A research team has recently developed a continuous rotational scanning photoacoustic computed tomography (PACT) system that allows rapid, high-resolution imaging of living organisms, a major advancement in biological imaging. Their findings, published in Laser & Photonics Reviews, open up new possibilities for observing dynamic processes in biological systems with unprecedented speed and detail.
In biomedical research, it has become increasingly important to track whole-body dynamics to better understand complex biological processes and disease progression in living organisms. Traditional imaging techniques like X-ray CT, MRI, PET, and optical imaging are commonly used with small animal models, each offering specific advantages. However, each method also has limitations, such as the potential for high radiation exposure with CT, lower resolution in some MRI applications, or challenges with soft tissue contrast in optical imaging. The search for a comprehensive imaging tool has led researchers to focus on PACT, a technology that combines the strengths of optical and ultrasound imaging.
The PACT system offers a unique approach, as it uses light absorption to generate ultrasound signals in biological tissues. This allows it to capture not only structural but also functional and molecular characteristics within the tissue, making it particularly useful for whole-body imaging. Traditional PACT systems, however, faced constraints due to lengthy imaging times and a limited field of view, typically capturing only one side of the body, which limited their application for observing whole-body dynamics in real time.
To overcome these limitations, the research team developed an advanced PACT system that uses a rapidly rotating hemispherical array of ultrasound transducers. This design enables the simultaneous collection of multiple data points and significantly speeds up imaging, addressing the time limitations of prior models. The continuous rotation of the ultrasound array allows 360° imaging of a small animal’s torso in only nine seconds and completes a whole-body scan in just 54 seconds. With this capability, the system achieves an impressive spatial resolution of around 212 micrometers, providing finely detailed images of tissue structures and processes.
This improved imaging speed and resolution allow the PACT system to track a range of biological parameters in real time, including structural details, drug distribution, and oxygen saturation levels. The system’s ability to monitor changes in hemoglobin oxygen saturation in particular offers a significant advantage, as it provides insights into oxygen transport and distribution across different tissues, a critical factor in understanding metabolic and vascular functions in living organisms. Monitoring these oxygen dynamics is especially important for studying disease mechanisms, cancer progression, and response to treatments, as oxygen saturation levels can indicate tissue health and vitality.
The study was led by Professor Chulhong Kim, a specialist in convergence engineering at POSTECH. Professor Kim’s team included researcher Seongwook Choi, who completed his Ph.D. at Stanford University and is part of the POSTECH Institute of Artificial Intelligence, and researcher Jinge Yang, a Ph.D. graduate from Caltech, now with POSTECH’s Department of Electrical Engineering. The team’s interdisciplinary collaboration brought together expertise in electrical, mechanical, and convergence engineering to address the technical challenges of this new imaging technology.
Professor Kim highlighted the significance of their work, emphasizing that the system not only matches the performance of established imaging techniques but also provides molecular and functional information, adding a new dimension to preclinical research capabilities. This could enable a deeper understanding of disease mechanisms, early disease detection, and better monitoring of treatment effects in animal models.
Dr. Choi pointed out the specific advantages of the PACT system for observing rapid biological processes, such as the dynamic distribution of oxygen, which is essential for life and often altered in disease states. By capturing these dynamics in real time, the system offers valuable insights that could help refine preclinical models and improve research into complex biological processes like blood flow, tumor growth, and drug metabolism.
The new PACT system’s continuous rotational scanning approach is expected to have a wide range of applications. Not only does it offer detailed insights into biological systems, but it also provides a safer and less invasive imaging alternative, using no ionizing radiation. This makes it especially appealing for longitudinal studies where subjects need to be imaged repeatedly over time.
The research team plans to continue refining the PACT technology, exploring ways to further increase its resolution and imaging speed while reducing its size and cost for potential wider use in preclinical and clinical research. Their work represents a significant step forward in biological imaging technology, potentially paving the way for new diagnostic tools that could translate from animal studies to human applications, particularly in fields like oncology, cardiovascular health, and personalized medicine.
In developing this advanced PACT system, the researchers utilized the OtaNano research infrastructure, a high-tech facility dedicated to nano-, micro-, and quantum technologies. This state-of-the-art infrastructure provided them with the necessary tools to explore and advance the limits of imaging technology.
Ultimately, the team’s innovations hold the promise of revolutionizing biomedical imaging by making it possible to visualize complex biological systems in real time with high accuracy, which could enhance our understanding of health and disease and inform the development of future medical treatments.