A new hand-held 3D photoacoustic scanner can produce detailed microvascular images in seconds, UK researchers have found, with the technology having the potential to assist with earlier detection of conditions including diabetes, arthritis and cancer.
Photoacoustic tomography (PAT) scanners use laser-generated ultrasound waves to visualise subtle changes in veins and arteries, however, earlier generations of the technology took several minutes to acquire images, which was too slow to be useful in a clinical setting.
In this study, published in the journal Nature Biomedical Engineering, researchers at University College London (UCL), UK, tested a custom-built photoacoustic scanner engineered to produce high-quality 3D scans in a few seconds or less.
Researchers said they used a parallelised sensor readout scheme, high-pulse repetition frequencies excitation lasers and compressed sensing techniques to enable significantly faster acquisition times from the new scanner.
During the investigations, they tested the scanner on volunteers and hospital patients at a variety of anatomical locations, including the wrist and nail bed, and showed it could visualise and quantify microvascular changes associated with diabetes, skin inflammation and rheumatoid arthritis.
‘These studies demonstrated that high-resolution 3D images to depths approaching 15 mm can be acquired, revealing capillary loops, venules, arterioles and large mm-scale arteries and veins, as well as other structures such as venous valves, skin sulci and hair follicles,’ the researchers wrote.
‘The level of image detail that it provides suggests that it could find application as a tool for the clinical detection, diagnosis and treatment monitoring of diseases such as diabetes or cancer that are characterised by microcirculatory abnormalities.’
Lead author Professor Paul Beard of UCL Medical Physics and Biomedical Engineering and the Wellcome/Engineering and Physical Sciences Research Council’s Centre for Interventional and Surgical Sciences, led earlier UCL research which was integral to the first development of this technology.
‘We’ve come a long way with photoacoustic imaging in recent years, but there were still barriers to using it in the clinic,’ he said.
‘The breakthrough in this study is the acceleration in the time it takes to acquire images, which is between 100 and 1,000 times faster than previous scanners.’
Professor Beard said the speed avoided motion-induced blurring during the scan and meant that rather than taking five minutes or longer, images could be acquired in real time, visualising 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,’ he said.
Senior study author Dr Andrew Plumb, associate professor of medical imaging at UCL and consultant radiologist at UCLH, said photoacoustic imaging could give clinicians more detailed information to facilitate early diagnosis, as well as a better understand of disease progression.
Previously, clinicians had not been able to see visualise the microvascular damage in the lower legs and feet of patients with diabetes, or characterise how it developed, he noted.
‘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,’ he said.
Dr Nam Huynh of UCL Medical Physics and Bioengineering, who was one of the photoacoustic scanner developers, said the technology had the potential to detect and monitor tumours.
‘It could also be used to help cancer surgeons better distinguish tumour tissue by visualising the blood vessels in the tumour, helping to ensure all of the tumour is removed during surgery and minimising the risk of recurrence,’ he said.
Further research is now needed with a larger group of patients to confirm the findings and the scanner’s clinical utility, the researchers said.
Image credit: Photoacoustic tomography image of diseased vasculature in the foot of a patient with type 2 diabetes – UCL.
