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1

Optical tomography in combustion  

Energy Technology Data Exchange (ETDEWEB)

The new methodology of optical infrared tomography of flames and hot gas flows was developed with a view to future industrial applications. In particular, the methodology for the tomographic reconstruction of an axisymmetric lab flame temperature profile was developed and tested in the lab using Fourier transform infrared spectroscopy techniques, including a new tomographic measurement scheme, sweeping scanning, having great potential for industrial applications with limited optical access. The results were compared to the reference point measurements on the same flame and the deviations are discussed. The methods are shown to have promising potential for future industrial applications. The new multichannel infrared spectrometer system as a first prototype of the infrared spectroscopic tomography system was developed for simultaneous fast transient infrared spectral measurements at several line-of-sights with a view to applications for tomographic measurements on full-scale industrial combustion systems. The system was successfully applied on industrial scale for simultaneous fast exhaust gas temperature measurements in the three optical ports of the exhaust duct of the large Diesel engine. The results were compared to the measurements performed by another system employing spectral properties of nitric oxides in the ultraviolet range. A good agreement was observed between the results obtained using the two different systems. In the context of the PhD project, it was also important to investigate the spectral properties of major combustion species such as carbon dioxide and carbon monoxide in the infrared range at high temperatures to provide the theoretical background for the development of the optical tomography methods. The new software was developed for the line-by-line calculations of the transmission spectra of a carbon dioxide/carbon monoxide mixture which is able to use within reasonable time the most recent but huge CDSD-4000 database containing updated high-temperature spectroscopic line-by-line data. The software was used for the line-by-line calculations of the transmission spectra of the carbon dioxide/carbon monoxide mixture at high temperatures and the results were compared to the measurements in the high-temperature flow gas cell carried out before the PhD project. The knowledge and experience gained in the PhD project is the first important step towards introducing the advanced optical tomography methods of combustion diagnostics developed in the project to future industrial applications. (Author)

Evseev, V.

2012-11-15

2

Optical Tomography in Combustion  

DEFF Research Database (Denmark)

The new methodology of optical infrared tomography of flames and hot gas flows was developed in the PhD project with a view to future industrial applications. In particular, the methodology for the tomographic reconstruction of an axisymmetric lab flame temperature profile was developed and tested in the lab using Fourier transform infrared spectroscopy techniques, including a new tomographic measurement scheme, sweeping scanning, having great potential for industrial applications with limited optical access. The results were compared to the reference point measurements on the same flame and the deviations are discussed. The methods are shown to have promising potential for future industrial applications. The new multichannel infrared spectrometer system as a first prototype of the infrared spectroscopic tomography system was developed in the PhD project for simultaneous fast transient infrared spectral measurements at several line-of-sights with a view to applications for tomographic measurements on full-scale industrial combustion systems. The system was successfully applied on industrial scale for simultaneous fast exhaust gas temperature measurements in the three optical ports of the exhaust duct of the large Diesel engine. The results were compared to the measurements performed by another system employing spectral properties of nitric oxides in the ultraviolet range. A good agreement was observed between the results obtained using the two different systems. In the context of the PhD project, it was also important to investigate the spectral properties of major combustion species such as carbon dioxide and carbon monoxide in the infrared range at high temperatures to provide the theoretical background for the development of the optical tomography methods. The new software was developed for the line-by-line calculations of the transmission spectra of a carbon dioxide/carbon monoxide mixture which is able to use within reasonable time the most recent but huge CDSD-4000 database containing updated high-temperature spectroscopic line-by-line data. The software was used for the line-by-line calculations of the transmission spectra of the carbon dioxide/carbon monoxide mixture at high temperatures and the results were compared to the measurements in the high-temperature flow gas cell carried out before the PhD project. The results and discussion are presented in a journal article [Evseev et al. JQSRT 113 (2012) 2222, 10.1016/j.jqsrt.2012.07.015] included in the PhD thesis as an attachment. The knowledge and experience gained in the PhD project is the first important step towards introducing the advanced optical tomography methods of combustion diagnostics developed in the project to future industrial applications.

Evseev, Vadim

2013-01-01

3

Amplified Dispersive Optical Tomography  

CERN Document Server

Optical coherence tomography (OCT) has proven to be a powerful technique for studying tissue morphology in ophthalmology, cardiology, and endomicroscopy. Its performance is limited by the fundamental trade-off between the imaging sensitivity and acquisition speed -- a predicament common in virtually all imaging systems. In this paper, we circumvent this limit by using distributed Raman post-amplification of the reflection from the sample. We combine the amplification with simultaneously performed dispersive Fourier transformation, a process that maps the optical spectrum into an easily measured time-domain waveform. The Raman amplification enables measurement of weak signals which are otherwise buried in noise. It extends the depth range without sacrificing the acquisition speed or causing damage to the sample. As proof of concept, single-shot imaging with 15 dB improvement in sensitivity at an axial scan rate of 36.6 MHz is demonstrated.

Goda, Keisuke; Jalali, Bahram

2008-01-01

4

Intraocular optical coherence tomography.  

Science.gov (United States)

Since its introduction as a diagnostic instrument, optical coherence tomography (OCT) has become an essential instrument for ophthalmologists as it offers accurate details on both the vitreoretinal interface and the retinal layers. Initially designed as a pre- and post-operative instrument, today we are attending to its introduction as an intraoperative tool. Inspired by the intravascular use of the OCT, we developed a prototype spectral domain OCT probe for intraocular use. It is therefore possible to make dynamic real-time scans from the vitreous and retina at the posterior pole and in the peripheral retina. This type of endo-OCT may therefore help surgeons during surgical procedures, making them safer and more accurate. PMID:25196763

Mura, Marco; Barca, Francesco

2014-01-01

5

Optical Coherence Tomography  

DEFF Research Database (Denmark)

Optical coherence tomography (OCT) has developed rapidly since its first realisation in medicine and is currently an emerging technology in the diagnosis of skin disease. OCT is an interferometric technique that detects reflected and backscattered light from tissue and is often described as the optical analogue to ultrasound. The inherent safety of the technology allows for in vivo use of OCT in patients. The main strength of OCT is the depth resolution. In dermatology, most OCT research has turned on non-melanoma skin cancer (NMSC) and non-invasive monitoring of morphological changes in a number of skin diseases based on pattern recognition, and studies have found good agreement between OCT images and histopathological architecture. OCT has shown high accuracy in distinguishing lesions from normal skin, which is of great importance in identifying tumour borders or residual neoplastic tissue after therapy. The OCT images provide an advantageous combination of resolution and penetration depth, but specific studies of diagnostic sensitivity and specificity in dermatology are sparse. In order to improve OCT image quality and expand the potential of OCT, technical developments are necessary. It is suggested that the technology will be of particular interest to the routine follow-up of patients undergoing non-invasive therapy of malignant or premalignant keratinocyte tumours. It is speculated that the continued technological development can propel the method to a greater level of dermatological use.

Mogensen, Mette; Themstrup, Lotte

2014-01-01

6

Doppler optical coherence tomography.  

Science.gov (United States)

Optical Coherence Tomography (OCT) has revolutionized ophthalmology. Since its introduction in the early 1990s it has continuously improved in terms of speed, resolution and sensitivity. The technique has also seen a variety of extensions aiming to assess functional aspects of the tissue in addition to morphology. One of these approaches is Doppler OCT (DOCT), which aims to visualize and quantify blood flow. Such extensions were already implemented in time domain systems, but have gained importance with the introduction of Fourier domain OCT. Nowadays phase-sensitive detection techniques are most widely used to extract blood velocity and blood flow from tissues. A common problem with the technique is that the Doppler angle is not known and several approaches have been realized to obtain absolute velocity and flow data from the retina. Additional studies are required to elucidate which of these techniques is most promising. In the recent years, however, several groups have shown that data can be obtained with high validity and reproducibility. In addition, several groups have published values for total retinal blood flow. Another promising application relates to non-invasive angiography. As compared to standard techniques such as fluorescein and indocyanine-green angiography the technique offers two major advantages: no dye is required and depth resolution is required is provided. As such Doppler OCT has the potential to improve our abilities to diagnose and monitor ocular vascular diseases. PMID:24704352

Leitgeb, Rainer A; Werkmeister, René M; Blatter, Cedric; Schmetterer, Leopold

2014-07-01

7

Second harmonic optical coherence tomography  

CERN Document Server

Second harmonic optical coherence tomography, which uses coherence gating of second-order nonlinear optical response of biological tissues for imaging, is described and demonstrated. Femtosecond laser pulses were used to excite second harmonic waves from collagen harvested from rat tail tendon and a reference nonlinear crystal. Second harmonic interference fringe signals were detected and used for image construction. Because of the strong dependence of second harmonic generation on molecular and tissue structures, this technique offers contrast and resolution enhancement to conventional optical coherence tomography.

Jiang, Y; Wang, Y; Chen, Z; Jiang, Yi; Tomov, Ivan; Wang, Yimin; Chen, Zhongping

2004-01-01

8

Flow-scanning optical tomography.  

Science.gov (United States)

We present a 3D tomography technique for in vivo observation of microscopic samples. The method combines flow in a microfluidic channel, illumination through a slit aperture, and a Fourier lens for simultaneous acquisition of multiple perspective angles in the phase-space domain. The technique is non-invasive and naturally robust to parasitic sample motion. 3D absorption is retrieved using standard back-projection algorithms, here a limited-domain inverse radon transform. Simultaneously, 3D differential phase contrast images are obtained by computational refocusing and comparison of complementary illumination angles. We implement the technique on a modified glass slide which can be mounted directly on existing optical microscopes. We demonstrate both amplitude and phase tomography on live, freely swimming C. elegans nematodes. PMID:25256716

Pégard, Nicolas C; Toth, Marton L; Driscoll, Monica; Fleischer, Jason W

2014-12-01

9

Interstitial Doppler optical coherence tomography  

Science.gov (United States)

Doppler optical coherence tomography (OCT) can image tissue structure and blood flow at micrometer-scale resolution but has limited imaging depth. We report a novel, linear-scanning, needle-based Doppler OCT system using angle-polished gradient-index or ball-lensed fibers. A prototype system with a 19-guage (diameter of ~0.9 mm) echogenic needle is constructed and demonstrates in vivo imaging of bidirectional blood flow in rat leg and abdominal cavity. To our knowledge, this is the first demonstration of Doppler OCT through a needle probe in interstitial applications to visualize deeply situated microcirculation.

Yang, Victor X. D.; Mao, You X.; Munce, Nigel; Standish, Beau; Kucharczyk, Walter; Marcon, Norman E.; Wilson, Brian C.; Vitkin, I. Alex

2005-07-01

10

Visible light optical coherence tomography  

Science.gov (United States)

We demonstrate for the first time optical coherence tomography (OCT) in the visible wavelength range with unprecedented sub-micrometer axial resolution, achieved by employing a photonic crystal fiber in combination with a sub-15fs Ti:sapphire laser (FEMTOLASERS). The shaped emission spectrum produced by the photonic crystal fiber ranges from 535 nm to 700 nm (centered at ~600 nm) resulting in ~0.9 micrometers axial OCT resolution in air corresponding to ~0.6 micrometers in biological tissue. Preliminary demonstration of the sub-micrometer resolution achieved with this visible light OCT setup is demonstrated on a 2.2 micrometers thick nitrocellulose membrane. The visible wavelength range not only enables extremely high axial resolution for OCT imaging, but also offers an attractive region for spectroscopic OCT.

Povazay, Boris; Apolonski, Alexander A.; Unterhuber, Angelika; Hermann, Boris; Bizheva, Kostadinka K.; Sattmann, Harald; Russell, Phillip S. J.; Krausz, Ferenc; Fercher, Adolf F.; Drexler, Wolfgang

2002-06-01

11

Optical Coherence Tomography: Advanced Modeling  

DEFF Research Database (Denmark)

Analytical and numerical models for describing and understanding the light propagation in samples imaged by optical coherence tomography (OCT) systems are presented. An analytical model for calculating the OCT signal based on the extended Huygens-Fresnel principle valid both for the single- and multiple-scattering regimes is derived. An advanced Monte Carlo model for calculating the OCT signal is also derived, and the validity of this model is shown through a mathematical proof based on the extended Huygens-Fresnel principle. From the analytical model, an algorithm for enhancing OCT images is developed, the so-called true-reflection algorithm in which the OCT signal may be corrected for the attenuation caused by scattering. The algorithm is verified experimentally and by using the Monte Carlo model as a numerical tissue phantom. Applications of extraction of optical properties from tissue are discussed. Finally, the Wigner phase-space distribution function is derived in a closed-form solution, which may have applications in OCT.

Andersen, Peter E.; Thrane, Lars

2013-01-01

12

MOEMS optical delay line for optical coherence tomography  

Science.gov (United States)

Micro-Opto-Electro-Mechanical optical coherence tomography, a lab-on-chip for biomedical applications is designed, studied, fabricated and characterized. To fabricate the device standard PolyMUMPS processes is adopted. We report the utilization of electro-optic modulator for a fast scanning optical delay line for time domain optical coherence tomography. Design optimization are performed using Tanner EDA while simulations are performed using COMSOL. The paper summarizes various results and fabrication methodology adopted. The success of the device promises a future hand-held or endoscopic optical coherence tomography for biomedical applications.

Choudhary, Om P.; Chouksey, S.; Sen, P. K.; Sen, P.; Solanki, J.; Andrews, J. T.

2014-09-01

13

Optical coherence tomography in late solar retinopathy  

Directory of Open Access Journals (Sweden)

Full Text Available Introduction. Solar retinopathy refers to retinal injury induced by direct or indirect solar viewing. Case report. We presented a patient who had observed partial solar eclipse 51 year before. He had bilaterally decreased vision and scar of the macular region at the time of presentation. The basic diagnostic tool applied in the presented patient, optical coherence tomography, showed hyporeflexivity of the outer retina in the segment of retinal pigment epithelialphotoreceptors complex with atrophy and thinning of the foveolar region. Conclusion. Optical coherence tomography is a powerful, non-invasive diagnostic tool which can ease the diagnosis and estimate the level and nature of the macular region damage.

Jankovi? Aleksandar

2011-01-01

14

Optical Coherence Tomography in Glaucoma  

Science.gov (United States)

Retinal nerve fiber layer (RNFL) thinning and optic nerve head cupping are key diagnostic features of glaucomatous optic neuropathy. The higher resolution of the recently introduced SD-OCT offers enhanced visualization and improved segmentation of the retinal layers, providing a higher accuracy in identification of subtle changes of the optic disc and RNFL thinning associated with glaucoma.

Berisha, Fatmire; Hoffmann, Esther M.; Pfeiffer, Norbert

15

Electronic Noise in Optical homodyne Tomography  

Science.gov (United States)

In experiments on homodyne tomography of light, the electronic noise of the detector often prevents the observation of the fine details of the quantum state's marginal distributions. We have shown that the noise contribution from the detector can be modeled by an equivalent inefficiency arising due to optical loss. We confirm this result using a non-classical squeezed light produced with an optical parametric amplifier.

Hoffman, Dallas; Appel, Jurgen; Figueroa, Eden; Lvovsky, Alex

2007-06-01

16

Optical coherence tomography in conjunction with bronchoscopy  

Energy Technology Data Exchange (ETDEWEB)

To evaluate the feasibility of and the potential for using optical coherence tomography in conjunction with conventional bronchoscopy in the evaluation of the airways. Methods: This was a pilot study based on an ex vivo experimental model involving three animals: one adult New Zealand rabbit and two Landrace pigs. An optical coherence tomography imaging catheter was inserted through the working channel of a flexible bronchoscope in order to reach the distal trachea of the animals. Images of the walls of the trachea were systematically taken along its entire length, from the distal to the proximal portion. Results: The imaging catheter was easily adapted to the working channel of the bronchoscope. High-resolution images of cross sections of the trachea were taken in real time, precisely delineating microstructures, such as the epithelium, submucosa, and cartilage, as well as the adventitia of the anterior and lateral tracheal walls. The corresponding layers of the epithelium, mucosa, and cartilage were clearly differentiated. The mucosa, submucosa, and trachealis muscle were clearly identified in the posterior wall. Conclusions: It is feasible to use an optical coherence tomography imaging catheter in combination with a flexible bronchoscope. Optical coherence tomography produces high resolution images that reveal the microanatomy of the trachea, including structures that are typically seen only on images produced by conventional histology. (author)

Rodrigues, Ascedio Jose; Takimura, Celso Kiyochi; Lemos Neto, Pedro Alves; Figueiredo, Viviane Rossi, E-mail: ascedio@gmail.com [Servico de Endoscopia Respiratoria, Hospital das Clinicas, Universidade de Sao Paulo (FM/USP), SP (Brazil)

2012-07-01

17

Optical coherence tomography in conjunction with bronchoscopy  

International Nuclear Information System (INIS)

To evaluate the feasibility of and the potential for using optical coherence tomography in conjunction with conventional bronchoscopy in the evaluation of the airways. Methods: This was a pilot study based on an ex vivo experimental model involving three animals: one adult New Zealand rabbit and two Landrace pigs. An optical coherence tomography imaging catheter was inserted through the working channel of a flexible bronchoscope in order to reach the distal trachea of the animals. Images of the walls of the trachea were systematically taken along its entire length, from the distal to the proximal portion. Results: The imaging catheter was easily adapted to the working channel of the bronchoscope. High-resolution images of cross sections of the trachea were taken in real time, precisely delineating microstructures, such as the epithelium, submucosa, and cartilage, as well as the adventitia of the anterior and lateral tracheal walls. The corresponding layers of the epithelium, mucosa, and cartilage were clearly differentiated. The mucosa, submucosa, and trachealis muscle were clearly identified in the posterior wall. Conclusions: It is feasible to use an optical coherence tomography imaging catheter in combination with a flexible bronchoscope. Optical coherence tomography produces high resolution images that reveal the microanatomy of the trachea, including structures that are typically seen only on images produced by conventional histology. (author)al histology. (author)

18

Optical tomography: forward and inverse problems  

International Nuclear Information System (INIS)

This is a review of recent mathematical and computational advances in optical tomography. We discuss the physical foundations of forward models for light propagation on microscopic, mesoscopic and macroscopic scales. We also consider direct and numerical approaches to the inverse problems that arise at each of these scales. Finally, we outline future directions and open problems in the field. (topical review)

19

Sonoluminescence optical confocal tomography of tissue  

Science.gov (United States)

In this paper, we report experiments on optical confocal tomography by use of sonoluminescence signal in both biological tissue and tissue-simulating media. A high-sensitive confocal scanning setup based on photon counting technique was developed. With the system, we obtained images of the objects embedded in tissue-simulating turbid media. The images showed a high contrast and a lateral resolution of about 100 [mu]m. We finally imaged a carbon stick buried in muscle tissue with the sonoluminescence confocal scanning tomography. This technique has potential applications in clinical diagnosis.

He, Yonghong; Xing, D. A.; Yao, Yong; Ueda, Ken-Ichi

20

Single-Scattering Optical Tomography  

CERN Document Server

We describe a novel tomographic imaging modality. The proposed technique utilizes visible or near-infrared light as a tissue probe in the ``mesoscopic'' scattering regime when the tissue layer exhibits sufficiently strong scattering so that its direct visual inspection is not possible, yet transmitted and reflected light are not diffuse. The forward model for light propagation in tissues is based on the scattering-order expansion of the radiative transport equation Green's function. The associated inverse problem is similar to the problem of inverting the Radon transform of x-ray tomography, except that the ray integrals are evaluated not along straight lines but along broken rays. As a result, the method does not require rotating the imaging device around the sample and taking multiple projections and, therefore, can be used in backscattering. An algebraic image reconstruction algorithm is numerically implemented using computer-generated data. An analytic image reconstruction formula analogous to the filtere...

Markel, V A; Markel, Vadim A.; Schotland, John C.

2007-01-01

 
 
 
 
21

Sonoluminescence optical confocal scanning tomography of tissue  

Science.gov (United States)

In this paper, we first report experiments on confocal tomography of sonoluminescence media with objects buried in both biological tissue and tissue-simulating media. A high-sensitive confocal scanning setup based on photon counting technique was developed. With the system, a carbon cube buried in tissue simulation medium was imaged with high contrast and a lateral resolution of about 100?m. For the tissue experiment a carbon stick buried in muscle tissue was optically sectioned with the sonoluminescence confocal scanning technique. The spatial resolution of the image at present is limited by the intensity of the sonoluminescence, and could be largely improved by increasing the intensity of emission by a sono-chemluminescence method. The optical tomography of sono-chemluminescence method has potential applications in clinical diagnosis.

He, Yonghong; Xing, Da

2001-06-01

22

Endoscopic Optical Coherence Tomography for Clinical Gastroenterology  

Directory of Open Access Journals (Sweden)

Full Text Available Optical coherence tomography (OCT is a real-time optical imaging technique that is similar in principle to ultrasonography, but employs light instead of sound waves and allows depth-resolved images with near-microscopic resolution. Endoscopic OCT allows the evaluation of broad-field and subsurface areas and can be used ancillary to standard endoscopy, narrow band imaging, chromoendoscopy, magnification endoscopy, and confocal endomicroscopy. This review article will provide an overview of the clinical utility of endoscopic OCT in the gastrointestinal tract and of recent achievements using state-of-the-art endoscopic 3D-OCT imaging systems.

Tsung-Han Tsai

2014-05-01

23

Pulse inversion ultrasound modulated optical tomography.  

Science.gov (United States)

Pulse inversion acoustic imaging is useful as it allows second harmonic imaging to be obtained with short acoustic pulses. This allows high axial resolution, but removes any overlap in the frequency spectra of fundamental and harmonic. We demonstrate pulse inversion ultrasound modulated optical tomography using an optical speckle based detection method. Inverted and non-inverted acoustic pulses combined with synchronized strobed illumination are applied to an optically scattering medium. Over the acquisition time of a camera, multiple pulses are summed and at the next frame the phase of the ultrasound is shifted by ?/2 and the process repeated. Combining the two frames allows a second harmonic signal to be obtained. A reduction in linewidth is observed (DC=9.26 mm, fundamental=4.02 mm, second harmonic=2.43 mm) in line scans of optically absorbing objects embedded in a scattering medium (thickness=16 mm, scattering coefficient=2.3 mm(-1), anisotropy factor=0.938). PMID:22627528

Ruan, Haowen; Mather, Melissa L; Morgan, Stephen P

2012-05-15

24

Dermascope guided multiple reference optical coherence tomography.  

