by Pohang University of Science and Technology

A transparent ultrasound transducer-based photoacoustic-ultrasound fusion probe, along with images of a rat’s rectum and a pig’s esophagus. Credit: POSTECH

A research team has developed the world’s first high-performance photoacoustic endoscopy based on a transparent ultrasonic transducer. Their findings were recently published in the journal Science Advances.

Endoscopic ultrasound is widely used in gastroenterology for cancer diagnosis, but it offers limited contrast in soft tissues and only provides structural information, ultimately reducing diagnostic sensitivity.

To address this, numerous studies have attempted to integrate photoacoustic technology with endoscopic ultrasound to provide more detailed information about tissue vasculature, thereby improving early cancer detection. However, achieving high-quality photoacoustic and ultrasound imaging simultaneously within an ultra-compact probe has proven challenging.

For obtaining high-resolution images, light and ultrasound must be aligned in the same direction. However, past efforts faced limitations in achieving this alignment. Ultimately, alignment could be achieved either by drilling a hole in the ultrasonic transducer to secure the light path or by tilting the optical system to align the two paths. Both approaches, however, come with trade-offs, often compromising the quality of either the ultrasound image or the photoacoustic image.

In this study, the research team developed an ultra-compact (1 mm²) transparent ultrasonic transducer capable of delivering high-resolution ultrasound and photoacoustic imaging simultaneously. To achieve this, they employed piezoelectric material (PMN-PT) known for its high permittivity and suitability for miniaturization.

The transducer was constructed using transparent materials, including indium tin oxide electrodes and urethane sound-absorbing layers, which preserve the transducer’s structure while allowing the light path to pass through. This design enables high-resolution ultrasound and photoacoustic imaging. The researchers successfully integrated the optical and acoustic systems within this ultra-compact probe and aligned the two imaging pathways.

To evaluate the technology, the team inserted the device into the channel of a commercial endoscope and captured images of a porcine esophagus. As a result, they were able to clearly visualize all layers from the esophageal mucosa down to the muscle layer, with ultrasound performance comparable to that of commercial endoscopes. Additionally, they obtained high-resolution photoacoustic images even at long distances, demonstrating the strong clinical potential of photoacoustic-ultrasound endoscopy.

Professor Chulhong Kim of POSTECH remarked, “This breakthrough is expected to overcome the limitations of existing photoacoustic-ultrasound systems and dramatically improve diagnostic accuracy.”

Professor Hee Man Kim of Yonsei Cancer Hospital added, “These successful experimental results with a transparent ultrasound transducer-based photoacoustic-ultrasound endoscopy system mark an important first step toward developing and localizing innovative diagnostic medical devices.”

More information: Jaewoo Kim et al, Enhanced dual-mode imaging: Superior photoacoustic and ultrasound endoscopy in live pigs using a transparent ultrasound transducer, Science Advances (2024). DOI: 10.1126/sciadv.adq9960

Journal information:Science Advances

Provided by Pohang University of Science and Technology

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