1. Articles from Benjamin J. Vakoc

    1-24 of 54 1 2 3 »
    1. Retinal Blood Vessel Caliber Estimation for Optical Coherence Tomography Angiography Images Based on 3D Superellipsoid Modeling

      Retinal Blood Vessel Caliber Estimation for Optical Coherence Tomography Angiography Images Based on 3D Superellipsoid Modeling

      Changes of retinal blood vessel calibers may reflect various retinal diseases and even several non-retinal diseases. We propose a new method to estimate retinal vessel calibers from 3D optical coherence tomography angiography (OCTA) images based on 3D modeling using superellipsoids. Taking advantage of 3D visualization of the retinal tissue microstructures in vivo provided by OCTA, our method can detect retinal blood vessels precisely, estimate their calibers reliably, and show the relative flow speed visually.

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    2. Balloon catheter-based radiofrequency ablation monitoring in porcine esophagus using optical coherence tomography

      Balloon catheter-based radiofrequency ablation monitoring in porcine esophagus using optical coherence tomography

      We present a microscopic image guidance platform for radiofrequency ablation (RFA) using a clinical balloon-catheter-based optical coherence tomography (OCT) system, currently used in the surveillance of Barrett’s esophagus patients. Our integrated thermal therapy delivery and monitoring platform consists of a flexible, customized bipolar RFA electrode array designed for use with a clinical balloon OCT catheter and a processing algorithm to accurately map the thermal coagulation process. Non-uniform rotation distortion was corrected using a feature tracking-based technique, which enables robust, frame-to-frame analysis of the temporal fluctuation of the complex OCT signal. With proper noise calibration, precise delineation of the thermal ...

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    3. Toward optical coherence tomography angiography-based biomarkers to assess the safety of peripheral nerve electrostimulation

      Toward optical coherence tomography angiography-based biomarkers to assess the safety of peripheral nerve electrostimulation

      Objective: Peripheral nerves serve as a link between the central nervous system and its targets. Altering peripheral nerve activity through targeted electrical stimulation is being investigated as a therapy for modulating end organ function. To support rapid advancement in the field, novel approaches to predict and prevent nerve injury resulting from the electrical stimulation must be developed to overcome the limitations of traditional histological methods. The present study aims to develop an optical imaging-based approach for real-time assessment of peripheral nerve injury associated with electrical stimulation.
 
 Approach: We developed an optical coherence tomography angiography system and a 3-D ...

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    4. Extended Coherence Length and Depth Ranging Using a Fourier-Domain Mode-Locked Frequency Comb and Circular Interferometric Ranging

      Extended Coherence Length and Depth Ranging Using a Fourier-Domain Mode-Locked Frequency Comb and Circular Interferometric Ranging

      Fourier-domain mode locking has been a popular laser design for high-speed optical-frequency-domain imaging (OFDI), but achieving long coherence lengths, and therefore imaging range, has been challenging. The narrow linewidth of a Fourier-domain mode-locked (FDML) frequency-comb (FC) laser could provide an attractive platform for high-speed as well as long-range OFDI. Unfortunately, aliasing artifacts arising from signals beyond the principal measurement depth of the free spectral range have prohibited the use of an FDML FC laser for imaging so far. To make the increased coherence length of an FDML FC laser available, methods to manage such artifacts are required. Recently, coherent circular ...

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    5. Demonstration of Triband Multi-Focal Imaging with Optical Coherence Tomography

      Demonstration of Triband Multi-Focal Imaging with Optical Coherence Tomography

      We demonstrate an extended depth of focus optical coherence tomography (OCT) system based on the use of chromatic aberration to create displaced focal planes in the sample. The system uses a wavelength-swept source tuning over three spectral bands and three separate interferometers, each of which interfaces to a single illumination/collection fiber. The resulting three imaged volumes are merged in post-processing to generate an image with a larger depth of focus than is obtained from each band individually. The improvements are demonstrated in structural imaging of a porous phantom and a lipid-cleared murine brain, and by angiographic imaging of human ...

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    6. Diagnostic Capability of Three-Dimensional Macular Parameters for Glaucoma Using Optical Coherence Tomography Volume Scans

      Diagnostic Capability of Three-Dimensional Macular Parameters for Glaucoma Using Optical Coherence Tomography Volume Scans

      Purpose : To compare the diagnostic capability of three-dimensional (3D) macular parameters against traditional two-dimensional (2D) retinal nerve fiber layer (RNFL) thickness using spectral domain optical coherence tomography. To determine if manual correction and interpolation of B-scans improve the ability of 3D macular parameters to diagnose glaucoma. Methods : A total of 101 open angle glaucoma patients (29 with early glaucoma) and 57 healthy subjects had peripapillary 2D RNFL thickness and 3D macular volume scans. Four parameters were calculated for six different-sized annuli: total macular thickness (M-thickness), total macular volume (M-volume), ganglion cell complex (GCC) thickness, and GCC volume of the innermost ...