Science.gov (United States)

In this paper, we report the feasibility of integrating a novel low cost optical coherence tomography (OCT) system with a dermascope for point-of-care applications. The proposed OCT system is based on an enhanced time-domain optical coherence tomographic system, called multiple reference OCT (MR-OCT), which uses a single miniature voice coil actuator and a partial mirror for extending the axial scan range. The system can simultaneously register both the superficial dermascope image and the depth-resolved OCT sub-surface information by an interactive beam steering method. A practitioner is able to obtain the depth resolved information of the point of interest by simply using the mouse cursor. The proposed approach of combining a dermascope with a low cost OCT provides a unique powerful optical imaging modality for a range of dermatological applications. Hand-held dermascopic OCT devices would also enable point of care and remote health monitoring. PMID:25401004

Dsouza, Roshan; Subhash, Hrebesh; Neuhaus, Kai; Hogan, Josh; Wilson, Carol; Leahy, Martin

2014-09-01

25

Optical coherence tomography of central serous chorioretinopathy  

Digital Repository Infrastructure Vision for European Research (DRIVER)

AIM:To observe the imaging features of the foveal photoreceptor layer in eyes with central serous chorioretinopathy(CSC)using frequency-domain optical coherence tomography(FD-OCT)and to find the relationship between best-corrected visual acuity(BCVA)and the morphology of thickness of the outer nuclear layer.METHODS: Totally 58 eyes from 54 CSC patients and 60 eyes from 30 healthy volunteers as the control group were selected. FD-OCT scan was performed on all the patients and volunteers. FD...

Feng Yan; Kai Meng; Bao-Cheng Men; Dan Liu

2013-01-01

26

Inverse scattering for optical coherence tomography.  

Science.gov (United States)

Inverse scattering theory for optical coherence tomography (OCT) is developed. The results are used to produce algorithms to resolve three-dimensional object structure, taking into account the finite beam width, diffraction, and defocusing effects. The resolution normally achieved only in the focal plane of the OCT system is shown to be available for all illuminated depths in the object without moving the focal plane. Spatially invariant resolution is verified with numerical simulations and indicates an improvement of the high-resolution cross-sectional imaging capabilities of OCT. PMID:16642179

Ralston, Tyler S; Marks, Daniel L; Carney, P Scott; Boppart, Stephen A

2006-05-01

27

Optical homodyne tomography with polynomial series expansion  

CERN Document Server

We present and demonstrate a method for optical homodyne tomography based on the inverse Radon trans- form. Different from the usual filtered back-projection algorithm, this method uses appropriate polynomial series to expand the Wigner function, the marginal distribution and discretize Fourier space. We show that this technique solves most technical difficulties encountered with kernel deconvolution based methods and recon- structs overall better and smoother Wigner functions. We also gives estimators of the reconstruction errors for both methods and shows improvement in noise handling properties and resilience to statistical errors.

Benichi, Hugo

2011-01-01

28

Phase-conjugate optical coherence tomography  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Quantum optical coherence tomography (Q-OCT) offers a factor-of-two improvement in axial resolution and the advantage of even-order dispersion cancellation when it is compared to conventional OCT (C-OCT). These features have been ascribed to the non-classical nature of the biphoton state employed in the former, as opposed to the classical state used in the latter. Phase-conjugate OCT (PC-OCT), introduced here, shows that non-classical light is not necessary to reap Q-OCT's a...

Erkmen, Baris I.; Shapiro, Jeffrey H.

2006-01-01

29

Nonlinear optical contrast enhancement for optical coherence tomography  

CERN Document Server

We present a new interferometric technique for measuring Coherent Anti-Stokes Raman Scattering (CARS) and Second Harmonic Generation (SHG) signals. Heterodyne detection is employed to increase the sensitivity in both CARS and SHG signal detection, which can also be extended to different coherent processes. The exploitation of the mentioned optical nonlinearities for molecular contrast enhancement in Optical Coherence Tomography (OCT) is presented. Numerical simulations for both coherent nonlinear processes are performed in order to determine the properties of the signal expected at the exit of the described nonlinear interferometer.

Vinegoni, C; Bredfeldt, J S; Marks, D L

2003-01-01

30

Improved image-forming optics for transmission optical projection tomography  

Science.gov (United States)

We demonstrate an improved image-forming optics for transmission optical projection tomography (TOPT), with which the parallel integral throughout an object can be obtained. This is performed by introducing a shutter with an appropriate diameter at the back focus of the objective lens. We evaluate and compare the performances of the improved and the conventional TOPT systems with different parameters to obtain the optimal configuration. The optimal reconstruction is achieved by the improved configuration with ? =0.8° ~1.6°, and the spatial resolution reaches 25 ?m. The Optimal configuration is validated by TOPT of a phantom sample and a five days chick embryo.

Wang, Yi; Wang, Ruikang

2007-02-01

31

In vivo cellular visualization of the human retina using optical coherence tomography and adaptive optics  

Energy Technology Data Exchange (ETDEWEB)

Optical coherence tomography (OCT) sees the human retina sharply with adaptive optics. In vivo cellular visualization of the human retina at micrometer-scale resolution is possible by enhancing Fourier-domain optical-coherence tomography with adaptive optics, which compensate for the eye's optical aberrations.

Olivier, S S; Jones, S M; Chen, D C; Zawadzki, R J; Choi, S S; Laut, S P; Werner, J S

2006-01-05

32

Optical coherence tomography - principles and applications  

Science.gov (United States)

There have been three basic approaches to optical tomography since the early 1980s: diffraction tomography, diffuse optical tomography and optical coherence tomography (OCT). Optical techniques are of particular importance in the medical field, because these techniques promise to be safe and cheap and, in addition, offer a therapeutic potential. Advances in OCT technology have made it possible to apply OCT in a wide variety of applications but medical applications are still dominating. Specific advantages of OCT are its high depth and transversal resolution, the fact, that its depth resolution is decoupled from transverse resolution, high probing depth in scattering media, contact-free and non-invasive operation, and the possibility to create various function dependent image contrasting methods. This report presents the principles of OCT and the state of important OCT applications. OCT synthesises cross-sectional images from a series of laterally adjacent depth-scans. At present OCT is used in three different fields of optical imaging, in macroscopic imaging of structures which can be seen by the naked eye or using weak magnifications, in microscopic imaging using magnifications up to the classical limit of microscopic resolution and in endoscopic imaging, using low and medium magnification. First, OCT techniques, like the reflectometry technique and the dual beam technique were based on time-domain low coherence interferometry depth-scans. Later, Fourier-domain techniques have been developed and led to new imaging schemes. Recently developed parallel OCT schemes eliminate the need for lateral scanning and, therefore, dramatically increase the imaging rate. These schemes use CCD cameras and CMOS detector arrays as photodetectors. Video-rate three-dimensional OCT pictures have been obtained. Modifying interference microscopy techniques has led to high-resolution optical coherence microscopy that achieved sub-micrometre resolution. This report is concluded with a short presentation of important OCT applications. Ophthalmology is, due to the transparent ocular structures, still the main field of OCT application. The first commercial instrument too has been introduced for ophthalmic diagnostics (Carl Zeiss Meditec AG). Advances in using near-infrared light, however, opened the path for OCT imaging in strongly scattering tissues. Today, optical in vivo biopsy is one of the most challenging fields of OCT application. High resolution, high penetration depth, and its potential for functional imaging attribute to OCT an optical biopsy quality, which can be used to assess tissue and cell function and morphology in situ. OCT can already clarify the relevant architectural tissue morphology. For many diseases, however, including cancer in its early stages, higher resolution is necessary. New broad-bandwidth light sources, like photonic crystal fibres and superfluorescent fibre sources, and new contrasting techniques, give access to new sample properties and unmatched sensitivity and resolution.

Fercher, A. F.; Drexler, W.; Hitzenberger, C. K.; Lasser, T.

2003-02-01

33

Optical coherence tomography - principles and applications  

International Nuclear Information System (INIS)

There have been three basic approaches to optical tomography since the early 1980s: diffraction tomography, diffuse optical tomography and optical coherence tomography (OCT). Optical techniques are of particular importance in the medical field, because these techniques promise to be safe and cheap and, in addition, offer a therapeutic potential. Advances in OCT technology have made it possible to apply OCT in a wide variety of applications but medical applications are still dominating. Specific advantages of OCT are its high depth and transversal resolution, the fact, that its depth resolution is decoupled from transverse resolution, high probing depth in scattering media, contact-free and non-invasive operation, and the possibility to create various function dependent image contrasting methods. This report presents the principles of OCT and the state of important OCT applications. OCT synthesises cross-sectional images from a series of laterally adjacent depth-scans. At present OCT is used in three different fields of optical imaging, in macroscopic imaging of structures which can be seen by the naked eye or using weak magnifications, in microscopic imaging using magnifications up to the classical limit of microscopic resolution and in endoscopic imaging, using low and medium magnification. First, OCT techniques, like the reflectometry technique and the dual beam technique were based on time-domain low coherence interferometry depth-scans. Later, Fourier-domain techniques have been developed and led to new imaging schemes. Recently developed parallel OCT schemes eliminate the need for lateral scanning and, therefore, dramatically increase the imaging rate. These schemes use CCD cameras and CMOS detector arrays as photodetectors. Video-rate three-dimensional OCT pictures have been obtained. Modifying interference microscopy techniques has led to high-resolution optical coherence microscopy that achieved sub-micrometre resolution. This report is concluded with a short presentation of important OCT applications. Ophthalmology is, due to the transparent ocular structures, still the main field of OCT application. The first commercial instrument too has been introduced for ophthalmic diagnostics (Carl Zeiss Meditec AG). Advances in using near-infrared light, however, opened the path for OCT imaging in strongly scattering tissues. Today, optical in vivo biopsy is one of the most challenging fields of OCT application. High resolution, high penetration depth, and its potential for functional imaging attribute to OCT an optical biopsy quality, which can be used to assess tissue and cell function and morphology in situ. OCT can already clarify the relevant architectural tissue morphology. For many diseases, however, including cancer in its early stages, higher resolution is necessary. New broad-bandwidth light sources, like photonic crystal fibres and superfluorescent fibre sources, and new contrasting techniques, give access to new sample properties and unmatched sensitivity and resolution

34

Correction of artefacts in optical projection tomography  

International Nuclear Information System (INIS)

A new imaging technique called optical projection tomography (OPT), essentially an optical version of x-ray computed tomography (CT), provides molecular specificity, cellular resolution and larger specimen coverage (?1 cubic centimetre) than was previously possible with other imaging techniques. It is ideally suited to gene expression studies in small animals. Reconstructed OPT images demonstrate several artefacts which reduce the overall image quality. In this paper, we describe methods to prevent smear artefacts due to illumination intensity fluctuation, ring artefacts due to CCD pixel sensitivity variation and a new 'detector edge' artefact caused by non-zero background signal. We also present an automated method to align the position of the rotational axis during image reconstruction. Finally, we propose a method to eliminate bowl artefacts due to projection truncation using a lower resolution OPT scan of the same specimen. This solution also provides OPT with the ability to obtain a high-resolution reconstruction from a region of interest of a specimen that is larger than the field of view. Implementation of these corrections and modifications increases the accuracy of the OPT imaging technique and extends its capabilities to obtain higher resolution data from within a whole specimen

35

Resolution improvement in emission optical projection tomography  

International Nuclear Information System (INIS)

A new imaging technique called emission optical projection tomography (eOPT), essentially an optical version of single-photon emission computed tomography (SPECT), provides molecular specificity, resolution on the order of microns to tens of microns, and large specimen coverage (? 1 cubic centimetre). It is ideally suited to gene expression studies in embryos. Reconstructed eOPT images suffer from blurring that worsens as the distance from the axis of rotation increases. This blur is caused in part by the defocusing of the lens' point-spread function, which increases with object distance from the focal plane. In this paper, we describe a frequency space filter based on the frequency-distance relationship of sinograms to deconvolve the distance-dependent point-spread function and exclude highly defocused data from the eOPT sinograms prior to reconstruction. The method is shown to reduce the volume at half-maximum of the reconstructed point-spread function to approximately 20% the original, and the volume at 10% maximum to approximately 6% the original. As an illustration, the visibility of fine details in the vasculature of a 9.5 day old mouse embryo is dramatically improved

36

Real-time phase-resolved optical coherence tomography and optical Doppler tomography.  

Science.gov (United States)

We have developed a novel real-time phase-resolved optical coherence tomography (OCT) and optical Doppler tomography (ODT) system using optical Hilbert transformation. By combining circularly polarized reference and linearly polarized sample signals, in-phase and quadrature interference components are produced in separate channels and treated as the real and imaginary parts of a complex signal to obtain the phase information directly. Using a resonant scanner at an axial scanning speed of 4 kHz in the reference arm of the interferometer, both structure and blood flow velocity images with 200 axial scans can be acquired at 20 frames per second with high sensitivity and large dynamic range. Real-time videos of in vivo blood flow in the chick chorioallantoic membrane using this interferometer are presented. PMID:19436351

Ding, Zhihua; Zhao, Yonghua; Ren, Hongwu; Nelson, J; Chen, Zhongping

2002-03-11

37

Optical coherence tomography velocimetry of colloidal suspensions.  

Science.gov (United States)

Optical coherence tomography velocimetry combined with a rheometer and optical modulation techniques provides increased sensitivity to the low shear rate motion of complex fluid systems. Optical modulation coupled with a new interferometer design yields improved signal to noise ratios and is demonstrated with optically opaque colloidal suspensions. Thus the measurable range of shear velocities with complex fluids can be as low as ?40 ?m s(-1), more than an order of magnitude improvement on the previous lower limit of ?700 ?m s(-1). Furthermore the apparatus demonstrates improved sensitivity to the measurement of velocity. The instrument was used to study two hard sphere colloidal systems, sterically stabilized PVP spheres of 1 ?m radius and sterically stabilized polystyrene spheres of 600 nm radius, which display shear banding behavior due to shear induced concentration gradients. OCT velocimetry also allows the velocity fluctuations of the system to be quantified as a function of the distance across the rheometer gap to help classify underlying unsteady or turbulent phenomena. PMID:25181574

Malm, A V; Harrison, A W; Waigh, T A

2014-11-01

38

An Optical Tomography System Using a Digital Signal Processor  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The use of a personal computer together with a Data Acquisition System (DAQ) as the processing tool in optical tomography systems has been the norm ever since the beginning of process tomography. However, advancements in silicon fabrication technology allow nowadays the fabrication of powerful Digital Signal Processors (DSP) at a reasonable cost. This allows this technology to be used in an optical tomography system since data acquisition and processing can be performed within the DSP. Thus, ...

Mohd Hafiz Fazalul Rahiman; Chiam Kok Thiam; Ruzairi Abdul Rahim

2008-01-01

39

Doppler optical coherence tomography in cardiovascular applications  

Science.gov (United States)

The study of flow dynamics in complex geometry vessels is highly important in various biomedical applications where the knowledge of the mechanic interactions between the moving fluid and the housing media plays a key role for the determination of the parameters of interest, including the effect of blood flow on the possible rupture of atherosclerotic plaques. Doppler Optical Coherence Tomography (DOCT), as a functional extension of Optical Coherence Tomography (OCT), is an optic, non-contact, noninvasive technique able to achieve detailed analysis of the flow/vessel interactions. It allows simultaneous high resolution imaging (˜10 µm typical) of the morphology and composition of the vessel and determination of the flow velocity distribution along the measured cross-section. We applied DOCT system to image high-resolution one-dimensional and multi-dimensional velocity distribution profiles of Newtonian and non-Newtonian fluids flowing in vessels with complex geometry, including Y-shaped and T-shaped vessels, vessels with aneurism, bifurcated vessels with deployed stent and scaffolds. The phantoms were built to mimic typical shapes of human blood vessels, enabling preliminary analysis of the interaction between flow dynamics and the (complex) geometry of the vessels and also to map the related velocity profiles at several inlet volume flow rates. Feasibility studies for quantitative observation of the turbulence of flows arising within the complex geometry vessels are discussed. In addition, DOCT technique was also applied for monitoring cerebral mouse blood flow in vivo. Two-dimensional DOCT images of complex flow velocity profiles in blood vessel phantoms and in vivo sub-cranial mouse blood flow velocities distributions are presented.

Bonesi, M.; Matcher, S.; Meglinski, I.

2010-06-01

40

Optical coherence tomography findings in optic disk melanocytoma  

Directory of Open Access Journals (Sweden)

Full Text Available A 49 years old male patient admitted to hospital with difficulty in reading. Distant visual acuity, anterior segment examination, and intraocular pressure measurements were normal in his both eyes. The fundus examination was normal in his right eye but in the left eye a pigmented lesion overlying and surrounding the optic disk was detected. Visual field examination (HFA II version 740 Humphrey Instruments, Inc SanLeandro, CA, Central 30-2 Threshold Test was unremarkable in his right eye but an enlarged blind spot was detected in his left eye. Optical coherence tomography (OCT scans showed high reflectance layer with optical shadowing behind it. OCT is a useful device in describing the actual size of melanocytoma and its follow up. OCT has a role to find out associated subretinal fluid, cystoid retinal edema, retinal traction and epiretinal membrane. We are presenting this case to emphasize the OCT findings of melanocytoma.

Ekrem Kad?o?lu

2011-06-01

 
 
 
 
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Optical tomography of the aurora and EISCAT  

Directory of Open Access Journals (Sweden)

Full Text Available Tomographic reconstruction of the three-dimensional auroral arc emission is used to obtain vertical and horizontal distributions of the optical auroral emission. Under the given experimental conditions with a very limited angular range and a small number of observers, algebraic reconstruction methods generally yield better results than transform techniques. Different algebraic reconstruction methods are tested with an auroral arc model and the best results are obtained with an iterative least-square method adapted from emission-computed tomography. The observation geometry used during a campaign in Norway in 1995 is tested with the arc model and root-mean-square errors, to be expected under the given geometrical conditions, are calculated. Although optimum geometry was not used, root-mean-square errors of less than 2% for the images and of the order of 30% for the distribution could be obtained. The method is applied to images from real observations. The correspondence of original pictures and projections of the reconstructed volume is discussed, and emission profiles along magnetic field lines through the three-dimensionally reconstructed arc are calibrated into electron density profiles with additional EISCAT measurements. Including a background profile and the temporal changes of the electron density due to recombination, good agreement can be obtained between measured profiles and the time-sequence of calculated profiles. These profiles are used to estimate the conductivity distribution in the vicinity of the EISCAT site. While the radar can only probe the ionosphere along the radar beam, the three-dimensional tomography enables conductivity estimates in a large area around the radar site.

Key words. Tomography · Aurora · EISCAT · Ionosphere · Conductivity

H. U. Frey

42

Medical imaging with optical coherence tomography  

Science.gov (United States)

Optical coherence tomography (OCT) is an emerging imaging modality which can generate high resolution, cross-sectional and three dimensional images of microstructure in biological systems. OCT is analogous to ultrasound B mode imaging, except that it uses light instead of sound. Imaging is performed by measuring the echo time delay of optical backscattering in the tissue as a function of transverse position. The penetration depth of OCT imaging is limited by attenuation from optical scattering to ˜ 2 to 3 mm in most tissues, however image resolutions of 1-10 um may be achieved. OCT functions as a type of ``optical biopsy" enabling in situ visualization of tissue microstructure with resolutions approaching that of conventional histopathology. Imaging can be performed in real time without the need to remove and process a specimen as in conventional biopsy. OCT technology utilizes advances in photonics and fiber optics such as femtosecond broadband lasers, high speed wavelength swept lasers and line scan camera technologies. Recent developments using Fourier domain detection achieve dramatic improvements in resolution and imaging speed. Three dimensional, volumetric imaging with extremely high voxel density is now possible, enabling microstructure and pathology to be visualized and rendered in a manner analogous to MR imaging. OCT is now widely accepted as a standard diagnostic in clinical ophthalmology, where it can image retinal pathology with unprecedented resolution improving the sensitivity of diagnosis and monitoring response to treatment. OCT is also being developed for other applications ranging from intravascular imaging in cardiology to endoscopic imaging for cancer detection. This presentation will discuss OCT technology and its applications.

Fujimoto, James G.

2010-03-01

43

Diffuse Optical Tomography for Brain Imaging: Theory  

Science.gov (United States)

Diffuse optical tomography (DOT) is a noninvasive, nonionizing, and inexpensive imaging technique that uses near-infrared light to probe tissue optical properties. Regional variations in oxy- and deoxy-hemoglobin concentrations as well as blood flow and oxygen consumption can be imaged by monitoring spatiotemporal variations in the absorption spectra. For brain imaging, this provides DOT unique abilities to directly measure the hemodynamic, metabolic, and neuronal responses to cells (neurons), and tissue and organ activations with high temporal resolution and good tissue penetration. DOT can be used as a stand-alone modality or can be integrated with other imaging modalities such as fMRI/MRI, PET/CT, and EEG/MEG in studying neurophysiology and pathology. This book chapter serves as an introduction to the basic theory and principles of DOT for neuroimaging. It covers the major aspects of advances in neural optical imaging including mathematics, physics, chemistry, reconstruction algorithm, instrumentation, image-guided spectroscopy, neurovascular and neurometabolic coupling, and clinical applications.

Yuan, Zhen; Jiang, Huabei

44

Optical coherence tomography examination of hair  

Science.gov (United States)

Human hair is a keratinous tissue composed mostly of flexible keratin, which can form a complex architecture consisting of distinct compartments or units (e.g. hair bulb, inner root sheath, shaft). Variations in hair shaft morphology can reflect ethnical diversity, but may also indicate internal diseases, nutritional deficiency, or hair and scalp disorders. Hair shaft abnormalities in cross section and diameter, as well as ultramorphological characterization and follicle shapes, might be visualized non-invasively by high-speed 2D and 3D optical coherence tomography (OCT). In this study, swept source OCT (ThorLabs) was used to examine human hair. Preliminary results showed that the high-speed OCT was a suitable and promising tool for non-invasive analysis of hair conditions.

Gong, Wei; Huang, Zheng; Xu, Jianshu; Yang, Hongqin; Li, Hui; Xie, Shusen

2014-09-01

45

Optical Tomography of Polydisperse Dry Foam  

Science.gov (United States)

Dry foam is a disordered packing of bubbles that distort into familiar polyhedral shapes. We have implemented a method that uses optical axial tomography to reconstruct the internal structure of a dry foam in three dimensions. The technique consists of taking a series of photographs of the dry foam against a uniformly illuminated background at successive angles. By summing the projections we create images of the cross section of the foam and analyze them to locate the Plateau borders and vertices. The vertices are then connected according to Plateau's rules to reconstruct the internal structure of the foam. Using this technique we are able to visualize a large number of bubbles of real 3D foams and obtain statistics of faces and edges.

Chieco, Anthony; Feitosa, Klebert; Korda, P. T.; Roth, A. E.; Durian, D. J.

