BackTable / VI / Podcast / Transcript #158

Podcast Transcript: Microwave Ablation for Liver Lesions

with Dr. Driss Raissi

Dr. Christopher Beck talks with Dr. Driss Raissi about his approach to Microwave Ablation of Liver Lesions, including workup, technique, and tips and tricks for a successful ablation treatment. You can read the full transcript below and listen to this episode here on BackTable.com.

Table of Contents

(1) Typical Microwave Ablation cases at the University of Kentucky

(2) Planning a Liver Ablation Procedure

(3) Ablation Zone Margins

(4) Maximizing the Single Probe Technique

(5) Ablation Variables: Temperature, Timing & Imaging Modalities

(6) Navigating Ablation Zones Post-Parenchymal Desiccation

(7) Techniques, Complications, and Limitations of Ablation

(8) Ablation Advice for IR Fellows and New Attendings

(9) Ablation of Peri-Cardiac Lesions

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Ep 158 Microwave Ablation for Liver Lesions with Dr. Driss Raissi
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[Dr. Christopher Beck]
Yeah. No, absolutely. Well, let's zero in particularly on the liver, it sounds like that's maybe the robust part of your practice. And I think that's an easy thing for people to wrap their minds around as far as microwave ablation with either primary or metastatic lesions. So if you can just start and walk us through pre-procedure. So how do you plan whenever you're approaching a tumor? So we can get into the clinical role, but before we do that, just talk about what you're looking for in a tumor? What are you looking at around the tumor? And how you're kind of planning your procedure around the anatomy of what you're about to ablate?

[Dr. Driss Raissi]
Most cases are reviewed in one of our tumor boards to gain consensus, to gain buy-in among all the different practitioners that we are indeed choosing the right treatment for that patient. And to allow all the different perspectives to be considered. We like to have a pre-procedural liver CT or MRI within two to four weeks, you don't want to be surprised by a tumor that looked like it was two centimeters. And then the day of ablation, it's five centimeters, it's like, "Oh, okay. Well, that's a different story."

[Dr. Christopher Beck]
Do you have a preference on CT or MRI or whatever cross-sectional you can get?

[Dr. Driss Raissi]
Not really, to be honest with you. I mean, I think maybe, I have a certain bias for having a CT. Obviously, it's not the best thing for imaging. HCC, probably MR is best, but personally, I have my own bias. I find it easier to correlate with the same day CT because I'm doing CT fluoroscopy for the ablation. So I think I like it, but I am happy to have anything, to be honest with you. CT or MRI, very happy. I mean, ideally, you want a Child-Pugh A patient or a very early stage zero on, if you go by BCLC, that's ideally.

But am I dealing with ideal cases? No, by any means. Child-Pugh patients are obviously considered, that might require more than microwave ablation, you want to go easy on them and they'll send you a Child-Pugh B patient, who has five lesions, you're like, "Wow," if I ablate them all the same day. Yeah, I guess, I could, but at the same time I try to split a lot of time, we'll do it over two sessions. You have three in the left, two in the right, we'll split them in over two weeks. Or sometimes, we'll combine them with other local regional therapy.

You have terrible mass in the left lobe, non-surgical candidate and you have a lesion that we are going to ablate on the right. So most of our patients, the majority when we looked at our numbers are actually Child-Pugh B. And I found a bunch of C's who just made it through.

[Dr. Christopher Beck]
Sure. So whenever you're evaluating a tumor, take away maybe the infiltrative HCC picture, but something that's kind of well-defined towards the periphery. Will you talk a little bit about how you decide on probe placement, the tract of the probes or basically, the approach that you're going to take? And which kind of probes that you use, if that's relevant to kind of how you think about tumor ablation?

[Dr. Driss Raissi]
Well, with time, I learned to appreciate the simplicity of having a one needle device. To me, that became the first thing. You know what? I want a one needle device. I do a lot of cryoablation and trying to bracket a tumor sounds very easy, and we all know from IRE NanoKnife, it's not that easy. It takes a long time, the needle, the deeper you go, it's all over the place. So I appreciate a one needle device. I take advantage of there is always a critical organ, not always, but often, you have a critical structure that may be at risk, even if it's just a major bile duct or the gallbladder.

So you try to take advantage of the fact that the most predictable area will be in front of the needle. So it's kind of intuitive, but ablation practitioners direct your needle towards the critical organ, you'll have more control and you know pretty much how far it's going to travel beyond that. There's a lot of things that people recommend about, "Well, hydrodissection or move this. Avoid the pleura, avoid the diaphragm." Honestly, in my practice and we've done hundreds and hundreds and hundreds, I learned that a simpler approach might be best.

Trying to create hydrodissection just makes the procedure two, three hours long, and Anesthesia gets frustrated. He starts to obscure your margins and you're like, "Oh, this is a great case to present." No, it looks like a mess. So I tried to take advantage of the physics of the probe that I'm working with. I mean, I look at my critical organ, see what it is, my critical structure, probably direct my needle at it, align my long axis with the long axis of the tumor. The long axis of the tumor and the long axis of the probe itself is probably where you're going to get most of your ablation.

Where the shorter axis, the side lobes are probably the ones that are going to suffer from maybe a little bit of heat-sink here and there, maybe from environmental factors, which is one of the things that I like, I'm always excited about. Not all livers are made the same, a fatty liver is not going to perform as well as a fibrotic liver as a very watery liver, et cetera, et cetera. And most importantly, like I just said before, I try to make it as simple as possible. Go from here, go from there. Try this tract, try that tract. I look at what is the shortest and the quickest way for me to get into that tumor and I do it.

[Dr. Christopher Beck]
I like that, keep it simple. There are two things I want to highlight for our audience because a lot of good tips kind of came out. And that was one that you take care to direct the tip of the needle towards your most critical organ. So if there is nothing in the way, and it's all liver, and the only thing that is right beyond the tumor is a little bit of gallbladder, then you direct your needle towards the gallbladder, is that right? Do I hear you correctly?

[Dr. Driss Raissi]
Yeah, yeah. Absolutely.

[Dr. Christopher Beck]
And the other thing I wanted to highlight was, you take advantage of the long axis of the tumor. So if you have a three by two centimeter HCC, then the long axis of your needle will go along that three centimeter axis of the tumor? Because you typically get an ablation zone that burns further back along the needle and less so around the side lobes.

[Dr. Driss Raissi]
Yeah, that is correct. And we all know that not all probes are made the same, but if there is one thing that they have in common is that they all have a longer axis than their shorter axis. No probe out there is a perfect circle. You have from the spherical, which is good. I like my spherical shape as close to a circle as possible to be rodlike, which is, for me, not very ideal. But if they have one thing in common, you could align their long axis along the probe with the long axis of the tumor.