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    7. Extended coherence length and depth ranging using a Fourier domain mode-locked frequency comb and circular interferometric ranging

      Extended coherence length and depth ranging using a Fourier domain mode-locked frequency comb and circular interferometric ranging

      Fourier domain mode-locking (FDML) has been a popular laser design for high speed optical frequency domain imaging (OFDI) but achieving long coherence lengths, and therefore imaging range, has been challenging. The narrow instantaneous linewidth of a frequency comb (FC) FDML laser could provide an attractive platform for high speed as well as long range OFDI. Unfortunately, aliasing artifacts arising from signals beyond the principle measurement depth of the free spectral range have prohibited the use of a FC FDML for imaging so far. To make the enhanced coherence length of FC FDML laser available, methods to manage such artifacts are ...

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    8. Quantitative depolarization measurements for fiber‐based polarization‐sensitive optical frequency domain imaging of the retinal pigment epithelium

      Quantitative depolarization measurements for fiber‐based polarization‐sensitive optical frequency domain imaging of the retinal pigment epithelium

      A full quantitative evaluation of the depolarization of light may serve to assess concentrations of depolarizing particles in the retinal pigment epithelium and to investigate their role in retinal diseases in the human eye. Optical coherence tomography (OCT) and optical frequency domain imaging (OFDI) use spatial incoherent averaging to compute depolarization. Depolarization depends on accurate measurements of the polarization states at the receiver but also on the polarization state incident upon and within the tissue. Neglecting this dependence can result in artifacts and renders depolarization measurements vulnerable to birefringence in the system and in the sample. In this work, we ...

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    9. Optical coherence tomography angiography based biomarkers to assess the safety of peripheral nerve electrostimulation

      Optical coherence tomography angiography based biomarkers to assess the safety of peripheral nerve electrostimulation

      Peripheral nerves connect and relay information between the central nervous system and its target organs. Small arteries traverse the epineurium and are responsible for supplying blood to the axons and cells within the nerves. Constriction or damage to these vessels can reduce perfusion leading to ischemic insults. Peripheral nerve electrostimulation has been approved for the treatment of epilepsy, depression and migraines, and is also being studied for the treatment of rheumatoid arthritis, Crohn’s disease, polycystic ovary syndrome, and type II diabetes. While the safety and efficacy of currently approved medical devices is well established, next generation devices may require ...

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    10. High-speed optical coherence tomography by circular interferometric ranging

      High-speed optical coherence tomography by circular interferometric ranging

      Existing three-dimensional optical imaging methods excel in controlled environments, but are difficult to deploy over large, irregular and dynamic fields. This means that they can be ill-suited for use in areas such as material inspection and medicine. To better address these applications, we developed methods in optical coherence tomography to efficiently interrogate sparse scattering fields, that is, those in which most locations (voxels) do not generate meaningful signal. Frequency comb sources are used to superimpose reflected signals from equispaced locations through optical subsampling. This results in circular ranging, and reduces the number of measurements required to interrogate large volumetric fields ...

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    11. Complex differential variance angiography with noise-bias correction for optical coherence tomography of the retina

      Complex differential variance angiography with noise-bias correction for optical coherence tomography of the retina

      Complex differential variance (CDV) provides phase-sensitive angiographic imaging for optical coherence tomography (OCT) with immunity to phase-instabilities of the imaging system and small-scale axial bulk motion. However, like all angiographic methods, measurement noise can result in erroneous indications of blood flow that confuse the interpretation of angiographic images. In this paper, a modified CDV algorithm that corrects for this noise-bias is presented. This is achieved by normalizing the CDV signal by analytically derived upper and lower limits. The noise-bias corrected CDV algorithm was implemented into an experimental 1 μm wavelength OCT system for retinal imaging that used an eye tracking ...