2011-11-01

46

Fused Entropy Algorithm in Optical Computed Tomography  

Directory of Open Access Journals (Sweden)

Full Text Available In most applications of optical computed tomography (OpCT, limited-view problems are often encountered, which can be solved to a certain extent with typical OpCT reconstructive algorithms. The concept of entropy first emerged in information theory has been introduced into OpCT algorithms, such as maximum entropy (ME algorithms and cross entropy (CE algorithms, which have demonstrated their superiority over traditional OpCT algorithms, yet have their own limitations. A fused entropy (FE algorithm, which follows an optimized criterion combining self-adaptively ME with CE, is proposed and investigated by comparisons with ME, CE and some traditional OpCT algorithms. Reconstructed results of several physical models show this FE algorithm has a good convergence and can achieve better precision than other algorithms, which verifies the feasibility of FE as an approach of optimizing computation, not only for OpCT, but also for other image processing applications.

Xiong Wan

2014-02-01

47

Optical Coherence Tomography for Tracking Canvas Deformation  

International Nuclear Information System (INIS)

Preliminary results of the application of optical coherence tomography (OCT), in particular in its spectral mode (SOCT), to tracking of deformations in paintings on canvas caused by periodical humidity changes are presented. The setup is able to monitor the position of a chosen point at the surface of a painting with micrometre precision, simultaneously in three dimensions, every 100 seconds. This allows recording of deformations associated with crack formation. For the particular painting model examined, it was shown that the surface moves in-plane towards the corner, and bulges outwards (Z-direction) in response to a rise in humidity. Subsequent to the first humidification/drying cycle, translation in the Z-direction is decreased, whilst in-plane translations increase somewhat. It was also shown that the response of the painting on canvas begins immediately on changing the relative humidity in the surroundings.

48

Mid-infrared optical coherence tomography.  

Science.gov (United States)

A time domain optical coherence tomography (OCT) system is described that uses mid-infrared light (6-8 microm). To the best of our knowledge, this is the first OCT system that operates in the mid-infrared spectral region. It has been designed to characterize bioengineered tissues in terms of their structure and biochemical composition. The system is based upon a free-space Michelson interferometer with a germanium beam splitter and a liquid nitrogen cooled HgCdTe detector. A key component of this work has been the development of a broadband quantum cascade laser source (InGaAs/AlInAs containing 11 different active regions of the three well vertical transition type) that emits continuously over the 6-8 microm wavelength range. This wavelength range corresponds to the so called "mid-infrared fingerprint region" which exhibits well-defined absorption bands that are specifically attributable to the absorbing molecules. Therefore, this technology provides an opportunity for optical coherence molecular imaging without the need for molecular contrast agents. Preliminary measurements are presented. PMID:18163721

Colley, Christopher S; Hebden, Jeremy C; Delpy, David T; Cambrey, Alison D; Brown, Robert A; Zibik, Evgeny A; Ng, Wing H; Wilson, Luke R; Cockburn, John W

2007-12-01

49

Optical coherence tomography of the eye  

Science.gov (United States)

Optical Coherence Tomography (OCT) is a new technique for high-resolution, cross-sectional imaging of tissue in which the time-of-flight delay of light reflected from internal tissue structures is resolved with high precision using interferometry. Tomographic images are obtained which are analogous to those provided by ultrasound except that image contrast relies on differences in optical rather than acoustic properties of tissue. The use of light rather than sound enables higher resolution (10 ?m) and non-contact imaging. A clinically viable high-sensitivity, fiber-optic based OCT instrument has been constructed based on engineering principles derived from optical communication theory. Computer algorithms have also been developed for quantitative image analysis and restoration. OCT has been used to image patients with a variety of ocular diseases. In patients with macular pathology, OCT images have been correlated with conventional clinical examination and fluorescein angiography. Optical coherence tomograms are effective in staging macular holes, evaluating the vitreoretinal interface in eyes at risk for a macular hole, and providing a structural assessment of macular hole surgery. In eyes with central serous chorioretinopathy, OCT can evaluate sensory retinal separations undetected at the slit-lamp. Serial OCT images of macular edema are able to track both the progression of macular thickening and the resolution of macular edema following laser photocoagulation. In patients with diabetic retinopathy, measurements of macular thickness correlate with visual acuity and OCT is more sensitive to small changes in retinal thickness than slit-lamp biomicroscopy. OCT may provide a novel method of defining occult choroidal neovascular membranes in patients with age-related macular degeneration. OCT can also profile the thickness of the retinal nerve fiber layer with high resolution which is potentially important for the objective assessment of early glaucoma progression. OCT images have been correlated with visual field performance and optic nerve appearance in a cross- section of patients with various stages of glaucoma. These studies suggest that OCT has the potential to become an important diagnostic tool for the practicing ophthalmologist. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617-253-5668; Fax 617-253-1690.)

Hee, Michael Richard

1997-10-01

50

Optical coherence tomography imaging in uveitis.  

Science.gov (United States)

Optical coherence tomography (OCT) is a non-contact noninvasive technique that allows in vivo imaging of the retina, choroid, optic nerve head, retinal nerve fiber layer, and the anterior structures of the eye. It was introduced into clinical practice two decades ago. Advances in OCT technology have been achieved by searching ultra-high-resolution OCT, adaptive optics OCT, eye-tracking OCT, and changes in signal detection technique from time-domain (TD) to spectral-domain (SD) detection. Today, SD OCT has become a part of routine uveitis practice. Apart from its diagnostic value in uveitis, OCT has enabled objective assessment of treatment response and provided predictive value for visual recovery and prognosis of uveitic entities. It is the standard diagnostic technique in the detection, monitoring of treatment, and determination of prognosis in uveitic macular edema as well as other inflammatory macular pathologies, including epiretinal membrane formation, vitreomacular traction, foveal atrophy, and lamellar/full-thickness macular holes. OCT has also shed light on the pathophysiology of several posterior uveitic entities. SD OCT has enabled visualization of four lines in the sensory retina which represent the external limiting membrane, the photoreceptor inner and outer segment junction, the photoreceptor outer segment and the retina pigment epithelium junction, and the retina pigment epithelium-choriocapillaris complex. Thus, we have gained substantial information about the pathologic and structural changes in uveitic conditions with primary or secondary outer retinal involvement. SD OCT has also provided invaluable information on the inner retinal and the vitreoretinal interface changes in uveitic conditions. With the introduction of enhanced depth imaging, visualization of the choroid and choriocapillaries has become possible. Therefore, OCT has become an indispensible ancillary test in the diagnosis and management of inflammatory diseases involving the retina and/or the choroid. As OCT technology continues to develop further it will provide new insights into the retinal and choroidal structure and the pathogenesis of posterior uveitic entities. PMID:23835664

Onal, Sumru; Tugal-Tutkun, Ilknur; Neri, Piergiorgio; P Herbort, Carl

2014-04-01

51

Applications of Doppler optical coherence tomography  

Science.gov (United States)

A major development in biomedical imaging in the last decade has been optical coherence tomography (OCT). This technique enables microscale resolution, depth resolved imaging of the detailed morphology of transparent and nontransparent biological tissue in a noncontact and quasi-noninvasive way. In the first part of this dissertation, we will describe the development and the performance of our home-made OCT systems working with different wavelength regions based on free-space and optical fiber Michelson interferometers. The second part will focus on Doppler OCT (DOCT), an important extension of OCT, which enables the simultaneous evaluation of the structural information and of the fluid flow distribution at a localized position beneath the sample surface. Much effort has been spent during the past few years in our laboratory aimed at providing more accurate velocity measurements with an extended dynamic range. We also applied our technique in different research areas such as microfluidics and hemodynamics. Investigations on the optical properties of the biological tissues (such as absorption and scattering) corresponding to different center wavelengths, have been performed in our laboratory. We used a 10 femtosecond Ti:sapphire laser centered at about 810 nm associated with a free-space Michelson interferometer. The infrared sources were centered at about 1310 and 1560 nm with all-fiber interferometers. Comparative studies using three different sources for several in vitro biological tissues based on a graphical method illustrated how the optical properties affect the quality of the OCT images in terms of the penetration depth and backscattering intensity. We have shown the advantage of working with 810-nm emission wavelength for good backscattering amplitude and contrast, while sources emitting at 1570 nm give good penetration depth. The 1330-nm sources provide a good compromise between the two. Therefore, the choice of the source will ultimately determine the longitudinal resolution and the imaging depth for OCT imaging. Doppler OCT is becoming an increasingly popular field of investigation within optical coherence tomography with potentially important applications in cardiovascular and microfluidic research. We have spent some of the effort on searching for accurate and efficient methods for processing the experimental data. We applied the pseudo Wigner time-frequency distribution method to the data processing of Doppler OCT and compared its performance to that of the short-time Fourier transform method, the Hilbert-based phase-resolved method and the autocorrelation method. We concluded that the pseudo Wigner-distribution signal processing method is overall more precise than other often-used methods in Doppler OCT for the analysis of cross-sectional velocity distributions, especially in the high velocity regime. We also discovered the advantage of using the time-domain instead of the frequency domain for Doppler OCT for some applications where precise Doppler-speed metrology is essential. Based on the fact that the obtained local OCT interference signal is almost a single periodic waveform, we have developed a novel, simple and less time-consuming processing method based on the zero-crossing points in an OCT signal for the measurement of the Doppler frequency in a laminar flow. This method was compared to other processing approaches currently used in Doppler OCT. The results show that in the case of laminar flow, the zero-crossing method gives the more precise results, especially in the higher velocity regime with a substantial economy in processing time and an increase in dynamic range which can reach 70 dB. This feature becomes a major advantage in metrology if one wants to measure velocities over several orders of magnitude. We have applied this technique to some real flow models and the preliminary results on flow velocity distributions obtained in the case of a microfluidic circuit and in that of a phantom of a blood vessel stenosis and bifurcation will be described in this thesis. We also proposed the method to

Xu, Zhiqiang

52

Nanoparticle contrast agents for optical coherence tomography  

Science.gov (United States)

Optical coherence tomography (OCT) provides real-time, objective, in-vivo, optical cross-sectional representations of the retina and optic nerve. Recent innovations in image acquisition, including the incorporation of Fourier/spectral-domain detection, have improved imaging speed, sensitivity and resolution. Still, there remain specific structures within ocular OCT images, such as retinal ganglion cells (RGCs), which are of clinical interest but consistently have low contrast. This makes it difficult to differentiate between surrounding layers and structures. The objectives of this project were: (1) To establish a reliable method for OCT imaging of the healthy and diseased mouse eye in order to provide a platform for testing the utility of OCT contrast agents for ocular imaging, (2) To develop antibody-conjugated gold nanoparticles suitable for targeting specific structures and enhancing OCT image contrast in the mouse eye, and (3) To examine the localized contrast-enhancing ability and biocompatibility of gold nanoparticle contrast agents in-vivo. Our organizing hypotheses were that nanoparticles could improve contrast by modulating the intensity of backscattered light detected by OCT and that they could be directed to ocular structures of interest using antibodies specific to cellular markers. A reproducible method for imaging the mouse retina and quantifying retinal thickness was developed and this technique was then applied to a mouse model for retinal ganglion cell loss, optic nerve crush. Gold nanorods were designed specifically to augment the backscattering OCT signal at the same wavelengths of light used in current ophthalmic OCT imaging schemes (resonant wavelength lambda = 840 nm). Anti-CD90.1 (Thy1.1) antibodies were conjugated to the gold nanorods and a protocol for characterization of the success of antibody conjugation was developed. Upon injection, the gold nanorods were found to remain in the vitreous post-injection, with many consumed by an early inflammatory response and only very few reaching the internal limiting membrane and passing into the retina. Our findings suggest that, while gold nanorods are able to locally increase OCT signal intensity in the vitreous, their utility in the retina may be limited.

Gabriele, Michelle Lynn

53

Motion contrast using optical coherence tomography  

Science.gov (United States)

Diagnosis of ophthalmic diseases like age-related macular degeneration is very important for treatment of the disease as well as the development of future treatments. Optical coherence tomography (OCT) is an optical interference technique which can measure the three-dimensional structural information of the reflecting layers within a sample. In retinal imaging, OCT is used as the primary diagnostic tool for structural abnormalities such as retinal holes and detachments. The contrast within the images of this technique is based upon reflectivity changes from different regions of the retina. This thesis demonstrates the developments of methods used to produce additional contrast to the structural OCT images based on the tiny fluctuations of motion experienced by the mobile scatterers within a sample. Motion contrast was observed for motions smaller than 50 nm in images of a variety of samples. Initial contrast method demonstrations used Brownian motion differences to separate regions of a mobile Intralipid solution from a static agarose gel, chosen in concentration to minimize reflectivity contrast. Zebrafish embryos in the range of 3-4 days post fertilization were imaged using several motion contrast methods to determine the capabilities of identifying regions of vascular flow. Vasculature identification was demonstrated in zebrafish for blood vessels of all orientations as small as 10 microns in diameter. Mouse retinal imaging utilized the same motion contrast methods to determine the contrast capabilities for motions associated with vasculature within the retina. Improved contrast imaging techniques demonstrated comparable images to fluorescein angiography, the gold standard of retinal vascular imaging. Future studies can improve the demonstrated contrast analysis techniques and apply them towards human retinal motion contrast imaging for ophthalmic diagnostic purposes.

Fingler, Jeffrey Paul

54

Ultrahigh-resolution endoscopic optical coherence tomography  

Science.gov (United States)

Early detection of gastrointestinal cancer is essential for the patient treatment and medical care. Endoscopically guided biopsy is currently the gold standard for the diagnosis of early esophageal cancer, but can suffer from high false negative rates due to sampling errors. Optical coherence tomography (OCT) is an emerging medical imaging technology which can generate high resolution, cross-sectional images of tissue in situ and in real time, without the removal of tissue specimen. Although endoscopic OCT has been used successfully to identify certain pathologies in the gastrointestinal tract, the resolution of current endoscopic OCT systems has been limited to 10 - 15 m for clinical procedures. In this study, in vivo imaging of the gastrointestinal tract is demonstrated at a three-fold higher resolution (tissue microstructures and architectural details at high resolution, and the features observed in the OCT images are well-matched with histology. The clinical feasibility study is conducted through delivering OCT imaging catheter using standard endoscope. OCT images of normal esophagus, Barrett's esophagus, and esophageal cancers are demonstrated with distinct features. The ability of high resolution endoscopic OCT to image tissue morphology at an unprecedented resolution in vivo would facilitate the development of OCT as a potential imaging modality for early detection of neoplastic changes.

Chen, Yu; Herz, Paul R.; Hsiung, Pei-Lin; Aguirre, Aaron D.; Mashimo, Hiroshi; Desai, Saleem; Pedrosa, Macos; Koski, Amanda; Schmitt, Joseph M.; Fujimoto, James G.

2005-01-01

55

Polarization sensitive optical coherence tomography in dentistry  

International Nuclear Information System (INIS)

Optical coherence tomography (OCT) is a noninvasive and noncontact technique for obtaining cross-sectional images of biologic structure, which was initially introduced to depict the transparent tissue of the eye. It employs the partial coherence properties of a light source to image structures with high resolution (< 20 (m). Recently, this technique has also been applied in turbid media. This tomographic imaging is analogous to conventional ultrasound B mode imaging, except that OCT measures the intensity of backreflected infrared light rather than acoustical waves. First applications, of OCT in dentistry for diagnosing periodontal disease have been reported by Colston et al. presenting in vitro OCT images of the dental and periodontal tissues of porcine premolar teeth. In this work, the feasibility of polarisation sensitive OCT for dental material is suggested. In contrast with conventional OCT, where the magnitude of backscattered light as a function of depth is imaged, backscattered light is used to image the magnitude of the birefringence in the sample as a function of depth. Partial loss of birefringence is known to be an early indication of incipient caries or tissue thermal damage. Applying this technique for caries diagnosis or guidance regarding optimal dosimetry for thermally mediated laser therapeutic procedures, polarisation sensitive OCT would represent a promising new technology for dentistry. (author)

56

Space-division multiplexing optical coherence tomography.  

Science.gov (United States)

High speed, high resolution and high sensitivity are desirable for optical coherence tomography (OCT). Here, we demonstrate a space-division multiplexing (SDM) technology that translates long coherence length of a commercially available wavelength tunable laser into high OCT imaging speed. We achieved an effective 800,000 A-scans/s imaging speed using a 100,000 Hz tunable vertical cavity surface-emitting laser (VCSEL). A sensitivity of 94.6 dB and a roll-off of < 2 dB over ~30 mm imaging depth were measured from a single channel in the prototype SDM-OCT system. An axial resolution of ~11 ?m in air (or ~8.3 ?m in tissue) was achieved throughout the entire depth range. An in vivo, 3D SDM-OCT volume of an entire Drosophila larva consisting of 400 x 605 A-scans was acquired in 0.37 seconds. Synchronized cross-sectional OCT imaging of three different segments of a beating Drosophila larva heart is demonstrated. The SDM technology provides a new orthogonal dimension for further speed improvement for OCT with favorable cost scaling. SDM-OCT also preserves image resolution and allows synchronized cross-sectional and three-dimensional (3D) imaging of biological samples, enabling new biomedical applications. PMID:23938839

Zhou, Chao; Alex, Aneesh; Rasakanthan, Janarthanan; Ma, Yutao

2013-08-12

57

Attenuation compensation for optical coherence tomography imaging  

Science.gov (United States)

Optical coherence tomography (OCT) is a noninvasive technique that provides micrometer-scale imaging of tissue. As most biological tissues are considered turbid, it causes attenuation of the OCT signal and limits the depth penetration. Although a few algorithms had been developed to compensate the attenuation, almost all of them need to extract the scattering parameters before doing the compensation procedure. Because the real biological samples are anisotropic and multilayer-like structure, it is not time-efficient to model and solve these scattering parameters. This paper introduces a new method to compensate the OCT signal attenuation in depth. By analyzing the input signal, a compensation function is adaptively derived for each A-scan line, which can be used effectively to compensate the energy loss in the large sections and enhance the details in the deep, dark-like areas. Three bio-samples, a piece of onion, a Poecilia Wingei fish and a piece of rabbit abdominal aorta, were used to test our method. OCT images obtained by a swept-source OCT system were processed by the proposed method. Results show the visualization of structures in OCT images has been evidently improved, especially in deep region.

Chang, Shoude; Flueraru, Costel; Mao, Youxin; Sherif, Sherif

2009-12-01

58

Multiplicative optical tomography of cardiac electrical activity  

International Nuclear Information System (INIS)

Cardiac electrical activity can be mapped today through the response of voltage-sensitive dyes; but poor transparency of muscle tissue has enforced shallow-depth imaging. We present a three-dimensional (3D) reconstruction method for electrical activity deep inside the myocardial wall. Our approach is nonlinear and differs substantially from standard diffusive optical tomography. It does not require matrix inversion, data regularization or a priori information concerning the original object. Opposite sides of a slab-shaped preparation are scanned in parallel by detection and illumination points with a constant vector offset between illumination and detection axes (biaxial scanning). Scanning is performed in two perpendicular directions. In each direction, a pair of 2D images is obtained under offsets of opposite signs. These two pairs are the input for a multiplicative reconstruction algorithm, whose output is a 3D image. The overall procedure was successfully tested on computer-generated sources that include points, lines and hemispheres, patterned after actual electrophysiological excitations. The algorithm is computationally efficient and stable with respect to varying noise levels in the raw data

59

Optical coherence tomography in vulvar intraepithelial neoplasia  

Science.gov (United States)

Vulvar squamous cell carcinoma (VSCC) is a gynecological cancer with an incidence of two to three per 100,000 women. VSCC arises from vulvar intraepithelial neoplasia (VIN), which is diagnosed through painful punch biopsy. In this study, optical coherence tomography (OCT) is used to differentiate between normal and VIN tissue. We hypothesize that (a) epidermal layer thickness measured in OCT images is different in normal tissue and VIN, and (b) quantitative analysis of the attenuation coefficient (?oct) extracted from OCT data differentiates VIN from normal vulvar tissue. Twenty lesions from 16 patients are imaged with OCT. Directly after data acquisition, a biopsy is performed. Epidermal thickness is measured and values of ?oct are extracted from 200 OCT scans of normal and VIN tissue. For both methods, statistical analysis is performed using Paired Mann-Whitney-test. Correlation between the two methods is tested using a Spearman-correlation test. Both epidermal layer thickness as well as the ?oct are different between normal vulvar tissue and VIN lesions (p<0.0001). Moreover, no correlation is found between the epidermal layer thickness and ?oct. This study demonstrates that both the epidermal thickness and the attenuation coefficient of vulvar epithelial tissue containing VIN are different from that of normal vulvar tissue.

Wessels, Ronni; de Bruin, Daniel M.; Faber, Dirk J.; van Boven, Hester H.; Vincent, Andrew D.; van Leeuwen, Ton G.; van Beurden, Marc; Ruers, Theo J. M.

2012-11-01

60

Complete denture analyzed by optical coherence tomography  

Science.gov (United States)

The complete dentures are currently made using different technologies. In order to avoid deficiencies of the prostheses made using the classical technique, several alternative systems and procedures were imagined, directly related to the material used and also to the manufacturing technology. Thus, at the present time, there are several injecting systems and technologies on the market, that use chemoplastic materials, which are heat cured (90-100°C), in dry or wet environment, or cold cured (below 60°C). There are also technologies that plasticize a hard cured material by thermoplastic processing (without any chemical changes) and then inject it into a mold. The purpose of this study was to analyze the existence of possible defects in several dental prostheses using a non invasive method, before their insertion in the mouth. Different dental prostheses, fabricated from various materials were investigated using en-face optical coherence tomography. In order to discover the defects, the scanning was made in three planes, obtaining images at different depths, from 0,01 ?m to 2 mm. In several of the investigated prostheses we found defects which may cause their fracture. These defects are totally included in the prostheses material and can not be vizualised with other imagistic methods. In conclusion, en-face OCT is an important investigative tool for the dental practice.

Negrutiu, Meda L.; Sinescu, Cosmin; Todea, Carmen; Podoleanu, Adrian G.

2008-02-01

 
 
 
 
61

VW Hyi: optical spectroscopy and Doppler tomography  

CERN Document Server

We present high quality optical spectroscopy of the SU UMa-subtype dwarf nova, VW Hyi taken while the system was in quiescence. An S-wave is executed by the emission cores of the Hydrogen Balmer lines and by the emission lines of He I, Ca II, Fe II and He II. Using Doppler tomography we show it originates in the accretion stream-disc impact region. The He II emission is strongly phase-dependent, suggesting it originates exclusively within a hot cavity at the initial impact. We map the ionization structure of the stream-disc interaction region. One possible interpretation of this is that the Balmer hotspot lies downstream of the He II hotspot in the outer accretion disc, with the He I and Ca II hotspots at intermediate locations between the two. This suggests that Balmer emission is suppressed until material has cooled somewhat downstream of the impact site and is able to recombine. We favour a phase offset of 0.15+/-0.04 between the photometric ephemeris and inferior conjunction of the mass donor. The white d...

