Medtronic PTEye Probe: New Tech to Identify Parathyroid Glands in Thyroid Surgery

[Dr. Michael Singer]
I do a fair bit of reoperative parathyroid surgery. What you see when you look at the pathology reports is, you'll see six, eight frozen sections, right inferior parathyroid gland, right inferior parathyroid gland, right inferior parathyroid gland, fat lymph node thyroid. That's just the way it-- Again, I'm wrong some of the time. I do a lot of this, and I'm pretty good at it. There are things that I think are a parathyroid gland, and there's just not.

By the way, this goes back to what I said about this earlier. It's okay to say that this is hard, like that it is hard. That's fine. What people have tried to figure out over the years is ways of identifying these glands. People have tried injection of different agents, for example, like methylene blue, or they tried injection of nanoparticles and all these other things. Ultimately the reason that's being done is because finding these glands–

Again, now we could be talking about in either thyroid or parathyroid surgery can be very challenging. This new technology that came out now probably was first initially described about maybe eight years ago at this point is based off of the idea of fluorescence imaging. Some, maybe all of your listeners will be familiar with the idea of fluorescence imaging as it relates to the most common agent that's used in it. It's what's called ICG or indocyanine green.

What happens with fluorescence imaging is you inject say an agent like indocyanine green that flows to the tissue. Then in fluorescence imaging, what happens is you have say a camera. The camera is stimulating that agent at a certain wavelength of light, and that then gives off a different wavelength of light, which can be say picked up by a camera. Again, some of your listeners are probably familiar with this, ICG is pretty commonly used now in surgical fields, whether in plastic surgery, colorectal surgery, any of your listeners who do say free flaps will probably be familiar with this. That's used for looking at vascularity of tissue, okay?

This is where the parathyroid thing just comes out of left field. Researchers, this is an incredible story, it was found by initially by a resident at Vanderbilt University, a general surgery resident, and what they figured out is that the parathyroid glands, when you don't inject anything, no ICG, no contrast agent, nothing else, that if you look at it and stimulate that tissue with the right wavelength, and you have a receiver, a camera or a probe with the right wavelength set up, that the parathyroid glands autofluoresce to a much higher degree to any other tissue in the neck.

If, again, this is without any injection, you point a camera at them with the right wavelength of light, and you have the right receiver on it, the parathyroid glands light up much more brightly than any of the surrounding tissues. It doesn't matter. Now there are FDA approved devices, both that are probe based, some of them are camera based, that allow you to use, again, autofluorescence so no injection. You basically point this at the field, you touch something with the probe, and very readily, and in a pretty sensitive and specific manner, it can differentiate, or those can differentiate parathyroid tissue from thyroid, fat, thymus, lymph nodes, basically everything else in the neck.

This is a little bit, and for anyone who does thyroid and parathyroid surgery, at least in 2024, probably most, if not all of your listeners use nerve monitoring. A little bit, this is similar to the idea of intraoperative nerve monitoring. Historically, what did we have? You could look at it and you could be like, "It's pearly white, the nerve has a racing stripe on it with the blood," all of those things that we still use, and then we're able to use the nerve monitor, one, just to tell us if the nerve's functioning, but a lot of people are using it to help them confirm, is that nerve or not?

This is the same thing. I tell this to people, and this is true for I think technologies in all these areas, this is not replacement for surgical experience, surgical knowledge, it's just not. What these are they give you additional pieces of information to then include in your surgical algorithm, in your own brain of like, "Is this a parathyroid gland and is it not?" Depending on which device you use, and how you use it can be used, say, more effectively, maybe for you in thyroid surgery, maybe it's more effective for you in parathyroid surgery, but again, it's an adjunct tool to help you differentiate parathyroid tissue from not.

[Dr. Gopi Shah]
Autofluorescence, could that be like the first pass device? Where I'm doing the surgery, and I think that looks more like parathyroid gland. I think what's next to it is fat. I clean it off. We're still in the body. We haven't taken anything out. Let's say for thyroid surgery, I can just see does it autofluorescence? That's my first pass tool, or do I need both tools? How does–

[Dr. Michael Singer]
Right, great question, and this is where we go now. We'll talk a little bit about thyroid surgery versus parathyroid surgery. It's an interesting thing. This is where you get into differences between say the way we do things in the United States versus the way things are done internationally. Because the way these tools are being used in the United States is very different than the way they're being used, particularly in parts of Europe, some parts of Asia. Let's first talk just about thyroid surgery.

