PAT imaging breakthrough could transform disease diagnosis

A new handheld scanner, developed at University College London (UCL) and trialled on hospital patients, can generate highly detailed 3D photoacoustic images in just seconds, offering the potential for early disease diagnosis.

Described in the journal Nature Biomedical Engineering, the technology can deliver photoacoustic tomography (PAT) imaging scans to doctors in real time, providing them with intricate images of blood vessels and helping inform patient care. The scanner could help to diagnose cancer, cardiovascular disease and arthritis in 3–5 years’ time, subject to further testing.

PAT uses laser-generated ultrasound waves to visualise subtle changes (an early marker of disease) in the less-than-millimetre-scale veins and arteries up to 15 mm deep in human tissues. However, up until now, existing PAT technology has been too slow to produce high enough quality 3D images for use by clinicians, particularly if the patient moves at all. By reducing that time to just a few seconds, image quality is improved and more suitable for people who are frail or poorly.

“We’ve come a long way with photoacoustic imaging in recent years, but there were still barriers to using it in the clinic,” said UCL Professor Paul Beard, corresponding author on the study.

“The breakthrough in this study is the acceleration in the time it takes to acquire images, which is between 100 and 1000 times faster than previous scanners.

“This speed avoids motion-induced blurring, providing highly detailed images of a quality that no other scanner can provide. It also means that rather than taking five minutes or longer, images can be acquired in real time, making it possible to visualise dynamic physiological events.

“These technical advances make the system suitable for clinical use for the first time, allowing us to look at aspects of human biology and disease that we haven’t been able to before.”

The team tested the scanner during preclinical tests on 10 patients with type 2 diabetes, rheumatoid arthritis or breast cancer, along with seven healthy volunteers; they also compared the PAT scans to clinical scans taken at University College London Hospitals NHS Foundation Trust (UCLH). In three diabetes patients, the scanner was able to produce detailed 3D images of the microvasculature in the feet, highlighting deformities and structural changes in the vessels. The scanner was also used to visualise the skin inflammation linked to breast cancer.

“One of the complications often suffered by people with diabetes is low blood flow in the extremities, such as the feet and lower legs, due to damage to the tiny blood vessels in these areas, but until now we haven’t been able to see exactly what is happening to cause this damage or characterise how it develops,” said senior author Andrew Plumb, a consultant radiologist at UCLH.

“In one of our patients, we could see smooth, uniform vessels in the left foot and deformed, squiggly vessels in the same region of the right foot, indicative of problems that may lead to tissue damage in future. Photoacoustic imaging could give us much more detailed information to facilitate early diagnosis, as well as better understand disease progression more generally.”

Beard said the new scanner could also be used to assess inflammatory arthritis, which requires scanning all 20 finger joints in both hands. This could be done in a few minutes — older PAT scanners take nearly an hour.

Image caption: Photoacoustic tomography image of diseased vasculature in the foot of a patient with type 2 diabetes. Image credit: UCL.