces an echo plus a CT, and I wasn't going to talk too much about the financial aspects here, but it's certainly one cardiac MR versus an echo and a CT are comparable in most places. It's hard to make generalizations about that kind of thing, but most places it's comparable, and it's no radiation. And more importantly, we think it gives you more information than you would get from an echo and a CT, which would be a more standard evaluation in most places. So this is a picture of a patient. It's just sort of an interesting finding that we found in one of the patients that you can actually see we do flow imaging as well. So the top picture is all you're looking is blood flow coming through the screen, so black is coming at us and white's going away from us. What's interesting is the patient actually had a bicuspid aortic valve that wasn't picked up before we picked up on the cardiac MRI. So we summarized some of these results in a poster presentation at the Society of Cardiovascular Magnetic Resonance a few years ago. Uh, at the time, we had 197 cardiac MRs. Now we have closer to 350. Uh, most, again, uh, a predominant male to female ratio, really young age, so I don't want to give you the impression that we do a lot of 3 year olds because we, we don't, but, uh, we had a 2, 2.5 year old all the way up to 24, and the majority of the patients in the late school age, the teenage years. Uh, the interesting findings are the right ventricular ejection fraction. So we, we consider a normal right ventricular ejection fraction to be 50%. And so we actually found about 15% of the patients had our right ventricular ejection fractions that were less than 50%. So quite interesting. So and no other good reason to have reduced right ventricular ejection fraction. And so if you did this normal study with these patients, you would have essentially maybe 1 or 2 less than 50%. So we think likely secondary to the pectus without anything else. So this is just a panel of an ax that we do a standard axial view, and I was trying to highlight if you can you can get a really good sense of the shape of the pectus. And I think one of the things that Eric was saying, if you just do a single slice through the chest, you really miss what is a three dimensional problem. Because one of the really interesting things we found is that where the pectus is and the shape of it and how the superior inferior dimension of the pectus varies dramatically. I mean, it's certainly a, a markedly, I think, heterogeneous geometry to this lesion, but you can get a sense for this, and this sequence takes all of about 3 minutes to do, uh, and you can really see. All of it. And up in the top left hand corner, you can really see where the pectus actually is pushing on the right atrial, right ventricular groove. So these are just some results from the paper. It's a little bit small, but uh I just wanted to highlight one thing is uh if you look at RV compression, uh, the patients with RV compression, uh, there were 7, there were 75 of them. And of the patients that had RV compression, the right ventricular ejection fractions are depressed. And if you look at patients who had compression of the free wall versus the groove between the right atrium and the right ventricle, they actually had more right ventricular decreased function as well. And that's all I had. So go ahead. So Michael, one, a couple of things that really strike me about this, uh, about this presentation, and every time I hear you talk about it, it just, uh, so sends a chill down my spine, um, not your presentation, but the data, OK. But I mean, you know, there even in my institution here, uh, among our colleagues there are some who feel that this is a cosmetic operation, uh, that the patients don't have it. The challenge that we have is is that kids are usually asymptomatic, but this is striking. Yeah, I think, and so we see this in congenital heart disease too, is that kids are asymptomatic all the way up until they're at the very end of whatever it is that, you know, for congenital heart disease. So I think that you can have right ventricular ejection fractions that are in the 40s and be asymptomatic. One thing that we don't do regularly is exercise testing, and I think exercise testing, at least for us on the congenital heart disease. Brings that out. So kids who have some decreased RVF, you can see it you know it actually manifests itself more during exercise and so you can see it during exercise testing sometimes. So when you say exercise testing, what do you mean? I'm talking about formal cardiopulmonary exercise testing that we would do in the lab on a treadmill with the oxygen monitoring, metabolic assessment. Good, good. So Vic, I'm one of those guys. Alright, OK, so, so I'm sitting at this end of the table as the guy who doesn't do much pectus and I'm, I'm actually very engaged here because I wanna be convinced. I wanna be convinced. I wanna start doing more of these, but I seem to frequently send patients away and say. It's cosmetic and I probably wouldn't fix it if it were me. I mean, I have a pectus and I am fine with it, so I, but I'm starting, I, I'm intrigued by the low ejection fraction, but I'm curious what the adult literature says about unrepaired pectus. Do, do. Is it just a measurement or is it actually stay tuned OK, OK, I'm going to wait and see. Yeah, no, no, we, we, we have Dawn is going to help us with that. OK. I, I do think there are a couple of questions that we don't know the answer to that probably need to be looked at, which is if I were to get a Pus cardiac