(1) Typical Microwave Ablation cases at the University of Kentucky

[Dr. Christopher Beck]
Wow, that's a topic in and of itself. I think there are a lot of people who are in academics right now that are a little jealous of your situation, but good for you guys. Good for you guys. All right. So we want to talk about ablation. Specifically, we're going to narrow it down to microwave ablation. Do you want to talk about what your ablation practice kind of looks like globally? Just give us a basic rundown of in a given week, how many ablations you're doing and where exactly do those parse out in terms of is it HCC? Is it mets? Is it a renal cell primary? I'm just curious about how the ablation practice is shaping up.

[Dr. Driss Raissi]
Yeah, our ablation practice is rather typical, it's large majority liver ablations and then a good amount of kidney ablations and the far in-between lung ablations, and the typical MSK ablations of bony lesions. As far as, how much do we do? We probably average six liver ablations a week, two to three renal ablations a week. And we looked at this retrospectively, HCC represents 70% of our liver ablations. Obviously, RCC or potential RCC represents 100% of our renal ablations.

And the other stuff is just the random metastatic lesion, the lesion that we're not really sure of, something in the lung. So probably a total of 68 minimum ablations we're going to do every week.

[Dr. Christopher Beck]
Okay. And a lot of that's HCC so I assume and I kind of knew this ahead of time, but UK has a big transplant service assuming?

[Dr. Driss Raissi]
Yeah, absolutely. I mean, that's really the pipeline that feeds our service . We have a very busy transplant center. They do a lot of transplants and I mean, in the state of Kentucky, HCC cirrhosis is as common as the flu, in the days that the flu used to be common.

[Dr. Christopher Beck]
Okay.

[Dr. Driss Raissi]
Now, it's not even common anymore, right? So that kind of feeds our pipeline. Our community, unfortunately, is very underserved. So a lot of patients reach us when they're beyond Milan. I mean, some of them are within Milan. So we're very honored to serve a really important role and the state offering patients options that otherwise, they might not be surgical candidates. So it's really an honor to be part of this practice.

[Dr. Christopher Beck]
That's awesome. So I thought we would drill down specifically on microwave, but actually, this is probably as good a place as any. In terms of your ablations, how much is microwave? How much is RF? How much is cryo?

[Dr. Driss Raissi]
So when I started my practice at the University of Kentucky, it was the good old days of radiofrequency ablations. And I think I have the honor to call it that way of doing the last radiofrequency ablation, I still remember, I recall it very, very vividly. I wasn't very happy with it. It was successful and all, I still remember the patient giving me a CD, thanking me for helping him. So I still remember it. But we've switched completely to microwave ablation when it comes to liver. So all our livers are microwave ablation. When it comes to obviously, either spinal ablations or bony ablations, I mean, we're still using radiofrequency ablation.

[Dr. Christopher Beck]
Okay.

[Dr. Driss Raissi]
For the lung, it really depends, there aren't that many cases. Some people will do cryo. Some people will microwave. That's still a debate, until we have some concrete data to tell us what we should really be doing. Although, the data out there still says that it may not even matter what you're doing when it comes to local tumor control. When it comes to renal lesions, I really shift my practice towards more microwave, more and more and more and more. There isn't really much out there.

Hopefully, one day, I'll have enough time and write what should maybe be considered strongly for microwave ablations of renal lesions. A lot of my colleagues still do a lot of cryo. I mean, I built the cryo service at the University of Kentucky, but at the same time, now I'm shifting. I'm shifting gears towards microwave ablations as I find that it does have a role. It does have a rather useful role.

(2) Planning a Liver Ablation Procedure

[Dr. Christopher Beck]
Yeah. No, absolutely. Well, let's zero in particularly on the liver, it sounds like that's maybe the robust part of your practice. And I think that's an easy thing for people to wrap their minds around as far as microwave ablation with either primary or metastatic lesions. So if you can just start and walk us through pre-procedure. So how do you plan whenever you're approaching a tumor? So we can get into the clinical role, but before we do that, just talk about what you're looking for in a tumor? What are you looking at around the tumor? And how you're kind of planning your procedure around the anatomy of what you're about to ablate?

[Dr. Driss Raissi]
Most cases are reviewed in one of our tumor boards to gain consensus, to gain buy-in among all the different practitioners that we are indeed choosing the right treatment for that patient. And to allow all the different perspectives to be considered. We like to have a pre-procedural liver CT or MRI within two to four weeks, you don't want to be surprised by a tumor that looked like it was two centimeters. And then the day of ablation, it's five centimeters, it's like, "Oh, okay. Well, that's a different story."

[Dr. Christopher Beck]
Do you have a preference on CT or MRI or whatever cross-sectional you can get?

[Dr. Driss Raissi]
Not really, to be honest with you. I mean, I think maybe, I have a certain bias for having a CT. Obviously, it's not the best thing for imaging. HCC, probably MR is best, but personally, I have my own bias. I find it easier to correlate with the same day CT because I'm doing CT fluoroscopy for the ablation. So I think I like it, but I am happy to have anything, to be honest with you. CT or MRI, very happy. I mean, ideally, you want a Child-Pugh A patient or a very early stage zero on, if you go by BCLC, that's ideally.

But am I dealing with ideal cases? No, by any means. Child-Pugh patients are obviously considered, that might require more than microwave ablation, you want to go easy on them and they'll send you a Child-Pugh B patient, who has five lesions, you're like, "Wow," if I ablate them all the same day. Yeah, I guess, I could, but at the same time I try to split a lot of time, we'll do it over two sessions. You have three in the left, two in the right, we'll split them in over two weeks. Or sometimes, we'll combine them with other local regional therapy.

You have terrible mass in the left lobe, non-surgical candidate and you have a lesion that we are going to ablate on the right. So most of our patients, the majority when we looked at our numbers are actually Child-Pugh B. And I found a bunch of C's who just made it through.

[Dr. Christopher Beck]
Sure. So whenever you're evaluating a tumor, take away maybe the infiltrative HCC picture, but something that's kind of well-defined towards the periphery. Will you talk a little bit about how you decide on probe placement, the tract of the probes or basically, the approach that you're going to take? And which kind of probes that you use, if that's relevant to kind of how you think about tumor ablation?

[Dr. Driss Raissi]
Well, with time, I learned to appreciate the simplicity of having a one needle device. To me, that became the first thing. You know what? I want a one needle device. I do a lot of cryoablation and trying to bracket a tumor sounds very easy, and we all know from IRE NanoKnife, it's not that easy. It takes a long time, the needle, the deeper you go, it's all over the place. So I appreciate a one needle device. I take advantage of there is always a critical organ, not always, but often, you have a critical structure that may be at risk, even if it's just a major bile duct or the gallbladder.

So you try to take advantage of the fact that the most predictable area will be in front of the needle. So it's kind of intuitive, but ablation practitioners direct your needle towards the critical organ, you'll have more control and you know pretty much how far it's going to travel beyond that. There's a lot of things that people recommend about, "Well, hydrodissection or move this. Avoid the pleura, avoid the diaphragm." Honestly, in my practice and we've done hundreds and hundreds and hundreds, I learned that a simpler approach might be best.