Smith, A J; Hynes, R I; Smith, Amanda J.; Haswell, Carole A.; Hynes, Robert I.

2006-01-01

62

Three dimensional time reversal optical tomography  

Science.gov (United States)

Time reversal optical tomography (TROT) approach is used to detect and locate absorptive targets embedded in a highly scattering turbid medium to assess its potential in breast cancer detection. TROT experimental arrangement uses multi-source probing and multi-detector signal acquisition and Multiple-Signal-Classification (MUSIC) algorithm for target location retrieval. Light transport from multiple sources through the intervening medium with embedded targets to the detectors is represented by a response matrix constructed using experimental data. A TR matrix is formed by multiplying the response matrix by its transpose. The eigenvectors with leading non-zero eigenvalues of the TR matrix correspond to embedded objects. The approach was used to: (a) obtain the location and spatial resolution of an absorptive target as a function of its axial position between the source and detector planes; and (b) study variation in spatial resolution of two targets at the same axial position but different lateral positions. The target(s) were glass sphere(s) of diameter ~9 mm filled with ink (absorber) embedded in a 60 mm-thick slab of Intralipid-20% suspension in water with an absorption coefficient ?a ~ 0.003 mm-1 and a transport mean free path lt ~ 1 mm at 790 nm, which emulate the average values of those parameters for human breast tissue. The spatial resolution and accuracy of target location depended on axial position, and target contrast relative to the background. Both the targets could be resolved and located even when they were only 4-mm apart. The TROT approach is fast, accurate, and has the potential to be useful in breast cancer detection and localization.

Wu, Binlin; Cai, W.; Alrubaiee, M.; Xu, M.; Gayen, S. K.

2011-03-01

63

Optical coherence tomography of central serous chorioretinopathy  

Directory of Open Access Journals (Sweden)

Full Text Available AIM:To observe the imaging features of the foveal photoreceptor layer in eyes with central serous chorioretinopathy(CSCusing frequency-domain optical coherence tomography(FD-OCTand to find the relationship between best-corrected visual acuity(BCVAand the morphology of thickness of the outer nuclear layer.METHODS: Totally 58 eyes from 54 CSC patients and 60 eyes from 30 healthy volunteers as the control group were selected. FD-OCT scan was performed on all the patients and volunteers. FD-OCT scan of 6mm horizontal line was performed, the scan depth was 1.9mm with a 5.8mm×5.8mm transverse area, the vertical and horizontal resolution was 5?m and 18?m respectively. The scan mode was 512×496. The morphological changes of FD-OCT on different stages of CSC were observed and the relationship between best-corrected visual acuity(BCVAand the morphology of thickness of the outer nuclear layer were analyzed.RESULTS: Simple serous neuroepithelial layer detachment and simple serous neuroepithelial layer detachment associated with pigment epithelial layer detachment at macula were about 84.5% of all the patients. Thickness of the outer nuclear layer was thinner from acute stage to chronic stage of CSC, and the relationship between thickness of the outer nuclear layer and BCVA was negative.CONCLUSION: FD-OCT can detect the detailed morphologic changes and pathological morphology at the foveal photoreceptor layer in eyes with CSC patients.

Feng Yan

2013-06-01

64

Quantum optical coherence tomography of a biological sample  

CERN Document Server

Quantum optical coherence tomography (QOCT) makes use of an entangled-photon light source to carry out dispersion-immune axial optical sectioning. We present the first experimental QOCT images of a biological sample: an onion-skin tissue coated with gold nanoparticles. 3D images are presented in the form of 2D sections of different orientations.

Nasr, Magued B; Nguyen, Nam; Rong, Guoxin; Yang, Linglu; Reinhard, Bjorn M; Saleh, Bahaa E A; Teich, Malvin C

2008-01-01

65

Development of Fourier domain optical coherence tomography  

Science.gov (United States)

Fourier domain optical coherence tomography (FD-OCT) is a high-speed, high-resolution, and noninvasive imaging technique that can obtain cross-sectional images of light scattering medium, such as biomedical tissues. In this thesis, I report three novel methods in FD-OCT technique including common-path endoscopic FD-OCT, streak-mode FD-OCT, and Doppler streak-mode FD-OCT. Finally, I apply the streak mode FD-OCT to ultrahigh-speed, noninvasive, live imaging of embryonic chick hearts. An extension of conventional FD-OCT technique is endoscopic FD-OCT, which can access internal organs by utilizing a miniaturized catheter design. However, its image signal suffers from the bending of the endoscopic catheter. To address this problem, a common-path endoscopic FD-OCT system was developed to avoid the polarization mismatch. Consequently, the OCT images were immune to the catheter bending. In addition, a Microelectromechanical system (MEMS) motor was integrated into the miniaturized probe to achieve circumferential scanning within lumen samples. In conventional FD-OCT, the imaging speed is limited by the slow line-scan rate of the camera. We developed the streak-mode FD-OCT technique, in which an area-scan camera is used instead of a line-scan camera to record the FD-OCT spectrum. Using this technique, high temporal resolution of 1000--2000 cross-sectional images of the sample were obtained in one second. Doppler FD-OCT is a functional extension of FD-OCT technique, which can measure the flow velocity within biomedical tissues. However, conventional techniques are not available to measure high speed flow due to slow imaging speed, phase wrapping, and fringe wash out issues. Based on the streak mode FD-OCT, a novel Doppler technique was developed that addressed these problems. It has been well established that cardiac dynamics play an important role in the early development of an embryonic heart. However, the mechanism by which cardiac dynamics affect the development of a peristaltic tube into a four-chambered heart is still unclear. This is mainly due to lack of investigative tools, such as an imaging technique with sufficiently high spatial and temporal resolution. Using streak-mode FD-OCT, 4D (3D + time) images of beating hearts have been reconstructed. This marks the first time that the embryonic animal heart has been 4D imaged using a megahertz OCT.

Wang, Rui

66

High speed optical tomography for flow visualization  

International Nuclear Information System (INIS)

A novel optical architecture (based on holographic optical elements) for making high speed tomographic measurements is presented. The system is designed for making density or species concentration measurements in a nonsteady fluid or combusting flow. Performance evaluations of the optical system are discussed and a test phase object has been successfully reconstructed using this optical arrangement

67

Mapping distributed brain function and networks with diffuse optical tomography  

Science.gov (United States)

Mapping of human brain function has revolutionized systems neuroscience. However, traditional functional neuroimaging by positron emission tomography or functional magnetic resonance imaging cannot be used when applications require portability, or are contraindicated because of ionizing radiation (positron emission tomography) or implanted metal (functional magnetic resonance imaging). Optical neuroimaging offers a non-invasive alternative that is radiation free and compatible with implanted metal and electronic devices (for example, pacemakers). However, optical imaging technology has heretofore lacked the combination of spatial resolution and wide field of view sufficient to map distributed brain functions. Here, we present a high-density diffuse optical tomography imaging array that can map higher-order, distributed brain function. The system was tested by imaging four hierarchical language tasks and multiple resting-state networks including the dorsal attention and default mode networks. Finally, we imaged brain function in patients with Parkinson's disease and implanted deep brain stimulators that preclude functional magnetic resonance imaging.

Eggebrecht, Adam T.; Ferradal, Silvina L.; Robichaux-Viehoever, Amy; Hassanpour, Mahlega S.; Dehghani, Hamid; Snyder, Abraham Z.; Hershey, Tamara; Culver, Joseph P.

2014-06-01

68

Optical Doppler tomography based on a field programmable gate array  

DEFF Research Database (Denmark)

We report the design of and results obtained by using a field programmable gate array (FPGA) to digitally process optical Doppler tomography signals. The processor fits into the analog signal path in an existing optical coherence tomography setup. We demonstrate both Doppler frequency and envelope extraction using the Hilbert transform, all in a single FPGA. An FPGA implementation has certain advantages over general purpose digital signal processor (DSP) due to the fact that the processing elements operate in parallel as opposed to the DSP. which is primarily a sequential processor.

Larsen, Henning Engelbrecht; Nilsson, Ronnie Thorup

2008-01-01

69

ASSESSMENT OF TISSUE OPTICAL CLEARING AS A FUNCTION OF GLUCOSE CONCENTRATION USING OPTICAL COHERENCE TOMOGRAPHY  

Digital Repository Infrastructure Vision for European Research (DRIVER)

One of the major challenges in imaging biological tissues using optical techniques, such as optical coherence tomography (OCT), is the lack of light penetration due to highly turbid structures within the tissue. Optical clearing techniques enable the biological samples to be more optically homogeneous, allowing for deeper penetration of light into the tissue. This study investigates the effect of optical clearing utilizing various concentrations of glucose solution (10%, 30%, and 50%) on porc...

Sudheendran, Narendran; Mohamed, Mohamed; Ghosn, Mohamad G.; Tuchin, Valery V.; Larin, Kirill V.

2010-01-01

70

Diagnosis and pathogenesis of congenital X-linked retinoschisis with optical coherence tomography.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This study shows how optical coherence tomography has been valuable in the diagnosis of congenital X-linked retinoschisis. An infant with convergent strabismus underwent serial optical coherence tomography examinations that helped to make the diagnosis of congenital X-linked retinoschisis. Optical coherence tomography is useful in the diagnosis of congenital X-linked retinoschisis and adds new information about pathogenesis. The authors recommend the use of optical coherence tomography in ped...

Dhingra, S.; Patel, Ck

2010-01-01

71

Topological sensitivity analysis in fluorescence optical tomography  

International Nuclear Information System (INIS)

Fluorescence tomography is a non-invasive imaging modality that reconstructs fluorophore distributions inside a small animal from boundary measurements of the fluorescence light. The associated inverse problem is stabilized by a priori properties or information. In this paper, cases are considered where the fluorescent inclusions are well separated from the background and have a spatially constant concentration. Under these a priori assumptions, the identification process may be formulated as a shape optimization problem, where the interface between the fluorescent inclusion and the background constitutes the unknown shape. In this paper, we focus on the computation of the so-called topological derivative for fluorescence tomography which could be used as a stand-alone tool for the reconstruction of the fluorophore distributions or as the initialization in a level-set-based method for determining the shape of the inclusions. (paper)

72

RADIAL COMPUTED TOMOGRAPHY OF AIR CONTAMINANTS USING OPTICAL REMOTE SENSING  

Science.gov (United States)

The paper describes the application of an optical remote-sensing (ORS) system to map air contaminants and locate fugitive emissions. Many ORD systems may utilize radial non-overlapping beam geometry and a computed tomography (CT) algorithm to map the concentrations in a plane. In...

73

Subsurface defect detection in materials using optical coherence tomography  

Science.gov (United States)

We have used optical coherence tomography to study the internal structure of a variety of non-biological materials. In particular, we have imaged internal regions from a commercial grade of lead zirconate titanate ceramic material, from a sample of single-crystal silicon carbide, and from a Teflon-coated wire. In each case the spatial positions of internal defects were determined.

Duncan, Michael D.; Bashkansky, Mark; Reintjes, John F.

1998-06-01

74

Time Domain Fluorescent Diffuse Optical Tomography: analytical expressions  

Science.gov (United States)

Light propagation in tissue is known to be favored in the Near Infrared spectral range. Capitalizing on this fact, new classes of molecular contrast agents are engineered to fluoresce in the Near Infrared. The potential of these new agents is vast as it allows tracking non-invasively and quantitatively specific molecular events in-vivo. However, to monitor the bio-distribution of such compounds in thick tissue proper physical models of light propagation are necessary. To recover 3D concentrations of the compound distribution, it is necessary to perform a model based inverse problem: Diffuse Optical Tomography. In this work, we focus on Fluorescent Diffuse Optical Tomography expressed within the normalized Born approach. More precisely, we investigate the performance of Fluorescent Diffuse Optical Tomography in the case of time resolved measurements. The different moments of the time point spread function were analytically derived to construct the forward model. The derivation was performed from the zero order moment to the second order moment. This new forward model approach was validated with simulations based on relevant configurations. Enhanced performance of Fluorescent Diffuse Optical Tomography was achieved using these new analytical solutions when compared to the current formulations.

Lam, S.; Lesage, F.; Intes, X.

2005-04-01

75

Characterization of the dental pulp using optical coherence tomography  

Science.gov (United States)

The inner structure of teeth, i.e. the root canal anatomy, is very complex. However a good knowledge of endodontic architecture is the first step towards successful endodontic treatment. Optical coherence tomography (OCT) is a powerful technique to generate images of hard and soft tissue. Its images show dependency on the optical properties of the tissue under analysis. Changes in the scattering and absorption of tissues can be observed through the OCT images. In this work, we used optical coherence tomography to perform in vitro studies of the inner structure of the first molar of albino rats (Rattus norvegicus). Focusing on the pulp chamber and in the root canal, we compare the images generated with the OCT technique to the histology. We are analyzing the feasibility of OCT to help on the diagnostic of endodontic diseases.

Kauffman, C. M. F.; Carvalho, M. T.; Araujo, R. E.; Freitas, A. Z.; Zezell, D. M.; Gomes, A. S. L.

2006-02-01

76

Imaging of dental implant osseointegration using optical coherent tomography  

Science.gov (United States)

Investigation of initial implant stability with different dental implant designs is an important task to obtain good quality dental implants. Failure of a dental implant is often related to failure to osseointegrate correctly. Optical Coherent Tomography is a competitive non-invasive method of osseointegration investigation. FD-OCT with Swept Source was used to obtain 3-D image of the peri-implant tissue (soft and hard) in the case of mandible fixed screw. 1350 nm centered laser source give better images than 850 nm laser source for hard tissue imaging. Present work suggests that Optical Coherent Tomography is a proper technique to obtain the image of the contact tissue-metal screw. OCT images are useful to evaluate optical properties of bone tissues.

Ionita, I.; Reisen, P.

2009-02-01

77

Signal-to-noise-ratio expressions in optical diffusion tomography  

Science.gov (United States)

Optical diffusion tomography is a technology that is employed to obtain images of the heterogeneous nature of turbid media by using optical radiation. Noise ultimately limits the achievable spatial resolution in these reconstructed images; therefore it is of interest to develop signal-to-noise-ratio expressions that relate spatial resolution in the images to the underlying system and material properties. In this study, Fourier-domain signal-to-noise-ratio expressions are derived for two types of optical diffusion tomography systems: those that use amplitude-modulated illumination sources and those that use continuous-wave illumination sources. The signal-to-noise-ratio expressions are compared for these two types of systems and are validated by laboratory data.

Matson, Charles L.

2002-05-01

78

Polarization-sensitive quantum optical coherence tomography: Experiment  

Science.gov (United States)

Polarization-sensitive quantum optical coherence tomography (PS-QOCT) makes use of a Type-II twin-photon light source for carrying out optical sectioning with polarization sensitivity. A BBO nonlinear optical crystal pumped by a Ti:sapphire psec-pulsed laser is used to confirm the theoretical underpinnings of this imaging paradigm. PS-QOCT offers even-order dispersion cancellation with simultaneous access to the group-velocity dispersion characteristics of the interstitial medium between the reflecting surfaces of the sample.

Booth, Mark C.; Saleh, Bahaa E. A.; Teich, Malvin Carl

2011-05-01

79

Polarization-Sensitive Quantum Optical Coherence Tomography: Experiment  

CERN Document Server

Polarization-sensitive quantum optical coherence tomography (PS-QOCT) makes use of a Type-II twin-photon light source for carrying out optical sectioning with polarization sensitivity. A BBO nonlinear optical crystal pumped by a Ti:sapphire psec-pulsed laser is used to confirm the theoretical underpinnings of this imaging paradigm. PS-QOCT offers even-order dispersion cancellation with simultaneous access to the group-velocity dispersion characteristics of the interstitial medium between the reflecting surfaces of the sample.

Booth, Mark C; Teich, Malvin Carl

2010-01-01

80

Photons-based medical imaging - Radiology, X-ray tomography, gamma and positrons tomography, optical imaging  

International Nuclear Information System (INIS)

This book describes the different principles used in medical imaging. The detection aspects, the processing electronics and algorithms are detailed for the different techniques. This first tome analyses the photons-based techniques (X-rays, gamma rays and visible light). Content: 1 - physical background: radiation-matter interaction, consequences on detection and medical imaging; 2 - detectors for medical imaging; 3 - processing of numerical radiography images for quantization; 4 - X-ray tomography; 5 - positrons emission tomography: principles and applications; 6 - mono-photonic imaging; 7 - optical imaging; Index. (J.S.)

 
 
 
 
81

Wavelength-encoded tomography based on optical temporal Fourier transform  

Science.gov (United States)

We propose and demonstrate a technique called wavelength-encoded tomography (WET) for non-invasive optical cross-sectional imaging, particularly beneficial in biological system. The WET utilizes time-lens to perform the optical Fourier transform, and the time-to-wavelength conversion generates a wavelength-encoded image of optical scattering from internal microstructures, analogous to the interferometery-based imaging such as optical coherence tomography. Optical Fourier transform, in principle, comes with twice as good axial resolution over the electrical Fourier transform, and will greatly simplify the digital signal processing after the data acquisition. As a proof-of-principle demonstration, a 150 -?m (ideally 36 ?m) resolution is achieved based on a 7.5-nm bandwidth swept-pump, using a conventional optical spectrum analyzer. This approach can potentially achieve up to 100-MHz or even higher frame rate with some proven ultrafast spectrum analyzer. We believe that this technique is innovative towards the next-generation ultrafast optical tomographic imaging application.

Zhang, Chi; Wong, Kenneth K. Y.

2014-09-01

82

Imaging techniques utilizing optical fibers and tomography  

Energy Technology Data Exchange (ETDEWEB)

Two-dimensional, time-dependent images generated by neutrons, gamma rays, and x-rays incident on fast scintillators are relayed to streak and video cameras over optical fibers. Three dimensions, two spatial and one temporal, have been reduced to two, one in space and time utilizing sampling methods permitting reconstruction of a time-dependent, two-dimensional image subsequent to data recording. The manner in which the sampling is done optimized the ability to reconstruct the image via a maximization of entropy algorithm. This method uses four linear fiber optic arrays typically 30 meters long and up to 35 elements each. A further refinement of this technique collapses the linear array information into four single fibers by wavelength multiplexing. This permits economical transmission of the data over kilometer distances to the recording equipment.

Wilke, M.; King, N.S.P.; Gray, N.; Johnson, D.; Esquibel, D.; Nedrow, P.; Ishiwata, S.

1985-01-01

83

Laser tomography adaptive optics: a performance study.  

Science.gov (United States)

We present an analytical derivation of the on-axis performance of adaptive optics systems using a given number of guide stars of arbitrary altitude, distributed at arbitrary angular positions in the sky. The expressions of the residual error are given for cases of both continuous and discrete turbulent atmospheric profiles. Assuming Shack-Hartmann wavefront sensing with circular apertures, we demonstrate that the error is formally described by integrals of products of three Bessel functions. We compare the performance of adaptive optics correction when using natural, sodium, or Rayleigh laser guide stars. For small diameter class telescopes (?5 m), we show that a small number of Rayleigh beacons can provide similar performance to that of a single sodium laser, for a lower overall cost of the instrument. For bigger apertures, using Rayleigh stars may not be such a suitable alternative because of the too severe cone effect that drastically degrades the quality of the correction. PMID:24323009

Tatulli, Eric; Ramaprakash, A N

2013-12-01

84

Positron emission tomography and optical tissue imaging  

Science.gov (United States)

A mobile compact imaging system that combines both PET imaging and optical imaging into a single system which can be located in the operating room (OR) and provides faster feedback to determine if a tumor has been fully resected and if there are adequate surgical margins. While final confirmation is obtained from the pathology lab, such a device can reduce the total time necessary for the procedure and the number of iterations required to achieve satisfactory resection of a tumor with good margins.

Falen, Steven W. (Carmichael, CA); Hoefer, Richard A. (Newport News, VA); Majewski, Stanislaw (Yorktown, VA); McKisson, John (Hampton, VA); Kross, Brian (Yorktown, VA); Proffitt, James (Newport News, VA); Stolin, Alexander (Newport News, VA); Weisenberger, Andrew G. (Yorktown, VA)

2012-05-22

85

Digital optical tomography system for dynamic breast imaging.  

Science.gov (United States)

Diffuse optical tomography has shown promising results as a tool for breast cancer screening and monitoring response to chemotherapy. Dynamic imaging of the transient response of the breast to an external stimulus, such as pressure or a respiratory maneuver, can provide additional information that can be used to detect tumors. We present a new digital continuous-wave optical tomography system designed to simultaneously image both breasts at fast frame rates and with a large number of sources and detectors. The system uses a master-slave digital signal processor-based detection architecture to achieve a dynamic range of 160 dB and a frame rate of 1.7 Hz with 32 sources, 64 detectors, and 4 wavelengths per breast. Included is a preliminary study of one healthy patient and two breast cancer patients showing the ability to identify an invasive carcinoma based on the hemodynamic response to a breath hold. PMID:21806275

Flexman, Molly L; Khalil, Michael A; Al Abdi, Rabah; Kim, Hyun K; Fong, Christopher J; Desperito, Elise; Hershman, Dawn L; Barbour, Randall L; Hielscher, Andreas H

2011-07-01

86

Optical coherence tomography--a new imaging method in ophthalmology.  

Science.gov (United States)

An improvement of examination methods in ophthalmology, technical digitalisation and knowledge of validity of examinations in various diseases contributes to early diagnostics, thereby leading to an opportunity for early treatment of eye disorders. Standard introduction of the so-called optical coherence tomography into the ophthamological clinical practice facilitated new options for a detailed analysis of pathological processes in the particular layers of the retina (Fig. 2, Ref. 5). Full Text (Free, PDF) www.bmj.sk. PMID:20568425

Svorenova, I; Strmen, P; Olah, Z

2010-01-01

87

Optical coherence tomography-based freeze-drying microscopy  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A new type of freeze-drying microscope based upon time-domain optical coherence tomography is presented here (OCT-FDM). The microscope allows for real-time, in situ 3D imaging of pharmaceutical formulations in vials relevant for manufacturing processes with a lateral resolution of <7 ?m and an axial resolution of <5 ?m. Correlation of volumetric structural imaging with product temperature measured during the freeze-drying cycle allowed investigation of structural changes in the product and ...

Mujat, Mircea; Greco, Kristyn; Galbally-kinney, Kristin L.; Hammer, Daniel X.; Ferguson, R. Daniel; Iftimia, Nicusor; Mulhall, Phillip; Sharma, Puneet; Pikal, Michael J.; Kessler, William J.

2012-01-01

88

Optical coherence tomography-based micro-particle image velocimetry.  

