Koichi Shimizu

Title : Suppression of scattering blur in macroscopic imaging of human body using NIR light

Abstract:

Near-infrared (NIR) light has relatively low attenuation in the human body, and reaches deeper in our body than visible light. We can visualize the internal structure of our body in transillumination imaging or oblique-illumination imaging with NIR light. However, the light is strongly scattered in body tissue which makes the quantitative spectral analysis difficult. It also makes the transillumination images seriously blurred.    

We have developed optical techniques to suppress the blur caused by light scattering. They are the extraction of the near-axis scattered component from the widely diffused light, and focusing the light in diffusive media using the time-reversal principle of phase-conjugate light. We have also developed new techniques to suppress the scattering blur in image processing. They are the convolution with the point spread function (PSF) derived from the diffusion equation, and deblurring by the neural network trained in deep learning. In the combination of these techniques, we can effectively suppress the blur caused by the scattering in body tissue. At the same time, we can estimate the depth of absorbers in the deblurring process. The effectiveness of these methods has been verified in simulation and experiments. With these techniques, we could reconstruct macroscopic 3-dimensional internal structure of a living mouse. We also expanded these techniques for functional imaging. The blood circulation changes in mouse brain and abdomen were visualized in transillumination imaging. The distribution of oxygen saturation in a human hand could be visualized as well. The NIR transillumination with the proposed technique has been applied to the medical care of the arteriovenous fistula in dialysis treatment.

Audience Take Away:

•  Audience will find the potential of a new non-invasive technique for biomedical imaging.
•  They can see some techniques to solve the problem of severe blur caused by light scattering.
•  They can understand the basic principle of functional transillumination imaging.
•  They will see some practical applications of the proposed techniques to animal and human bodies.
•  They will see how the new deep learning techniques are used in transillumination imaging.

Biography:

Koichi Shimizu received M.S. (1976) and Ph.D. (1979) degrees, from University of Washington (UW), Seattle, USA. He was Research Associate in UW 1974-79. He was an Assistant Professor, an Associate Professor, and a Professor in Hokkaido University, Sapporo, Japan in 1979-2016. He is currently a Professor Emeritus of Hokkaido University and a Professor of Waseda University, Kitakyushu, Japan.

He has been engaged in the studies of biomedical engineering including those of wave propagation in biological media, optical measurement, biotelemetry and biological effects of electromagnetic field. He served as an associate editor of IEEE Trans. ITB in 1999?2007. He has been a Fellow of the Electromagnetics Academy, and an editorial board member of Scientific Reports, Nature.