Radiology: Twists and turns of microvessels seen on US could aid cancer treatment

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acoustic angiography - 195.81 Kb
Maximum intensity projections through three-dimensional acoustic angiographic image data for four animals. Source: Radiology (doi: 10.1148/radiol.12112000 )

A new ultrasound approach which provides information on microvessel morphology could eventually lead to a quick, inexpensive, bedside method of identifying cancers when tumors are less than a centimeter in size, according to preclinical research published July 6 online in Radiology.

Abnormalities in vessel structure can reveal underlying disease or the early onset of cancer. Measuring the twists and bends—or tortuosity—of vessels also could offer insights into the effects of therapy.

"The correlation between vessel tortuosity and cancer is well-established,” Paul Dayton, PhD, of the University of North Carolina, Chapel Hill, explained in a release. “What's new about our finding is that we can visualize these vessels in minutes with a very quick scan, using very inexpensive imaging methods."

The method described by Dayton, acoustic angiography, combines high-spatial-resolution ultrasound imaging using microbubble contrast agents with an algorithm for vessel segmentation. Microbubble contrast agents allow the detection of blood flow which would otherwise be obscured by tissue signal noise, according to Dayton and colleagues.

To determine whether this method could form a quantitative basis for distinguishing healthy from diseased tissue, acoustic angiographic images were taken of seven healthy and 10 tumor-bearing rats. A distance metric (DM) and sum of angles metric (SOAM) were then applied to the image data and compared between the two study groups.

Both of the metrics measured significantly higher in each rat within the tumor population. The average DM of the tumor population was 23.8 percent higher than that of the control group, while the average SOAM was 50.7 percent higher in tumor-bearing rats.

“The fact that animals within both control and tumor-bearing populations had significant differences from the aggregate pool of their respective groups suggests that heterogeneity is present within the microvasculature of these rodents, although our results also demonstrated there is a greater degree of vascular heterogeneity in the presence of cancer,” wrote the authors.

Dayton said previous research involving preclinical MRI has demonstrated that vessels can unbend with effective therapy, and future research with acoustic angiography should help determine how effective the ultrasound method can be in assessing therapy effectiveness in humans.

“The limitation that we must now address is that our method works only for tumors at a shallow depth into tissue, such as melanomas or thyroid cancer. Our next studies will focus on this imaging-depth issue as well as evaluating the ability of this technology to determine a tumor's response to therapy,” said Dayton.