Cavitation in soft tissue relies on dissolved gas pockets so small (nanometer scale) that their surface tension is extremely high, roughly 200 to 300 times normal, making it very hard to trigger and control bubble formation there, which is why doing this safely in the body was once thought impossible. The lungs are different: they contain much larger gas pockets at higher partial pressure, so applying focused ultrasound there risks producing large bubbles that can rupture lung tissue, which is why histotripsy cannot currently be used to treat lung cancer.
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The proximity of the heart to the lungs means histotripsy near the heart has to be done carefully to avoid the lung's large gas pockets.
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Current FDA approval for histotripsy covers liver cancer, with clinical trials underway for pancreas and kidney treatment.
261 words · auto-generated from the episode video
7:06Right. So there's dissolved gases in the fluid. But it's the future by the lung. So the dissolved gas pockets in the tissue, like in our liver, in our pancreas, heart, they are nanometer gas pockets. Really, really tight. And it's very hard to damage cavitation from those nanometer gas pockets because their surface tension are extremely high. We're talking about 200 to 300 times of the time. And then, you know, can possibly control the generation
7:50and the activity of cavitation in your human body to do things like non-invasive surgery. That was considered impossible. That was okay. I see. I see the point. Yeah. And like in lungs, because the lungs have so much, such a higher, let's say partial pressure of gases. Just so many large bubbles. You're going long and use ultrasound, you're gonna explode the lungs. Interesting. Okay. So people don't want to go too long to do this cavitation thing. And I also need to say that histotripsy is great, but so far we cannot treat lung cancer because lung is just full of large air bubbles.
8:32But it has been used to treat other parts. Yeah, yeah, yeah. And it's kind of scary that the heart is right next to the lungs. So there are ways that you need to do it very carefully. We'll talk later, but right now, the clinical use of histotripsy, so far the FDA approval is to treat liver cancer. And then clinical trials of pancreas and kidney and other things. So we are, you know, away from them.