In thyroid surgery, there's different parts of it. One, like you suggested is, how am I going to find that parathyroid gland? Is this a parathyroid gland? Is it fat? Is it a lymph node? Is it thymus? The surgeons who have really developed this into a routine, where this isn't just randomly using it one day off the shelf, but where they're using this on a consistent basis now as a tool within thyroid surgery, the way they start is with autofluorescence. "Is that a parathyroid gland? Is it not?" Also going back a little bit to what I said before about helping them to find it earlier in the surgery. Finding it earlier in the surgery allows them to just manage that gland better. Now, at this point, you have some divergence in the way people do it. Some people could then continue with the surgery as they have been. Then only at the end of the case do they add that second pass, as you're suggesting, where they then use ICG. We're now talking about, this is where it starts to get a little bit confusing. This is no really longer autofluorescence, but actually fluorescence with ICG and used essentially in the traditional way of using the ICG to tell you about the vasculature or the vascular intactness, essentially, of that parathyroid gland. If the gland doesn't, say, light up, what does that mean?

Does it mean it's really been compromised? Is it that it's just positioned in a way where, say maybe, for example, the vasculature has been turned on itself in an uncomfortable position? Then it allows you, and this is where research really still is not clear, is, so what does that mean? Should I explant this gland and reimplant it?

I think that one of the important things to keep in mind, and this is probably true for technology across the board, at least the way I think about technology, is it can't just be a nice tool. It has to change what we're going to do. The ultimate question is, if you use that ICG, again, in the context of fluorescence imaging of that parathyroid, and it doesn't light up, does it change what you're going to do?

Or does it mean, oh, my goodness, this gland is no longer vascularly intact, and therefore I'm going to reimplant it or not? Some people use it, autofluorescence to help them find the glands, and then fluorescence, essentially, at the end to make determinations about how intact they think the vascular supply is. The more even, and I would say most sophisticated users of this technology, autofluorescence helps them find the gland.

Now, before they do additional dissection, they then inject ICG, because what that does for them is, and people use different terms. They talk about angiography, parathyroid angiography, but essentially what they're using is for the ICG to show them where the vascular supply is to those parathyroid glands, and they then change their surgical approach based off of understanding, oh, the vascular supply is coming from below, or from the side, or from above, which is–

When you think about it, is an incredibly advanced way of dealing with parathyroid glands. Now, those users, these are people who I think are really at the most cutting edge, and I would also argue the most invested in this technology. What I will say for them is they have incredible results.

Because one of the things that we've learned from this, and again, this is where you can learn from things even if you don't use it, is that our understanding of parathyroid vascular supply in the context of thyroid surgery is extremely rudimentary. As these people have been doing these angiography studies, or what they call angiography, what we've started to really learn is to understand how complex and varied parathyroid blood supply is.

I think even for those people who are saying, "I'm never injecting ICG to look at parathyroid gland blood supply," there's a lot of data that's coming out about where the blood supply tends to be from these studies that can be used even if you're never going to use that technology.

Again, in Europe, people are doing like you're suggesting, a combination, where they're using the autofluorescence to help them find the gland, and then they're using ICG to, say, for example, identify the blood supply, and then at the end determine whether they think that gland is intact from a vascular perspective or not. That is not nearly as widely being performed in the United States, that combination.

American surgeons, I think, for a whole bunch of reasons, were, I'd say, more cautious in terms of using some of these technologies. I think some of it goes back to what I said before about, I think we as a group tend to be somewhat dismissive of how common a problem hypoparathyroidism is, and so to date, people haven't been as willing to, say, invest as much effort in trying to prevent it as maybe we should.

In the United States, people are using more of the autofluorescence aspect of it within thyroid surgery. That was a very long-winded answer to your relatively short question.

[Dr. Gopi Shah]
I have never used one of these devices. Just to paint the picture, when you're using maybe a probe, is it a probe for the autofluorescence part of it where you're going to touch it? I liked your comparison with nerve monitoring, because that's something that most people are probably very familiar with. You touch it, and it gives you some audible, ding, ding, ding, that is parathyroid or how does that part work?

