Optoacoustic device images biological tissues without direct contact
Optoacoustic device images biological tissues without direct contact lead image
In most cases, acquiring optoacoustic (OA) signals from a biological tissue involves direct physical contact of a transducer or an acoustic coupling medium with the tissue surface. Such parameters limit the use of the technology in important applications such as open surgeries or wounds.
One approach looks to bridge much of the gap between direct-contact and non-contact devices. Özsoy et al. developed an air-coupled transducer that provides optimal sensitivity for OA signal detection. By using coaxially aligned optical and acoustic foci through a multimode optical fiber, the device was able to raster-scan a variety of objects, including a mouse ear and a set of 50 micrometer-thick sutures used to mimic tissue.
“Our design enabled efficient delivery of light for optoacoustic excitation as well as high sensitivity for detecting the generated ultrasound,” said author Xosé Luís Deán-Ben. “In this way, we achieved an optimal signal-to-noise ratio of the optoacoustic images acquired with safe light exposure levels.”
OA techniques leverage optical excitation and acoustic detection to generate images of tissue structures based on optical absorption within tissues, of particular importance in skin conditions.
Sensitivity has historically been an issue with non-contact OA in biomedical devices, in large part due to the suboptimal alignment between the illumination and detection fields.
“The major challenges we are facing stem from the strong acoustic mismatch between air and piezoelectric ultrasound sensors,” Deán-Ben said. “This prevents efficient detection of the weak ultrasound waves generated inside biological tissues and propagating through air.”
Deán-Ben hopes the work inspires others to find innovative approaches to imaging tissues. The group plans to use the transducers in different microscopic and macroscopic optoacoustic imaging systems.
Source: “Optoacoustic imaging with an air-coupled transducer using coaxially-aligned focused illumination,” by Cagla Özsoy, Jianuo Xu, Jiao Li, Francisco Montero de Espinosa, Daniel Razansky, and Xosé Luis Deán-Ben, AIP Advances (2022). The article can be accessed at https://doi.org/10.1063/5.0078053 .
