Mayo Clinic collaboration leads to new techniques for high-fidelity ultrasound super-resolution imaging

Conventional ultrasound techniques are used to diagnose and monitor cancer patients around the world. However, clinical ultrasound is limited when attempting to distinguish between subtle vascular changes. Collaborations between researchers from the University of Illinois and Mayo Clinic are leading to improved imaging techniques that will provide better information for patient treatment.

Pengfei Song, assistant professor in Electrical and Computer Engineering (ECE), graduate faculty member in Bioengineering and faculty member of the Beckman Institute for Advanced Science and Technology, Matthew Lowerison, postdoctoral researcher at Beckman, Yoram Bresler, founder professor in ECE and graduate faculty member in Bioengineering, Chengwu Huang, postdoctoral researcher at the Mayo Clinic Department of Radiology, and Shigao Chen, Professor of Radiology at the Mayo Clinic, are developing a new ultrasound technique to generate high-resolution microvascular images using microbubbles - tiny, FDA-approved gas bubbles surrounded by a lipid membrane.

Normally, human vasculature is very ordered, but cancers tend to grow with a chaotic network of blood vessels that feed the fast-growing tumor. Imaging vasculature is useful for diagnosing patients with many types of cancer, and for determining whether the patient is responding or resistant to their current therapy.

“Imaging blood with ultrasound is difficult because the signal is very low. Microbubbles make this easier because we can track them as they move to produce a trajectory map of the blood vessels,” said Lowerison. “It’s like watching a snowstorm; normally, you can’t see airflow, but the snowflakes carried by the wind make it easier to follow the direction and speed.”

Researchers can track the microbubbles moving through blood vessels, but the bubbles move quickly and overlap, making them difficult to pinpoint – especially in microvasculature like capillaries. In their research, the group used ultrafast imaging, which has hundreds of times the frame rate of conventional ultrasound, to image tumors engrafted onto chicken embryos, and developed a new algorithm to separate populations of the microbubbles spatially and temporally, and also to reduce data acquisition time, which has been one of the major hurdles for clinical translation of the technique.

“Cancer is the immediate application that would benefit from this technique because we know angiogenesis is an important biomarker throughout almost all phases of cancer … we can talk about detection, diagnosis, and therapy response and evaluation. The best part is we can immediately image cancer patients using the new technique: we use FDA-approved microbubbles that are already widely used in the clinic” explained Song.

The researchers are working with commercial partners and their newest generation ultrasound scanners to implement the technique on clinical platforms and image liver and colorectal cancers. The Cancer Center at Illinois and the Beckman Institute of Advanced Science and Technology have been providing the space for this study.

The NIH, National Cancer Institute (NCI), National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), and the National Institute of Neurological Disorders and Stroke (NINDS) supported this research.

The paper, "Short Acquisition Time SuperResolution Ultrasound Microvessel Imaging via Microbubble Separation," is available online from Scientific Reports.