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    12. Diagnostic Capability of Peripapillary 3D Retinal Nerve Fiber Layer Volume for Glaucoma Using Optical Coherence Tomography Volume Scans

      Diagnostic Capability of Peripapillary 3D Retinal Nerve Fiber Layer Volume for Glaucoma Using Optical Coherence Tomography Volume Scans

      Purpose To determine the diagnostic capability of peripapillary 3-dimensional (3D) retinal nerve fiber layer (RNFL) volume measurements from spectral domain optical coherence tomography (OCT) volume scans for open angle glaucoma (OAG). Design Assessment of diagnostic accuracy. Methods Setting: Academic clinical setting. Study population : 180 patients (113 OAG and 67 normal subjects). Observation procedures : One eye per subject was included. Peripapillary 3D RNFL volumes were calculated for global, quadrant, and sector regions, using four different sized annuli. Peripapillary 2D RNFL thickness circle scans were also obtained. Main outcome measures : Area under the receiver operating characteristic curve (AUROC) values, sensitivity, specificity, positive ...

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    13. Simultaneous measurements of lymphatic vessel contraction, flow and valve dynamics in multiple lymphangions using optical coherence tomography

      Simultaneous measurements of lymphatic vessel contraction, flow and valve dynamics in multiple lymphangions using optical coherence tomography

      Lymphatic dysfunction is involved in many diseases including lymphedema, hypertension, autoimmune responses, graft rejection, atherosclerosis, microbial infections, cancer and cancer metastasis. Expanding our knowledge of lymphatic system function can lead to a better understanding of these disease processes and improve treatment options. Here, optical coherence tomography (OCT) methods were used to reveal intraluminal valve dynamics in 3D, and measure lymph flow and vessel contraction simultaneously in three neighboring lymphangions of the afferent collecting lymphatic vessels to the popliteal lymph node in mice. Flow measurements were based on Doppler OCT techniques in combination with exogenous lymph labelling by Intralipid. Through these ...

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    14. Murine chronic lymph node window for longitudinal intravital lymph node imaging

      Murine chronic lymph node window for longitudinal intravital lymph node imaging

      Chronic imaging windows in mice have been developed to allow intravital microscopy of many different organs and have proven to be of paramount importance in advancing our knowledge of normal and disease processes. A model system that allows long-term intravital imaging of lymph nodes would facilitate the study of cell behavior in lymph nodes during the generation of immune responses in a variety of disease settings and during the formation of metastatic lesions in cancer-bearing mice. We describe a chronic lymph node window (CLNW) surgical preparation that allows intravital imaging of the inguinal lymph node in mice. The CLNW is ...

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    15. 16  MHz wavelength-swept and wavelength-stepped laser architectures based on stretched-pulse active mode locking with a single continuously chirped fiber Bragg grating

      16  MHz wavelength-swept and wavelength-stepped laser architectures based on stretched-pulse active mode locking with a single continuously chirped fiber Bragg grating

      We demonstrate a novel high-speed and broadband laser architecture based on stretched pulse active mode locking that provides a wavelength-swept and wavelength-stepped output. The laser utilizes a single intracavity 8.3 meter chirped fiber Bragg grating to generate positive and negative dispersion, and can be operated with or without an intracavity fixed Fabry–Perot etalon to generate wavelength-swept and wavelength-stepped (frequency comb) outputs, respectively. Using a four-path delay line at the output, we achieved 16.3 MHz repetition rates and a 62 nm lasing bandwidth centered at 1550 nm. Single-sided double-pass coherence lengths of 1.25 mm for the wavelength-swept ...

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    16. Laser thermal therapy monitoring using complex differential variance in optical coherence tomography

      Laser thermal therapy monitoring using complex differential variance in optical coherence tomography

      Conventional thermal therapy monitoring techniques based on temperature are often invasive, limited by point sampling, and are indirect measures of tissue injury, while techniques such as magnetic resonance and ultrasound thermometry are limited by their spatial resolution. The visualization of the thermal coagulation zone at high spatial resolution is particularly critical to the precise delivery of thermal energy to epithelial lesions. In this work, an integrated thulium laser thermal therapy monitoring system was developed based on complex differential variance (CDV), which enables the 2D visualization of the dynamics of the thermal coagulation process at high spatial and temporal resolution with ...

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    17. In vivo label-free measurement of lymph flow velocity and volumetric flow rates using Doppler optical coherence tomography

      In vivo label-free measurement of lymph flow velocity and volumetric flow rates using Doppler optical coherence tomography

      Direct in vivo imaging of lymph flow is key to understanding lymphatic system function in normal and disease states. Optical microscopy techniques provide the resolution required for these measurements, but existing optical techniques for measuring lymph flow require complex protocols and provide limited temporal resolution. Here, we describe a Doppler optical coherence tomography platform that allows direct, label-free quantification of lymph velocity and volumetric flow rates. We overcome the challenge of very low scattering by employing a Doppler algorithm that operates on low signal-to-noise measurements. We show that this technique can measure lymph velocity at sufficiently high temporal resolution to ...

