Saturday, June 13, 2015

A new ultrasound technique to improve cancer diagnostics. Interview with Sarah Shelton

North Carolina: “Paul Dayton's  lab does ultrasound research. The overall goal is to make existing ultrasound technology better and use it for something relevant to disease. I’m focusing on cancer angiogenesis – the abnormal process of blood vessel growth in tumors. Malignant tumors have these twisted blood vessels. Benign tumors are not like that. So we use a contrast agent that harmlessly flows through the blood vessels so that we can use ultrasound to image the vasculature of tumors. The contrast agents are microbubbles, which are micron-sized spheres just slightly smaller than red blood cells. We inject the microbubbles intravenously, and, they travel through the vasculature. The microbubbles reflect ultrasound so that we can get an image of blood vessels. We have a unique approach for imaging these microbubbles  which is called acoustic angiography.”

How are the bubbles imaged, exactly?

“We use the frequency of the ultrasound. A low frequency excites the bubbles, and then we use a high frequency transducer to receive signals that come back from the excited microbubbles. This way, we don’t see any tissue; we isolate the signal from the microbubbles so that we’re only getting images of the microbubbles. And because the microbubbles are only in the vasculature, by proxy, we are only imaging the vasculature.
“The high frequency gives us high-resolution images. This allows us to see smaller structures.  The frequency separation also lets us reject background signal from structures other than microbubbles. This is important because there’s actually a lot of stuff in the background – tissue, fat, other parts of the tumor. But in our images of vasculature, the background is black.”

How could this help patients?

“We hope it will add valuable information to the diagnostic process. For example, to diagnose breast cancer, people first get a mammogram. If something looks suspicious, they go back in for a second look – often with ultrasound imaging. What doctors actually look at is a gray-scale image. There are clinical grades – if the mass looks like this, then it looks like cancer. There are metrics to determine if it’s a benign or malignant mass. 
“Our hope is that our acoustic angiography method can do a better job at distinguishing what is and is not cancer. Our method might be able to help patients avoid getting biopsied. That’s long term. We would need many more trials and more sophisticated transducers – the equipment that picks up the signals so that we can image the vasculature.”

Is this in clinical trials?

“The trial just got underway. We’re adding an ultrasound before people get biopsied. So we’ll have our images and we’ll have biopsy results to see what we were actually looking at. Then we’ll do a study to see whether the radiologists think our images add information that they’re not getting from the other ultrasound images, regarding vascular structure.
“In animal models, we’ve shown that if you look at our acoustic angiography images of a tumor, you don’t have to know anything about imaging or ultrasound or even tumor biology to notice that cancerous tumors are very different from healthy tissue.
“If someone simply tells you that cancer makes twisted blood vessels, then you could look at two images and say, ‘this one is cancer and this one is not.’”

How else could acoustic angiography be used?

“Down the road, we could possibly track response to treatment. We could see if the tumor vasculature is changing in response to therapy. We hypothesize that the vasculature may indicate whether someone is responding to treatment. We think this vascular change would appear before the tumor would actually shrink. Right now, that’s how a treatment is judged – if a tumor is smaller after a certain amount of treatment.
“If we could produce an earlier indication of whether a treatment is working, then we could potentially know earlier whether doctors should switch treatment. This, obviously, is way down the road. But it’s something we’re thinking about now.”