Trying to create hydrodissection just makes the procedure two, three hours long, and Anesthesia gets frustrated. He starts to obscure your margins and you're like, "Oh, this is a great case to present." No, it looks like a mess. So I tried to take advantage of the physics of the probe that I'm working with. I mean, I look at my critical organ, see what it is, my critical structure, probably direct my needle at it, align my long axis with the long axis of the tumor. The long axis of the tumor and the long axis of the probe itself is probably where you're going to get most of your ablation.

Where the shorter axis, the side lobes are probably the ones that are going to suffer from maybe a little bit of heat-sink here and there, maybe from environmental factors, which is one of the things that I like, I'm always excited about. Not all livers are made the same, a fatty liver is not going to perform as well as a fibrotic liver as a very watery liver, et cetera, et cetera. And most importantly, like I just said before, I try to make it as simple as possible. Go from here, go from there. Try this tract, try that tract. I look at what is the shortest and the quickest way for me to get into that tumor and I do it.

[Dr. Christopher Beck]
I like that, keep it simple. There are two things I want to highlight for our audience because a lot of good tips kind of came out. And that was one that you take care to direct the tip of the needle towards your most critical organ. So if there is nothing in the way, and it's all liver, and the only thing that is right beyond the tumor is a little bit of gallbladder, then you direct your needle towards the gallbladder, is that right? Do I hear you correctly?

[Dr. Driss Raissi]
Yeah, yeah. Absolutely.

[Dr. Christopher Beck]
And the other thing I wanted to highlight was, you take advantage of the long axis of the tumor. So if you have a three by two centimeter HCC, then the long axis of your needle will go along that three centimeter axis of the tumor? Because you typically get an ablation zone that burns further back along the needle and less so around the side lobes.

[Dr. Driss Raissi]
Yeah, that is correct. And we all know that not all probes are made the same, but if there is one thing that they have in common is that they all have a longer axis than their shorter axis. No probe out there is a perfect circle. You have from the spherical, which is good. I like my spherical shape as close to a circle as possible to be rodlike, which is, for me, not very ideal. But if they have one thing in common, you could align their long axis along the probe with the long axis of the tumor.

(3) Ablation Zone Margins

[Dr. Christopher Beck]
Yep. So let's talk a little bit about margins. So actually, there's two things I want to talk about. I want to talk about results in a fibrotic liver and a fatty liver, but first, I wanted to talk about margins. So will you kind of talk about maybe, for the younger interventionalist or some of the trainees out there, you're trying to ablate the tumor, but also, talk about how margins play a role in your ablation zone?

[Dr. Driss Raissi]
Yeah. I mean, if you just go by the data, what does the data tell us? The data tells us if you're dealing with HCC, you need to ensure that you get .5 centimeter surgical margin. And if you're dealing with colorectal, you need one centimeter. And you can find data also that says, one centimeter for both, one centimeter for HCC and one centimeter colo-recs. But you know what? Where does that data come from? Where does that data come from? That data comes from surgical resection, open surgical resection where you have the benefit of looking right directly at the tumor or using beautiful high-resolution images of intraop ultrasound.

And I don't feel like anybody has ever raised that question, where is that data coming from? And why did I start asking myself that question? Because my surgeon started becoming super happy with me when I started, "Oh yeah, I gave you a two centimeter margin." And I thought they were going to be like, Hey Driss, take it easy, this guy doesn't have too much liver." No, no, they were cheering me up. There were like, "Oh, that looks great. That is awesome. That is beautiful."

With time, I mean, I've been doing this for a long time. They started seeing that this patient actually did rather okay. The extra centimeter didn't make them too sick. The extra centimeter ensured they didn't have very early recurrences or they never had any recurrences at all in that surgical bed, where some of my more junior colleagues may have had, let's just say and don't tell them, this is just between you and me, I'm hoping this is a secret…

[Dr. Christopher Beck]
Yeah. You, me and the BackTable audience, I got you.

[Dr. Driss Raissi]
... may have had a little bit more recurrences with a more conservative .5 surgical margin. So I started getting a little bit wilder and excited about ensuring, you know what? I'm going to give you a good surgical margin, I haven't written any paper about it, but that made me think, "We're going by this data that has absolutely nothing to do with percutaneous microwave ablation, maybe I'm up to something."

[Dr. Christopher Beck]
But that also raises the point. So whenever you're talking about margins, I think the other side of the coin is preservation of healthy liver, or maybe not healthy liver tissue, preservation of liver tissue, right? And so, it's a balancing act, but basically in your practice what you say or how you approach it is, if you're going to ablate it, you might as well come in and ablate it and give them nice clean margins. And if you're dealing with Child-Pugh A and Child-Pugh B, then that's just the cost of doing business?

[Dr. Driss Raiss]
Yeah, yeah. Correct. And often honestly, one centimeter, two centimeters, it's not what we think. My surgeon and colleagues, I go with them and do intraoperative microwave ablation once in a while, I may see when they do the resections, it has nothing to do with our 20, 30 cubicle centimeters of ablation, really that we do. I mean, when they chop the liver, they chop it.

[Dr. Christopher Beck]
Gotcha.

[Dr. Driss Raissi]
And obviously, that's why you're concerned because patients might be compensated. But our ablations, even if you take it maximum all, I have a four, five centimeter ablation zone. It's nothing compared with what they resect. So a lot of our practice really is based on data that really just doesn't apply to what we do.

[Dr. Christopher Beck]
The topic that I want to go back to before I forget is, ablations in a cirrhotic liver versus ablations in a steatotic liver, how do they differ and how do you approach them?

[Dr. Driss Raissi]
Do I approach them any differently? I actually don't. I don't really do anything different for them, I'm just cognizant of it. We wrote a paper about ablation. We wanted to see, are there any predictors for the success of your ablation. And we found that different tumor environments basically, background liver might actually affect the likelihood that you have early recurrence or not. And it kind of makes sense, right? I mean, a fatty liver, if you just go by the physics of microwave ablation, less water molecules, probably you will have less microwave energy delivery efficiency. That's just how it works.

Microwave ablation energy is more effective, the more watermark molecules, it'll be more effective, the less water molecules it'll be less effective. Same thing for fibrotic livers. And if you look at most of the microwave ablation devices, the data you receive is based on ex vivo healthy livers. So that made me think well, I get this company that shows me, basically, I'm in the Society of Interventional Radiology annual conference and I'm in an ablation workshop and I'm trying, I go there and try one of the operation probes and I'm like, "Oh wow, I just ablated five by five, this is beautiful, but hold on a second, this is a totally healthy liver. This is not a cirrhotic liver full of fat or full of fibrotic nodules. It's not going to be five by five."

