Researchers from the Keck School of Medicine of USC and the California Institute of Technology (Caltech) have demonstrated a new noninvasive imaging technique that can quickly produce 3D images of the human body. The study, funded by the National Institutes of Health, was published in Nature Biomedical Engineering.
The new method combines ultrasound and photoacoustic imaging to simultaneously capture images of tissue and blood vessels. The technology aims to address limitations found in current medical imaging techniques such as ultrasound, X-ray, CT, and MRI, which can be costly, time-consuming, or limited in what they can reveal about the body.
To demonstrate its versatility, researchers used the system to image several regions: the brain, breast, hand, and foot. Brain imaging was performed on patients with traumatic brain injury who were undergoing surgery and had portions of their skull temporarily removed. The system was able to capture both tissue structure and blood vessels across areas up to 10 centimeters wide in about 10 seconds.
"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. It's an exciting step forward in noninvasive diagnostics that doesn't use ionizing radiation or strong magnets," said Lihong Wang, PhD, co-senior author and professor at Caltech.
The research team combined rotational ultrasound tomography (RUST) with photoacoustic tomography (PAT) for the first time in humans. RUST uses an arc of detectors instead of a single one to create 3D images of tissues. PAT directs laser light at the area being imaged; hemoglobin molecules absorb this light and emit ultrasonic frequencies detected by RUST's sensors to form 3D images of blood vessels.
This system builds on previous work by the USC-Caltech team showing PAT's ability to image brain activity.
Compared with existing tools like MRI or CT scans, RUS-PAT is less expensive to build and does not require ionizing radiation. It also provides more detailed images than standard ultrasound.
"When we think about the critical limitations of current medical imaging, including expense, field of view, spatial resolution and time to scan, this platform addresses many of them," Liu said.
By successfully imaging different parts of the body—brain, breast, hand and foot—the researchers highlighted potential uses across various health care applications. Brain scans are important for diagnosing stroke or neurological disease; breast scans support cancer care; rapid foot scans could help people with diabetic complications or vascular disease.
"Photoacoustics opens up a new frontier of human study, and we believe this technology will be critical for the development of new diagnostics and patient-specific therapies," said Jonathan Russin, MD, co-first author from University of Vermont.
"This approach clearly has the potential to help clinicians identify at-risk limbs and inform interventions to preserve function in diabetic foot disease and other vascular conditions," said Tze-Woei Tan, MD from Keck School of Medicine.
Before clinical use is possible for RUS-PAT—especially for brain imaging—challenges remain because signals are distorted by the skull. The Caltech team is working on solutions such as adjusting ultrasound frequency. Additional improvements are needed for 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. We're now continuing to refine the system as we move toward future clinical use," Liu said.
Other contributors include Yang Zhang, Shuai Na, Karteekeya Sastry, Li Lin, Junfu Zheng, Yilin Luo, Xin Tong, Yujin An, Peng Hu and Konstantin Maslov from Caltech Optical Imaging Laboratory.
