Caltech’s PACTER Takes a Leap Forward in 3D Medical Imaging

Caltech's PACTER Enhances Medical Imaging: Simplifies Procedures, Enables 3D, Reduces Complexity
Caltech’s PACTER Enhances Medical Imaging: Simplifies Procedures, Enables 3D, Reduces Complexity
(Credit: Caltech)

Caltech has made significant strides in the field of medical imaging with the enhancement of its photoacoustic imaging technology, known as PATER (Photoacoustic Topography Through an Ergodic Relay). This breakthrough, led by Caltech’s Bren Professor of Medical Engineering and Electrical Engineering, Lihong Wang, along with postdoctoral scholar Yide Zhang, streamlines procedures, facilitates 3D imaging, and reduces operational complexity.

Enhancing Photoacoustic Imaging with Ergodic Relay Technology

Photoacoustic imaging involves pulsing laser light into tissue, causing the tissue’s molecules to vibrate. These vibrations serve as a source of ultrasonic waves for internal structure imaging, similar to ultrasound. However, early versions of this technology required arrays of hundreds of sensors pressed against the tissue’s surface, making it complex and costly.

Wang and Zhang addressed this challenge by incorporating an ergodic relay device, reducing the need for numerous transducers. The ergodic relay slows down the flow of information (vibrations) into a transducer. To understand this, consider data transmission in computing: serial transmission sends data in a single stream through one channel, while parallel transmission sends multiple pieces of data simultaneously through multiple channels.

This innovative approach not only simplifies the process but also improves the efficiency of photoacoustic imaging. The findings were published in the journal Nature Biomedical Engineering, showcasing Caltech’s commitment to advancing medical imaging techniques for better, faster, and more accessible healthcare. The team’s dedication to refining existing technologies demonstrates how progress in science often involves optimizing and enhancing what we already know.

Wang has designed this cutting-edge system equipped with 512 sensors, reminiscent of a store boasting multiple cash registers. The sensors work simultaneously, each capturing specific data on ultrasonic vibrations generated by laser pulses.

Explaining the intricacies of the system, Wang highlights the challenge of handling the rapid burst of ultrasonic vibrations. Utilizing a concept termed an “ergodic relay,” Wang describes it as a chamber where sound can reverberate. As the ultrasonic vibrations traverse through the ergodic relay, they undergo a temporal stretching. To draw a parallel with a cash register scenario, it’s akin to having an additional staff member advising customers to take a few rounds around the store before approaching the cashier, preventing the cashier from being overwhelmed.

Enter PACTER (Photoacoustic Computed Tomography Through an Ergodic Relay), the latest evolution of this technology. This upgraded version revolutionizes the system, enabling it to function with a solitary transducer. Through sophisticated software, this lone transducer can now amass data equivalent to what 6,400 transducers could collect.

According to Wang, who holds the esteemed Andrew and Peggy Cherng Medical Engineering Leadership Chair, and serves as the executive officer for medical engineering, PACTER boasts two significant improvements over its predecessor, PATER.

PACTER: Advancements in 3D Imaging and Calibration Elimination

Firstly, PACTER has the ability to generate three-dimensional images, a notable advancement compared to PATER’s limitation to two-dimensional images. This leap forward was made possible by the development of enhanced software, marking a significant stride in the field of imaging technology. The unveiling of PACTER marks a promising chapter in the relentless pursuit of refining and advancing medical imaging capabilities.

PACTER presents a second significant advancement over its predecessor, PATER: it eliminates the need for calibration before each use.

“With PATER, we had to calibrate it each time to use it and that’s just not practical. We got rid of this per-use single-time calibration,” Wang says.

Previously, calibration was a crucial step due to the system’s firing of a laser pulse into tissue, causing an “echo” that would bounce back into the transducer. This echo interfered with the transducer’s ability to sense direct ultrasound information. Wang unveils the ingenious solution implemented in PACTER—a component called a “delay line” is incorporated into the system. This delay line compels the echo to travel a longer physical path on its return journey to the transducer, ensuring that it arrives after the direct ultrasound information has been successfully received.

“Even though I always said this was possible, I knew it would be challenging,” Wang says.

The details of this groundbreaking work are outlined in the paper titled “Ultrafast longitudinal imaging of haemodynamics via single-shot volumetric photoacoustic tomography with a single-element detector,” published in the November 30 issue of Nature Biomedical Engineering. The collaborative effort involved several researchers, including Peng Hu (PhD ’23), Lei Li (PhD ’19), Rui Cao, Anjul Khadria, Konstantin Maslov, Xin Tong, and Yushun Zeng, Laiming Jiang, and Qifa Zhou from USC.

It is noteworthy that the research received financial support from the National Institutes of Health, underscoring the significance and potential impact of this cutting-edge technology in the realm of medical engineering. The elimination of the calibration requirement, coupled with other advancements, positions PACTER as a formidable player in the quest for refined and efficient medical imaging capabilities.

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Source(s): SciTechDaily

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