All Articles from Benjamin J. Vakoc -Optical Coherence Tomography News

Articles from Benjamin J. Vakoc

1-24 of 51 1 2 3 »
1. Extended Coherence Length and Depth Ranging Using a Fourier-Domain Mode-Locked Frequency Comb and Circular Interferometric Ranging
  
  Explore journals.aps.org Jan 10 2019 Tunable Sources
  
  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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  Mentions: Brett E. Bouma Massachusetts Institute of Technology Massachusetts General Hospital
2. Demonstration of Triband Multi-Focal Imaging with Optical Coherence Tomography
  
  Explore MDPI Open Access Journals Platform Dec 2 2018
  
  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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  Mentions: Brett E. Bouma Massachusetts General Hospital Harvard University
3. Diagnostic Capability of Three-Dimensional Macular Parameters for Glaucoma Using Optical Coherence Tomography Volume Scans
  
  Explore IOVS Journal Oct 24 2018 Ophthalmology
  
  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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  Mentions: Brett E. Bouma Johannes F. de Boer Johns Hopkins University
4. Extended coherence length and depth ranging using a Fourier domain mode-locked frequency comb and circular interferometric ranging
  
  Explore arxiv.org Oct 24 2018 Tunable Sources
  
  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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  Mentions: Brett E. Bouma Massachusetts Institute of Technology Massachusetts General Hospital
5. Quantitative depolarization measurements for fiber‐based polarization‐sensitive optical frequency domain imaging of the retinal pigment epithelium
  
  Explore Wiley Online Library Jul 16 2018 Ophthalmology
  
  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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  Mentions: Brett E. Bouma Massachusetts General Hospital Harvard University
6. Optical coherence tomography angiography based biomarkers to assess the safety of peripheral nerve electrostimulation
  
  Explore SPIE Digital Library Mar 20 2018
  
  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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  Mentions: Massachusetts General Hospital Daniel X. Hammer Harvard University
7. High-speed optical coherence tomography by circular interferometric ranging
  
  Explore Nature Publishing Group Feb 1 2018
  
  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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  Mentions: Massachusetts General Hospital Harvard University Benjamin J. Vakoc
8. Complex differential variance angiography with noise-bias correction for optical coherence tomography of the retina
  
  Explore OSA | OSA Publishing Jan 13 2018 Ophthalmology
  
  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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  Mentions: Brett E. Bouma Massachusetts Institute of Technology Heidelberg Engineering
9. Diagnostic Capability of Peripapillary 3D Retinal Nerve Fiber Layer Volume for Glaucoma Using Optical Coherence Tomography Volume Scans
  
  Explore American Journal of Ophthalmology Aug 11 2017 Ophthalmology
  
  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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  Mentions: Brett E. Bouma Johannes F. de Boer Massachusetts General Hospital
10. Simultaneous measurements of lymphatic vessel contraction, flow and valve dynamics in multiple lymphangions using optical coherence tomography
  
  Explore Wiley Online Library Jul 12 2017 Oncology
  
  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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  Mentions: Massachusetts General Hospital Harvard University Benjamin J. Vakoc
11. Murine chronic lymph node window for longitudinal intravital lymph node imaging
  
  Explore Nature Publishing Group Jul 11 2017
  
  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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  Mentions: Massachusetts General Hospital Harvard University Sungkyunkwan University
12. 16 MHz wavelength-swept and wavelength-stepped laser architectures based on stretched-pulse active mode locking with a single continuously chirped fiber Bragg grating
  
  Explore OSA | OSA Publishing Jun 26 2017 Tunable Sources
  
  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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  Mentions: Massachusetts Institute of Technology Massachusetts General Hospital Harvard University
13. Laser thermal therapy monitoring using complex differential variance in optical coherence tomography
  
  Explore Wiley Online Library Sep 14 2016
  
  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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  Mentions: Brett E. Bouma Massachusetts General Hospital Harvard University
14. In vivo label-free measurement of lymph flow velocity and volumetric flow rates using Doppler optical coherence tomography
  
  Explore Nature Publishing Group Jul 6 2016
  
  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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  Mentions: Brett E. Bouma Massachusetts Institute of Technology Massachusetts General Hospital
15. Systems and methods for providing beam scan patterns for high speed doppler optical frequency domain imaging
  
