Researchers combine photoacoustic and fluorescence imaging in tiny package

September 21, 2020

WASHINGTON -- Researchers have demonstrated a new endoscope that uniquely combines photoacoustic and fluorescent imaging in a device about the thickness of a human hair. The device could one day provide new insights into the brain by enabling blood dynamics to be measured at the same time as neuronal activity.

"Combining these imaging modalities could improve our understanding of the brain's structure and behavior in specific conditions such as after treatment with a targeted drug," said research team leader Emmanuel Bossy from the CNRS/ Université Grenobe Alpes Laboratoire Interdisciplinaire de Physique. "The endoscope's small size helps minimize damage to tissue when inserting it into the brains of small animals for imaging."

In The Optical Society (OSA) journal Biomedical Optics Express, Bossy's research team, in collaboration with Paul C. Beard's team from University College London, describe their new multi-modality endoscope and show that it can acquire photoacoustic and fluorescent images of red blood cells and fluorescent beads.

Two images are better than one

Acquiring fluorescence and photoacoustic images with the same device provides automatically co-registered images with complementary information. Fluorescent signals, which are created when a fluorescent marker absorbs light and re-emits it with a different wavelength, are most useful for labeling specific regions of tissue. On the other hand, photoacoustic images, which capture an acoustic wave generated after the absorption of light, do not require labels and thus can be used to image blood dynamics, for example.

The new endoscope uses a technique called optical wavefront shaping to create a focused spot of light at the imaging tip of a very small multi-mode optical fiber. "Light propagating into a multi-mode fiber is scrambled, making it impossible to see through the fiber," said Bossy. "However, this type of fiber is advantageous for endoscopy because it is extremely small compared to the bundles of imaging fibers used for many medical endoscopic devices."

To see through the multi-mode optical fiber, the researchers used the spatial light modulator to send specific light patterns through the fiber and create a focus spot at the imaging end. When the focus spot hits the sample, it creates a signal that can be used to build up an image point by point by raster scanning the spot over the sample. Although other researchers have used multimode fibers for fluorescence endoscopy, the new work represents the first time that photoacoustic imaging has been incorporated into this type of endoscope design.

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.
-end-
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).

DOI: https://doi.org/10.1364/BOE.400686.

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. For more information, visit osa.org.

Media Contact: mediarelations@osa.org

The Optical Society

Related Brain Articles from Brightsurf:

Glioblastoma nanomedicine crosses into brain in mice, eradicates recurring brain cancer
A new synthetic protein nanoparticle capable of slipping past the nearly impermeable blood-brain barrier in mice could deliver cancer-killing drugs directly to malignant brain tumors, new research from the University of Michigan shows.

Children with asymptomatic brain bleeds as newborns show normal brain development at age 2
A study by UNC researchers finds that neurodevelopmental scores and gray matter volumes at age two years did not differ between children who had MRI-confirmed asymptomatic subdural hemorrhages when they were neonates, compared to children with no history of subdural hemorrhage.

New model of human brain 'conversations' could inform research on brain disease, cognition
A team of Indiana University neuroscientists has built a new model of human brain networks that sheds light on how the brain functions.

Human brain size gene triggers bigger brain in monkeys
Dresden and Japanese researchers show that a human-specific gene causes a larger neocortex in the common marmoset, a non-human primate.

Unique insight into development of the human brain: Model of the early embryonic brain
Stem cell researchers from the University of Copenhagen have designed a model of an early embryonic brain.

An optical brain-to-brain interface supports information exchange for locomotion control
Chinese researchers established an optical BtBI that supports rapid information transmission for precise locomotion control, thus providing a proof-of-principle demonstration of fast BtBI for real-time behavioral control.

Transplanting human nerve cells into a mouse brain reveals how they wire into brain circuits
A team of researchers led by Pierre Vanderhaeghen and Vincent Bonin (VIB-KU Leuven, Université libre de Bruxelles and NERF) showed how human nerve cells can develop at their own pace, and form highly precise connections with the surrounding mouse brain cells.

Brain scans reveal how the human brain compensates when one hemisphere is removed
Researchers studying six adults who had one of their brain hemispheres removed during childhood to reduce epileptic seizures found that the remaining half of the brain formed unusually strong connections between different functional brain networks, which potentially help the body to function as if the brain were intact.

Alcohol byproduct contributes to brain chemistry changes in specific brain regions
Study of mouse models provides clear implications for new targets to treat alcohol use disorder and fetal alcohol syndrome.

Scientists predict the areas of the brain to stimulate transitions between different brain states
Using a computer model of the brain, Gustavo Deco, director of the Center for Brain and Cognition, and Josephine Cruzat, a member of his team, together with a group of international collaborators, have developed an innovative method published in Proceedings of the National Academy of Sciences on Sept.

Read More: Brain News and Brain Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.