Science.gov (United States)

We present a new application of optical coherence tomography (OCT), widely used in biomedical imaging, to flow analysis in near-wall hydrodynamics for marine research. This unique capability, called OCT micro-particle image velocimetry, provides a high-resolution view of microscopic flow phenomena and measurement of flow statistics within the first millimeter of a boundary layer. The technique is demonstrated in a small flow cuvette and in a water tunnel. PMID:24322073

Mujat, Mircea; Ferguson, R Daniel; Iftimia, Nicusor; Hammer, Daniel X; Nedyalkov, Ivaylo; Wosnik, Martin; Legner, Hartmut

2013-11-15

89

Imaging nanoparticle flow using magneto-motive optical Doppler tomography  

Science.gov (United States)

We introduce a novel approach for imaging solutions of superparamagnetic iron oxide (SPIO) nanoparticles using magneto-motive optical Doppler tomography (MM-ODT). MM-ODT combines an externally applied temporally oscillating high-strength magnetic field with ODT to detect nanoparticles flowing through a microfluidic channel. A solenoid with a cone-shaped ferrite core extensively increased the magnetic field strength (Bmax = 1 T, \

Kim, Jeehyun; Oh, Junghwan; Milner, Thomas E.; Nelson, J. Stuart

2007-01-01

90

Wavelet domain compounding for speckle reduction in optical coherence tomography  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Visibility of optical coherence tomography (OCT) images can be severely degraded by speckle noise. A computationally efficient despeckling approach that strongly reduces the speckle noise is reported. It is based on discrete wavelet transform (DWT), but eliminates the conventional process of threshold estimation. By decomposing an image into different levels, a set of sub-band images are generated, where speckle noise is additive. These sub-band images can be compounded to suppress the additi...

Ou, H.; Sun, C.; Xu, J.; Yang, Vxd; Chui, Pc; Lam, Eym; Wong, Kky

2013-01-01

91

Signal processing in optical coherence tomography for aerospace material characterization:  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Based on a customized time-domain optical coherence tomography (OCT) system, a series of signal processing approaches have been designed and reviewed. To improve demodulation accuracy and image quality, demodulation approaches such as median filter, Hilbert transform, and envelope detector were investigated with simulated as well as experimental data. Without noise, the Hilbert transform has the best performance, but after considering the narrow-band noise in the modulated signal, the envelop...

Liu, P.; Groves, R. M.; Benedictus, R.

2013-01-01

92

Optical reflectance tomography using TCSPC laser radar  

Science.gov (United States)

Tomographic signal processing is used to transform multiple one-dimensional range profiles of a target from different angles to a two-dimensional image of the object. The range profiles are measured by a time-correlated single-photon counting (TCSPC) laser radar system with approximately 50 ps range resolution and a field of view that is wide compared to the measured objects. Measurements were performed in a lab environment with the targets mounted on a rotation stage. We show successful reconstruction of 2D-projections along the rotation axis of a boat model and removal of artefacts using a mask based on the convex hull. The independence of spatial resolution and the high sensitivity at a first glance makes this an interesting technology for very long range identification of passing objects such as high altitude UAVs and orbiting satellites but also the opposite problem of ship identification from high altitude platforms. To obtain an image with useful information measurements from a large angular sector around the object is needed, which is hard to obtain in practice. Examples of reconstructions using 90 and 150° sectors are given. In addition, the projection of the final image is along the rotation axis for the measurement and if this is not aligned with a major axis of the target the image information is limited. There are also practical problems to solve, for example that the distance from the sensor to the rotation centre needs to be known with an accuracy corresponding to the measurement resolution. The conclusion is that that laser radar tomography is useful only when the sensor is fixed and the target rotates around its own axis.

Henriksson, Markus; Olofsson, Tomas; Grönwall, Christina; Brännlund, Carl; Sjöqvist, Lars

2012-09-01

93

Fast optical transillumination tomography with large-size projection acquisition.  

Science.gov (United States)

Techniques such as optical coherence tomography and diffuse optical tomography have been shown to effectively image highly scattering samples such as tissue. An additional modality has received much less attention: Optical transillumination (OT) tomography, a modality that promises very high acquisition speed for volumetric scans. With the motivation to image tissue-engineered blood vessels for possible biomechanical testing, we have developed a fast OT device using a collimated, noncoherent beam with a large diameter together with a large-size CMOS camera that has the ability to acquire 3D projections in a single revolution of the sample. In addition, we used accelerated iterative reconstruction techniques to improve image reconstruction speed, while at the same time obtaining better image quality than through filtered backprojection. The device was tested using ink-filled polytetrafluorethylene tubes to determine geometric reconstruction accuracy and recovery of absorbance. Even in the presence of minor refractive index mismatch, the weighted error of the measured radius was <5% in all cases, and a high linear correlation of ink absorbance determined with a photospectrometer of R(2) = 0.99 was found, although the OT device systematically underestimated absorbance. Reconstruction time was improved from several hours (standard arithmetic reconstruction) to 90 s per slice with our optimized algorithm. Composed of only a light source, two spatial filters, a sample bath, and a CMOS camera, this device was extremely simple and cost-efficient to build. PMID:18704687

Huang, Hsuan-Ming; Xia, Jinjun; Haidekker, Mark A

2008-10-01

94

An Optical Tomography System Using a Digital Signal Processor  

Directory of Open Access Journals (Sweden)

Full Text Available The use of a personal computer together with a Data Acquisition System (DAQ as the processing tool in optical tomography systems has been the norm ever since the beginning of process tomography. However, advancements in silicon fabrication technology allow nowadays the fabrication of powerful Digital Signal Processors (DSP at a reasonable cost. This allows this technology to be used in an optical tomography system since data acquisition and processing can be performed within the DSP. Thus, the dependency on a personal computer and a DAQ to sample and process the external signals can be reduced or even eliminated. The DSP system was customized to control the data acquisition process of 16x16 optical sensor array, arranged in parallel beam projection. The data collected was used to reconstruct the cross sectional image of the pipeline conveyor. For image display purposes, the reconstructed image was sent to a personal computer via serial communication. This allows the use of a laptop to display the tomogram image besides performing any other offline analysis.

Mohd. Hafiz Fazalul Rahiman

2008-03-01

95

Optical Tomography Diagnostics on an FRC Plasma  

Science.gov (United States)

Field Reversed Configuration (FRC) plasmas are too hot and too dense for probes to survive inside. This means that it is necessary to use non-invasive techniques to determine the plasma's properties. We have developed a diagnostic for using visible light radiation to determine the shape and position of an FRC plasma. Visible light does not require the expensive detectors or lasers of other diagnostic techniques, but should still allow us to generate a picture of the outside edge of the plasma. This data should be especially interesting when the FRC plasma spins as it undergoes instability. Two optical fan arrays are installed inside the current experimental setup, 90 degrees out of phase, at the edge of the quartz tube. By using a ball lens and optical fibers it is possible to get line averaged values for the visible light at a range of angles. The data obtained can then be analyzed; inversion techniques and singular-value decompositions (SVD) can be used to generate a map of the plasma. The most intense light comes from line radiation from the edge of the plasma, while density data from the interferometer is chord-averaged from the center. By combining the two techniques one gets a more complete picture of the overall plasma profile. This will also be useful when analyzing radiation data from a bolometer. These inversion techniques could also be used for other future experiments, for example, a pinhole x-ray diagnostic.

Bass, Cameron; Leonard, Matthew

2003-10-01

96

Optical coherence tomography in pulmonary imaging: feasibility study  

Science.gov (United States)

We suggest that Optical coherence tomography (OCT) is a potential imaging modality capable of assisting diagnosis in pulmonary medicines. OCT can provide extremely high resolution imaging and be performed with flexible fiber-optic bronchoscopy with small diameter endoscopic probes. In this study, animal models of trachea, and lung surface were to investigate utility of OCT in pulmonary. Normal, malignant, and infectious disease animal model samples measured by OCT were compared to standard histologic H&E light microscopic imaging of the same sites.

Jung, Woonggyu; Zhang, Jun; Wilder-Smith, Petra B. B.; Reza, Minaaraghi; Brenner, Matthew; Shin, YongJin; Nelson, J. Stuart; Chen, Zhongping

2004-07-01

97

"Quantum-optical coherence tomography" with classical light  

CERN Document Server

Quantum-optical coherence tomography (Q-OCT) is an interferometric technique for axial imaging offering several advantages over conventional methods. Chirped-pulse interferometry (CPI) was recently demonstrated to exhibit all of the benefits of the quantum interferometer upon which Q-OCT is based. Here we use CPI to measure axial interferograms to profile a sample accruing the important benefits of Q-OCT, including automatic dispersion cancellation, but with 10 million times higher signal. Our technique solves the artifact problem in Q-OCT and highlights the power of classical correlation in optical imaging.

Lavoie, Jonathan; Resch, Kevin J; 10.1364/OE.17.003818

2009-01-01

98

Algorithm for localized adaptive diffuse optical tomography and its application in bioluminescence tomography  

Science.gov (United States)

A reconstruction algorithm for diffuse optical tomography based on diffusion theory and finite element method is described. The algorithm reconstructs the optical properties in a permissible domain or region-of-interest to reduce the number of unknowns. The algorithm can be used to reconstruct optical properties for a segmented object (where a CT-scan or MRI is available) or a non-segmented object. For the latter, an adaptive segmentation algorithm merges contiguous regions with similar optical properties thereby reducing the number of unknowns. In calculating the Jacobian matrix the algorithm uses an efficient direct method so the required time is comparable to that needed for a single forward calculation. The reconstructed optical properties using segmented, non-segmented, and adaptively segmented 3D mouse anatomy (MOBY) are used to perform bioluminescence tomography (BLT) for two simulated internal sources. The BLT results suggest that the accuracy of reconstruction of total source power obtained without the segmentation provided by an auxiliary imaging method such as x-ray CT is comparable to that obtained when using perfect segmentation.

Naser, Mohamed A.; Patterson, Michael S.; Wong, John W.

2014-04-01

99

Monitoring of tissue modification with optical coherence tomography  

Science.gov (United States)

An experimental monitoring of tissue modification of in vitro and in vivo rabbit dura mater with administration of osmotical agents, 40% glucose solution and glycerol, using optical coherence tomography was presented. The preliminary results of experimental study of influence of osmotical liquids (glucose solutions, glycerol) of rabbit dura mater were reported. The significant decreasing of the light from surface and increasing of the light from the deep of dura mater under action of osmotical solutions and the increasing of OCT imaging depth were demonstrated. Experiments showed that administration of osmolytes to dura mater allowed for effective and temporary control of its optical characteristics, which made dura mater more transparent, increased the ability of light penetrating the tissue, and consequently improved the optical imaging depth. It is a significant study, which can improve penetration of optical imaging of cerebral function and acquire more information of the deep brain tissue.

Zhang, Wei; Luo, Qingming; Yao, Lei; Cheng, Haiying; Zeng, Shaoqun

2002-04-01

100

Simultaneous measurement of group refractive index and thickness of optical samples using optical coherence tomography  

International Nuclear Information System (INIS)

Optical coherence tomography (OCT), based on a Michelson interferometer and utilizing low coherence light as the optical source, is a novel technique for the noninvasive imaging of optical scattering media. A simple OCT scheme based on a 3x3 fiber coupler is presented for the simultaneous measurement of the refractive index and thickness of optical samples. The proposed system enables the refractive index and thickness to be determined without any prior knowledge of the sample parameters and is characterized by a simple and compact configuration, a straightforward measurement procedure, and a low cost. The feasibility of the proposed approach is demonstrated experimentally using BK7 and B270 optical glass samples.

 
 
 
 
101

Tomography  

International Nuclear Information System (INIS)

Apparatus is described for generating a two-dimensional back-projected image of a slice of an object in tomography. The apparatus uses optical techniques to perform the functions of filtering and back projection. Central to the technique is a cylindrical drum which rotates at a fast rate and whose rotational axis tilts at a slower rate. The novel method overcomes the problem of image blurring due to motion which occurs in many tomographic techniques. It also has the advantages of being less expensive and simpler compared to tomography using digital processing techniques which require fast computers. (UK)

102

Optical Coherence Tomography: Modeling and Applications  

DEFF Research Database (Denmark)

An analytical model is presented that is able to describe the performance of OCT systems in both the single and multiple scattering regimes simultaneously. This model inherently includes the shower curtain effect, well-known for light propagation through the atmosphere. This effect has been omitted in previous theoretical models of OCT systems. It is demonstrated that the shower curtain effect is of utmost importance in the theoretical description of an OCT system. The analytical model, together with proper noise analysis of the OCT system, enables calculation of the SNR, where the optical properties of the tissue are taken into account. Furthermore, by using the model, it is possible to determine the lateral resolution of OCT systems at arbitrary depths in the scattering tissue. During the Ph.D. thesis project, an OCT system has been constructed, and the theoretical model is verified experimentally using this system. A demonstration of the imaging capabilities of the OCT system is given. Moreover, a novel truereflection OCT imaging algorithm, based on the new OCT model presented in this thesis, is demonstrated. Finally, a theoretical analysis of the Wigner phase-space distribution function for the OCT geometry, i.e., reflection geometry, is developed. As in the new OCT model, multiple scattered photons has been taken into account together with multiple scattering effects. As an important result, a novel method of creating images based on measurements of the momentum width of the Wigner phase-space distribution is presented, and compared with conventional OCT.

Thrane, Lars

2001-01-01

103

A miniature forward-imaging optical coherence tomography (OCT) probe  

Science.gov (United States)

Optical coherence tomography (OCT) has had a tremendous global health impact upon the current ability to diagnose, treat, and monitor multiple eye diseases. We propose that a miniature forward-imaging OCT probe can be developed for real-time ocular imaging. A miniature 25-gauge forward-imaging probe was designed and developed to use with an 850 nm spectral-domain optical coherence tomography (SDOCT) system (Bioptigen, Inc. Durham, NC). Imaging parameters were determined. Ocular tissues were examined with the miniature OCT probe. A miniature SDOCT probe was developed with the scanning driver within the hand piece. The SDOCT fiber-scanning probe maximally transmitted power of 800 ?W. The scanning range was 3 mm when the probe tip was held 3 to 5 mm from the tissue surface. The axial resolution was 6 ?m and the lateral resolution was 30-35 ?m. The 25-gauge forward-imaging probe was used to image cellophane tape, eyelid skin, cornea, conjunctiva, sclera, iris, anterior lens, anterior chamber angle, retina, retinal tear, retinal detachment, optic nerve head, and optic nerve sheath. Images obtained from the miniature probe appeared similar to images from a 3 mm scanning range of a commercial large handheld OCT probe (Bioptigen, Inc. Durham, NC).

Joos, Karen M.; Shen, Jin-Hui

2012-03-01

104

A Review on the use of Optical Coherence Tomography in Medical Imaging  

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Full Text Available Optical Coherence Tomography (OCT is a Three-dimensional imaging technique with ultrahigh spatial resolution even in highly scattering media. It is based on measurements of the reflected light from tissue discontinuities. Optical coherence tomography delivers high resolution images, because the test is based on light, rather than sound or radio frequency. Optical coherence tomography provides a 1 to 15 µm resolution but only a depth of 1 to 2 mm can be imaged in opaque tissues such as arteries or skin. In transparent tissues such as the eye, greater imaging depths are possible. In addition, optical coherence tomography is capable of providing information about tissue composition. This paper, aims at reviewing the working principle of Optical Coherence Tomography and the quality of the image produced through this technique. A major drawback of Optical Coherence Tomography image is that, it suffers from speckle noise.

A. Stella

2011-02-01

105

Integrated intravascular optical coherence tomography ultrasound imaging system  

Science.gov (United States)

We report on a dual-modality optical coherence tomography (OCT) ultrasound (US) system for intravascular imaging. To the best of our knowledge, we have developed the first integrated OCT-US probe that combines OCT optical components with an US transducer. The OCT optical components mainly consist of a single-mode fiber, a gradient index lens for light-beam focusing, and a right-angled prism for reflecting light into biological tissue. A 40-MHz piezoelectric transducer (PZT-5H) side-viewing US transducer was fabricated to obtain the US image. These components were integrated into a single probe, enabling both OCT and US imaging at the same time. In vitro OCT and ultrasound images of a rabbit aorta were obtained using this dual-modality imaging system. This study demonstrates the feasibility of an OCT-US system for intravascular imaging, which is expected to have a prominent impact on early detection and characterization of atherosclerosis. PMID:20210424

Yin, Jiechen; Yang, Hao-Chung; Li, Xiang; Zhang, Jun; Zhou, Qifa; Hu, Changhong; Shung, K. Kirk; Chen, Zhongping

2010-01-01

106

Multispectral guided fluorescence diffuse optical tomography using upconverting nanoparticles  

Energy Technology Data Exchange (ETDEWEB)

We report on improved image detectability for fluorescence diffuse optical tomography using upconverting nanoparticles doped with rare-earth elements. Core-shell NaYF{sub 4}:Yb{sup 3+}/Er{sup 3+}@NaYF{sub 4} upconverting nanoparticles were synthesized through a stoichiometric method. The Yb{sup 3+}/Er{sup 3+} sensitizer-activator pair yielded two anti-Stokes shifted fluorescence emission bands at 540?nm and 660?nm, here used to a priori estimate the fluorescence source depth with sub-millimeter precision. A spatially varying regularization incorporated the a priori fluorescence source depth estimation into the tomography reconstruction scheme. Tissue phantom experiments showed both an improved resolution and contrast in the reconstructed images as compared to not using any a priori information.

Svenmarker, Pontus, E-mail: pontus.svenmarker@physics.umu.se [Department of Physics, Lund University, P.O. Box 118, SE-221 00 Lund (Sweden); Department of Physics, Umeå University, SE-901 87 Umeå (Sweden); Centre for Microbial Research (UCMR), Umeå University, SE-901 87 Umeå (Sweden); Xu, Can T.; Liu, Haichun; Wu, Xia; Andersson-Engels, Stefan [Department of Physics, Lund University, P.O. Box 118, SE-221 00 Lund (Sweden)

2014-02-17

107

A Low-Cost Method for Optical Tomography  

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Full Text Available INTRODUCTION: In this study, arrangement of a low-cost optical tomography device compared to other methods such as frequency domain diffuse tomography or time domain diffuse tomography is reported. This low-cost diffuse optical imaging technique is based on the detection of light after propagation in tissue. These detected signals are applied to predict the location of in-homogeneities inside phantoms. The device is assessed for phantoms representing homogenous healthy breast tissues as well as those representing healthy breast tissues with a lesion inside.METHODS: A diode laser at 780nm and 50 mW is used as the light source. The scattered light is then collected from the outer surface of the phantom by a detector. Both laser and detector are fiber coupled. The detector fiber may turn around the phantom to collect light scattered at different angles. Phantoms made of intralipid as the scattering medium and ink as the absorbing medium are used as samples. Light is collected after propagation in the phantoms and the capability of the device in collecting data and detecting lesions inside the phantoms is assessed. The fact that the detection fiber orbits around the sample and detects light from various angles has eliminated the need to use several detectors and optical fibers. The results obtained from experiments are compared with the results obtained from a finite element method (FEM solution of diffusion equation in cylindrical geometry written in FORTRAN.RESULTS: The graphs obtained experimentally and numerically are in good accordance with each other. The device has been able to detect lesions up to 13 mm inside the biological phantom.CONCLUSION: The data achieved by the optical tomography device is compared with the data achieved via a FEM code written in FORTRAN. The results indicate that the presented device is capable of providing the correct pattern of diffusely backscattered and transmitted light. The data achieved from the device is in excellent correlation with the numerical solution of the diffusion equation. Therefore, results indicate the applicability of the reported device. This device may be used as a base for an optical imaging. It is also capable of detecting lesions inside the phantoms

Mohammad Ali Ansari

2012-07-01

108

Speckle contrast optical tomography: A new method for deep tissue three-dimensional tomography of blood flow.  

Science.gov (United States)

A novel tomographic method based on the laser speckle contrast, speckle contrast optical tomography (SCOT) is introduced that allows us to reconstruct three dimensional distribution of blood flow in deep tissues. This method is analogous to the diffuse optical tomography (DOT) but for deep tissue blood flow. We develop a reconstruction algorithm based on first Born approximation to generate three dimensional distribution of flow using the experimental data obtained from tissue simulating phantoms. PMID:24761306

Varma, Hari M; Valdes, Claudia P; Kristoffersen, Anna K; Culver, Joseph P; Durduran, Turgut

2014-04-01

109

Enhanced optical clearing of skin in vivo and optical coherence tomography in-depth imaging  

Science.gov (United States)

The strong optical scattering of skin tissue makes it very difficult for optical coherence tomography (OCT) to achieve deep imaging in skin. Significant optical clearing of in vivo rat skin sites was achieved within 15 min by topical application of an optical clearing agent PEG-400, a chemical enhancer (thiazone or propanediol), and physical massage. Only when all three components were applied together could a 15 min treatment achieve a three fold increase in the OCT reflectance from a 300 ?m depth and 31% enhancement in image depth Zthreshold.

Wen, Xiang; Jacques, Steven L.; Tuchin, Valery V.; Zhu, Dan

2012-06-01

110

Spectral domain optical coherence tomography imaging in optic disk pit associated with outer retinal dehiscence  

Science.gov (United States)

A 37-year-old Bangladeshi male presented with an inferotemporal optic disk pit and serous macular detachment in the left eye. Imaging with spectral domain optical coherence tomography (OCT) revealed a multilayer macular schisis pattern with a small subfoveal outer retinal dehiscence. This case illustrates a rare phenotype of optic disk maculopathy with macular schisis and a small outer retinal layer dehiscence. Spectral domain OCT was a useful adjunct in delineating the retinal layers in optic disk pit maculopathy, and revealed a small area of outer retinal layer dehiscence that could only have been detected on high-resolution OCT. PMID:25349471

Wong, Chee Wai; Wong, Doric; Mathur, Ranjana

2014-01-01

111

Diagnosis and pathogenesis of congenital X-linked retinoschisis with optical coherence tomography.  

