A new non-invasive medical imaging technique simultaneously creates 3D images of both tissues and blood vessels in the human body. The method combines ultrasound and photoacoustic imaging.
The technique was developed by researchers at the Keck School of Medicine at the University of Southern California (USC) and engineers at the California Institute of Technology (Caltech). The method was tested in a proof-of-concept study, the results of which were published in Nature Biomedical Engineering.
Current standard medical imaging techniques such as ultrasound, X-ray, CT scans and MRI have limitations. These include cost, scan time, image depth and level of detail. The new technique could be an alternative, according to the researchers. The method creates fast, three-dimensional images, without ionising radiation or strong magnetic fields.
A combination of RUST and PAT
Called RUS-PAT (Rotational Ultrasound and Photoacoustic Tomography), the technique combines two methods:
- Rotational Ultrasound Tomography (RUST) to create 3D images of tissues using sound waves;
- Photoacoustic Tomography (PAT) to image blood vessels using laser light.
During the study, different parts of the body were scanned, including the brain, breast, hand and foot. In brain scans of patients with traumatic brain injury, the technique was able to image both tissue structures and blood vessels in an area 10 centimetres wide within about 10 seconds.
Cheaper, no radiation and more detail
RUS-PAT offers several advantages over existing imaging techniques, according to the researchers. For instance, the new method is cheaper than an MRI scanner, avoids radiation like X-ray and CT scans, and provides more detailed images than conventional ultrasound. The researchers see potential in RUS-PAT for the diagnosis of stroke, brain injury, breast cancer and diabetic foot, among others.
Lihong Wang, professor of medical technology and electrical engineering at Caltech, says: "We have devised a new method that changes the way ultrasound and photoacoustic systems work together. This allows us to achieve much more comprehensive imaging at meaningful depths, without ionising radiation or strong magnets." Jonathan Russin, neurosurgeon at the University of Vermont and co-author, points out the importance of photoacoustics: "Photoacoustics opens a new era in human research. We believe this technology will be crucial for the development of new diagnostics and patient-specific therapies."
Challenges
The technique is still under development. Thus, brain scans in particular present challenges. The skull can interfere with signals in this case. The team is still looking for ways to improve image quality, such as adjustments in the ultrasound frequencies used. "This is an early but important proof-of-concept study showing that RUS-PAT can produce medically relevant images for different parts of the body. We are now working to further refine the system for future clinical use," said Charles Liu, professor of neurosurgery at Keck School of Medicine and co-principal author of the study.
In addition to Liu, Wang and Russin, Tze-Woei Tan, Yang Zhang, Shuai Na, Karteekeya Sastry, Li Lin, Junfu Zheng, Yilin Luo, Xin Tong, Yujin An, Peng Hu and Konstantin Maslov (Caltech Optical Imaging Laboratory) also collaborated in the study.