And that got me thinking, what factors in the underlying liver might affect my microwave ablation efficiency. And obviously, there are several. The fact that it's a live liver, the fact that it is a diseased liver, the fact that it is a fatty liver. What if it's an iron overloaded liver? We haven't really considered how these underlying liver pathologies might actually affect your final ablation zone.

[Dr. Christopher Beck]
So anecdotally, do you find that... I mean, excluding healthy livers, which virtually or infrequently happen, but comparing fatty liver to cirrhotic liver, which one do you get better ablation zones in, just anecdotally?

[Dr. Driss Raissi]
Cirrhotic livers, not fatty livers.

(4) Maximizing the Single Probe Technique

[Dr. Christopher Beck]
So another thing that I wanted to touch upon was, how do you get such big ablation zones with two centimeter margins with one probe?

[Dr. Driss Raissi]
First, I will have to say, it depends on the tumor itself.

[Dr. Christopher Beck]
Okay. All right, that's fair.

[Dr. Driss Raissi]
If it's a 15 millimeter lesion, then you could accomplish it rather easily. But yeah, we're talking about probably, how you're going to accomplish that with a three, three and a half centimeter? So because then you're pushing the ability, most microwave probes out there are going to give you anywhere between 3.5, four. Nowadays, between four and five, I will say, that's pretty much it. And that's the data we are provided with based on ex vivo data, which is not the real data.

I mean, it's in vivo data, you're probably going to lose .8 to 1.2 centimeters. How are you going to do it? Well, this is not endorsed by any of the companies or by the device that I use, this simply comes from doing a lot of cases and wanting to help patrons and accomplish things that doesn't seem like I could accomplish just by following the IFUs. So one thing that is very common in my practice is to overlap ablation zones and how do they overlap ablation zones? Well, it is a skill. You have to overlap them correctly to achieve a good ablation zone that doesn't look like all over the place. How do you overlap an ablation zone?

Well first, you accomplish your first ablation, that can be a first application depending on what type of products you're using is going to give you sort of a predictable circle like spherical or oblong first ablation, maybe 3.5 by four or 4.5 maximum. But you're dealing with a lesion that's four point something and the only way you're going to ablate it perfectly and achieve a surgical margin is, you're going to have to ablate more. So it depends where the tumor is, that's the first thing. Where in the 3D dimension is the extent of the tumor that you haven't covered? If it's along the long axis of the tumor, it's actually the easy part.

All you have to do is pull back and perform another ablation. If it's superior, inferior, left, right, I think you could imagine what I'm trying to mention, then you're going to have to have some skill to direct your needle appropriately. One thing that has lowered, I totally believe because I think we just have such good results and we haven't dealt with any significant complications, any major complications is, I teach most of my junior partners and something that I do by my practice which is, try to limit the number of new liver punctures. You have the ability to pull back a little bit and direct your needle. That's why we have a gantry that can oblique up to some of the 15 degrees, 30 degrees, if you are using CT or ultrasound, you could easily follow your needle in an oblique plane.

Try to do everything through the same puncture. Try to be cognizant of where the tumor that may be beyond your tumor margin be and pull back and direct towards the new area and perform a new ablation. So overlapping is just performing secondary and tertiary ablations in order to expand your final ablation zones. And I said, preferably without pulling the needle back completely out of the liver. Sometimes, I do it. Sometimes, I perform a second puncture, but I try to limit the number of new punctures. And I have to say, we've done pretty well ablating up to seven centimeter lesions. And I've seen other colleagues in the rest of the country ablating even beyond that.

[Dr. Christopher Beck]
So if you have a lesion that's around five centimeters, you know you're not going to be able to get there with one probe. Is your approach still to start on one end of the tumor and just kind of ablate kind of march sequentially, I'm just making it up that it's left or right, but it could be front to back, but you just kind of march from one margin all the way to the other side with a single probe, but ablating at different sites along the tumor?

[Dr. Driss Raissi]
Correct. And it's honestly, as simple as you just put it.

[Dr. Christopher Beck]
So what's the downside? Because I have to say, it's different for my practice and that most of the time, if I have a lesion that is three centimeters or more and so I'm looking at a five centimeter ablation zone, I'll just bracket the tumor and then do a single ablation. So I think I kind of heard your answer, but why not just bracket the tumor? Because even though having a single probe is simple, but also, placing two probes in parallel, I mean, I think it's in the wheelhouse?

[Dr. Driss Raissi]
I agree with you. I mean, it's something that I did in my radiofrequency ablation days when I use multiple probes, but I think I just became addicted to the simplicity of one probe. And my anesthesiologist has become addicted to seeing me do an ablation in even the most complicated ones where I have to do multiple sequential ablations in under... The average ablation for me is 20 minutes including everything. If it's a little bit complicated and I have to do overlapping sequential ablations, it might take 45 minutes. So obviously at the end, it comes to what you become comfortable with, what devices you have available. And I think that's really about it. I mean, if a bracket then works for you then stick to it.

(5) Ablation Variables: Temperature, Timing & Imaging Modalities

[Dr. Christopher Beck]
Sure. Sure. So going back a little bit to basically, ablation times like time of procedure. So whenever you're ablating, can you speak a little bit about the temperature at which you ablate? Are you trying to hit a target temperature and how long do you keep the probe active?

[Dr. Driss Raissi]
Am I trying to achieve a certain temperature? I actually don't, I have stopped a long time ago monitoring the temperature.

[Dr. Christopher Beck]
Sure.

[Dr. Driss Raissi]
I think I did it early on with temperature control. And I learned most of the time, I'm achieving anything between 70, 80 degrees, which made me think, "Oh okay, you know what? After 100 cases, why do I need to keep doing this?" So I believe that what I was doing was rather predictable and reliable and it was the same thing over and over and over. So I stopped doing it.

[Dr. Christopher Beck]
And how long do you ablate for? So there's temperature and you say, "Don't really pay attention to that," and just to clarify for the audience, 70 or 80 centigrade, clearly it's not 70 or 80 fahrenheit? And then also, how long do you ablate?

[Dr. Driss Raissi]
I mean, it depends on the lesion, right? I mean, everything is temperature curve time-based.

[Dr. Christopher Beck]
Sure.

[Dr. Driss Raissi]
I mean, we know one thing about microwave ablation is most of the active heating happens there in the initial three minutes, between three to four minutes depending on what devices are out there. And beyond four or five minutes mostly, while it's still active, the acts of diffusion of microwave energy, you're benefiting mostly from the passive diffusion of heat. So most of my cases, the bread-and-butter cases are anywhere between three and four minutes. For your big tumors, you're going to have to push it to 10 minutes to maximize benefit. And the IFUs, that's where they stop, at least for the device I use, they stop at 10 minutes.

[Dr. Christopher Beck]
Okay.