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    18. Systems and methods for providing beam scan patterns for high speed doppler optical frequency domain imaging

      Systems and methods for providing beam scan patterns for high speed doppler optical frequency domain imaging

      An exemplary apparatus and/or an exemplary method can be provided using which, it is possible (e.g., with at least one first arrangement) to measure an amplitude and/or a phase of at least one electromagnetic radiation provided from a particular portion of a sample. Further, it is possible (e.g., using at least one second arrangement) to scan a location of the particular portion along a path from a first point of the sample to a second point of the sample. In addition, it is possible to control the scan (e.g., with the second arrangement) such that ...

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    19. Apparatus for applying a plurality of electro-magnetic radiations to a sample

      Apparatus for applying a plurality of electro-magnetic radiations to a sample

      An apparatus for applying electro-magnetic radiations to a sample is provided. The apparatus can include an arrangement which has a specific portion with a plurality of channels. One channel(s) can facilitate a first radiation to be forwarded to the sample within an anatomical structure, and another channel(s) can facilitate a second radiation to be forwarded to the sample. The first radiation can have a first wavelength band, and the second radiation can have a second wavelength band, which can be substantially different from the first wavelength band. The first radiation can be delivered to a first area of ...

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    20. Apparatus and method for utilization of a high-speed optical wavelength tuning source

      Apparatus and method for utilization of a high-speed optical wavelength tuning source

      Exemplary embodiments of apparatus, source arrangement and method for, e.g., providing high-speed wavelength tuning can be provided. According to one exemplary embodiment, at least one arrangement can be provided which is configured to emit an electromagnetic radiation that (i) has a spectrum whose mean frequency changes at an absolute rate that is greater than about 6000 (or 2000) terahertz per millisecond, (ii) whose mean frequency changes over a range that is greater than about 10 terahertz, and/or (iii) has an instantaneous line width that is less than about 15 gigahertz. According to another exemplary embodiment, at least one ...

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    21. Methods and systems for optical imaging or epithelial luminal organs by beam scanning thereof

      Methods and systems for optical imaging or epithelial luminal organs by beam scanning thereof

      Arrangements, apparatus, systems and systems are provided for obtaining data for at least one portion within at least one luminal or hollow sample. The arrangement, system or apparatus can be (insertable via at least one of a mouth or a nose of a patient. For example, a first optical arrangement can be configured to transceive at least one electromagnetic (e.g., visible) radiation to and from the portion. A second arrangement may be provided at least partially enclosing the first arrangement. Further, a third arrangement can be configured to be actuated so as to position the first arrangement at a ...

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    22. Apparatus, method and system for performing phase-resolved optical frequency domain imaging

      Apparatus, method and system for performing phase-resolved optical frequency domain imaging

      Apparatus, system and method are provided which utilize signals received from a reference and a sample. In particular, a radiation is provided which includes at least one first electro-magnetic radiation directed to the sample and at least one second electro-magnetic radiation directed to the reference. A frequency of the radiation varies over time. An interference can be detected between at least one third radiation associated with the first radiation and at least one fourth radiation associated with the second radiation. It is possible to obtain a particular signal associated with at least one phase of at least one frequency component ...

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    23. Multi-functional angiographic OFDI using frequency-multiplexed dual-beam illumination

      Multi-functional angiographic OFDI using frequency-multiplexed dual-beam illumination

      Detection of blood flow inside the tissue sample can be achieved by measuring the local change of complex signal over time in angiographic optical coherence tomography (OCT). In conventional angiographic OCT, the transverse displacement of the imaging beam during the time interval between a pair of OCT signal measurements must be significantly reduced to minimize the noise due to the beam scanning-induced phase decorrelation at the expense of the imaging speed. Recent introduction of dual-beam scan method either using polarization encoding or two identical imaging systems in spectral-domain (SD) OCT scheme shows potential for high-sensitivity vasculature imaging without suffering from ...

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    24. Compensation of spectral and RF errors in swept-source OCT for high extinction complex demodulation

      Compensation of spectral and RF errors in swept-source OCT for high extinction complex demodulation

      We provide a framework for compensating errors within passive optical quadrature demodulation circuits used in swept-source optical coherence tomography (OCT). Quadrature demodulation allows for detection of both the real and imaginary components of an interference fringe, and this information separates signals from positive and negative depth spaces. To achieve a high extinction (∼60 dB) between these positive and negative signals, the demodulation error must be less than 0.1% in amplitude and phase. It is difficult to construct a system that achieves this low error across the wide spectral and RF bandwidths of high-speed swept-source systems. In a prior work ...

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    1-24 of 54 1 2 3 »
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    1. (54 articles) Benjamin J. Vakoc
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