DARWIN · Dual capillary waveguide endoscope

Dual capillary waveguide endoscope

The overall goal of collaborative projects such as the BRAIN initiative and the Human Brain project is to understand how the dynamics of neural activity is transformed into the human cognition, emotion and behaviour. Optical techniques are unique to achieve this goal because of their scalability, allowing the study from sub-cellular compartments to the whole brain while providing high temporal accuracy, critical to resolve the millisecond-timescale neuronal activity signals. In the last decade, the development of proteins expressed in genetically modified virus enable cell-type specific imaging and manipulation of neural activity commonly referred as optogenetics. These studies have been carried out typically using an invasive approach where the skull is removed because the resolution and penetration depth of optical imaging in biological tissue is severely degraded by scattering, limiting the non-invasive approaches. For deep brain imaging with diffraction limited optical resolution, endoscopic approaches are required to avoid the loss of resolution due to scattering. But its typical cross section is between 0.6 and 1 mm, which can produce tissue damaged when inserted. One of the goals of the action is use capillary multimode waveguides that have a smaller cross section (~350um) to reduce the tissue damage. However, coherent light propagating through a this small waveguides is seemingly randomized through fiber mode variations in phase velocity, leading to a granular speckle pattern at the far end of the fiber. Imaging through them therefore requires special methods. Another objective of the action is to explore new ways of calibration and imaging. Because fluorescence imaging requires exogenous agents (dyes or genetically modified cells) to produce the contrast required to image, other complementary imaging techniques are being explored. One of this techniques is photoacoustic imaging that relies on endogenous contrast agents such as light absorption. Photoacoustic imaging an emerging multi-wave imaging modality that couples light excitation to acoustic detection via the photoacoustic effect (sound generation via light absorption), relies on detecting ultrasound waves that are very weakly scattered in biological tissue. The other goal of the action is to not only design an ultra-thin endoscope for fluorescence imaging, but also for photoacoustic imaging and take advantage of the hollow core of the capillary to place a device capable of detecting ultrasound waves providing images in both modalities. This combination can enable simultaneous monitoring of fast spatio-temporal neurodynamics and vasular hemodynamics, hence providing unprecedented capabilities for neural activity detection. The project demonstrated the feasibility of building a small endoscope capable of image using complementary imaging techniques and perform proof-of-concept experiments.

Текст от CORDIS, на английски · Данни: CORDIS, © Европейски съюз