[Dr. Driss Raissi]
Have I gone beyond? Yeah, sometimes. Have I achieved bigger ablation margins? I think so. Just maybe, a few millimeters here and there, two, three millimeters. Obviously, it's like beating a dead horse, you probably have already achieved the maximum ablation you can achieve and you can keep it for one hour and it's not going to become 20 centimeters by any means, but you can gain two or three millimeters here or here. You may or might not remember what we said before, not all livers perform the same. You got your fatty livers, what am I going to do? Well, we're going to underperform, you get fibrotic livers with nice even effects who are going to overperform.

And that's why being a physician, being an interventionalist is an art, you can just stick to your IFUs, or you can just try to help your patient the best you can. And if it goes well then you stick to it. If it doesn't go well, you're like, "Yeah, maybe I need to do something different."

[Dr. Christopher Beck]
Yep. Clearly, you have kind of a feel for it. And that's what comes with doing a whole lot of ablations, but one of the things I wanted to highlight is that, you kind of mentioned two different time points, you either take it to 10 minutes because you're trying to get the max out of your probe, you're trying to get every inch or every millimeter out of the probe or really the workhorse and the timing is probably within the first five minutes. And that seems to be what a lot of people talk about, has that been your experience also?

[Dr. Driss Raissi]
No, absolutely.

[Dr. Christopher Beck]
And let's talk a little bit about the modality of which you used for your ablations. And I think that's very operator dependent, but I think I heard you allude to it earlier, but how do you do your ablations? Is it a combination of CT, ultrasound, CT fluoro?

[Dr. Driss Raissi]
Yeah. I guess, at this point, I can call myself a dinosaur, a very young one, if I might say. But it's a little bit unusual, but I am fully reliant on CT. Which is a little bit unusual and I know that because most of my junior partners are almost appalled by the idea that I do all my cases under CT and they're like, "Whoa." But then they are like, "Oh, how did you do that case in 20 minutes?" I'm like, "I don't know." I can't explain it, it just happens.

So yeah, I am fully reliant on CT. I am incredibly reliant on landmarks. It just became intuitive for me, just to look at the pre-procedural imaging, look at my anatomy, look at my hepatic veins, portal veins, bile ducts, calcifications, clips, spine, anything I could use to guide my needle. I mean, I use things that I'm not even aware I'm using there in the ablation.

[Dr. Christopher Beck]
Sure.

[Dr. Driss Raissi]
And initial CT placement, two minutes ablate, we're done. If there is sequential ablation involved, it's going to need a little bit more time, that's really what my ablation is. I try to optimize things with my anesthesiologists, I try to optimize positioning, I try to optimize tidal volumes. I try to optimize what type of ventilator settings they're using. I kind of do a lot of micromanagement, that's a little bit atypical in order to make my procedure as efficient as possible and my needle placement with CT guidance only as quick as possible.

My junior colleagues and I'm supporting them as a division chief. I've obtained for them two very nice units that use ultrasound navigational guidance for needle placement. They love it. And that's really what 50% of my partner's use currently, which is initial navigational ultrasound placement. And then obviously, the ablation is monitored under CT fluoroscopy.

(6) Navigating Ablation Zones Post-Parenchymal Desiccation

[Dr. Christopher Beck]
That's pretty slick. I've seen some of the newer ultrasound units where you can upload like a PET or an MRI. And also, going back to how you kind of do your procedure. Sometimes, I'm a little bit CT heavy depending on the lesion, but I think that also speaks to that, I also prefer a CT going in like a pre-procedural CT. I mean, I'll take anything, I'm like you, I'll take anything that I can get. But sometimes, it's nice whenever you're doing your ablation under CT, to have a CT to optimize for landmarks.

After you've done your ablation, do you do anything afterwards as far as... So you think you have a good ablation zone based on landmarks, you've monitored periodically with CT, kind of looking at the ablation zone, one of the challenges to me that comes up is, once you microwave one ablation zone that then when you're moving your needle, things are a little bit distorted. Your initial look at the liver is usually the best before even a probe is in the body. And so, what do you do to help yourself plan for that next ablation zone where you're about to march the needle along?

[Dr. Driss Raissi]
Can you clarify that question a little bit? Is it regarding sequential ablation of the same lesion or are you trying to ablate a secondary lesion somewhere else?

[Dr. Christopher Beck]
Actually, I feel like it applies to both. But let's just stick with one lesion, when you're trying to mark your way along the lesion, I feel like once you've put in the probe and done an ablation zone, everything starts to look a little bit funny. And so, do you just kind of know that your needle placement is the one true thing and then everything's referenced off the original needle placement?

[Dr. Driss Raissi]
I think I understand what you're referring to. So ablation desiccates the tissue. Your first ablation is going to shrivel the ablation zone, the capsule is going to look different, things just change. I think I take a first snapshot of where things are because of my heavy reliance on landmarks. I stick to my landmarks. I stick to my gut. I will repeat another CT, that combination of my initial gut of where the landmarks, where the second ablation was supposed to be and the repeat ablation is really what I do. So I think it's a complex, hard to explain cognitive effort of hitting it right on the nail.

And I think I'm doing well, just depending on the results, but I think it would be very hard if somebody asked me something like, "Can you write it up on a piece of paper?" I'm like, "I can't." It just seems to work whatever I do, just have a very good idea of what you're doing initially and where things are and when you're going to go and you already know what's going to happen to that ablation surgical field. So you kind of have an idea of where things are going to go. And I could say that that's one of the weaknesses of ultrasound, after you mess up that ablation zone the first time, things are kind of like, "I don't know, I'm not sure." There's a lot of artifacts that pop in with all that gas.

[Dr. Christopher Beck]
Yeah, I'll second that. Once the ablation zone is really or once the ablation has kind of gotten going ultrasound can sometimes go out of the window. I think it speaks to whether you've done a lot of these or a handful of these and just clearly, you have a good feel for it. But one of the things that I'll do pretty commonly is, you can expect things around your ablation zone to contract, not always, but different things around the liver that are outside of your ablation zone will kind of give you an indication whether things are contracting towards your ablation zone.

And then usually what I'll try and do is, I try and reference my next sequential ablation, if I'm going to move that needle relative to my needle. So I know the needle position was true if it was on the left side of a tumor then if I'm going to move, I mean clearly, I want to move relative to the initial needle placement. So I'll move it over a centimeter and a half relative to where the needles are following the ablation. After you've done the ablation, do you get any imaging with the patient on the table, not just imaging, but post contrast imaging to take a look at your ablation zone?

[Dr. Driss Raissi]
I was going to actually mention that as a clarification to your previous question because I don't want to make it sound like I'm Superman. I don't need anything, I have these eyes.

[Dr. Christopher Beck:
No, that's what it sounds like to me. It sounds like you're Superman, right?

