New 3D Imaging Tech Combines Ultrasound & Light for Detailed Views of Human Tissue

A new medical imaging technique developed by researchers at Caltech and the University of Southern California (USC) promises to deliver detailed, three-dimensional color images of the human body, revealing both tissue structure and blood vessel function. The method, called RUS-PAT (rotational ultrasound tomography combined with photoacoustic tomography), has already been successfully used to image multiple parts of the human body and could significantly improve diagnostics for conditions ranging from breast cancer to diabetic neuropathy and brain disorders.

The findings, published in January 16, 2026, in Nature Biomedical Engineering, address limitations inherent in existing imaging technologies like ultrasound, CT scans, and MRI.

The Challenges with Current Imaging Methods

Traditional ultrasound is a widely used, affordable, and rapid imaging tool, but it primarily provides two-dimensional images of tissue shape with a limited field of view. Photoacoustic imaging offers a complementary approach, utilizing laser light to visualize blood vessels and blood flow in color. However, it struggles to provide the same level of detailed structural information as ultrasound.

While computed tomography (CT) and magnetic resonance imaging (MRI) offer more comprehensive imaging, they often come with drawbacks. These include the need for contrast agents, exposure to ionizing radiation (in the case of CT), high costs, and lengthy scan times, making frequent use impractical.

RUS-PAT: A Synergistic Approach

RUS-PAT was designed to overcome these limitations by combining the strengths of both ultrasound and photoacoustic imaging. The foundation for photoacoustic tomography was laid over two decades ago by Lihong Wang, the Bren Professor of Medical Engineering and Electrical Engineering and the Andrew and Peggy Cherng Medical Engineering Leadership Chair at Caltech. Photoacoustic tomography works by sending short pulses of laser light into tissue. When tissue molecules absorb this light, they vibrate and generate acoustic signals that can be measured and converted into detailed images.

“But it’s not like one plus one,” explains Wang. “We needed to find an optimal way of combining the two technologies.” The key innovation lies in a simplified and more practical design. Traditional ultrasound systems rely on numerous transducers, making integration with photoacoustic imaging complex, and expensive. Photoacoustic imaging, however, only requires ultrasound detection. This insight led Wang to explore whether ultrasound waves could be used to mimic the light excitation process in photoacoustic imaging.

The resulting system utilizes a single, wide-field ultrasound transducer to send sound waves throughout the tissue. The same detectors then capture signals from both imaging modalities. A small number of arc-shaped detectors rotate around a central point, effectively functioning as a full hemispheric detector while significantly reducing complexity and cost.

Potential Applications and Early Results

“The novel combination of acoustic and photoacoustic techniques addresses many of the key limitations of widely used medical-imaging techniques in current clinical practice, and, importantly, the feasibility for human application has been demonstrated here in multiple contexts,” says Dr. Charles Y. Liu, a co-author of the study, professor at the Keck School of Medicine of USC, director of USC’s Neurorestoration Center, and chair of neurosurgery at the Rancho Los Amigos National Rehabilitation Center.

Because RUS-PAT can image tissues accessible to light, it has broad potential clinical applications. In breast cancer imaging, the technique could help pinpoint tumor location while simultaneously providing information about its biological activity. For patients with diabetic neuropathy, it could allow physicians to monitor both nerve structure and oxygen supply in a single scan. Researchers also envision applications in brain research, where the technology could be used to study brain anatomy and blood flow dynamics concurrently.

Currently, the system can image tissue up to approximately 4 centimeters deep. The use of endoscopic tools to deliver light could potentially extend this depth. Each RUS-PAT scan takes less than one minute to complete.

Study Details and Funding

The study, titled “Rotational ultrasound and photoacoustic tomography of the human body,” was co-led by Yang Zhang, Shuai Na, and Dr. Jonathan J. Russin. Zhang and Na, who conducted the work as postdoctoral researchers at Caltech, are now based at Tsinghua University and Peking University in Beijing, respectively. Dr. Russin is affiliated with the Keck School of Medicine of USC and the Rancho Los Amigos National Rehabilitation Center in Downey, California.

Additional contributors from Caltech included Karteekeya Sastry, Li Lin, Junfu Zheng, Yilin Luo, Xin Tong, Yujin An, Peng Hu, and former research scientist Konstantin Maslov. Dr. Tze-Woei Tan from the Keck School of Medicine of USC also contributed to the research. The research was funded by the National Institutes of Health.

The system has already undergone testing on human volunteers and patients and is now in the early stages of transitioning towards clinical use.