Team develops kilohertz label-free non-contact quantitative mapping of optical properties for strongly turbid media

The capacity to quantify optical properties (i.e., absorption and scattering) of strongly turbid media has main impacts on the characterization of organic tissues, fluid fields, and lots of others. However, the duty of quantitative imaging of optical properties for strongly turbid media is intrinsically difficult, as photon scattering hinders direct measurement over size scales bigger than the imply free path. Few present imaging applied sciences can quantify absorption and scattering properties of strongly turbid media in a wide-field non-contact format, and none have been proven to map quantitative optical properties with high-speed (e.g., okayHz) capabilities.

In a brand new paper printed in Light: Science & Application, Professor Yanyu Zhao, Professor Yubo Fan, and colleagues at Beihang University developed a brand new optical imaging methodology that for the primary time can quantify optical properties of strongly turbid media in addition to purposeful chromophore concentrations in tissue in a multi-kHz high-speed, label-free, non-contact, and wide-field method. Their work was primarily based on an rising diffuse optical know-how named spatial frequency area imaging (SFDI). It can quantify optical properties of turbid media in a label-free, non-contact method, and its camera-based detection scheme makes it intrinsically wide-field. It tasks spatially modulated sinusoidal gentle patterns of various phases onto the pattern utilizing a digital-micromirror-device (DMD) and collects the reflectance pictures.

However, present SFDI applied sciences make the most of a continuous-tone technique and generate these sinusoidal patterns with 8-bit grayscale, which correspondingly has a restricted most projection pace of 290 Hz decided by the DMD {hardware}. Consequently, whereas SFDI usually requires 5 projection patterns for the measurement of optical properties at a single wavelength, present SFDI applied sciences are severely restricted for high-speed functions.

To tackle the bottleneck of measurement pace, the researchers proposed a halftone technique to considerably improve the pace of SFDI by roughly two orders of magnitude, with no additional value or modification on system {hardware}. Specifically, they first demonstrated the sinusoidal patterns generated by the halftone technique for 1-bit DMD projection, which led to a most projection charge of 23 okayHz, roughly two orders of magnitude sooner than that in present SFDI applied sciences. They then validated the proposed halftone-SFDI in opposition to standard SFDI measurements by means of experiments on an array of optical phantoms with a variety of optical properties in addition to in vivo human tissue. They additionally demonstrated dynamic monitoring of wide-field optical properties and purposeful chromophore concentrations within the rat mind cortex with the proposed halftone-SFDI. Enabled by the proposed methodology, they lastly demonstrated okayHz high-speed dual-wavelength monitoring of wide-field optical properties of a highly-dynamic circulation subject.

“To the best of our knowledge, this is the first demonstration of label-free non-contact imaging of quantitative optical properties of strongly turbid media with a speed of kilohertz,” they famous.

“This work has several important implications for scientific research and engineering applications. For example, mapping brain cortex functions is of fundamental significance for brain science, neuroscience, and cognitive psychology. With shortwave-infrared wavelengths, the halftone-SFDI can provide kHz wide-field quantification of water content in the turbid combustion flow, which could have a substantial impact on the design and optimization of those engines and dramatically reduce related energy cost.” they added.

“The presented technique can spatially map quantitative optical absorption and scattering properties with a maximum speed of 7.6 kHz in strongly turbid media, and can map absolute functional chromophore concentrations in tissue with a maximum speed of 3.8 kHz. This breakthrough could open a new venue for both fundamental research and translational applications including brain science and fluid dynamics.” the scientists forecast.