[Dr. Driss Raissi]
Yeah. I have these eyes that can see everything and I know everything, I do it with my eyes closed. Yeah, sometimes I use contrast when I'm not really sure, is this the right vein, the left vein? Which branch of the vein? And my technicians will give me a look of like, "Oh doctor, I see. Now, you need more, now you need contrast. Okay, ha ha ha." So sometimes, I use contrast, if I feel like I don't have a good hang of the case, I cannot clarify, there are these livers where the soft tissue contrast is just terrible. I mean, you keep staring at it and you're like, "I don't see anything." I am a heavy, heavy user of liver windows during ablation. I really suggest that people take advantage of it, it shows you a lot more than you will see in the normal soft tissue window.

But as far as post-procedural contrast, I don't think I've done one for four or five years. I will say that some of my colleagues do, the majority don't just because the majority have just kind of fallen into my practice. And if you review, there are no guidelines about it. And I think in the standards of SIR practice, it specifically says, some practitioners might do contrast, while others don't. So there is no support for doing post-procedural imaging or not, because it does have its pitfalls, too.

And we've discovered that from the literature on early contrast imaging of renal lesions. And I'm not sort of comparing apples to oranges here, but if you see some kind of rim enhancement here and there, what does it mean? I don't know. I mean, maybe it's just reactive. So when do I do it? And when I used to do it, I used to do it before when I used to have a gut bad feeling of like, "I think maybe he's bleeding, I think I crushed some branch." So that's really what I used to kind of like, "Let's just take a look." And that kind of almost gave me like a feedback of like, "Actually I'm doing well. Actually I'm doing well." That made me do it less and less and less to where I just stopped doing it.

(7) Techniques, Complications, and Limitations of Ablation

[Dr. Christopher Beck]
Sure. It didn't seem like it was changing overall what you were going to do next and then kind of become superfluous. Can we talk a little bit about specifically, when you're in the liver and how you approach lesions where you know you're going to have some heat-sink. So a lesion that either brackets a blood vessel or is wedged in-between a portal and a hepatic vein, how do you approach those and is your approach any different, truly?

[Dr. Driss Raissi]
I think the first thing that I tell myself is, "You're not going to have heat-sink, don't worry about it."

[Dr. Christopher Beck]
Yeah, just deny. Yeah, okay.

[Dr. Driss Raissi]
Yeah, yeah. It's microwave ablation. I like my device. I think it's a happy relationship. Once in a while, they're like, "Yeah, that's a perfect lesion, that's perfectly bracketed by the middle hepatic and the right hepatic."

[Dr. Christopher Beck]
Sure.

[Dr. Driss Raissi]
And then you're like, "Oh, gee. I see some margins." I wish I was a little bit more aggressive and what do I do? I think I've seen a recent paper published this year, I don't remember who the author was, where they actually recommended hepatic venous occlusion during ablation. And I was like, "I mean, that's interesting." I mean, I guess, I'll have to see a 100 cases to believe that the addition of that step to my practice may be beneficial. I guess you'll need a special CT to do it." But really, what do I do? Honestly, I'm usually more aggressive. At the cost of potentially I might form some good thrombus in that vein, too. I mean, you might thrombose it.

So I think I'm a little bit more aggressive and honestly, I still regret it when I have once in a while some recurrence. Interestingly, the recurrence is usually not as early as you might think. It's not usually within four to six weeks. I've had recurrence in those cases at three to six months, so it's probably a couple sales here and there, tiny little satellites that you've missed because of the heat-sink. I have to say, kudos to microwave ablation, I don't think the heat-sink is nearly as what it was with radiofrequency ablation.

Yeah, just to summarize my answer to your question is, I'm a little bit more aggressive. And often, I wish I was even more aggressive because that's when I treat the recurrence, I just go like, "You know what? I'm going to hit it really hard." And most of the time, nothing happens other than a beautiful big ablation zone.

[Dr. Christopher Beck]
Let me ask you this, how do you handle lesions that are directly adjacent to a dilated bile duct? Is it a similar approach? Actually, I'll just leave it to you. How do you handle lesions that are directly adjacent to a big bile duct?

[Dr. Driss Raissi]
Big bile duct. So when do I start being concerned? Well, the bile ducts have to be of a good size, four or five millimeters and I'm like, "Oh, that's a big one." And then the other one is what type of ducts am I talking about? Some peripheral ducts that big, I mean okay, we'll just atrophy it and move on. I start getting concerned when it's the main right or the main left, that's the concern.

[Dr. Christopher Beck]
Sure.

[Dr. Driss Raissi]
Obviously, we'll try to take advantage of directing the tip of the needle towards it. But my first step is, does this patient need to be optimized, what's his biliary? His biliary is high, you'll get an ERCP or a PTBD, depending if you're a good candidate for one thing or the other. So I mean, I'll try to drop that bilirubin. I'll try to decompress these bile ducts and I think that's the bad thing to do. Decompress your bile ducts before you ablate that patient. And if you cannot, then take advantage of the physical properties of the needle. Hopefully, it's not diffused bile ducts all over the place, because then you're going to be really stuck.

I would say, 10 years ago, I was in a national conference where the panelists were contraindications to microwave ablation is dilated bile ducts. For two to three years, we did my ablation practice, I was like absolutely not, "Nonsense." That's really what it was, total nonsense, absolute nonsense. Then we're going to start denying people left and right for so many reasons. I mean, put a PTBD in it and send them to your friendly ERCP guy to decompress him if it's a bile issue.

Otherwise, like with most patients it can probably be ablated, but obviously, if it's a biliary level of six, seven, eight and there are dilated bile ducts all over the liver, then you may be causing a lot of harm. But most importantly, as an interventional radiologist, you're in a very good position, even if you run into a complication to treat and help that patient afterwards.

[Dr. Christopher Beck]
Can you just for some of the younger listeners, can you kind of talk about what the unsaid risk is whenever you're having a lesion that's really close to a bile duct?

[Dr. Driss Raissi]
It depends how dilated it is, that will be the first thing that I'm going to say.

[Dr. Christopher Beck]
Sure, sure.

[Dr. Driss Raissi]
The worst thing you're going to deal with is, that patient is going to deal with a stricture of their bile duct. I mean, if it's at the main right, I mean, that's a bad stricture. He's going to get obstructed and he's going to come back to you with cholangitis so that's one thing. The other thing, if you injure that bile duct, you're going to end up with a sort of biloma, a leak infection. If he was cooking just a little bit of a cholangitis before your case, or he's one of those patients who has altered surgical anatomy, or previous history of sphincterotomy, he has a few bacteria brewing in there and right after your ablation in two to three days, he might develop pretty bad infected biloma.

So bile is not forgiving and that's why we try to stay away from the gallbladder. As we all know, bile has a few bacteria just lingering there, waiting to cause problems. And it's not pretty to ablate somebody and have this terrible stricture comes back to you with cholangitis and these strictures are very tough to deal with and you may not even be able to cross it. You don't want to have just an external drain for one of these poor patients without the ability to reconstruct his bile duct.

