Photoacoustic and ultrasound imaging combine for clearer mapping of blood vessels

20 Jan 2026

Keck School of Medicine and Caltech image both tissue and blood vessels simultaneously.

A project at USC Keck School of Medicine and Caltech has developed an imaging platform offering improved views of both blood vessels and tissue.

Described in Nature Biomedical Engineering, the new method has the potential to address current gaps in medical imaging, according to the researchers.

In particular the technique aims to counter the individual limitations of imaging modalities such as ultrasound, X-ray, computed tomography and magnetic resonance imaging when used on their own, including the cost and time taken to perfrom adequate imaging operations.

"You cannot understate the importance of medical imaging for clinical practice," commented Charles Liu from Keck School of Medicine. "Our team has identified key limitations of existing techniques and developed a novel approach to address them."

The researchers combined two imaging methods, rotational ultrasound tomography (RUST) and photoacoustic tomography (PAT), to create a hybrid modality christened RUS-PAT. Ultrasonography provides a morphological assessment of soft tissue, while PAT visualizes blood vessels to enable 3D panoramic imaging.

Like a standard ultrasound, RUST directs sound waves at an area being imaged, but employs an arc of detectors to recreate a 3D volumetric image of the body’s tissues.

PAT directs a beam of laser light at the same area, which is absorbed by hemoglobin molecules in the blood. These molecules vibrate and give off ultrasonic frequencies, which are measured by the same detectors to create 3D images of blood vessels.

"We've devised a novel method that changes how ultrasound and photoacoustic imaging systems work together, which allows us to achieve far more comprehensive imaging at meaningful depths,"said Caltech's Lihong Wang, co-senior author of the paper and a pioneer of photoacoustic imaging. "It's an exciting step forward in noninvasive diagnostics that doesn’t use ionizing radiation or strong magnets."

Imaging of brain and breast

According to the project's presentations, RUS-PAT uses only a single-element transmission transducer rather than a large number of discrete transmission elements. Additionally, RUS-PAT employs its arc-shaped detection arrays "in a cost-effective way, instead of using high-cost, dense, hemispherical arrays," to achieve three-dimensional panoramic ultrasonic detection.

In trials imaging the human head, breast, hand and foot, RUS-PAT successfully imaged a 10-centimeter-diameter field of view at submillimeter isotropic resolution with a 10-second imaging time for each modality. It did so while avoiding the use of ionizing radiation, the damaging nature of which has remained a major challenge in medical imaging.

Brain imaging plays a central role in the diagnosis and treatment of stroke, traumatic brain injury and neurological disease, while breast imaging supports care for one of the most common cancers worldwide, so the impact of RUS-PAT in clinical practice could be significant.

One major challenge before then for brain applications is that the human skull distorts the system's signals, making it hard to collect clear images. The Caltech team is exploring novel approaches to solve this problem, including adjustments to ultrasound frequency. Further improvements are also needed to ensure consistent image quality across scans.

"This is an early but important proof-of-concept study, showing that RUS-PAT can create medically meaningful images across multiple parts of the body," said Charles Liu. "We're now continuing to refine the system as we move toward future clinical use."