Science.gov (United States)

This study shows how optical coherence tomography has been valuable in the diagnosis of congenital X-linked retinoschisis. An infant with convergent strabismus underwent serial optical coherence tomography examinations that helped to make the diagnosis of congenital X-linked retinoschisis. Optical coherence tomography is useful in the diagnosis of congenital X-linked retinoschisis and adds new information about pathogenesis. The authors recommend the use of optical coherence tomography in pediatric retinal disease, even if the macula appears normal on indirect ophthalmoscopy. PMID:20349904

Dhingra, Sumit; Patel, C K

2010-01-01

112

Custom software for third generation optical computed tomography  

International Nuclear Information System (INIS)

The advanced radiotherapy techniques based on increased complexity of radiation delivery methods necessitate verification of computer calculated dose distribution by an accurate dosimetric method. The only emergent candidate with true three dimensional nature is the gel dosimeter. In spite of the three dimensional nature of the Optical Computed Tomography (OCT), most work so far has only used two-dimensional evaluations of the three dimensional data set. Recently this limitation has been overcome by applying the cone beam CT imaging principle to optical imaging. A CCD camera based OCT scanner was setup for gel dosimetry using the geometry suggested by J Wolodzko et al. and J Kevin. In an earlier work by the co-author the iradon function in Matlab was used for reconstruction of mid-slices assuming the cone angle to be negligible. In this study software was developed based on the algorithm by Feldkamp, Davis and Kress FDK to reconstruct the images for Optical Computed Tomography Scanner. Results are compared with the previous work of the co-author

113

Measuring retinal contributions to the optical Stiles-Crawford effect with optical coherence tomography  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The directional component of the retinal reflection, i.e., the optical Stiles-Crawford effect (SCE), is well established to result from the waveguiding property of photoreceptors. Considerable uncertainty, however, remains as to which retinal reflections are waveguided and thus contribute. To this end we have developed a retina camera based on spectral-domain optical coherence tomography (SD-OCT) that axially resolves (~5 ?m) these reflections and permits a direct investigation of the SCE or...

Gao, Weihua; Cense, Barry; Zhang, Yan; Jonnal, Ravi S.; Miller, Donald T.

2008-01-01

114

Ultrasound modulated optical tomography in optical diffuse medium using acoustic radiation force  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Ultrasound modulated optical tomography (UOT) is a hybrid technique which combines optical contrast with ultrasound (US) resolution to achieve deeper tissue imaging. However, the technique is currently limited due to the weak modulation signal strength and consequently a low Signal-to-Noise Ratio (SNR). One potential way to increase the SNR of UOT is to increase the ultrasound induced particle displacement, by either increasing the ultrasound amplitude or using the acoustic radiation force (A...

Li, Rui

2011-01-01

115

Wavefront sensorless modal deformable mirror correction in adaptive optics: optical coherence tomography.  

Science.gov (United States)

We present a method for optimization of optical coherence tomography images using wavefront sensorless adaptive optics. The method consists of systematic adjustment of the coefficients of a subset of the orthogonal Zernike bases and application of the resulting shapes to a deformable mirror, while optimizing using image sharpness as a merit function. We demonstrate that this technique can compensate for aberrations induced by trial lenses. Measurements of the point spread function before and after compensation demonstrate near diffraction limit imaging. PMID:24322136

Bonora, S; Zawadzki, R J

2013-11-15

116

Backscattering spectroscopic contrast with angle-resolved optical coherence tomography.  

Science.gov (United States)

Backscattering spectroscopic contrast using angle-resolved optical coherence tomography is demonstrated as a powerful method for determining scatterer diameter with subwavelength resolution. By applying spectroscopic digital processing algorithms to interferograms acquired in the frequency domain with a wavelength-swept laser centered at 1295 nm, it was shown that differences in wavelength-dependent backscattering from 0.3 and 1 microm diameter microspheres can be clearly resolved. The observed backscattering spectra were found to be consistent with Mie theory. High levels of speckle noise reduction achieved by angular compounding increased the spatial resolution at which backscattering spectra could be accurately differentiated. PMID:17975629

Desjardins, Adrien E; Vakoc, Benjamin J; Tearney, Guillermo J; Bouma, Brett E

2007-11-01

117

Capturing the vital vascular fingerprint with optical coherence tomography.  

Science.gov (United States)

Using fingerprints as a method to identify an individual has been accepted in forensics since the nineteenth century, and the fingerprint has become one of the most widely used biometric characteristics. Most of the modern fingerprint recognition systems are based on the print pattern of the finger surface and are not robust against spoof attaching. We demonstrate a novel vital vascular fingerprint system using Doppler optical coherence tomography that provides highly sensitive and reliable personal identification. Because the system is based on blood flow, which only exists in a livng person, the technique is robust against spoof attaching. PMID:23913068

Liu, Gangjun; Chen, Zhongping

2013-08-01

118

Research progress on anterior segment optical coherence tomography in glaucoma  

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Full Text Available Glaucoma is the second blindness disease in the world, and there are more primary angle closed glaucoma in China. The anatomy changes of the anterior chamber have close relationships with the development of glaucoma. Anterior segment optical coherence tomography(AS-OCThas the advantages of fast, non-contact, high resolution and accurate quantitative measurement, which provides a kind of important method for finding the pathogenesis of primary angle closed glaucoma, for early diagnosis and treatment of glaucoma, and for the postoperative evaluation of glaucoma.

Li Zhao

2014-04-01

119

Dispersion compensation in Fourier domain optical coherence tomography.  

Science.gov (United States)

In this work, we propose a numerical technique to compensate for errors due to dispersion effects in Fourier domain optical coherence tomography. The proposed technique corrects for errors in depth measurements and resolution loss due to dispersion. The results show that, by using this technique, errors in thickness measurement are reduced from about 5% to less than 0.1% depending on the sample length and the amount of dispersion. Also, an improvement in the resolution from about 50 ?m to less than 10 ?m is demonstrated. PMID:25322365

Al-Saeed, Tarek A; Shalaby, Mohamed Y; Khalil, Diaa A

2014-10-10

120

Optical coherence tomography shows retinal abnormalities associated with optic nerve disease.  

Science.gov (United States)

Optical coherence tomography (OCT) of the macula in patients with primary optic neuropathy has revealed the presence of structural changes in the neurosensory retina in addition to the nerve fibre layer. Subretinal fluid has been documented in papilloedema and non-arteritic ischaemic optic neuropathy, and may account for decreased visual acuity in affected patients. Subretinal fluid has also been described from other causes of optic nerve head swelling including diabetic papillopathy and papillitis. Drugs used in the treatment of multiple sclerosis, such as corticosteroids and fingolimod can cause decreased vision due to central serous and cystoid macular oedema sometimes confused with recurrent optic neuritis. A subset of patients with various types of optic atrophy show microcystic changes in the inner nuclear layer on spectral domain OCT imaging. The pathophysiology and visual significance of these retinal changes remain unclear, but may affect the diagnosis and management of optic nerve disorders. PMID:24627251

Tawse, Kirstin L; Hedges, Thomas R; Gobuty, Marisa; Mendoza-Santiesteban, Carlos

2014-07-01

 
 
 
 
121

Optical tomography for measuring dose distribution in radiation therapy  

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Full Text Available The dosimetry is used to verify the dose magnitude with artificial samples (phantoms before giving the planned radiation therapy to the patient. Typically, dose distribution is measured only in a single point or on a two-dimensional matrix plane. New techniques of radiation therapy ensure more detailed planning of radiation dose distribution which will lead to the need of measuring the radiation dose distribution three-dimensionally. The gel dosimetry is used to indicate and determine the ionizing radiation three-dimensionally. The radiation causes changes in chemical properties of the gel. The radiation dose distribution is defined by measuring the chemical changes. A conventional method is the magnetic resonance imaging and a new possibility is optical computed tomography (optical-CT. The optical-CT is much cheaper and more practical than magnetic resonance imaging. In this project, an optical-CT based method device was built by aiming at low material costs and a simple realization. The constructed device applies the charge coupled device camera and fluorescent lamp technologies. The test results show that the opacity level of the radiated gel can be measured accurately enough. The imaging accuracy is restricted by the optical distortion, e. g. vignetting, of the lenses, the distortion of a fluorescent lamp as the light source and a noisy measuring environment.

Kauppinen Matti

2014-01-01

122

Dental imaging using laminar optical tomography and micro CT  

Science.gov (United States)

Dental lesions located in the pulp are quite difficult to identify based on anatomical contrast, and, hence, to diagnose using traditional imaging methods such as dental CT. However, such lesions could lead to functional and/or molecular optical contrast. Herein, we report on the preliminary investigation of using Laminar Optical Tomography (LOT) to image the pulp and root canals in teeth. LOT is a non-contact, high resolution, molecular and functional mesoscopic optical imaging modality. To investigate the potential of LOT for dental imaging, we injected an optical dye into ex vivo teeth samples and imaged them using LOT and micro-CT simultaneously. A rigid image registration between the LOT and micro-CT reconstruction was obtained, validating the potential of LOT to image molecular optical contrast deep in the teeth with accuracy, non-invasively. We demonstrate that LOT can retrieve the 3D bio-distribution of molecular probes at depths up to 2mm with a resolution of several hundred microns in teeth.

Long, Feixiao; Ozturk, Mehmet S.; Intes, Xavier; Kotha, Shiva

2014-02-01

123

Full-depth epidermis tomography using a Mirau-based full-field optical coherence tomography.  

Science.gov (United States)

With a Gaussian-like broadband light source from high brightness Ce(3+):YAG single-clad crystal fiber, a full-field optical coherence tomography using a home-designed Mirau objective realized high quality images of in vivo and excised skin tissues. With a 40 × silicone-oil-immersion Mirau objective, the achieved spatial resolutions in axial and lateral directions were 0.9 and 0.51 ?m, respectively. Such a high spatial resolution enables the separation of lamellar structure of the full epidermis in both the cross-sectional and en face planes. The number of layers of stratum corneum and its thickness were quantitatively measured. This label free and non-invasive optical probe could be useful for evaluating the water barrier of skin tissue in clinics. As a preliminary in vivo experiment, the blood vessel in dermis was also observed, and the flowing of the red blood cells and location of the melanocyte were traced. PMID:25401013

Tsai, Chien-Chung; Chang, Chia-Kai; Hsu, Kuang-Yu; Ho, Tuan-Shu; Lin, Ming-Yi; Tjiu, Jeng-Wei; Huang, Sheng-Lung

2014-09-01

124

Imaging of oral pathological tissue using optical coherence tomography  

Science.gov (United States)

Oral squamous cell carcinoma (OSCC) constitutes 90% of oral cancer. Early detection is a cornerstone to improve survival. Interaction of light with tissues may highlight changes in tissue structure and metabolism. We propose optical coherence tomography (OCT), as a non-invasive diagnosis method, being a new high-resolution optical technique that permits tri-dimensional (3-D), real-time imaging of near surface abnormalities in complex tissues. In this study half of the excisional biopsy was directed to the pathologist and the other half was assigned for OCT investigation. Histopathology validated the results. Areas of OSCC of the buccal mucosa were identified in the OCT images. The elements obserced included extensive epithelial down-growth, the disruption of the basement membrane, with areas of erosion, an epithelial layer that was highly variable in thickness and invasion into the sub-epithelial layers. Therefore, OCT appears to be a highly promising imaging modality.

Canjau, Silvana; Todea, Carmen; Sinescu, Cosmin; Duma, Virgil-Florin; Topala, Florin I.; Podoleanu, Adrian G.

2014-01-01

125

A new tool for painting diagnostics: Optical coherence tomography  

Science.gov (United States)

Nondestructive techniques have seen successful growth in the last few years, and, among them, optical ones are widespread and extremely well received in the field of painting diagnostics because of their effectiveness and safety. At present, many techniques for nondestructive investigations of paintings are available; nevertheless, none of them is suitable for a quantitative characterization of varnish. However, varnish removal, either partial or complete, is a fundamental part of the cleaning process, which is an essential step in painting conservation. This critical process has been carried out, up to now, without the possibility of any non-destructive measurement for assessing the actual varnish thickness, but with microscopic observation of a detached microfragment. Optical coherence tomography (OCT) is a noninvasive technique that is well established for biomedical applications. In this work, we present a novel application of OCT to measure the varnish film thickness for painting diagnostics.

Arecchi, T.; Bellini, M.; Corsi, C.; Fontana, R.; Materazzi, M.; Pezzati, L.; Tortora, A.

2006-07-01

126

Transversal phase resolved polarization sensitive optical coherence tomography  

International Nuclear Information System (INIS)

We present a novel optical coherence tomography (OCT) method to measure backscattered intensity and birefringence properties (retardation and fast axis orientation) and apply it to imaging of human ocular tissue. The method is based on a Mach Zehnder interferometer, on transversal scanning, and on a polarization sensitive two-channel detection. A highly stable carrier frequency is generated by acousto-optic modulators (AOMs). This allows a phase sensitive demodulation by the lock-in technique. Since the recording of individual interference fringes is avoided by this method the amount of data to be recorded and processed is considerably reduced. We demonstrate this method on human cornea and anterior chamber angle and present, to the best of our knowledge, the first OCT images of retardation and fast axis orientation of the anterior chamber angle region in vivo

127

Optical Coherence Tomography for live imaging of mammalian development.  

Science.gov (United States)

Understanding the nature and mechanism of congenital defects of the different organ systems in humans has heavily relied on the analysis of the corresponding mutant phenotypes in rodent models. Optical Coherence Tomography (OCT) has recently emerged as a powerful tool to study early embryonic development. This non-invasive optical methodology does not require labeling and allows visualization of embryonic tissues with single cell resolution. Here, we will discuss how OCT can be applied for structural imaging of early mouse and rat embryos in static culture, cardiodynamic and blood flow analysis, and in utero embryonic imaging at later stages of gestation, demonstrating how OCT can be used to assess structural and functional birth defects in mammalian models. PMID:21962442

Larina, Irina V; Larin, Kirill V; Justice, Monica J; Dickinson, Mary E

2011-10-01

128

Parry-Romberg syndrome studied by optical coherence tomography.  

Science.gov (United States)

A case of Parry-Romberg syndrome that was studied by fluorescein angiography and optical coherence tomography (OCT) is described. OCT revealed the existence of retinal nerve fiber layer edema and abnormalities of the vitreoretinal interface. The presence of diffused retinal edema throughout the papillomacular area and the formation of thick retinal folds with intraretinal diffuse macular edema were also evident. Fluorescein angiography demonstrated optic disc swelling, engorgement of the retinal vessels, and mottling of the pigment epithelium. The retinal nerve fiber layer edema and the hyperreflectivity of the retinal surface indicate abnormalities and thickening of the vitreoretinal interface, as shown on OCT, and may further contribute to the retinal involvement in Parry-Romberg syndrome. PMID:18254359

Theodossiadis, Panagiotis G; Grigoropoulos, Vlassis G; Emfietzoglou, Ioannis; Papaspirou, Alexis; Nikolaidis, Pantelis; Vergados, Ioannis; Theodossiadis, George P

2008-01-01

129

Diffuse optical tomography: Present status and its future  

Science.gov (United States)

Diffuse optical tomography (DOT) is one of the emerging modalities for the non-invasive imaging of thick biological tissues using near-infrared (NIR) light. This article reviews the fundamentals and development of DOT technology since its advent in the early 1990s, including the modeling of light propagation in biological tissues which strongly scatter and weakly absorb NIR light, the optical properties of biological tissues in the NIR wavelength range, three typical measurement methods, image reconstruction algorithms, and so forth. Then various studies are referred to for improvement of the DOT images, which are essentially low in quality due to the ill-conditioned and underdetermined problem. Studies and clinical applications presently attracting much attention are discussed in some detail. Finally, the expected future developments are summarized.

Yamada, Yukio; Okawa, Shinpei

2014-05-01

130

Numerical modelling and image reconstruction in diffuse optical tomography.  

Science.gov (United States)

The development of diffuse optical tomography as a functional imaging modality has relied largely on the use of model-based image reconstruction. The recovery of optical parameters from boundary measurements of light propagation within tissue is inherently a difficult one, because the problem is nonlinear, ill-posed and ill-conditioned. Additionally, although the measured near-infrared signals of light transmission through tissue provide high imaging contrast, the reconstructed images suffer from poor spatial resolution due to the diffuse propagation of light in biological tissue. The application of model-based image reconstruction is reviewed in this paper, together with a numerical modelling approach to light propagation in tissue as well as generalized image reconstruction using boundary data. A comprehensive review and details of the basis for using spatial and structural prior information are also discussed, whereby the use of spectral and dual-modality systems can improve contrast and spatial resolution. PMID:19581256

Dehghani, Hamid; Srinivasan, Subhadra; Pogue, Brian W; Gibson, Adam

2009-08-13

131

Non-diffusing photochromic gel for optical computed tomography phantoms  

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This study examines photochromic response in radiation sensitive hydrogels. Genipin, crosslinked, gelatin gel can support high resolution images because the chromophores do not diffuse. A low power, 633 nm He-Ne laser was used to write lines into the gels by a photobleaching reaction. Optical cone-beam computed tomography (CBCT) scans mapped the high resolution images in 3D with 0.25 mm voxel resolution. A straight line was written into a deformed gel and then readout in its relaxed, initial shape. The curved, photo-bleached line demonstrated deformable 3D dosimetry is possible with this system to the balloon edge. High resolution, photochromic images provide key information for characterizing optical CT scanners and 3D dosimeters. Many, ionizing radiation, dosimeter materials demonstrate either a photochromic or photothermal response, allowing this approach to be widely used in quantitative 3D scanning.

Jordan, K.

2013-06-01

132

Indocyanine green enhanced co-registered diffuse optical tomography and photoacoustic tomography.  

Science.gov (United States)

To overcome the intensive light scattering in biological tissue, diffuse optical tomography (DOT) in the near-infrared range for breast lesion detection is usually combined with other imaging modalities, such as ultrasound, x-ray, and magnetic resonance imaging, to provide guidance. However, these guiding imaging modalities may depend on different contrast mechanisms compared to the optical contrast in the DOT. As a result, they cannot provide reliable guidance for DOT because some lesions may not be detectable by a nonoptical modality but may have a high optical contrast. An imaging modality that relies on optical contrast to provide guidance is desirable for DOT. We present a system that combines a frequency-domain DOT and real-time photoacoustic tomography (PAT) systems to detect and characterize deeply seated targets embedded in a turbid medium. To further improve the contrast, the exogenous contrast agent, indocyanine green (ICG), is used. Our experimental results show that the combined system can detect a tumor-mimicking phantom, which is immersed in intralipid solution with the concentrations ranging from 100 to 10 ?M and with the dimensions of 0.8 cm × 0.8 cm × 0.6 cm, up to 2.5 cm in depth. Mice experiments also confirmed that the combined system can detect tumors and monitor the ICG uptake and washout in the tumor region. This method can potentially improve the accuracy to detect small breast lesions as well as lesions that are sensitive to background tissue changes, such as the lesions located just above the chest wall. PMID:24343437

Xu, Chen; Kumavor, Patrick D; Alqasemi, Umar; Li, Hai; Xu, Yan; Zanganeh, Saeid; Zhu, Quing

2013-12-01

133

Retinal oximetry using ultrahigh-resolution optical coherence tomography  

Directory of Open Access Journals (Sweden)

Full Text Available Yufeng Ye,1,2 Hong Jiang,2,3 Meixiao Shen,4 Byron L Lam,2 Delia Cabrera DeBuc,2 Lili Ge,2,4 Mitra Sehi,2 Jianhua Wang21Hangzhou First People’s Hospital, Hangzhou, China; 2Bascom Palmer Eye Institute, 3Neurology, University of Miami, Miami, FL, USA; 4School of Ophthalmology and Optometry, Wenzhou Medical College, Wenzhou, Zhejiang, ChinaBackground: The purpose of this study was to investigate the repeatability of retinal oximetry using slit-lamp adapted ultrahigh-resolution optical coherence tomography (SL-UHR-OCT.Methods: SL-UHR-OCT was developed and fringe patterns were obtained for a major retinal artery and a major retinal vein. A-scans at the central wavelengths of 805 nm and 855 nm were analyzed for calculating optical density ratios (ODRs, from which the percentage oxygen saturation was calculated. Measurements were made on two occasions for each person. Repeatability and coefficients of repeatability were calculated.Results: The mean ODRs of the artery were 0.79 ± 0.86 and 0.88 ± 0.97 in sessions 1 and 2, respectively. The mean ODRs of the vein were ?0.08 ± 0.69 and 0.14 ± 0.77 between the two sessions, and were significantly lower than that of the artery (P < 0.05. The coefficients of repeatability were 1.44 and 1.81 for the artery and vein, respectively. The mean oxygen saturation of the major retinal artery was 94% ± 45% and 98% ± 51% in sessions 1 and 2, respectively, and the mean oxygen saturation of the major retinal vein was 48% ± 36% and 60% ± 40% between sessions.Conclusion: Optical coherence tomographic oximetry for evaluating retinal oxygen saturation was subject to variation, although the averaged measurements in repeated sessions were matched. Further work on reducing variation will be needed.Keywords: ultrahigh-resolution optical coherence tomography, oximetry

Ye Y

2012-12-01

134

Optical spectroscopy and Doppler tomography of Cygnus X-2  

CERN Document Server

We present phase resolved optical spectroscopy and Doppler tomography of V1341 Cygni, the optical counterpart to the neutron star low mass X-ray binary Cygnus X-2. We derive a radial velocity curve for the secondary star, finding a projected radial velocity semi-amplitude of K2 = 79 +/- 3 km/s, leading to a mass function of 0.51 +/- 0.06 Msun, ~30% lower than the previous estimate. We tentatively attribute the lower value of K2 (compared to that obtained by other authors) to variations in the X-ray irradiation of the secondary star at different epochs of observations. The limited phase coverage and/or longer timebase of previous observations may also contribute to the difference in K2. Our value for the mass function implies a primary mass of 1.5 +/- 0.3 Msun, somewhat lower than previous dynamical estimates, but consistent with the value found by analysis of type-I X-ray bursts from this system. Our Doppler tomography of the broad He II 4686 line reveals that most of the emission from this line is produced o...

Elebert, P; Torres, M A P; García, M R

2009-01-01

135

Endoscopic optical coherence tomography for imaging the tympanic membrane  

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Optical coherence tomography (OCT) is an imaging modality that enables micrometer-scale contactless subsurface imaging of biological tissue. Endoscopy, as another imaging method, has the potential of imaging tubular organs and cavities and therefore has opened up several application areas not accessible before. The combination of OCT and endoscopy uses the advantages of both methods and consequently allows additional imaging of structures beneath surfaces inside cavities. Currently, visual investigations on the surface of the human tympanic membrane are possible but only with expert eyes. up to now, visual imaging of the outer ear up to the tympanic membrane can be carried out by an otoscope, an operating microscope or an endoscope. In contrast to these devices, endoscopy has the advantage of imaging the whole tympanic membrane with one view. The intention of this research is the development of an endoscopic optical coherence tomography (EOCT) device for imaging the tympanic membrane depth-resolved and structures behind it. Detection of fluids in the middle ear, which function as an indicator for otitis media, could help to avoid the application of antibiotics. It is possible to detect a congeries of fluids with the otoscope but the ambition is to the early detection by OCT. The developed scanner head allows imaging in working distances in the range from zero up to 5 mm with a field of view of 2 mm. In the next step, the scanner head should be improved to increase the working distance and the field of view.

Burkhardt, Anke; Walther, Julia; Cimalla, Peter; Bornitz, Matthias; Koch, Edmund

2011-06-01

136

Visualisation of transient processes in biofilms by optical coherence tomography.  