So these are good conversations to have with your patients when you're dealing with one of these cases, there are tools that you have to deal with and try to not run into those problems. Drain your patients, have that bilirubin drop down and take advantage of the physical properties of the needle. If not, have a good conversation with your patient, it's cancer, bile issues, one thing is going to give.

[Dr. Christopher Beck]
True, agreed. So let me take a left turn a little bit. I know we've been talking a lot about HCC, and this could still be HCC, it can be multifocal HCC. Do you have a limit as to the number of lesions that you want to ablate before you start thinking about another treatment modality?

[Dr. Driss Raissi]
That's a good question, right Chris? Because it doesn't seem like there is anything written in the letters where people just kind of mention things here and there. You want to go by Milan criteria and say, "No more than three." I mean, we're going to lose a lot of patients.

[Dr. Christopher Beck]
Yeah. Seems conservative, right?

[Dr. Driss Raissi]
Yeah, we're going to lose a lot of patients. Then somebody told me once, "Oh, four." And I'm like, "Based on what? Why four? Because it's one more than three?"

[Dr. Christopher Beck]
Yeah.

[Dr. Driss Raissi]
Yeah. I mean obviously, you can do more. My surgical colleagues, when they start doing their burns, they're like, "Oh yeah, I burned eight lesions." Yeah. I mean, you have the benefit of doing an intraop. So they don't seem to have a limit of how many lesions they Zap intraoperatively. So should we have a limit? Well, maybe. I mean, sometimes it's very tedious and if you ablate eight lesions in the same session knowing that you are ablating let's say, I don't know, 30, 40, CC's of liver, that adds up to potentially sending the patient into liver failure. So we have to be smart about it.

So I usually take up to six lesions. But what do I do? I try to do what I think makes sense. Why do they have the same sessions? So if I have them in the right maybe, and if I feel like, you know what? The left will take care of the patient so I can freely maneuver in his right lobe now when he has a healthy left, okay. And vice versa, but if I'm going to try to target left and right, a total of three lesions, three lesions here, especially in a patient with HCC, it could be dicey.

So what I do is, I actually divide my sessions. I'm like, "Come to me. Right lobe will give you three or four lesions in that right lobe and then we'll take care of the other one, two, three lesions, whatever you have in the left lobe." The test of time, within two to three weeks. And look at his life, it seems like he has tolerated it. There's no reason to rush. Why are we rushing? We might be dealing with dire consequences.

[Dr. Christopher Beck]
Okay. And so, if I heard you correctly, about three or four weeks in-between treatment sessions, if you're going to take on the right lobe, then you're going to take on the left lobe in the second session, you wait about three or four weeks?

[Dr. Driss Raissi]
Yeah, yeah. I never take it to four, sometimes it goes to four just because of scheduling. I usually, actually go for two to three.

[Dr. Christopher Beck]
Oh, okay. Gotcha. So after you've done all the oblations, everything in your mind from a post-procedure standpoint has been done and you have good adequate margins from your perspective, what does it look like as far as how these patients get plugged into the IR system afterwards? How often are you seeing them? How often do they get imaging after the ablation?

[Dr. Driss Raissi]
Yeah. After the ablation, we usually perform a phone call to see how they're doing in 48 to 72 hours. And then we do a two-week Telehealth clinic visit, thank God for Telehealth, it has helped us tremendously.

[Dr. Christopher Beck]
Is that new with COVID? Was Telehealth a COVID result? Or did y'all have that place beforehand?

[Dr. Driss Raissi]
We had it in place beforehand, but it was because of some of the difficulties that we have here, getting patients to come back. We serve a lot of underserved patients who live three to four hours away. A lot of our patients are from Appalachia and although I say, Telehealth, it's truly Telehealth. A lot of our visits are actually by the telephone, not by the internet because actually, I mean, rural communities, a lot of them don't have internet.

[Dr. Christopher Beck]
Sure.

[Dr. Driss Raissi]
The final follow-up is four to six weeks with an MRI, MRI or CT, depending on the case. So that's usually the follow-up, four to six weeks imaging follow-up.

[Dr. Christopher Beck]
For the first imaging follow-up and the first clinic visit afterwards, does that first imaging service your baseline? Or is that actually an MRI or a CT to which, if you see a small amount of residual disease, that you will go in and treat based on that?

[Dr. Driss Raissi]
That's just a very good question actually, Chris. That's a very excellent, excellent question.

[Dr. Christopher Beck]
That's why they pay me the mid to low range bucks to come across with the good questions.

[Dr. Driss Raissi]
Mid to low, who do I need to talk to?

[Dr. Christopher Beck]
Actually going back, they pay me the zero bucks to ask the tough questions.

[Dr. Driss Raissi]
Tough crowd you work with.

[Dr. Christopher Beck]
That's right.

[Dr. Driss Raissi]
If nothing to see here, we're good. We assume it's good and we continue our 3-months follow-up. So we'll take those out of the conversation. If there is anything tiny, anything left to be seen, whether it's by contrast enhancement, the usual thing, beautiful, smooth, rim enhancement is assumed to be pulse inflammatory. If you have a big chunk of the tumor that correlates exactly with the tumor that's enhancing an arterial phase and wash it out while viewing his face, you're like, "Wow, that was not a good case." That's when I would like, "I don't think I did that one. That was not me."

[Dr. Christopher Beck]
One of the fellows did that.

[Dr. Driss Raissi]
One of the fellows did that. Yeah, yeah, yeah. It wasn't me, I was outside of the room, I was just telling them what to do. So that's the case where it's a slam-dunk. You know what? We need to repeat it. When it's sort of questionable, it looks kind of nodular, I see it on diffusion, we take the tumor board, have our diagnostic radiologist input take a look at them and we make the decisions there.

(8) Ablation Advice for IR Fellows and New Attendings

[Dr. Christopher Beck]
So kind of rounding out this conversation and this probably comes up all the time especially, you're at a teaching institution, what's some good advice that you either give your younger colleagues or your IR fellows who are starting their ablation practice, whether it's from techniques or whether it's from building a practice? What's some of the invaluable advice that you've learned along the way?

[Dr. Driss Raissi]
Well, the first thing I would say is, find a device that you're comfortable with and stick to it. Stick to it and know it very well. Fellows in training and junior colleagues, they're very attracted to shiny new objects, the newest hottest trend in the market and in social media like, "Oh, I've seen this one on Instagram, we definitely need to use this probe." Yeah, just find something that's reliable. Something that you'll have the opportunity to use over and over and over. And when you start, start slow. I didn't start on my first year doing peri-cardiac lesions, that is like, "Oh yeah, I want to ablate lesions who are three millimeters from the pericardium." That's probably a recipe for problems.

So start slow, stick to your easy shots because these are the cases where you're becoming comfortable with that device. As you get comfortable with that device, you'll be able to move on to the next stage of your ablation career and get closer and closer to dicier territories. So I would say, those are my two biggest pieces of advice. Start slow, get comfortable, know your device.

