University of Minnesota
Department of Biomedical Engineering

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Taner Akkin

Taner Akkin








Biomedical Optics and Imaging

Dr. Akkin's research interests lie in the development and use of non-contact, non-invasive optical imaging tools to study structural and functional disorders in biological tissue with high spatiotemporal resolution. Using phase- and polarization-sensitive interferometric techniques, Akkin lab images tissue microstructure in real-time with a few micron spatial resolution and function with sub-nanometer scale optical path length resolution. Since functional recovery may be possible only when the tissue structure is intact, detecting structural changes (function) during physiological activity prior to any structural loss or permanent damage is the main thrust of the work. Applications in medicine are possible as the techniques use back-scattered light.

Brain Imaging and Mapping with Serial Optical Coherence Scanner

Large-scale brain imaging and mapping at microscopic resolution is feasible with intrinsic optical contrasts. Akkin lab combined multi-contrast optical coherence tomography (OCT) and a tissue slicer to form a serial optical coherence scanner (SOCS). It distinguishes white matter and gray matter and visualizes nerve fiber tracts that are as small as a few tens of micrometers. Axonal birefringence highlights the location and myelination of nerve fibers, while the axis orientation contrast indicates the fiber alignment in the plane. SOCS can reveal biomarkers for disease onset and progression in cerebrum and cerebellum, and support development of therapeutics.

Depth-resolved Optical Imaging of Neural Action Potentials

Akkin lab has demonstrated non-contact depth-resolved optical imaging of neural action potentials by measuring sub-nanometer range transient structural changes. Fast signals detected by phase-sensitive optical coherence tomography (OCT) are coincident with the action potential arrival to the measurement site. Squid giant axon preparation was used to study these changes in presence of different environmental (i.e. temperature) and physiological (i.e. ionic concentrations) conditions. Experiments with voltage sensitive dyes allowed comparison of the phase and intensity signals at several depths. A functional OCT cross-sectional scanner was used to show that two-dimensional monitoring of small-scale neural activity would be feasible.

Integration of Polarization-Maintaining Fiber Technology into OCT

Akkin lab has reported polarization-maintaining-fiber (PMF) based OCT systems. These systems are phase and polarization sensitive and are implemented in time-domain, in spectral-domain, and with swept-source technology. Conventional OCT is useful; however, often times the reflectivity images are not descriptive enough to indicate different structures in complex tissue. Polarization-sensitive OCT (PS-OCT), on the other hand, provides additional contrasts based on birefringence, which is the optical anisotropy shared by many tissues including muscle, tendon and nerve. The PMF based PS-OCT devices are capable of generating reflectivity, birefringence/retardance and axis orientation images of tissue, as well as the bidirectional blood flow, all simultaneously. These systems combine the advantages of fiber technology with the straight forward operation and analyses of bulk setups. In this field, Akkin lab develops these custom made systems for disease-oriented applications.


Akkin lab has reported on several differential phase sensors based on low-coherence interferometry. The sensors are capable of measuring extremely small (Angstrom level) optical path length changes at specific depths. The applications include imaging tissue response to electrical or photothermal stimulation, detection of neural activity, and reflection-mode measurement of Faraday rotation with a small field-depth factor.

Selected Publications

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Courses Taught