A novel hand-held scanner has been designed to create exceptionally detailed 3D photoacoustic images within seconds, making it ready for clinical use for the very first time and offering possibilities for earlier disease detection.
Researchers from UCL have developed an innovative hand-held scanner capable of producing highly detailed 3D photoacoustic images in mere seconds, marking a significant advancement for clinical applications and potential early disease identification.
As reported in Nature Biomedical Engineering, the research team demonstrated that their technology can provide real-time photoacoustic tomography (PAT) imaging scans to medical professionals, manufacturing precise and intricate visuals of blood vessels that aid in enhancing patient care.
Photoacoustic tomography uses ultrasound waves generated by lasers to detect subtle changes—early indicators of disease—in veins and arteries that are under a millimeter in size and up to 15mm deep within human tissue.
Previously, existing PAT technology was too slow to produce the high-quality 3D images necessary for clinical application.
During a PAT scan, patients need to remain absolutely still; any motion during a slower scan risks blurring the images and rendering them unsuitable for clinical use.
Older PAT scanners required over five minutes to capture an image—by drastically reducing this duration to a few seconds or even less, the image quality is significantly enhanced, making it more suitable for vulnerable or ailing individuals.
Researchers anticipate that the new scanner could facilitate the diagnosis of cancer, cardiovascular diseases, and arthritis within three to five years, pending further validation.
Professor Paul Beard, a corresponding author from UCL Medical Physics and Biomedical Engineering and the Wellcome/EPSRC Centre for Interventional and Surgical Sciences, remarked: “Photoacoustic imaging has progressed impressively in recent years, but obstacles to its clinic usage persisted.”
“The major breakthrough of our study is the vastly improved speed of acquiring images, which is 100 to 1,000 times faster than previous devices.”
“This increased speed prevents blurring caused by movement, yielding highly detailed images unmatched by other scanners. Moreover, it allows for the real-time visualization of physiological changes.”
“These advancements render the system viable for clinical implementation for the first time, enabling us to explore various aspects of human biology and disease that have previously eluded us.”
“More extensive research with larger patient groups is required to substantiate our findings.”
Professor Beard pointed out that a key application for the new scanner could be the evaluation of inflammatory arthritis, necessitating the examination of all 20 finger joints in both hands. The new scanner can accomplish this in just a few minutes, contrasting sharply with nearly an hour required by older PAT scanners, which is too lengthy for elderly and frail patients.
Testing the scanner on patients
In the study, the research team assessed the scanner through pre-clinical trials with 10 patients diagnosed with type-2 diabetes, rheumatoid arthritis, or breast cancer, alongside seven healthy volunteers.
For three patients with type-2 diabetes, the scanner provided intricate 3D renditions of the microvasculature in their feet, revealing deformities and structural transformations in the blood vessels. Additionally, it was utilized to visualize skin inflammation related to breast cancer.
Andrew Plumb, an Associate Professor of Medical Imaging at UCL and a consultant radiologist at UCLH, who co-authored the study, stated: “A common complication for diabetes patients is reduced blood flow in the extremities like feet and lower legs, resulting from damage to the small blood vessels in these areas. However, until now, we lacked the means to observe and analyze the exact damages or how they evolve.”
“In one patient, we observed smooth, uniform vessels in the left foot contrasted with deformed, irregular vessels in the right foot, indicating potential issues leading to tissue damage in the future. Photoacoustic imaging might provide comprehensive insights for early diagnosis and enrich our understanding of disease progression.”
Photoacoustic tomography
Since its inception in 2000, PAT has been recognized as having the potential to transform our understanding of biological mechanisms and enhance the clinical evaluation of significant diseases such as cancer.
This technology operates via the photoacoustic effect, where materials absorb light and emit sound waves.
PAT scanners employ short bursts of laser light directed at biological tissues. The energy absorbs, contingent on the target’s color, resulting in slight increases in heat and pressure that generate a faint ultrasound wave carrying tissue information. This entire procedure transpires in just a fraction of a second.
Early research led by UCL physicists and engineers (under Professor Beard) revealed that the ultrasound wave could be detected through light.
In the early 2000s, they developed a system where sound wave-induced minute changes in a thin plastic film are measurable through a finely-tuned laser beam, unveiling tissue structures previously unseen.
How PAT could assist in disease detection
For some conditions, such as peripheral vascular disease (PVD) arising from diabetes, early indicators of alterations in small blood vessels indicative of the disease are undetectable with conventional imaging modalities like MRI scans.
However, PAT can visualize these changes, presenting opportunities for timely treatment before tissue damage occurs, which can help prevent poor healing and the need for amputations. PVD affects over 25 million people in the USA and Europe.
Moreover, many tumors feature a dense array of small blood vessels that are too minute for detection using other imaging methods.
Dr Nam Huynh from UCL Medical Physics and Biomedical Engineering, who collaborated with Dr Edward Zhang on developing the scanner, explained: “Photoacoustic imaging could facilitate tumor detection and ongoing monitoring easily. It can assist surgeons in distinguishing tumor tissue from normal tissues by visualizing the tumor’s blood vessels, ensuring complete tumor removal during surgery, and minimizing recurrence risks. I envision numerous practical applications for this technology.”
Dr. Huynh emphasized that a significant advantage of this technology lies in its sensitivity to hemoglobin, the light-absorbing compound that generates ultrasound waves.
Improving and testing scanner speed
In the current study, UCL researchers aimed to resolve the speed limitations by decreasing the image acquisition time. They accomplished this via innovations in scanner design and enhanced imaging algorithms.
Unlike earlier PAT scanners that measured ultrasound waves over 10,000 points on the tissue surface sequentially, the new scanner detects them at multiple points simultaneously, greatly accelerating the image acquisition process.
The research team applied similar mathematical methods to those used in digital image compression, enabling the reconstruction of high-quality images from thousands (instead of tens of thousands) of ultrasound measurements, further hastening the imaging process. These advancements reduced imaging time to mere seconds or even less than a second, eliminating motion blur and allowing real-time imaging of dynamic physiological changes.
Scientists noted the necessity for further investigations with a broader patient sample to validate their results and assess the scanner’s practical clinical applications.
The groundwork for developing photoacoustic tomography for medical imaging commenced in 2000; however, its historical roots trace back to 1880 when Alexander Graham Bell, an alumnus of UCL, discovered the transformation of sunlight into audible sound shortly after inventing the telephone.
In 2019, members of the UCL research team established DeepColor Imaging, a spin-off company marketing a variety of scanners rooted in PAT technology globally.
This research received support from Cancer Research UK, the Engineering & Physical Sciences Research Council, Wellcome, the European Research Council, and the National Institute for Health Research University College London Hospitals Biomedical Research Centre.