MR in an 8 year old and then I did it again when he was 15, and he had an RVEF of 45, is it going to be 45 again when 15 or is it going to be 30 right or is it gonna normalize? I mean, I don't think we know that the answer to that question because that part we haven't looked at. So Michael, what, what about the fact about the growth of the heart, right? No, I, I don't think, yeah, I think it's a great question because we certainly see as kids age, I think that it seems like the heart gets extruded into the left chest, uh, with pectus as the. Older kids with pectus have their heart more in the left chest as it it's sort of we call it extrusion for lack of a better term, um, and whether that's a growth developmental phenomenon, I don't know it's an interesting question because we don't have any long, at least not much where we scan the same patient over and over again. Can we, Jenny, can we put two polls out? I want to ask of the audience who is getting CT and. What is their first choice, CT or MRI? And the second question is, of those who get CT, will you now consider switching to MRI? And, and I have 11 other question. Let's say I want to start doing MRI. Is this something that my radiologists, do I, is there a certain protocol on how to do that, or will they know? What to order or how to do it right, so I think the anatomical assessment is very straightforward. It's a very short, uh, study if you're just looking for the depression and how much the sternum has gone in, uh, do a cardiac MR. Uh, I think most centers now should be are doing cardiac MR. Uh, it's, there's not, there's nothing unusual about, about the study. It's they're fairly basic, uh, sequences. Uh, so most scanners, most, uh. Uh, centers, I think will be able to do it. But if you're not doing any pediatric MRI right now, uh, then it might, uh, pediatric, sorry, pediatric cardiac MRI, then it may be a challenge to centers which, which, which don't do any pediatric cardiac MRI. Eric, can you comment on, um, I mean, do patients need to have sedation or anything like that or they're able to tolerate the cardiac MRI usually or. Yeah, usually they, they tolerate it very well. Um, It's quite a tight space inside an MRI, but we've actually found that it's actually children do great inside an MRI machines. They have no problems. We also use a lot of video goggle technology so they can watch a movie during the procedure so that kind of relays or relieves some of their anxiety, and they're able to just lie there and get the study done without much difficulty. Adults are a little more challenging. I think I'm a little bit claustrophobic. I find it hard being inside an MRI machine, but. I have actually done an MRI with the goggles on. It's actually great. It's, it's, it, it's, uh, it's a great anxiolytic really. It's so many, you're not limited by artifact and other things by motion artifact and no, we don't, we don't use sedation, as Michael said, we don't use any, uh, contrast either, so it's great. So can you, can if the patient has had a pectus and has a bar in, can you do an MRI? Sure, you can get pictures, you can get. Pictures of almost exactly as I showed you with the bar in the only you may get some localized artifact where the bar is right on top of the heart, so it's just a small artifact there, but the susceptibility artifacts as we call them, are pretty minimal from a pectus bar. So the, the other thing, the, the other takeaway message for, for the audience that's listening is, is that the pectus index, which is, I think, still largely used by the vast majority of individuals. Um, may miss someone who has, uh, who on exam has an obvious pectus, uh, but the pectus itself, the, you know, the pectus index would be normal, and despite the fact that they have a significant pectus, right, number 1, OK, um, and then number 2, if you don't use, uh, the cardiac MRI protocol, you could be missing then patients who, though they are asymptomatic. Have decrements or at least some um abnormality in their cardiac function. I think that's true that's true. Can I have a couple questions from the audience actually um so Mark Saxton first of all wants to adjust the poll and say what about those who don't believe in getting either of those, uh, CT or MRI because it doesn't change our management and also really wanted to say, you know, going back to I think what you addressed is, um, um. Why are we getting these numbers maybe for insurance, but he says, you know, in a patient with a barrel chest and a normal Haller index, despite an obvious pectus deformity. Because they have an obvious pectus on exam and CT, why do you feel the need to bother with these other measurements? How do they help in your decision making? Is it for informed consent? Why do we? Yes, so is it Mark? Yes, hi Mark. I mean, a very practical issue is that the insurance company will not pay for the operation. Uh, there needs to be some, uh, abnormality that, uh, that fits their, uh, their, their tech assessment and at least in our region here, uh, there's one, particular healthcare payer that unless the pectus index is, is X and that there is evidence of cardiac dysfunction or abnormality, they will not pay for it and this is not an inexpensive operation to perform, so we need some metric that, uh. That that that coincides with the health care payers uh criteria uh in order for this not to be a self pay so very practical question. So and you stop me when you want me to stop these questions coming, but, um, so then a follow up that is so do insurance companies accept the correction