Caltech’s recent advancements in photoacoustic imaging have led to the development of an enhanced technology known as PACTER, which marks a significant stride in medical imaging. This upgraded version streamlines the process by minimizing the requirement for numerous sensors, facilitates three-dimensional imaging, and removes the need for calibration prior to each use, thus enhancing the practicality and efficiency of the technology.
Caltech’s refined photoacoustic imaging technology, PACTER, offers simplified operations, 3D imaging capabilities, and reduced operational complexities, representing a noteworthy leap in the field of medical imaging.
Scientific advancement sometimes involves discovering entirely new concepts, while at other times, it’s about enhancing existing methods to make them faster and more efficient.
The latest research from Lihong Wang’s lab at Caltech, where he serves as the Bren Professor of Medical Engineering and Electrical Engineering, exemplifies the latter. Published in Nature Biomedical Engineering, the paper by Wang and postdoctoral scholar Yide Zhang details their work on refining a photoacoustic imaging technique first introduced in 2020.
This technique, known as PATER (Photoacoustic Topography Through an Ergodic Relay), is a focus of Wang’s research group.
Enhancing Photoacoustic Imaging Techniques
Photoacoustic imaging involves pulsing laser light into tissue, causing the tissue’s molecules to vibrate and produce ultrasonic waves. These waves then help image internal structures similarly to ultrasound imaging.
Earlier versions of Wang’s photoacoustic imaging required numerous sensors (transducers) to capture the ultrasonic vibrations, which complicated and increased the cost of the technology.
Wang and Zhang have reduced the number of necessary transducers by employing an ergodic relay. This device slows down the rate of vibration flow into a transducer. To analogize, if serial transmission of data is like a single cash register in a store, parallel transmission is like multiple registers operating simultaneously. Wang’s 512-sensor system is akin to the latter.
The ergodic relay in Wang’s design extends the ultrasonic vibrations in time, akin to customers walking laps around a store before reaching a single cashier, preventing the cashier from becoming overwhelmed.
PACTER: The Next Step Forward
PACTER (Photoacoustic Computed Tomography Through an Ergodic Relay) is an evolution of this technology, enabling the system to function with a single transducer, equivalent in data collection to 6,400 transducers.
PACTER has two significant improvements over PATER. Firstly, it can create 3D images, a leap enabled by advanced software. Zhang describes the challenge of managing increased data through a single transducer and their innovative solution of expanding one transducer into thousands of virtual ones to simplify 3D image reconstruction.
Secondly, PACTER eliminates the need for per-use calibration, a process required by PATER due to the interference of laser light echoes in the transducer. PACTER solves this with a delay line, allowing the echo to arrive after the direct ultrasound information has been received.
The research paper titled “Ultrafast longitudinal imaging of haemodynamics via single-shot volumetric photoacoustic tomography with a single-element detector” was published in the November 30 issue of Nature Biomedical Engineering. The team includes Peng Hu, Lei Li, Rui Cao, Anjul Khadria, Konstantin Maslov, Xin Tong, Yushun Zeng, Laiming Jiang, and Qifa Zhou, with funding from the National Institutes of Health.