  Explore uspto.gov Jun 28 2016 Patents
  
  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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  Mentions: Guillermo J. Tearney Brett E. Bouma Massachusetts General Hospital
16. Apparatus for applying a plurality of electro-magnetic radiations to a sample
  
  Explore uspto.gov Nov 17 2015 Patents
  
  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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  Mentions: Guillermo J. Tearney Brett E. Bouma Massachusetts General Hospital
17. Apparatus and method for utilization of a high-speed optical wavelength tuning source
  
  Explore uspto.gov Nov 3 2015 Patents
  
  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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  Mentions: Guillermo J. Tearney Brett E. Bouma Massachusetts General Hospital
18. Methods and systems for optical imaging or epithelial luminal organs by beam scanning thereof
  
  Explore uspto.gov Jul 21 2015 Patents , Probes
  
  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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  Mentions: Guillermo J. Tearney Brett E. Bouma Massachusetts General Hospital
19. Apparatus, method and system for performing phase-resolved optical frequency domain imaging
  
  Explore uspto.gov Jun 23 2015 Patents
  
  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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  Mentions: Guillermo J. Tearney Brett E. Bouma Johannes F. de Boer
20. Multi-functional angiographic OFDI using frequency-multiplexed dual-beam illumination
  
  Explore opticsinfobase.org Mar 31 2015
  
  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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  Mentions: Massachusetts General Hospital Harvard University Wang Yuhl Oh
21. Compensation of spectral and RF errors in swept-source OCT for high extinction complex demodulation
  
  Explore opticsinfobase.org Feb 23 2015
  
  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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  Mentions: Massachusetts General Hospital Benjamin J. Vakoc
22. Monte Carlo modeling of angiographic optical coherence tomography
  
  Explore opticsinfobase.org Nov 20 2014
  
  Optical coherence tomography (OCT) provides both structural and angiographic imaging modes. Because of its unique capabilities, OCT-based angiography has been increasingly adopted into small animal and human subject imaging. To support the development of the signal and image processing algorithms on which OCT-based angiography depends, we describe here a Monte Carlo-based model of the imaging approach. The model supports arbitrary three-dimensional vascular network geometries and incorporates methods to simulate OCT signal temporal decorrelation. With this model, it will be easier to compare the performance of existing and new angiographic signal processing algorithms, and to quantify the accuracy of vascular segmentation ...
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  Mentions: Massachusetts General Hospital Harvard University Benjamin J. Vakoc
23. Complex differential variance algorithm for optical coherence tomography angiography
  
  Explore opticsinfobase.org Oct 7 2014
  
  We describe a complex differential variance (CDV) algorithm for optical coherence tomography based angiography. The algorithm exploits both the intensity and phase changes of optical coherence tomography (OCT) signals from flowing blood to achieve high vascular contrast, and also intrinsically reject undesirable phase signals originating from small displacement axial bulk tissue motion and instrument synchronization errors. We present this algorithm within a broader discussion of the properties of OCT signal dynamics. The performance of the algorithm is compared against two other existing algorithms using both phantom measurements and in vivo data. We show that the algorithm provides better contrast for ...
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  Mentions: Massachusetts Institute of Technology Massachusetts General Hospital Harvard University
24. A rapid, dispersion-based wavelength-stepped and wavelength-swept laser for optical coherence tomography
  
  Explore opticsinfobase.org Feb 5 2014 Tunable Sources
  
  Abstract: Optical-domain subsampling enables Fourier-domain OCT imaging at high-speeds and extended depth ranges while limiting the required acquisition bandwidth. To perform optical-domain subsampling, a wavelength-stepped rather than a wavelength-swept source is required. This preliminary study introduces a novel design for a rapid wavelength-stepped laser source that uses dispersive fibers in combination with a fast lithium-niobate modulator to achieve wavelength selection. A laser with 200 GHz wavelength-stepping and a sweep rate of 9 MHz over a 94 nm range at a center wavelength of 1550 nm is demonstrated. A reconfiguration of this source design to a continuous wavelength-swept light for conventional ...
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  Mentions: Massachusetts General Hospital Harvard University Benjamin J. Vakoc
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