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
“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
“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.”