or the depression index. Or is it a mix of all of these? It's a, so what I have found, and Becky, please chime in, is, is that, um, we're, we're seeing an increased number of individuals that are denied. Uh, but yet in the conversations with the peer to peer, uh, if I provide with them not only if I provide them not only with the fact that they have a pectus index, but I have other criteria that would also suggest, even though the pectus index may be norm Halloran is may be normal, that the correction in the depression, but yet in addition to that, we have evidence of cardiac dysfunction. OK, so that bundle has been very, very effective in reversing those denials which is, which are coming now increasingly. It, it, this is helpful. I, I'm glad that we're going over this. I think, uh, Mark Saxon again has another question is why, why do you care, Michael, about the relationship between the sternum. And the ventricle. So I think we believe that when the when the sternum, when the pectus orientation is such that the sternum is pressing on the free wall of the right ventricle, that it actually does affect right ventricular function. We have pretty good data suggesting that the RV ejection fractions. We have some other data from a little more advanced technique showing that the right ventricular strain is markedly decreased in the free wall as well. It creates an abnormal curvature. I think what it means in the long term, I don't think we know, but it certainly creates an abnormality in right ventricular function. And then one last thing is, uh, well, now a whole bunch more questions are coming in. So we'll, we'll get to the pain stuff later. There's some questions about PCA and pain management. So, uh, David, we'll get to your question when we get to more discussions on pain. And then one more comment is that some insurance companies are in, they say the Upper Midwest are focusing more on symptoms and not on the higher index, I think. I think having all that information is helpful. Um, it can't hurt, um, and sometimes, so the insurance companies care about if it's, let's say it's a Marfan patient and they have a dilated root and that kind of thing, does that go into the calculus for whether you do this or not? It would, it does. Because we take great care to try and make sure we report aortic root dimensions and things like that. And so is that something that could be seen on just your routine. Uh, the typical studies that are done, uh, without you could certainly, yeah, you could get a root measurement on a CT for sure. You, you, you wouldn't get the mitral valve prolapse question, which was what I was getting at with the, um, you know, again you could combine the CT and MR or CT and echo, sorry, and probably get that, but you know, we, we report it from MR. So can I ask a poll question? Yeah, OK, so, um. What, um, at what point in time is there a point in time in the, uh, sort of age of a patient who undergoes a pectus operation, uh, where the heart would go back, so you mentioned the extrusion of the heart into the left side of the chest. Is there a critical window at what point in time we should correct the pectus to allow that heart to be to reposition? I, I, I don't know. I, I don't know. I don't think we have at least, so we haven't looked at that specifically, and again we have very little longitudinal data. M, you want a poll in the audience about that or no? Well, yeah, because I don't think they'll, OK, so I guess the question is at what age? I just want to clarify for Jenny, she's putting the poll in at, at what age does it matter? So when is, you know, when, when is too young, when is young too young? When is too young? This will be an interesting yeah sorry Becky I didn't mean to well uh and and again not to monopolize but I will, uh, uh, so, uh. The, um, how, uh, you know, from a, from a cardiologist who who sees neonates, etc. OK, or your colleague, uh, Doctor Hirscher sent me a 3 year old or 4-year-old actually with a Haller index of 36, what should I do with that? That's an excellent question. Uh, was this a patient with congenital heart disease? This was, uh, it was a patient with Marfan's. Oh, OK. 34-year-old mother says that, um, at 4 years of age he was running around fine. At 6 years of age. He's now running and then stops and just, just really, you know. So I, I think the short answer is I, I don't know what you guys would know better than I would what the outcomes of pectus repair are at the age of 6. I mean, I don't know, but it, it would seem to me to be aggressive in a Marfan patient to just assume that all of the exercise. intolerance was due to pectus. If he didn't have other evidence of restrictive lung disease or something like that, he's probably old enough to get some sort of limited exercise test, even on a bike where you could get some idea of what his aerobic capacity was maybe. We're putting the pole up now. I give her some choices, so I, we'll see. I'm curious how this gets answered. I put 3 to 56 to 89 to 11, other. Good. Are you OK with those choices? Yeah, OK, we'll see what people say. Mike, what do you think of the, is the, um, Importance of like sort of the compliance of the chest wall, is there a difference, like, you know, say a 4 year old has a, a less stiff wall than like a 16 or 18 year old, does that, have you seen differences in the compression of the, of the ventricle or the, or the physiologic, uh, implications of that as the chest wall. Less compliant. At least when we looked at the data as a whole, we didn't see any age dependence on the