In the United States, more than one-fourth of adults over age 40 have an eye disease, including glaucoma, cataracts or age-related macular degeneration, or a chronic health condition that affects the eyes, such as diabetic retinopathy. These conditions are a strain on an individual's health as well as on the health-care system, yet early diagnosis and management can help to prevent more than 90% of severe vision loss.
Chao Zhou, a professor of biomedical engineering in the McKelvey School of Engineering at Washington University in St. Louis, has been working to improve optical coherence tomography (OCT) systems that can conduct high-resolution imaging of the eyes. Now, with an up to $20 million contract from the Advanced Research Projects Agency for Health (ARPA-H), he plans to create a portable OCT system based on photonic integrated circuits (PIC) and custom-designed electronic integrated circuits that could offer advanced eye screening to many more patients and at a lower cost. The technology also could be used in other applications, such as cardiology, dermatology, dentistry, endoscopy and urology.
The contract is part of ARPA-H's first call for proposals for unconventional approaches to improving health outcomes across patient populations, communities, diseases and health conditions through breakthrough research and technological advancements. It is the first ARPA-H contract awarded to Washington University.
Traditional OCT systems are expensive, complex, bulky and labor-intensive to assemble and calibrate. The proposed system would weigh a few pounds, take high-resolution 3D scans of the retina in less than a second and be a fraction of the cost of the traditional systems.
The integration of photonic and electronic integrated circuits simplifies the assembly process and lowers production costs, making OCT more accessible to a wider range of health-care facilities and patients. Integrating components on a photonic chip also enhances overall stability and robustness, making these systems less susceptible to environmental influences and wear and tear, ensuring a longer lifespan and lower maintenance costs."
Chao Zhou, professor of biomedical engineering, McKelvey School of Engineering, Washington University in St. Louis
Zhou's group invented the space-division multiplexing optical coherence tomography (SDM-OCT), a technique that takes multiple high-definition OCT images simultaneously with a single detector and is at least 10 times faster than existing OCT scanners, which creates fewer opportunities for errors from patient movement. However, these systems required extensive time and labor to assemble components for each channel, which limited their broad use.
With the ARPA-H funding, Zhou and collaborators will assemble the components in a photonic chip using advancements in complementary metal-oxide-semiconductor (CMOS) processes used in the semiconductor industry. This will streamline manufacturing and lower costs. Once functioning, they will conduct studies using the device on adult and pediatric patients.
Developing a fully integrated photonic-integrated chip (PIC)-OCT system is very impactful yet also very challenging, the researchers said, so the team has divided its work into eight parts, ranging from developing components to testing. At the end of the five-year project, the team expects to have developed photonic and electronic chips and portable PIC-OCT prototypes specifically for ophthalmic imaging.
The proposed system is more than 50 times faster than existing state-of-the-art commercial OCT systems at a fraction of the cost, the researchers said. By optimizing and integrating the photonic and electronic circuits, the researchers can create an integrated image acquisition and signal processing engine with benefits that extend into other areas of health care, such as glucose sensing and portable skin imagers.
Collaborating with Zhou are:
- Shu-Wei Huang, an assistant professor of electrical, computer and energy engineering and of biomedical engineering at the University of Colorado Boulder;
- Aravind Nagulu, an assistant professor of electrical and systems engineering at the McKelvey School of Engineering;
- Rithwick Rajagopal, MD, PhD, an associate professor of ophthalmology and visual sciences at Washington University School of Medicine;
- Margaret Reynolds, MD, an assistant professor of ophthalmology and visual sciences at Washington University School of Medicine; and
- Lan Yang, the Edwin H. & Florence G. Skinner Professor of electrical and systems engineering at the McKelvey School of Engineering.
Yang said it is in her long-term interest to transform knowledge in photonics research into technologies and tangible products with a far-reaching societal impact, with health-care applications at the top of her agenda.
"I'm excited to be part of this multidisciplinary team that aims to develop a new OCT system with capabilities and features enabled by advancements in nanofabrication processes for optoelectronic devices driven by various industries, from telecommunication to data centers and consumer electronics," Yang said. "Our proposed portable OCT system, based on photonic integrated circuits (PIC), will provide advanced and cost-effective eye screening and extend its benefits to other medical fields."
Rajagopal said that eye doctors have benefitted from the diagnostic insights offered by OCT technology for the past 15 years, but the systems are limited by scan-speed and field-of-view.
Most modern scanners can only image the very center of the retina -; the macula -; and require cooperative patients who have the mobility to maneuver into and stay steady on a desktop system for at least 30-60 seconds (or more), Rajagopal said.
"I am enthusiastic about the potential clinical benefits offered by Dr. Zhou's new system, as it may allow us to perform much higher-resolution scans and include simultaneous peripheral scanning in addition to the retinal center, all while taking a fraction of the time required by currently available systems," Rajagopal said. "We may therefore be able to scan patients who are unable to cooperate for traditional ocular imaging, including young children and adults with disabilities, without the need for pupillary dilation or sedated exams."
The team will work with commercial foundries to fabricate the photonic and electronic integrated circuits.
"Not only does this fully integrated PIC-OCT system outperform conventional OCT systems, but it also boasts excellent manufacturability and robustness and reduces device footprint," Zhou said. "In addition, mass production would significantly reduce manufacturing costs, paving the way for widespread future dissemination."
While the team already has several U.S. and international patents related to the SDM-OCT, it is working with Washington University's Office of Technology Management on patent applications for the improved design. They will also work with ARPA-H Project Accelerator Transition Innovation Office and with the Food & Drug Administration on regulatory considerations to clear the pathway for future clinical translation.
"I am very excited to be part of this world-class team to pursue this ambitious project that makes OCT a true point-of-care solution," Huang said. "It is a perfect example showing how PIC technology can be transformative in areas other than communication and computing."
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