Science.gov (United States)

Biofilms occur in natural and engineered water systems. In technical processes, biofouling lowers the water quality and increases the frictional resistance in tubes. In wastewater treatment plants, biofilms are used for the removal of organic and inorganic pollutants. For improvement of antifouling strategies and for process optimisation in wastewater treatment plants, analytical techniques for online monitoring of biofilms are needed. Optical coherence tomography (OCT) is a non-invasive optical tomography technique, which is increasingly applied in medical diagnostics. It reveals photon-reflecting structures in tissue with lateral and axial resolution in the range of 10 microm. In this paper, we demonstrate the capabilities of OCT for the monitoring of biofilm structures and their detachment. OCT is able to reveal spatially resolved structural information on biofilm without staining. A main focus of this work is set on the ability of OCT to monitor transient processes with temporal resolution in a second to minute scale. These key features of OCT allow online monitoring of biofilm growth and detachment in a flow channel. Three-dimensional (3D) imaging quality, spatial resolution, and temporally resolved profiling of biofilms are demonstrated. The results give rise to the hope that OCT may evolve to a standard tool for monitoring of biofilm density. PMID:17462698

Haisch, C; Niessner, R

2007-06-01

137

Optical coherence tomography findings and retinal changes after vitrectomy for optic disc pit maculopathy  

Science.gov (United States)

Purpose: To study the optical coherence tomography (OCT) patterns in optic disc pit maculopathy and retinal changes after vitreous surgery. Materials and Methods: Retrospective review of consecutive cases with optic disc pit maculopathy seen at two tertiary eye institutes from January 2005 to June 2009. Results: Twenty-four eyes of 23 patients are included. The presenting visual acuity ranged from 20/400 to 20/20 (median:20/80). The median age at presentation was 24 years (range, 6-57 years). Optical coherence tomography demonstrated a combination of retinoschisis and outer layer detachment (OLD) in 19 (79.17%) eyes, OLD only in 3 (12.5%) eyes and retinoschisis only in 2 (8.33%) eyes. An obvious communication (outer layer hole) between the schisis and OLD was seen in 14 (73.68%) of the 19 eyes with both features. Of the 21 eyes with retinoschisis, schisis was present in multiple layers in 15 (71.43%) and single layer in 6 (28.57%) eyes. Eleven eyes underwent pars plana vitrectomy including creation of posterior vitreous detachment (PVD), fluid-air exchange, low intensity laser photocoagulation at the temporal edge of the optic disc pit and non-expansile perfluoropropane gas (14%) injection. Five (45.45%) of 11 eyes undergoing vitrectomy had complete resolution and 4 (36.36%) eyes had partial resolution of maculopathy. Visual acuity improved in 8 (72.72%) of 11 eyes. Conclusion: Optical coherence tomography demonstrates multiple layer schisis and outer layer detachment as main features of optic disc pit maculopathy. Vitrectomy with PVD induction, laser photocoagulation and gas tamponade results in anatomical and visual improvement in most cases with optic disc pit maculopathy. PMID:23619493

Sanghi, Gaurav; Padhi, Tapas R; Warkad, Vivekanand U; Vazirani, Jayesh; Gupta, Vishali; Dogra, Mangat R; Gupta, Amod; Das, Taraprasad

2014-01-01

138

Optical coherence tomography demonstrating macular retinal nerve fiber thinning in advanced optic disc drusen  

Science.gov (United States)

Optic disc drusen (ODD) are extracellular proteinaceous excrescences in the optic nerve head. They enlarge over time and can cause damage to nerve fibers with resulting loss of visual field. The authors report a case of advanced ODD in which macular optical coherence tomography demonstrated retinal nerve fiber thinning. A single case report of a 42-year-old woman with known ODD presented to the eye clinic with worsening field of vision which was impacting on her daily life. The patient was subject to full ophthalmic examination as well as Goldmann visual field testing, optic disc photography and optical coherence tomography (OCT) of both her optic discs and maculae. ODD although rare, can be visually devastating. No treatment is currently available however patients should be counseled about progressive nature of ODD and the potential for visual loss. OCT imaging of the maculae as well as optic discs may serve a role in monitoring the damage disc drusen cause to the eye. PMID:25136235

Hassan, Ali; Gouws, Pieter

2014-01-01

139

Integrated modeling of the GMT laser tomography adaptive optics system  

Science.gov (United States)

Laser Tomography Adaptive Optics (LTAO) is one of adaptive optics systems planned for the Giant Magellan Telescope (GMT). End-to-end simulation tools that are able to cope with the complexity and computational burden of the AO systems to be installed on the extremely large telescopes such as GMT prove to be an integral part of the GMT LTAO system development endeavors. SL95, the Fortran 95 Simulation Library, is one of the software tools successfully used for the LTAO system end-to-end simulations. The goal of SL95 project is to provide a complete set of generic, richly parameterized mathematical models for key elements of the segmented telescope wavefront control systems including both active and adaptive optics as well as the models for atmospheric turbulence, extended light sources like Laser Guide Stars (LGS), light propagation engines and closed-loop controllers. The library is implemented as a hierarchical collection of classes capable of mutual interaction, which allows one to assemble complex wavefront control system configurations with multiple interacting control channels. In this paper we demonstrate the SL95 capabilities by building an integrated end-to-end model of the GMT LTAO system with 7 control channels: LGS tomography with Adaptive Secondary and on-instrument deformable mirrors, tip-tilt and vibration control, LGS stabilization, LGS focus control, truth sensor-based dynamic noncommon path aberration rejection, pupil position control, SLODAR-like embedded turbulence profiler. The rich parameterization of the SL95 classes allows to build detailed error budgets propagating through the system multiple errors and perturbations such as turbulence-, telescope-, telescope misalignment-, segment phasing error-, non-common path-induced aberrations, sensor noises, deformable mirror-to-sensor mis-registration, vibration, temporal errors, etc. We will present a short description of the SL95 architecture, as well as the sample GMT LTAO system simulation results.

Piatrou, Piotr

2014-08-01

140

Spectral Optical Coherent Tomography of Optic Nerve in Diagnosis of Primary Open-angle Glaucoma  

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Full Text Available The aim of the work is to study the assessment opportunities of the optic nerve morphometric parameters in patients with primary open-angle glaucoma of various stages using spectral optical coherent tomography (OCT.Materials and Methods. 82 patients with various stages of primary open-angle glaucoma have been examined. Objective parameters registration of the optic nerve has been performed by the means of the optic coherent tomograph Cirrus HD-OCT, Carl Zeiss (Germany.Results. There was determined statistically significant reduction of the dimension and the area of neuroretinal zonule as the glaucoma process progressed.Conclusion. The use of spectral OCT in the follow-up of patients with glaucoma will let a physician optimize glaucoma management, as OCT technique enables to monitor optic disc changes progressing in microscopic scale.

A.P. Shakhalova

2011-05-01

 
 
 
 
141

Optical diffraction tomography in an inhomogeneous background medium  

International Nuclear Information System (INIS)

The filtered back-propagation algorithm (FBP algorithm) is a computationally fast and efficient inversion algorithm for reconstructing the 3D index of refraction distribution of weak scattering samples in free space from scattered field data collected in a set of coherent optical scattering experiments. This algorithm is readily derived using classical Fourier analysis applied to the Born or Rytov weak scattering models appropriate to scatterers embedded in a non-attenuating uniform background. In this paper, the inverse scattering problem for optical diffraction tomography (ODT) is formulated using the so-called distorted wave Born and Rytov approximations and a generalized version of the FBP algorithm is derived that applies to weakly scattering samples that are embedded in realistic, multiple scattering ODT experimental configurations. The new algorithms are based on the generalized linear inverse of the linear transformation relating the scattered field data to the complex index of refraction distribution of the scattering samples and are in the form of a superposition of filtered data, computationally back propagated into the ODT experimental configuration. The paper includes a computer simulation comparing the generalized Born and Rytov based FBP inversion algorithms as well as reconstructions generated using the generalized Born based FBP algorithm of a step index optical fiber from experimental ODT data

142

A combined reconstruction-classification method for diffuse optical tomography  

International Nuclear Information System (INIS)

We present a combined classification and reconstruction algorithm for diffuse optical tomography (DOT). DOT is a nonlinear ill-posed inverse problem. Therefore, some regularization is needed. We present a mixture of Gaussians prior, which regularizes the DOT reconstruction step. During each iteration, the parameters of a mixture model are estimated. These associate each reconstructed pixel with one of several classes based on the current estimate of the optical parameters. This classification is exploited to form a new prior distribution to regularize the reconstruction step and update the optical parameters. The algorithm can be described as an iteration between an optimization scheme with zeroth-order variable mean and variance Tikhonov regularization and an expectation-maximization scheme for estimation of the model parameters. We describe the algorithm in a general Bayesian framework. Results from simulated test cases and phantom measurements show that the algorithm enhances the contrast of the reconstructed images with good spatial accuracy. The probabilistic classifications of each image contain only a few misclassified pixels.

143

Optimisation of post mortem cardiac computed tomography compared to optical coherence tomography and histopathology - Technical note  

DEFF Research Database (Denmark)

Introduction: Coronary atherosclerosis is a leading cause of mortality. New technological developments in computed tomography (CT), including dual energy, iterative reconstructions and high definition scanning, could significantly improve the non-invasive identification of atherosclerosis plaques. Here, a new method for optimising cardiac coronary CT with optical coherence tomography (OCT) and histopathology is presented. Materials and methods: Twenty human hearts obtained from autopsies were used. A contrast agent that solidifies after cooling was injected into the coronary arteries. CT scanning was performed on the heart alone as well as with the heart in a chest phantom. We used eight different CT protocols and the newest CT technique to image every heart. The OCT and CT images were compared with their corresponding histological sections. A procedure for ensuring the correct alignment of the images was also developed. Results: We have succeeded in developing a new method for post-mortem coronary CT angiography in which an autopsy heart is placed in a chest phantom to simulate clinical CT. Conclusion: The new method permits comparison of CT with OCT and histopathology. This method can also be used for evaluating coronary artery disease, including characterising plaques, and will eventually allow for the detection of rupture-prone plaques, which we will assess in a future study. Clinical testing is our ultimate goal. © 2013 Elsevier Ltd.

Precht, Helle; Leth, Peter Mygind

2014-01-01

144

Radiographic, microcomputer tomography, and optical coherence tomography investigations of ceramic interfaces  

Science.gov (United States)

Imagistic investigation of the metal-ceramic crowns and fixed partial prostheses represent a very important issue in nowadays dentistry. At this time, in dental office, it is difficult or even impossible to evaluate a metal ceramic crown or bridge before setting it in the oral cavity. The possibilities of ceramic fractures are due to small fracture lines or material defects inside the esthetic layers. Material and methods: In this study 25 metal ceramic crowns and fixed partial prostheses were investigated by radiographic method (Rx), micro computer tomography (MicroCT) and optical coherence tomography (OCT) working in Time Domain, at 1300 nm. The OCT system contains two interferometers and one scanner. For each incident analysis a stuck made of 100 slices was obtain. These slices were used in order to obtain a 3D model of the ceramic interface. Results: RX and MicroCT are very powerful instruments that provide a good characterization of the dental construct. It is important to observe the reflections due to the metal infrastructure that could affect the evaluation of the metal ceramic crowns and bridges. The OCT investigations could complete the imagistic evaluation of the dental construct by offering important information when it is need it.

Sinescu, Cosmin; Negrutiu, Meda Lavinia; Ionita, Ciprian; Topala, Florin; Petrescu, Emanuela; Rominu, Roxana; Pop, Daniela Maria; Marsavina, Liviu; Negru, Radu; Bradu, Adrian; Rominu, Mihai; Podoleanu, Adrian Gh.

2010-12-01

145

Speckle noise reduction in optical coherence tomography of paint layers.  

Science.gov (United States)

We present and characterize a sequential angular compounding method for reducing speckle contrast in optical coherence tomography images of paint layers. The results are compared with postprocessing methods, and we show that the compounding technique can improve the speckle contrast ratio in B-scans by better than a factor of 2 in exchange for a negligible loss of resolution. As a result, image aesthetics are improved, thin layers become more distinct, and edge-detection algorithms work more efficiently. The effect of varying the angular scan size and number of averages is investigated, and it is found that a degree of statistical correlation between speckle patterns exists, even for relatively large changes in angle of incidence. Angular compounding is also performed on three-dimensional data sets and compared with a method whereby en face slices are averaged over depth. PMID:20062495

Hughes, Michael; Spring, Marika; Podoleanu, Adrian

2010-01-01

146

Imaging of mouse embryonic eye development using optical coherence tomography  

Science.gov (United States)

Congenital abnormalities are often caused by genetic disorders which alter the normal development of the eye. Embryonic eye imaging in mouse model is important for understanding of normal and abnormal eye development and can contribute to prevention and treatment of eye defects in humans. In this study, we used Swept Source Optical Coherence Tomography (SS-OCT) to image eye structure in mouse embryos at 12.5 to 17.5 days post coitus (dpc). The imaging depth of the OCT allowed us to visualize the whole eye globe at these stages. Different ocular tissues including lens, cornea, eyelids, and hyaloid vasculature were visualized. These results suggest that OCT imaging is a useful tool to study embryonic eye development in the mouse model.

Syed, Saba H.; Kasiraj, Alyssa; Larina, Irina V.; Dickinson, Mary E.; Larin, Kirill V.

2010-02-01

147

Imaging port wine stains by fiber optical coherence tomography  

Science.gov (United States)

We develop a fiber optical coherence tomography (OCT) system in the clinical utility of imaging port wine stains (PWS). We use our OCT system on 41 patients with PWS to document the difference between PWS skin and contralateral normal skin. The system, which operates at 4 frames/s with axial and transverse resolutions of 10 and 9 ?m, respectively, in the skin tissue, can clearly distinguish the dilated dermal blood vessels from normal tissue. We present OCT images of patients with PWS and normal human skin. We obtain the structural parameters, including epidermal thickness and diameter and depth of dilated blood vessels. We demonstrate that OCT may be a useful tool for the noninvasive imaging of PWS. It may help determine the photosensitizer dose and laser parameters in photodynamic therapy for treating port wine stains.

Zhao, Shiyong; Gu, Ying; Xue, Ping; Guo, Jin; Shen, Tingmei; Wang, Tianshi; Huang, Naiyan; Zhang, Li; Qiu, Haixia; Yu, Xin; Wei, Xunbin

2010-05-01

148

Optical Coherence Tomography and Raman Spectroscopy of the retina  

Energy Technology Data Exchange (ETDEWEB)

Imaging the structure and correlating it with the biochemical content of the retina holds promise for fundamental research and for clinical applications. Optical coherence tomography (OCT) is commonly used to image the 3D structure of the retina and while the added functionality of biochemical analysis afforded by Raman scattering could provide critical molecular signatures for clinicians and researchers, there are many technical challenges to combining these imaging modalities. We present an ex vivo OCT microscope combined with Raman spectroscopy capable of collecting morphological and molecular information about a sample simultaneously. The combined instrument will be used to investigate remaining technical challenges to combine these imaging modalities, such as the laser power levels needed to achieve a Raman signal above the noise level without damaging the sample.

Evans, J W; Zawadzki, R J; Liu, R; Chan, J; Lane, S; Werner, J S

2009-01-16

149

Optical coherence tomography examination of patients with hyperopic ametropic amblyopia  

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Full Text Available AIM: To investigate the changes of retina in amblyopic eye by measuring macular retinal thickness in hyperopicametropic amblyopic patients.METHODS: Optical coherence tomography(OCTwas used to measure the macular retinal thickness value in 17 amblyopic patients(20 eyesand 14 healthy controls(20 eyes. The result was processed as retinal thickness value and thickness map by computer. The data were analyzed by SPSS 13.0 software package. RESULTS: The retinal thickness of central sector or region in amblyopic eyes were thicker than those in normal eyes(PPP>0.05. CONCLUSION: The macular retina thickness of the central region is thicker in hyperopic ametropic amblyopic patient. OCT is a noninvasive, noncontact technique that visualizes the retinal structure in vivo, this technique may be used to find the potential initial neural site of the visual deficit in this condition.

Hong-Chao Xu

2013-08-01

150

Imaging nanoparticle flow using magneto-motive optical Doppler tomography  

Energy Technology Data Exchange (ETDEWEB)

We introduce a novel approach for imaging solutions of superparamagnetic iron oxide (SPIO) nanoparticles using magneto-motive optical Doppler tomography (MM-ODT). MM-ODT combines an externally applied temporally oscillating high-strength magnetic field with ODT to detect nanoparticles flowing through a microfluidic channel. A solenoid with a cone-shaped ferrite core extensively increased the magnetic field strength (B{sub max} = 1 T, {nabla}B{sup 2}=220T{sup 2}m{sup -1}) at the tip of the core and also focused the magnetic field in microfluidic channels containing nanoparticle solutions. Nanoparticle contrast was demonstrated in a microfluidic channel filled with an SPIO solution by imaging the Doppler frequency shift which was observed independently of the nanoparticle flow rate and direction. Results suggest that MM-ODT may be applied to image Doppler shift of SPIO nanoparticles in microfluidic flows with high contrast.

Kim, Jeehyun [Beckman Laser Institute and Medical Clinic, University of California, 1002 Health Sciences Road East, Irvine, CA 92612 (United States); Oh, Junghwan [Biomedical Engineering Department, University of Texas, Austin, TX 78712 (United States); Milner, Thomas E [Biomedical Engineering Department, University of Texas, Austin, TX 78712 (United States); Nelson, J Stuart [Beckman Laser Institute and Medical Clinic, University of California, 1002 Health Sciences Road East, Irvine, CA 92612 (United States)

2007-01-24

151

Imaging nanoparticle flow using magneto-motive optical Doppler tomography  

International Nuclear Information System (INIS)

We introduce a novel approach for imaging solutions of superparamagnetic iron oxide (SPIO) nanoparticles using magneto-motive optical Doppler tomography (MM-ODT). MM-ODT combines an externally applied temporally oscillating high-strength magnetic field with ODT to detect nanoparticles flowing through a microfluidic channel. A solenoid with a cone-shaped ferrite core extensively increased the magnetic field strength (Bmax = 1 T, ?B2=220T2m-1) at the tip of the core and also focused the magnetic field in microfluidic channels containing nanoparticle solutions. Nanoparticle contrast was demonstrated in a microfluidic channel filled with an SPIO solution by imaging the Doppler frequency shift which was observed independently of the nanoparticle flow rate and direction. Results suggest that MM-ODT may be applied to image Doppler shift of SPIO nanoparticles in microfluidic flows with high contrast

152

Gauss Newton method for image reconstruction in diffuse optical tomography  

Science.gov (United States)

We present a regularized Gauss-Newton method for solving the inverse problem of parameter reconstruction from boundary data in frequency-domain diffuse optical tomography. To avoid the explicit formation and inversion of the Hessian which is often prohibitively expensive in terms of memory resources and runtime for large-scale problems, we propose to solve the normal equation at each Newton step by means of an iterative Krylov method, which accesses the Hessian only in the form of matrix-vector products. This allows us to represent the Hessian implicitly by the Jacobian and regularization term. Further we introduce transformation strategies for data and parameter space to improve the reconstruction performance. We present simultaneous reconstructions of absorption and scattering distributions using this method for a simulated test case and experimental phantom data.

Schweiger, Martin; Arridge, Simon R.; Nissilä, Ilkka

2005-05-01

153

Optical coherence tomography of the epidermal sulfakrilate surface strippings  

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Full Text Available Method of the epidermal surface biopsy (ESB with the adhesive compositions is the alter-native to the classic his-tological examination. Materials and Methods. In this study medical adhesive "Sulfacrylate" was used, small portions of which had been spread on an object glass, and then on different skin areas. To study the structural organization of the samples ESB the technique of optical coherence tomography (??? was used. Results. We obtained the pictures that visualize the structural organization of the different layers of the epidermis in lichen planus, hyperkeratosis, scabies and other skin diseases. Conclusion. This technique allows non-invasive measurement of high-precision structure of different layers of the epidermis, which can be useful both for research and for the practical dermatology.

Utz S.R.

2013-09-01

154

Optical tractography of the mouse heart using polarization-sensitive optical coherence tomography.  

Science.gov (United States)

We developed a method to image myocardial fiber architecture in the mouse heart using a Jones matrix-based polarization-sensitive optical coherence tomography (PSOCT) system. The "cross-helical" laminar structure of myocardial fibers can be clearly visualized using this technology. The obtained myocardial fiber organization agrees well with existing knowledge acquired using conventional histology and diffusion tensor magnetic resonance imaging. PMID:24298414

Wang, Yuanbo; Yao, Gang

2013-01-01

155

Optical coherence tomography: Monte Carlo simulation and improvement by optical amplification  

Digital Repository Infrastructure Vision for European Research (DRIVER)

An advanced novel Monte Carlo simulation model of the detection process of an optical coherence tomography (OCT) system is presented. For the first time it is shown analytically that the applicability of the incoherent Monte Carlo approach to model the heterodyne detection process of an OCT system is firmly justified. This is obtained by calculating the heterodyne mixing of the reference and sample beams in a plane conjugate to the discontinuity in the sample probed by the system. Using this ...

Tycho, Andreas; Bjarklev, Anders Overgaard; Andersen, Peter E.

2006-01-01

156

Foveal thickness after phacoemulsification as measured by optical coherence tomography  

Directory of Open Access Journals (Sweden)

Full Text Available Gerasimos Th Georgopoulos, Dimitrios Papaconstantinou, Maria Niskopoulou, Marilita Moschos, Ilias Georgalas, Chrysanthi KoutsandreaGlaucoma Department, Medical School, Athens University, Athens, GreeceBackground: Despite a significant body of research, no consistency on postoperative foveal thickness as measured by optical coherence tomography (OCT, can be recorded. The purpose of our study was to evaluate the effect of uncomplicated cataract surgery in the thickness of the retina in the foveal area during the early postoperative period.Methods: In a prospective study, 79 eyes were assessed by OCT, on day 1, and weeks 2 and 4 after uncomplicated phacoemulsification with intraocular lens implantation in the Athens University Clinic. The outcome measure was the thickness of the retina in the foveal area.Results: The thickness of the retina preoperatively is significantly smaller (150.4 ± 18.8 (p < 0.05 than the thickness of the retina on day 1 (171.8 ± 21 and week 2 (159.7 ± 19 and returned to the initial levels on week 4 (152 ± 17.1. The estimated correlation coefficients between preoperative and postoperative thickness of the retina were significant (p < 0.05. Conversely, no association was found between postoperative visual acuity and thickness of the retina, neither between the phacoemulsification energy and retinal thickness. Operation time, although inversely related with postoperative visual acuity, was not associated with the thickness of the retina.Conclusions: Following phacoemulsification, an increase in the foveal thickness was detected in the early postoperative period, quantified and followed up by OCT. The foveal thickness returned to the preoperative level, 1 month following surgery in our study. No association was shown between intraoperative parameters and increased postoperative retinal thickness.Keywords: optical coherence tomography, phacoemulsification, retinal thickness

Gerasimos Th Georgopoulos

2008-08-01

157

Correlation characteristics of optical coherence tomography images of turbid media with statistically inhomogeneous optical parameters  

International Nuclear Information System (INIS)

Noisy structure of optical coherence tomography (OCT) images of turbid medium contains information about spatial variations of its optical parameters. We propose analytical model of statistical characteristics of OCT signal fluctuations from turbid medium with spatially inhomogeneous coefficients of absorption and backscattering. Analytically predicted correlation characteristics of OCT signal from spatially inhomogeneous medium are in good agreement with the results of correlation analysis of OCT images of different biological tissues. The proposed model can be efficiently applied for quantitative evaluation of statistical properties of absorption and backscattering fluctuations basing on correlation characteristics of OCT images.

