Adding sound sensitivity
The researchers added photoacoustic imaging by incorporating an additional, very thin optical fiber with a special sensor tip that is sensitive to sound. Because commercially available fiber optic acoustic sensors are not sensitive or small enough for this application, the researchers used a very sensitive fiber optic sensor recently developed by Beard's research team.
"The focused spot of light allows us to build the image pixel by pixel while also increasing the strength of fluorescence and photoacoustic signals because it concentrates the light at the focal spot," explained Bossy. "This concentrated light combined with a sensitive detector made it possible to obtain images using only one laser pulse per pixel, whereas commercial fiber optic acoustic sensors would have required many laser pulses."
The researchers fabricated a prototype microendoscope that measured just 250 by 125 microns squared and used it to image fluorescent beads and blood cells using both imaging modalities. They successfully detected multiple 1-micron fluorescent beads and individual 6-micron red blood cells.
Because fluorescence endoscopy in rodent's brain has been performed by other scientists, the researchers are confident that their dual modality device will work in similar conditions. They are now continuing work to increase the device's acquisition speed, with a goal of acquiring a few images per second.
Paper: S. Mezil, A. M. Caravaca-Aguirre, E. Z. Zhang, P. Moreau, I. Wang, P. C. Beard, E. Bossy, "Single-shot hybrid photoacoustic-fluorescent microendoscopy through a multimode fiber with wavefront shaping," Biomed. Opt. Express, volume 11, issue 10, pp. 5717-5727 (2020).
About Biomedical Optics Express
Biomedical Optics Express is OSA's principal outlet for serving the biomedical optics community with rapid, open-access, peer-reviewed papers related to optics, photonics and imaging in biomedicine. The journal scope encompasses fundamental research, technology development, biomedical studies and clinical applications. It is published monthly by The Optical Society and edited by Christoph Hitzenberger, Medical University of Vienna, Austria. Biomedical Optics Express is online at OSA Publishing.
About The Optical Society
Founded in 1916, The Optical Society (OSA) is the leading professional organization for scientists, engineers, students and business leaders who fuel discoveries, shape real-life applications and accelerate achievements in the science of light. Through world-renowned publications, meetings and membership initiatives, OSA provides quality research, inspired interactions and dedicated resources for its extensive global network of optics and photonics experts.
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