[Dr. Michael Singer]
I'll say this just because I like to be very upfront. There are different technologies. One of them is probe-based. It's actually produced by Medtronic. I say that on purpose, because I am a consultant for Medtronic. I just want to disclose that.

I don't really care about which technology you use. I'm interested in people using, or at least trying some of one form of these technologies. There are two versions that are available. One is this probe-based system. t's exactly as you described, very similar to nerve monitoring, where you touch it, there's some additional details in terms of the background of how exactly you get these numbers.

Essentially, if you get a certain response, the likelihood that that's a parathyroid gland is very high. It's both visual and audible. There are advantages and disadvantages to that. Certainly, for people, say, for example, who use nerve monitoring, it just feels very intuitively similar.

The disadvantage is you really need to have some sense of what a parathyroid gland looks like to trial it. Because otherwise you essentially have to paint-- Just like using the nerve monitor, you need to have some idea where the nerve is, otherwise you're going to literally just walk around painting the whole field.

The advantage of the camera-based systems, I think, is it is more helpful for having this global view. Theoretically, in thyroid surgery, or parathyroid surgery, I guess, for that matter, what's nice to some degree, with the camera systems, at least in theory, is that you open up the field, and now I take out this camera, and I look at the field, and that's projected then onto a monitor in the operating room.

Theoretically, if you see a parathyroid gland, or if the camera sees it, and has enough of a response, you're going to see these bright spots on the screen. It gives you a much more global view. There are different options. To me, again, it's not about one versus the other. They each have advantages, disadvantages. I don't think that's really the point of our conversation right now. I'm happy to talk about it.

To me it's just more about being familiar with this technology that's out there, and trialing some. What I say to people with this is, I think what's important is that people just acknowledge to themselves, what is the challenge that they encounter with parathyroid glands? I have no idea what one looks like.

I need something that can look at the field and say, "Hey, there's something over there, and there's something over there." Or is it that they're pretty good at it, but they still get it wrong a fair bit of the time and they need something that they essentially can use almost like a rapid frozen section. Those are different challenges. Or, for example, maybe their challenge is, "Hey, I can find that parathyroid gland, but I have no idea how to keep the vascular supply intact.

This is where you, I think, as an individual surgeon, have to say to yourself, what challenge do I have? Just be honest. You don't have to say that out loud. You don't say that to the rep. You don't necessarily say that to the patient. Just for myself, what is it? It's okay if the answer is, I have no idea what a parathyroid gland looks like. Then, let's use something to help you.

The same thing with the vascular supply and so on and so forth. What I will say that's interesting is that these technologies really were developed, and there's a number of reasons why, with the initial idea of using them to help find parathyroid glands, to help assess vascular supply in the context of parathyroid glands.

Then once these companies came out with that, and they actually started introducing it to surgeons, guess what surgeons said? "Wait, you have a device that can help you find parathyroid glands. Why are you talking to me about thyroid surgery?" It's so funny. You see the companies, or you start talking to them about it, and they're like, "Why are you talking about thyroid surgery?" What's the obvious potential utility of a device that helps you find parathyroid glands?

Parathyroid surgery, because I think everyone who's done any number of parathyroid cases knows those amazingly challenging and frustrating cases where you're looking, you're looking, you're looking, you're looking, and you can't find the gland. That idea of finding parathyroids in parathyroid surgery, I think we're all familiar about it.

By the way, Gopi, this goes back to you, even if you are doing them in practice now, just for residency, where you're like, "Oh my God, I was in that case for four hours with doctor," or whatever else, he or she was getting so frustrated I am never doing one of those cases ever again.


[Dr. Gopi Shah]
Michael, can we quickly talk about the Medtronic probe, the PTEye? Is that a fluorescence or an autofluorescence technology?

[Dr. Michael Singer]
I don't want to confuse people because once you start talking about-- It's like talking to patients about thyroid versus parathyroid. They have the same word in them. Patients are like, "Wait, thyroid, parathyroid." It's the same thing here.

The device, all of these devices, they're designed for fluorescence. It happens to be that parathyroid glands have this quality, this intrinsic, what's called a fluorophore. There's something in there that almost acts like you've ejected ICG into the gland. What's important is, is that currently, currently this is very important, the device is FDA-approved for autofluorescence to help confirm something to be a parathyroid gland or not. That's what it's for.