[Dr. Christopher Beck]
Got it. And how about resources for some interventional radiologists out there? Are there any papers or sites that you've looked at that, as you were kind of getting your ablation practice off the ground that you thought these were good foundational papers that either help you participate in tumor boards or help educate referring ducts?

[Dr. Driss Raissi]
I think one of the things that I've tried to do when dealing with through my referring colleagues is radiofrequency ablation is rather what's trusted out there. And people now know that radiofrequency ablation works so when you talk to surgeons and hepatologists, radiofrequency ablation is something that instills trust in them like, "Oh, okay. Yeah, we know about it. We know it's being compared to surgical resection. We know it's rather comparable up to 3.5 centimeter lesions." It's something that they now feel comfortable with. So your first step is to know the literature that compares microwave ablation to radiofrequency ablation. So you can sell microwave ablation as equivalent or non-inferior to radiofrequency ablation.

[Dr. Christopher Beck]
Sure.

[Dr. Driss Raissi]
So there is a paper that I like which is in the International Journal of Hyperthermia and it's a rather recent one from 2019, which compares micro ablation to radiofrequency ablation in hepatocellular carcinoma. It's a systematic review and meta-analysis comparing both modalities. I think they looked at 14 cities, a combination of retrospective studies and control cohort studies for lesions specifically larger than three centimeters and it found no significant difference. You're not going to find papers out there comparing five centimeter radiofrequency ablation because it would inherently have its limitations and the local control starts to drop after 3.5.

Also, one of my favorite articles actually, recently actually, was in 2019 by de Jong et al, which was a systematic review of microwave ablation itself published in 2019 European Journal of Radiology. I think it was called, microwave ablation systematic review of various FDA approved devices. Why do I like that article and I use it in a lot of my presentations? Because you would learn a lot of the physical properties of microwave ablation. You'll learn that not all microwave ablation devices are made the same. Some have different properties than others. Some may be better than others.

And you will also see something very important. You will see how the performance in ex vivo models has nothing to do with in vivo models, which if you're a fellow, you're going to see all these excited numbers in ex vivo model so I'm like, "Oh gee, I can ablate at six centimeter lesion with one probe and be done." No, you won't.

[Dr. Christopher Beck]
Right.

[Dr. Driss Raissi]
So I really like that paper by the de Jong et al.

(9) Ablation of Peri-Cardiac Lesions

[Dr. Christopher Beck]
Okay, nice. And what we'll do afterwards is for those audience members, we'll link about those articles in the show notes. All right. Driss, is there anything that we did not cover? Any stone left unturned that you wanted to turn over for us?


[Dr. Driss Raissi]
What could we say? My favorite topic is actually microwave ablation of pericardial lesions. Because there isn't really much out there, right? I think the University of Wisconsin did some lab research on some porcine live pig models and based on that because the first question is, what is a pericardial lesion? What does that even mean?

[Dr. Christopher Beck]
Sure.

[Dr. Driss Raissi]
How close? Two centimeters, one centimeter, .5 millimeters, what does it even mean? Do you go by how big the lesion is or should you go by what you think your end ablation margin should be? The logic says, you should go in my opinion by the end margin ablation zone because that's where you think maybe the heat energy is reaching. Our colleagues at Madison University of Wisconsin, I mean, did a pretty interesting paper where they estimated that it was safe to ablate peri-cardiac lesions up to five millimeters within the pericardium, based on the final ablation zone. And so I decided just to copy it and do it and we did it and I think we had like 15 patients and we published in the Journal of Translational Gastroenterology and Hepatology.


And actually, we agree with them and we can care that it is correct. There were some nuances that we discovered that with peri-cardiac lesions, everything that kind of looks next to the heart is peri-cardiac. There is a lot of things that might help your procedure be successful and safe. The diaphragm doesn't have the same thickness from periphery to its center, it doesn't. There is a big epicardial fat and what do they say about fat? Fat is a great insulator for heat. So not all patients are made the same, some patients have good epicardial fat and some patients don't. And remember, you always have the tip of the needle to direct towards the heart, which will give you some level of control.


So that's one of the exciting things, we like to push the possibilities a little bit when it comes to microwave ablation. Another topic that we presented at the Society of Interventional Radiology last year is the feasibility of freely going through the lung with microwave ablation, instead of doing 20,000 ancillary maneuvers in order to microwave dome lesions. You might end up with pneumothorax here and there, but that's what happens in a lung biopsy. Sometimes, you might end up with a pleural effusion here and there, but that's about it.


And if I can do my ablation zone and decrease the patient's anesthesia time, I mean, for some of these patients, probably a two hour anesthesia time is not good for them. And the likelihood of pneumothorax or what I call, line complications, did not seem to be more than lung biopsies.


[Dr. Christopher Beck]
Well, I think one, after talking with you for an hour, I'm not surprised that you would be the one to try the approach where you just go through the lung right into the dome, but that's good. So yeah. So for the audience, we'll link to both of those papers. All right. So guys, to our audience, thank you for listening. If you guys enjoyed the podcast, but want more, please check out the show notes of this episode. Those are going to usually be available about one week after we put out the podcast and you can find those at backtable.com.

If you enjoyed the podcast and want to support the show, here are two easy ways. First, take one second and hit the subscribe button on whatever platform you're listening on. This helps platforms like iTunes or Spotify know that you, our audience value what we're doing and you're interested in getting our latest content as we're producing it. Second, if you're really getting a lot of value from these podcasts. Please go to iTunes, leave us a short review, this helps us in a lot of different ways. Plus, we love getting the feedback. That wraps things up, we'll see you next time on the BackTable Podcast. Driss, thank you man, appreciate it.

[Dr. Driss Raissi]
You bet, thanks for having me.

Podcast Contributors

Dr. Driss Raissi discusses Microwave Ablation for Liver Lesions on the BackTable 158 Podcast

Dr. Driss Raissi

Dr. Driss Raissi is the Chief of the Division of Vascular and Interventional Radiology with UK Healthcare in Kentucky.

Dr. Christopher Beck discusses Microwave Ablation for Liver Lesions on the BackTable 158 Podcast

Dr. Christopher Beck

Dr. Chris Beck is a practicing interventional radiologist with Regional Radiology Group in New Orleans.

Cite This Podcast

BackTable, LLC (Producer). (2021, October 3). Ep. 158 – Microwave Ablation for Liver Lesions [Audio podcast]. Retrieved from https://www.backtable.com

Disclaimer: The Materials available on BackTable.com are for informational and educational purposes only and are not a substitute for the professional judgment of a healthcare professional in diagnosing and treating patients. The opinions expressed by participants of the BackTable Podcast belong solely to the participants, and do not necessarily reflect the views of BackTable.

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Liver Ablation Procedure Prep
Liver Cancer Condition Overview
Microwave Ablation Procedure Prep