1. Hrebesh M. Subhash

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    1. Mentioned In 49 Articles

    2. Characterization of light distribution and optimization of detector position for multiple reference optical coherence tomography

      Characterization of light distribution and optimization of detector position for multiple reference optical coherence tomography

      A time-domain optical coherence tomography system with respect to multiple reflections in the reference arm is simulated with Zemax and the optimal detector position is discussed based on the wavefront error. Multiple reference optical coherence tomography (MR-OCT) is a novel optical imaging platform using a single miniature actuator and partial mirror to recirculate light multiple times within the interferometric system. The recirculation corresponds to multiple path delays extending effectively the axial scan-range. The simulation of MR-OCT with lenses of 5 mm diameter shows that it is suitable to build a compact system using low-cost components. Subsequently MR-OCT enables an affordable ...

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    3. Signal simulation and signal processing for multiple reference optical coherence tomography

      Signal simulation and signal processing for multiple reference optical coherence tomography

      The generation of a synthetic MR-OCT signal is presented and compared to a real acquired signal. Multiple reference optical coherence tomography (MR-OCT) is a novel time-domain interferometric system. The MR-OCT principle is adding a partial mirror to extend the axial scan range, which effectively extends the scan depth for imaging. The actuation of the scan mirror required for time-domain OCT, was demonstrated to operate with a low cost miniature voice coil, such as a speaker extracted from a smartphone or CD/DVD pick-up system. Building a compact and cost-effective optical imaging system will enable affordable medical diagnosis at low-resource setting ...

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    4. Developing cross-correlation as a method for microvessel imaging using clinical intravascular optical coherence tomography systems

      Developing cross-correlation as a method for microvessel imaging using clinical intravascular optical coherence tomography systems

      Current clinical intravascular optical coherence tomography (IV-OCT) imaging systems have limited in-vivo flow imaging capability because of non-uniform catheter rotation and inadequate A-line scan density. Thus any flow-localisation method that seeks to identify sites of variation within the OCT image data-sets, whether that is in amplitude or phase, produces non-representative correlation (or variance) maps. In this study, both mean and the variation within a set of cross-correlation maps, for static OCT imaging was used to differentiate flow from nonflow regions. Variation was quantified by use of standard deviation. The advantage of this approach is its ability to image flow, even ...

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    5. High resolution coherence domain depth-resolved nailfold capillaroscopy based on correlation mapping optical coherence tomography

      High resolution coherence domain depth-resolved nailfold capillaroscopy based on correlation mapping optical coherence tomography
      ...ence domain depth-resolved nailfold capillaroscopy based on correlation mapping optical coherence tomography Hrebesh M. Subhash ; Sean O'Gorman ; Kai Neuhaus ; Martin Leahy; High resolution coherence domain depth-resolv...
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    6. Variation in cross-correlation as a discriminator for microvessel imaging using clinical intravascular optical coherence tomography systems

      Variation in cross-correlation as a discriminator for microvessel imaging using clinical intravascular optical coherence tomography systems
      ... imaging using clinical intravascular optical coherence tomography systems Shiju Joseph ; Clément Rousseau ; Hrebesh M. Subhash ; Martin Leahy ; David Adlam; Variation in cross-correlation as a discriminator for microve...
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    7. Nano-sensitive optical coherence tomography (nsOCT) for depth resolved characterization of 3D submicron structure

      Nano-sensitive optical coherence tomography (nsOCT) for depth resolved characterization of 3D submicron structure

      Nowadays optical coherence tomography (OCT) is a rapidly developing technique with various applications, including biomedical imaging and diagnosis. One of the main shortcomings of current OCT techniques is low resolution and sensitivity to structural changes (typically about 10 microns). The best ultra-high resolution OCT techniques demonstrate sensitivity to structural changes and depth resolution of about 1 micron. Since many applications of interest (such as cancer) depend on structural changes at the nanoscale, OCT would definitely benefit from improved structural resolution and sensitivity. A new spectral encoding of spatial frequency (SESF) approach for quantitative characterization of the structure with nanoscale sensitivity ...