This is where some technologies really just do it. This thing was brought into my operating room the first time, and I'm a somewhat skeptical surgeon. You have people show up in your operating room all the time with devices, technologies, and they're like, "Oh, this thing is going to change the way everything you do." You're like, "Whatever."

Then you use it and it turns the operating room purple and you're like, "Okay, so what? How does that help?" This is one of the first devices or one of the only devices that I've ever used where I used it and I was like, "Wow, this thing does what it's supposed to do and really does it pretty accurately without any-- It's not complex.

Maybe I have a comfort level like Ashley was saying, because I use nerve monitoring, maybe it was just very intuitive it's use. It really does what it's supposed to do. What I say to people is a little bit, this is when nerve monitoring first came out, and one of the issues they had with getting surgeons to adopt it is, surgeons would stimulate something, say with the nerve probe that wasn't the nerve.

They would say, "Oh, this technology stinks." They'd say, "Oh, this technology doesn't work. That's the nerve and it's not stimulating." Guess what? It wasn't the nerve. It's the same thing here. You have to be open to the possibility that as much as you do, and I'm talking about for myself, as much as I do, there are times where I'm wrong.

I'm like, "Oh yes, that--" I have residents, so I'm forced to be pretty honest because nowadays they'll call me out. Historically, you would have just sat there and afterwards we'll gone over to your resident and co-resident and be like, "This guy doesn't know what he's doing." There's times where you stimulate something and you think it's a parathyroid gland and it's just not.

You have to trust the technology to some extent, because the technology is not perfect either. It has false negatives, false positive, those kinds of things. I've used the camera-based system as well, and there's different versions of it. I think that the camera-based system has advantages too.

The camera-based system, one advantage of it, at least in its current formulation, is that it allows you to look at both fluorescence, and if you're interested in looking at vascularity, allows you to do fluorescence imaging also. I think the other big advantage of it is it gives you a global view.

This isn't like, "Oh, I'm testing this one micro area." It's assessing the whole area. If you have listeners who are actually interested in trying these technologies, I would encourage them to try both and see what they feel more comfortable with and what works in their hands. A little bit this is what I was saying before about just everyone has to know what their challenge is for anyone to say, "Oh no, no, no, the one that you should use is this."

Everyone has different challenges. You have to figure out which of these devices, if you find them helpful at all, maybe you won't find them helpful at all, but which of these devices potentially helps you address the challenges, you as the individual surgeon really are trying to deal with.

[Dr. Gopi Shah]
Would you say that it has changed the way you do thyroid and parathyroid surgery? If so, how?

[Dr. Michael Singer]
I would say the two areas that it's had the biggest impact, and maybe this is not surprising. At this point, my practice has largely, not exclusively, but it's largely become parathyroid surgery. I think that the areas that it's had the biggest impact is probably in parathyroid surgery. There are definitely instances where in thyroid surgery I find it's already made differences for me. Say, for example, in say reoperative central neck dissections, where there's a ton of scar tissue, parathyroid glands are genuinely at risk in those cases.

I think that in those cases it's already been helpful to me in certain instances. Where I could tell you it's made probably the single biggest difference is in parathyroid surgery it has eliminated, in my practice, the need for getting frozen sections. Now the reality is that I don't get very many frozen sections to begin with.

Some people use frozen sections on a routine basis. Some people use them only in challenging cases, all these other things. Even though I don't always get them, I still do occasionally get frozen sections. The way I use this technology now, it's eliminated that. I don't want to say 100%. You're right, there is nothing that we use that's 100% of the time, 100% accurate. It's eliminated that need.

One of the things that that does, particularly in more challenging cases, maybe cases of a bilateral neck exploration, is it's almost an automatic and immediate, that's the key, frozen section. One of the annoying things with frozen sections is, if you could get that result instantly, it helps you.

When it takes 25 minutes to get the result back, because it's not almost real time, it doesn't allow you to make surgical decisions as readily. You're like, "Oh, okay, now I'm going to wait for that biopsy result. I'm going to go and do something else, and then I'm going to come back to this question that I have." Whereas with this, it's like the nerve monitor in the sense that it immediately tells you.

Then you can say, "I now know I've found this gland. Let me move to the next gland." Or, "Now I've found all four glands," or however else it is. That, I think for me, it allows me to make certain surgical decisions and then moves much more quickly than I would have in the past.