Research

A significant contribution has resulted in the creation of new label-free optical microscopy and optical coherence tomography (OCT) methods and techniques for high resolution (super-resolution) imaging with nano-sensitivity to structural changes, non-destructive testing, diagnostic and its application to different samples, including biomedical samples and human beings in vivo. The left image is of 400 nm diameter spheres obtained using conventional microscopy and fragments of this image formed using label-free srSESF microscopy.

nano-sensitive OCT (nsOCT)

We developed nano-sensitive OCT (nsOCT) to dramatically improve sensitivity of the OCT to structural changes. Together with reconstruction of the conventional 3D OCT image we propose to directly translate information about particular local structure from Fourier domain to the image domain and map this information into the corresponding location within 3D image. As a result, submicron axial structure can be visualized and nanoscale structural alterations within each voxel can be detected.

Nanoparticle contrast agent for NIR Photoacoustic Imaging and Photothermal OCT

We have synthesised nanostructures with unique and tunable optical properties, especially surface plasmons - collective conduction electron oscillations. One such plasmonic nanostructure is Nanostar with surface plasmon resonance (SPR) in the near infrared (NIR) region of the spectrum that lies within the second optical window (1000 – 1400 nm). Gold nanostars were utilised as contrast agent for in vivo NIR Photoacoustic Imaging and monitoring of photothermal capability of nanostars to destroy tumours in vivo by inducing localised hyperthermia. Opto-thermal simulations of NIR nanostars are being performed to investigate its photothermal efficacy by finite element method using COMSOL Multiphysics and DEVICE. Theoretical thermal relaxivity and diffusion model will then be investigated experimentally by detecting photothermal related phase changes using Photothermal OCT.

Tissue Viability Imaging technology is based on polarization spectroscopy measurement of the absorption of light by the (RBCs) blood cells within the red and green wavelength regions. By use of polarized light it is possible to “see through” the top layer of the skin and probe the underlying dermal layer for information about the microvascular status.

The technique works by illuminating an area of tissue with laser light to produce a high contrast random interference effect known as a speckle pattern. Blood cells flowing through the region of interest cause the speckle pattern to change and appear blurred, which leads to a reduction in local contrast. High flow rates show up as areas of low contrast and conversely, low flow rates are defined by regions of high contrast.

The Photoacoustic technique is based on detection of ultrasound waves generated in tissue by the absorption of optical pulses (time-domain) or modulated light (frequency-domain) followed by the thermo-elastic expansion of the absorbing volumes. The Photoacoustic uses absorption as contrast mechanism thus we can use as imaging (microcirculation) and spectroscopy (SO2 mapping).

In collaboration with Prof. Steve Jacques from OHSU, we developed numerical simulation based Monte Carlo. This simulation called Monte Carlo XYZ which has the ability to map 3D distribution of Fluence and Energy Deposition in biological tissue. Additional feature has been added which enable us to simulate photoacoustic signal based on the energy deposition.