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    8. Photothermal optical coherence tomography for depth-resolved imaging of mesenchymal stem cells via single wall carbon nanotube

      Photothermal optical coherence tomography for depth-resolved imaging of mesenchymal stem cells via single wall carbon nanotube
      ...l coherence tomography for depth-resolved imaging of mesenchymal stem cells via single wall carbon nanotubes Hrebesh M. Subhash ; Emma Connolly ; Mary Murphy ; Valerie Barron ; Martin Leahy; Photothermal optical coheren...
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    9. Dermascope assisted interactive patient interface for multiple reference optical coherence tomography

      Dermascope assisted interactive patient interface for multiple reference optical coherence tomography

      There has been a growing interest in the development of a low cost depth-resolved non-invasive dermis imaging tool for both clinical and fundamental investigations of skin diseases. Multiple reference optical coherence tomography (MR-OCT) is a recently developed miniature time-domain low coherence interferometeric imaging platform, which promises to fit into robust, cost-effective designs that are virtually solid state, typical of handheld devices. In this paper we demonstrate the feasibility of MR-OCT for dermis imaging applications by incorporating it in a dermascope, which provides simultaneous imaging of dermis and an interactive tool for beam steering and registration of the OCT imaging beam ...

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    10. Voice coil based robust and miniature optical delay for multiple reference optical coherence tomography

      Voice coil based robust and miniature optical delay for multiple reference optical coherence tomography

      Multiple reference optical coherence tomography (MR-OCT) is a recently developed time-domain interferometeric imaging platform, which promises to fit into robust, cost-effective designs that are virtually solid state. An optical delay is created by the reference mirror which is mounted on a piezo-electric transducer (PZT) and the key element of MR-OCT technology is the presence of a partial mirror in front of the reference mirror. However, the limited axial displacement range at higher scanning-frequencies are a limitation of a PZT-based optical delay. Moreover, PZT-based actuators require a relatively high operational voltage and are expensive. In this paper we present a voice ...

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    11. Imaging mesenchymal stem cells containing single wall nanotube nanoprobes in a 3D scaffold using photo-thermal optical coherence tomography

      Imaging mesenchymal stem cells containing single wall nanotube nanoprobes in a 3D scaffold using photo-thermal optical coherence tomography
      ...e wall nanotube nanoprobes in a 3D scaffold using photo-thermal optical coherence tomography Emma Connolly ; Hrebesh M. Subhash ; Martin J. Leahy ; Niall Rooney ; Frank Barry ; Mary Murphy ; Valerie Barron; Imaging mese...
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    12. Nano-sensitive optical coherence tomography

      Nano-sensitive optical coherence tomography

      Depth resolved label-free detection of structural changes with nanoscale sensitivity is an outstanding problem in the biological and physical sciences and has significant applications in both the fundamental research and healthcare diagnostics arenas. Here we experimentally demonstrate a novel label-free depth resolved sensing technique based on optical coherence tomography (OCT) to detect structural changes at the nanoscale. Structural components of the 3D object, spectrally encoded in the remitted light, are transformed from the Fourier domain into each voxel of the 3D OCT image without compromising sensitivity. Spatial distribution of the nanoscale structural changes in the depth direction is visualized in ...

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    13. Feature Of The Week 1/6/14: In Vivo Full-Field En Face Optical Coherence Tomography

      Feature Of The Week 1/6/14: In Vivo Full-Field En Face Optical Coherence Tomography

      The correlation mapping processing algorithm was developed by our group and utilises the time varying speckle effect produced from moving scatterers to provide contrast against static tissue. The technique has previously been applied to images acquired with frequency-domain OCT systems and hence in a cross-sectional geometry. In this work, a full-field optical coherence tomography system has been developed for the purpose of performing non-scanning en face flow imaging. The light source is centred at 840 nm with a bandwidth of 50 nm resulting in an axial resolution of 8 µm in air. Microscope objectives with a numerical aperture of 0 ...

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  2. About Hrebesh M. Subhash

    Hrebesh M. Subhash

    Hrebesh Molly Subhash is with the Biophotonics & Imaging Lab in the School of Medicine at the Oregon Health & Science University. Hrebesh is currently a research associate in Biophotonics and Imaging Laboratory (BAIL), School of Medicine, OHSU Hospital at Portland, OR USA. He works with Prof. R. K. Wang, who is the director of BAIL. His current research activity involves the development of novel optical coherence domain imaging techniques for both anatomical and functional imaging.

    He received his Ph.D. degree in Human Sensing and Functional Sensor Engineering in 2008 from Yamagata University, Yonezawa, Japan. He earned his bachelor's degree in Applied Electronics from the University of Kerala in 1998; his master's in Applied Electronics from the University of Bharathiar in 2000; and his M. Phil in Photonics from the International School of Photonics at the Cochin University of Science and Technology in 2004.

    He was a member of Dr. P.K . Gupta's Biomedical Application Section of RRCAT , Indore. I worked with the Optical Imaging Laboratory led by Dr. Divaker Rao and played a key role in developing the first indigenous Optical Coherence Tomography setup in India.