Brillouin Microscopy and Endoscopy

Seminar | October 29 | 12-1 p.m. | 293 Cory Hall

 Electrical Engineering and Computer Sciences (EECS)

Brillouin imaging can extract viscoelastic properties with micron-level resolution in a label-free, non-invasive way. The conventional bulk-optics based Brillouin system has already been applied to various biological samples. While the utility of Brillouin imaging has been demonstrated, the intrinsically weak scattering process means that recent work in instrumentation has aimed to maximize the efficiency of existing technology, as well as making it more compact and portable. For more systematic optimization strategies, the theoretical parameters to evaluate the performance of arbitrary Brillouin spectrometers have been proposed for the first time. This enables the optimisation of Brillouin systems in general. In this talk, I present the latest developments in Brillouin instrumentation. This also includes software-based reconstruction techniques to enhance the SNR of the system. These methods are more attractive for their wider applicability and have been found to be capable of extracting useful Brillouin shift value with low SNR in simulation and experiment.

One application of Brillouin imaging in particular - the in vivo assessment of arterial stiffness, i.e. Brillouin Endoscopy, is seen to have much potential as a diagnosis tool for cardiovascular diseases, despite some challenges. We thus present recent effort on the optimisation and miniaturisation of the existing technology into a flexible, fibre-based device has provided some solutions. The main consideration for creating a fibre-based Brillouin system is the strong background generated by the fibre. So far, a proof-of-concept device that does not require filtering has been constructed and the measurements in typical liquids have been achieved. Alternatively, a more efficient, single-path set-up is also discussed as it may yield higher throughput.

Recently, the meaning of Brillouin measurements and its correlation to stiffness has been further investigated. It has been shown that the influence of water content in the mechanical behavior of hydrated samples may dominate the Brillouin shift value. The addition of a Raman mode to measure this relative change in hydration may help to yield more accurate mechanical measurements. The correlative study of hydrogels was thus demonstrated as to show that inelastic spectroscopy in tandem is viable.

Finally, to maximise the information from the hyperspectral data that is obtained from BI, the power of some multivariate analysis algorithms is discussed as alternatives for future work, the application in live cell imaging is highlighted.

Speaker bio:
Peter Török graduated with an MSc in Electrical Engineering (Microelectronics) from the Technical University of Budapest, Hungary and a DPhil in Physical Sciences from the University of Oxford. After postdoctoral positions at the Universities of Cambridge and Oxford, he was appointed Lecturer in Photonics at Imperial College London in 2002, where he was promoted Reader in Photonics and Professor of Optical Physics in 2005 and 2009, respectively. In 2018, Peter moved to NTU where he has joint appointments with the Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Lee Kong Chian School of Medicine and the Singapore Centre for Environmental Life Sciences Engineering (SCLESE), where he is Director of Imaging.

Peter has rich experience in designing and building precision optical system also including instruments that have been sold to world-leading companies. He has spent most of his working life in optical and confocal microscopy, polarized light imaging, optical data storage, electromagnetic imaging theory, compressive/single-pixel imaging, reconfigurable optics and various metrology applications, information theoretic aspects of imaging and spectroscopic imaging, including Raman and Brillouin modalities. At NTU his group mostly concentrates on highly interdisciplinary applications of optics working in collaboration with colleagues in life- and biomedical sciences.