compression on the RV or or where the pectus was or what it looked like. So the geometric sort of configuration is a function of age, so we didn't see that. I don't know whether we see a difference in what the maximum excursion is during inspiration versus expiration versus age. Do you know? I don't think we have that. So, um, I want to read you some results of the polls that we've been doing, OK, so. 70% get CT. Of those who get CT 73% would switch now to MRI based on what they just heard, so that's a pretty impressive influence you just had, and I, and I would have to say I'm gonna be one of those numbers. I mean, I'm definitely gonna go back and talk to our radiologist. Um, but. But 80% said they would skip the CT or MRI because it doesn't matter so and there's a lot of comments that you can read about, uh, here about people that really don't know the utility of that. So, so, um, uh, Eric. Um, Cincinnati Children's is one of the sort of earlier institutions to really draw attention to the cumulative risk of cancer as a result of radiation. Um, for those who are perhaps of the 30% who are not persuaded to switch to MRI who still continue to do CT, how can you scare the hell out of them as far as risk associated with CTs and kids, little babies, right, so I think, uh. You know, there is data out there that shows that your, um, the earlier you get a CT and then the higher the dose of that CT, uh, the greater your long term risk is of developing, uh, potentially developing a malignancy, which is what the concern is. Um, you know, uh, so pediatric tissues, you know, the cells divide a lot more, more frequently, a lot more rapidly. They have a lot more time to develop breaks in in in in their structure, and you can so that increases your likelihood, as I say long term of having complications from a CT scan. You know the risk overall. A CT, as I say, if you, if you use a standard CT dose, you can get up to about 7 millisieverts of radiation, which is, which is a reasonable amount of radiation. It's about 2 years' worth of background radiation from doing a CT, and that's in one go. You can use very, very low dose techniques which I think a lot of places do like we did. We used to use just one or two slices or you can just just drop the moderation and give quite a bit. But as I say, it depends on where you are. Some people just do a standard CT for a pectus and where they get a reasonable amount of dose from that. Yeah, I think, I think, uh, the jury in some ways though is still out as regards, again, they're not like a lot of things unfortunately in this area, there are not a large number of really good longitudinal studies as regards the effect of, of, of radiation, uh, but certainly there is data there that that suggests that there is an increased risk from having even one CT. We worry more about patients who have multiple CTs back to back or within a short period of time, but there is data that says just even from one CT that there is an increased risk of malignancy long term and that the younger you are, that risk increases over your lifetime. Just, uh, so. Majority of the people, 50% say that age must be greater than 9 to 11 years of age, um, and then there's other, and I'm waiting to hear what the other is, but there were some people that actually 30% of the people said that they think that anything over 5 years of age, uh, so I don't know if, I don't know if the technology allows us to answer the question, ask, ask them why, OK, to get the response, but the, the, the surgeon who's done the largest number in the world. So the surgeon Dr. Park, who does the largest number of practices in Korea, right, in Korea, right, would argue that 9 is 2, is, is you can go younger than 9. You can go younger than much, much younger than 9. In fact, their paper would suggest that, uh, you know, patients older than 3 years is safe. I mean, 3 year olds enough, and the earlier the better. Is that right? Even though they're growing and changing, it's better to do it earlier, but shorter bars. OK, right, so one of the, one of the, one of the limitations as far as having the bars that go all the way around to the mid-axillary line is, is that with growth you can impede then the growth of the chest wall and so the, um, modification that needs to be considered if you're going to do a younger patient would be that the bars need to be shorter, not too short, but can you convert. If you do them when they're really young and their cartilage is still growing, can you convert an excavatum into a carinatum if you correct them too early? I've done it so it can happen, yeah, um, yeah, but there are risk factors. I mean, those, those patients with connective tissue, and that would be a good segue for, for Derek, uh, uh, section, um, at least the report from the Hopkins group is, is that that's where you saw the overcorrection of the, uh, or the carronotum sort of recurring. Um, but what, uh, what Park would suggest that is, is that, you know, one of the more, one of the more challenging patients are those with the asymmetric pectuses. Uh, and even though there are those proponents who say that you can modify the bar in order to adjust that, I think, you know, the vast majority of us, at least in my experience, it has not been that effective. And so the question is that Park raises, at least in his experience again, the largest number. So is, is that if you, he sees fewer asymmetric patients, uh, because he feels that because he corrects them when they're, so. Um, would this be a good segue then to, uh, Doctor Derek Nielsen, please?