Ready, Aim, Ablate: Optimizing the Liver Ablation Zone

[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 interventionalists 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 a .5 centimeter surgical [ablation zone] margin….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? 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 [ablation zone] 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... 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]
...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]
...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...