158

Fiber optic-based optical coherence tomography (OCT) for dental applications  

Science.gov (United States)

We have developed a hand-held fiber optic based optical coherence tomography (OCT) system for scanning of the oral cavity. We have produced, using this scanning device, in vivo cross-sectional images of hard and soft dental tissues in human volunteers. Clinically relevant anatomical structures, including the gingival margin, periodontal sulcus, and dento- enamel junction, were visible in all the images. The cemento- enamel junction and the alveolar bone were identified in approximately two thirds of the images. These images represent, or our knowledge, the first in vivo OCT images of human dental tissue.

Everett, Matthew J.; Colston, Bill W., Jr.; Da Silva, Luiz B.; Otis, Linda L.

1998-09-01

159

Fiber-optic polarization diversity detection for rotary probe optical coherence tomography.  

Science.gov (United States)

We report a polarization diversity detection scheme for optical coherence tomography with a new, custom, miniaturized fiber coupler with single mode (SM) fiber inputs and polarization maintaining (PM) fiber outputs. The SM fiber inputs obviate matching the optical lengths of the X and Y OCT polarization channels prior to interference and the PM fiber outputs ensure defined X and Y axes after interference. Advantages for this scheme include easier alignment, lower cost, and easier miniaturization compared to designs with free-space bulk optical components. We demonstrate the utility of the detection system to mitigate the effects of rapidly changing polarization states when imaging with rotating fiber optic probes in Intralipid suspension and during in vivo imaging of human airways. PMID:24978556

Lee, Anthony M D; Pahlevaninezhad, Hamid; Yang, Victor X D; Lam, Stephen; MacAulay, Calum; Lane, Pierre

2014-06-15

160

Spectral domain optical coherence tomography imaging in optic disk pit associated with outer retinal dehiscence  

Directory of Open Access Journals (Sweden)

Full Text Available Chee Wai Wong,1,2 Doric Wong,1,2 Ranjana Mathur1,2 1Singapore National Eye Centre, Singapore; 2Singapore Eye Research Institute, Singapore Abstract: A 37-year-old Bangladeshi male presented with an inferotemporal optic disk pit and serous macular detachment in the left eye. Imaging with spectral domain optical coherence tomography (OCT revealed a multilayer macular schisis pattern with a small subfoveal outer retinal dehiscence. This case illustrates a rare phenotype of optic disk maculopathy with macular schisis and a small outer retinal layer dehiscence. Spectral domain OCT was a useful adjunct in delineating the retinal layers in optic disk pit maculopathy, and revealed a small area of outer retinal layer dehiscence that could only have been detected on high-resolution OCT. Keywords: retinal imaging, maculopathy, macular schisis

Wong CW

2014-10-01

 
 
 
 
161

Characterization of tissue optical properties for prostate PDT using interstitial diffuse optical tomography  

Science.gov (United States)

Photodynamic therapy (PDT) is an important treatment modality for localized diseases such as prostate cancer. In prostate PDT, light distribution is an important factor because it is directly related to treatment efficacy. During PDT, light distribution is determined by tissue optical property distributions (or heterogeneity). In this study, an interstitial diffuse optical tomography (iDOT) method was used to characterize optical properties in tissues. Optical properties (absorption and reduced scattering coefficients) of the prostate gland were reconstructed by solving the inverse problem using an adjoint model based on diffusion equation using a modified matlab public user code NIRFAST. In the modified NIRFAST method, linear sources were modeled for the reconstruction. Cross talking between absorption coefficients and reduced scattering coefficients were studied to have minimal effect, and a constrained optical property method (set either absorption coefficient or reduced scattering coefficient to be homogeneous) is also studied. A prostate phantom with optical anomalies was used to verify the iDOT method. The reconstructed results were compared with the known optical properties, and the spatial distribution of optical properties for this phantom was successfully reconstructed.

Liang, Xing; Wang, Ken Kang-hsin; Zhu, Timothy C.

2012-02-01

162

Measuring optical properties of a blood vessel model using optical coherence tomography  

Science.gov (United States)

In this paper we develop the concept of a tissue-engineered optical phantom that uses engineered tissue as a phantom for calibration and optimization of biomedical optics instrumentation. With this method, the effects of biological processes on measured signals can be studied in a well controlled manner. To demonstrate this concept, we attempted to investigate how the cellular remodeling of a collagen matrix affected the optical properties extracted from optical coherence tomography (OCT) images of the samples. Tissue-engineered optical phantoms of the vascular system were created by seeding smooth muscle cells in a collagen matrix. Four different optical properties were evaluated by fitting the OCT signal to 2 different models: the sample reflectivity ? and attenuation parameter ? were extracted from the single scattering model, and the scattering coefficient ? s and root-mean-square scattering angle ? rms were extracted from the extended Huygens-Fresnel model. We found that while contraction of the smooth muscle cells was clearly evident macroscopically, on the microscopic scale very few cells were actually embedded in the collagen. Consequently, no significant difference between the cellular and acellular samples in either set of measured optical properties was observed. We believe that further optimization of our tissue-engineering methods is needed in order to make the histology and biochemistry of the cellular samples sufficiently different from the acellular samples on the microscopic level. Once these methods are optimized, we can better verify whether the optical properties of the cellular and acellular collagen samples differ.

Levitz, David; Hinds, Monica T.; Tran, Noi; Vartanian, Keri; Hanson, Stephen R.; Jacques, Steven L.

2006-02-01

163

Optical coherence tomography today: speed, contrast, and multimodality.  

Science.gov (United States)

In the last 25 years, optical coherence tomography (OCT) has advanced to be one of the most innovative and most successful translational optical imaging techniques, achieving substantial economic impact as well as clinical acceptance. This is largely owing to the resolution improvements by a factor of 10 to the submicron regime and to the imaging speed increase by more than half a million times to more than 5 million A-scans per second, with the latter one accomplished by the state-of-the-art swept source laser technologies that are reviewed in this article. In addition, parallelization of OCT detection, such as line-field and full-field OCT, has shortened the acquisition time even further by establishing quasi-akinetic scanning. Besides the technical improvements, several functional and contrast-enhancing OCT applications have been investigated, among which the label-free angiography shows great potential for future studies. Finally, various multimodal imaging modalities with OCT incorporated are reviewed, in that these multimodal implementations can synergistically compensate for the fundamental limitations of OCT when it is used alone. PMID:25079820

Drexler, Wolfgang; Liu, Mengyang; Kumar, Abhishek; Kamali, Tschackad; Unterhuber, Angelika; Leitgeb, Rainer A

2014-07-01

164

Retina-simulating phantom for optical coherence tomography.  

Science.gov (United States)

Optical coherence tomography (OCT) is a rapidly growing imaging modality, particularly in the field of ophthalmology. Accurate early diagnosis of diseases requires consistent and validated imaging performance. In contrast to more well-established medical imaging modalities, no standardized test methods currently exist for OCT quality assurance. We developed a retinal phantom which mimics the thickness and near-infrared optical properties of each anatomical retinal layer as well as the surface topography of the foveal pit. The fabrication process involves layer-by-layer spin coating of nanoparticle-embedded silicone films followed by laser micro-etching to modify the surface topography. The thickness of each layer and dimensions of the foveal pit are measured with high precision. The phantom is embedded into a commercially available, water-filled model eye to simulate ocular dispersion and emmetropic refraction, and for ease of use with clinical OCT systems. The phantom was imaged with research and clinical OCT systems to assess image quality and software accuracy. Our results indicate that this phantom may serve as a useful tool to evaluate and standardize OCT performance. PMID:24042445

Baxi, Jigesh; Calhoun, William; Sepah, Yasir Jamal; Hammer, Daniel X; Ilev, Ilko; Pfefer, T Joshua; Nguyen, Quan Dong; Agrawal, Anant

2014-02-01

165

Optical coherence tomography characterisation of idiopathic central serous chorioretinopathy  

Science.gov (United States)

Aim: To describe retinal findings in patients with idiopathic central serous chorioretinopathy (ICSC) as assessed by optical coherence tomography (OCT), and to compare them to fluorescein angiography (FA) findings. Methods: Case series of 39 eyes from 36 patients with ICSC. Complete ophthalmological examination, last generation OCT (StratusOCT, Software version 3.1) and FA were performed. Six radial scans using OCT were performed and repeated. Singular findings were recorded, OCT images were measured and the results compared with those of FA. The main outcome measures were FA and OCT findings. Results: Two patterns of distinct OCT findings are described. In the first one, an optically empty vaulted area of different heights was observed under the neurosensory retina in 36 eyes, being related to fluorescein filled areas; in 35 of them, highly characteristic small bulges could be observed protruding from the retinal pigment epithelium (RPE), angiographically related to leaking spots. In the second pattern, three eyes showed an almost semicircular space under the RPE, with thinner overlying retina. Conclusions: OCT may offer a new approach to the staging and knowledge of ICSC, and may help the understanding of the mechanisms of the disease. PMID:15834085

Montero, J A; Ruiz-Moreno, J M

2005-01-01

166

Optical coherence tomography today: speed, contrast, and multimodality  

Science.gov (United States)

In the last 25 years, optical coherence tomography (OCT) has advanced to be one of the most innovative and most successful translational optical imaging techniques, achieving substantial economic impact as well as clinical acceptance. This is largely owing to the resolution improvements by a factor of 10 to the submicron regime and to the imaging speed increase by more than half a million times to more than 5 million A-scans per second, with the latter one accomplished by the state-of-the-art swept source laser technologies that are reviewed in this article. In addition, parallelization of OCT detection, such as line-field and full-field OCT, has shortened the acquisition time even further by establishing quasi-akinetic scanning. Besides the technical improvements, several functional and contrast-enhancing OCT applications have been investigated, among which the label-free angiography shows great potential for future studies. Finally, various multimodal imaging modalities with OCT incorporated are reviewed, in that these multimodal implementations can synergistically compensate for the fundamental limitations of OCT when it is used alone.

Drexler, Wolfgang; Liu, Mengyang; Kumar, Abhishek; Kamali, Tschackad; Unterhuber, Angelika; Leitgeb, Rainer A.

2014-07-01

167

Optical coherence tomography: imaging architect for dermal microdialysis in psoriasis  

Science.gov (United States)

Optical coherence tomography (OCT) has been used as part of a ground breaking translational study to shed some light on one of the worlds most prevalent autoimmune diseases; psoriasis. The work successfully integrates the fields of optical imaging, biochemistry and dermatology in conducting a dermal microdialysis (DMD) trial for quantitative histamine assessment amongst a group of psoriasis sufferers. The DMD process involves temporary insertion of microscopic hollow tubes into a layer of skin to measure the levels of histamine and other important biological molecules in psoriasis. For comparison purposes, DMD catheters were implanted into healthy, peri-lesional and lesional skin regions. The catheters' entry and exit points and their precise locations in the epidermal layer of the skin were confirmed using OCT thus obtaining high resolution, wide-field images of the affected skin as well as catheter placement whilst local microdialysis enabled a tissue chemistry profile to be obtained from these three skin regions including histamine, a local immune system activator known to contribute towards itch and inflammation. Together these tools offer a synergistic approach in the clinical assessment of the disease. In addition, OCT delivered a non-invasive and rapid method for analyzing the affected skin architecture.

O'Connell, M.-L.; O'Connor, W.; Ramsay, B.; Guihen, E.; Ho, W. L.; Leahy, M. J.

2011-03-01

168

Correlation of endoscopic optical coherence tomography with histology  

Science.gov (United States)

Optical Coherence Tomography (OCT) is a noninvasive optical imaging technique that allows high-resolution cross- sectional imaging of tissue microstructure. We have recently developed a system for endoscopic OCT (EOCT) to examine the gastrointestinal tract of humans in vivo. Compared to endoscopic ultrasonic devices it offers a higher resolution and does not require coupling gels or fluids. EOCT may lead to a versatile tool for biopsy site selection or optical biopsy itself. The EOCT unit is comprised of an interferometer unit with a high speed scanning reference arm and an endoscopically compatible radially scanning probe as the sample arm. Fast data acquisition allows real-time display. Temporal averaging for speckle reduction and a transformation to correct nonlinear scanning were included in the EOCT control software, both in real-time. During in vivo clinical trials, we have observe the structure of the mucosa and submucosa in several gastrointestinal organs as well as glands, blood vessels, pits, villi and crypts. The purpose of this study was to correlate images acquired in vitro with EOCT to corresponding histological sections. EOCT images were obtained on fresh specimens, which were then fixed in formalin and submitted for standard histology. Tissues examined were normal specimens, which were then fixed in formalin and submitted for standard histology. Tissues examined were normal specimens of stomach, ileum, colon and rectum. It was shown that he thickness of the mucosa correlates well with the first bright layer in EOCT. The R2-value was determined to be 0.69. The submucosa and the muscularis propria could be identified. Furthermore, we were able to show the effect of pressure on the tissue on the visible details in the EOCT images.

Westphal, Volker; Rollins, Andrew M.; Willis, Joseph; Sivak, Michael J., Jr.; Izatt, Joseph A.

2000-04-01

169

Fast tomographic reconstruction strategy for diffuse optical tomography.  

Science.gov (United States)

Diffuse Optical Tomography (DOT) has been growing significantly in the past two decades as a promising tool for in-vivo and non-invasive imaging of tissues using near-infrared light. It can improve our ability to probe complex biologic interactions dynamically and to study disease and treatment responses over time in near real time. Recent advances on the transfer of techniques from laboratory to clinics have led to the development of various diagnostic applications such as imaging of the female breast and infant brain. The potential value of the promising tool, however, can be limited by the reconstruction time for tomographically imaging tissue optical properties. The current solution procedure in DOT consumes a considerable amount of time due to discretization of the problem domain and nonlinear nature of tissue optical properties. It is becoming ever more important to develop faster imaging tools as measurement data sets increase in size as a result of the application of newer generation instruments. Here we provide a fast solution strategy that significantly reduces imaging effort for DOT. The fast imaging strategy adopts advanced model-order reduction (MOR) techniques for reducing system complexity, while preserving (to the greatest possible extent) system input-output behavior for the forward problem. Our results demonstrate that the MOR-based imaging method can be an order of magnitude faster than the conventional approach while maintaining a relatively small error tolerance. The goal is to develop inexpensive, noninvasive imaging system that can run at patient's bedside in real time and produce data continuously over a long period of time. PMID:19333294

Zhai, Yuhu; Cummer, Steven A

2009-03-30

170

Optical tomography for diagnosis of two-phase flows; Optische Tomographie fuer die Diagnostik von Zweiphasenstroemungen  

Energy Technology Data Exchange (ETDEWEB)

Optical tomography is a potential method for investigations of two-phase flows. Its advantages are high speed, non-invasiveness, high resolution and low-cost sensors, but there is the problem of nonlinear shading of the measuring field with complete interruption of the measuring beam by reflection and diffraction of light at the phase boundaries. The authors investigated the applicability of the method and propose optimisation measures. [German] Die optische Tomographie stellt ein potentielles Messverfahren fuer die Untersuchung von Zweiphasenstroemungen dar. Fuer die Entwicklung einer solchen Technik sprechen ihre Faehigkeit zur schnellen und nichtinvasiven Messung transienter Stroemungsvorgaenge mit hoher Aufloesung bei gleichzeitig niedrigen Sensorkosten. Im Gegensatz zu tomographischen Messverfahren mit linearen Abbildungseigenschaften existiert bei der optischen CT in klaren Fluiden das Problem der nichtlinearen Abschattung des Messfeldes bei vollstaendiger Messstrahlunterbrechung durch Reflexion und Brechung des Lichtes an Phasengrenzen. Im Rahmen einer Teststudie wurde zunaechst die prinzipielle Eignung der optischen CT in Verbindung mit Standard-Rekonstruktionsverfahren der Computertomographie fuer das vorliegende Anwendungsfeld untersucht. Darueber hinaus wurde ein spezieller binaerer Rueckprojektionsalgorithmus zur Rekonstruktion von Gasblasengeometrien aus Momentanwertmessungen getestet. Die Ergebnisse dieser Untersuchungen haben gezeigt, dass lineare Rekonstruktionsverfahren nur fuer weniger komplexe Objektraumverteilungen befriedigende Rekonstruktionsergebnisse erreichen. So entstehen aufgrund der Nichtlinearitaetseffekte Artefakte in Form von tiefenabhaengigen Schwaechungsverteilungen in starken Absorbern. Der vorgeschlagene binaere Rekonstruktionsalgorithmus kann auch fuer komplexere Absorberanordnungen noch ausreichend gut Einzelblasen geometrisch getrennt rekonstruieren. Die exakte Rekonstruktion aller Einzelblasenformen ist dabei aber infolge der genannten Probleme nicht moeglich. An dieser Stelle bestehen Ansatzpunkte zur Entwicklung verbesserter Bildrekonstruktionsalgorithmen, welche einmal die a-priori vorliegenden Informationen ueber das Untersuchungsobjekt, wie typische Blasenformen und Grenzflaechenkonvexitaet, verarbeiten und zum anderen die Mehrinformation einer dreidimensionalen Messung fuer stroemende Fluide beruecksichtigen. Fuer die nahe Zukunft ist die Fertigstellung eines optisch-tomographischen Sensors und dessen Einsatz in einer Testschleife sowie eine Weiterentwicklung der Bildrekonstruktionsalgorithmen geplant. Eine darueber hinausgehende Zielrichtung ist die Anwendung des optischen Messverfahrens zur Untersuchung optisch trueber Fluide mittels optischer Streulichttomographie. (orig.)

Hampel, U. [Forschungszentrum Rossendorf e.V. (FZR) (Germany). Inst. fuer Sicherheitsforschung; Schleicher, E.; Silva, M. [Technische Univ. Dresden (Germany). Inst. fuer Biomedizinische Technik

1999-12-01

171

Root canal filling evaluation using optical coherence tomography  

Science.gov (United States)

Endodontic therapy consists in cleaning and shaping the root canal system, removing organic debris and sealing the intra-canal space with permanent filling materials. The purpose of this study was to evaluate various root canal fillings in order to detect material defects, the marginal adaptation at the root canal walls and to assess the quality of the apical sealing. 21 extracted single-root canal human teeth were selected for this study. We instrumented all roots using NiTi rotary instruments. All canals were enlarged with a 6% taper size 30 GT instrument, 0,5 mm from the anatomical apex. The root canals were irrigated with 5% sodium hypochlorite, followed by 17% ethylenediaminetetraacetic acid (EDTA). After the instrumentation was completed, the root canals were obturated using a thermoplasticizable polymer of polyesters. In order to assess the defects inside the filling material and the marginal fit to the root canal walls, the conebeam micro-computed tomography (CB?CT) was used first. After the CB?CT investigation, time domain optical coherence tomography working in en face mode (TDefOCT) was employed to evaluate the previous samples. The TDefOCT system was working at 1300 nm and was doubled by a confocal channel at 970 nm. The results obtained by CB?CT revealed no visible defects inside the root-canal fillings and at the interfaces with the root-canal walls. TDefOCT investigations permit to visualize a more complex stratificated structure at the interface filling material/dental hard tissue and in the apical region.

Negrutiu, Meda L.; Sinescu, Cosmin; Topala, Florin; Nica, Luminita; Ionita, Ciprian; Marcauteanu, Corina; Goguta, Luciana; Bradu, Adrian; Dobre, George; Rominu, Mihai; Podoleanu, Adrian Gh.

2010-04-01

172

Assessment of tissue optical clearing as a function of glucose concentration using optical coherence tomography  

Science.gov (United States)

In imaging of turbid biological samples using optical techniques, optical clearing methods can compensate for the lack of light penetration due to strong attenuation. The addition of optical clearing agents into scattering media increases the optical homogeneity of the sample and reduces its turbidity, allowing for the increased light penetration. In this study we investigated the extent of optical clearing in porcine skin by utilizing various concentrations of glucose solution. A goldplated mirror was fixed beneath the tissue and percentage clearing was determined by measuring the change in intensity of optical coherence tomography light returning from the mirror over time. A ratio of percentage clearing per tissue thickness for 10%, 30%, and 50% glucose was determined to be to be (4.7 +/- 1.6%) mm-1 (n = 6), (10.6 +/- 2.0%) mm-1 (n = 7), and (21.8 +/- 2.2%) mm-1 (n = 5), respectively. Although the extent of optical clearing in porcine skin was more significant for 50% glucose, the osmotic stress on the sample can cause considerable morphology change, thus a suitable concentration must be chosen for particular circumstances.

Sudheendran, Narendran; Mohamed, Mohamed; Ghosn, Mohamad G.; Tuchin, Valery V.; Larin, Kirill V.

2011-03-01

173

Optimization of image-forming optics for transmission optical projection tomography  

Science.gov (United States)

A new optical system for transmission optical projection tomography (TOPT) is presented to reduce the divergence of the projection data from the true parallel projections. This is performed by introducing an iris at the back focus of the objective lens. The influence of the defocusing on TOPT is demonstrated by computational simulations and experiments. We compare the performances of the new and conventional TOPT systems in order to optimize the optical system for three-dimensional imaging of the embryos of small animals. The optimal imaging performance is given by the new system with numerical apertures between 0.007 and 0.014, with which the spatial resolution of 25 ?m is achieved. The optimal configuration is validated by TOPT of a phantom sample and a fixed five-day chick embryo.

Wang, Yi; Wang, Ruikang K.

2007-09-01

174

Dispersion manipulation in optical coherence tomography with Fourier-domain optical delay line  

Science.gov (United States)

In the last decade, Fourier-domain optical delay lines (FD-ODL) based on pulse shaping technology have emerged as a practical device for high-speed scanning and dispersion compensation in imaging interferometry such as optical coherence tomography(OCT). In this study, we investigate the effect of first- and second-order dispersion on the photocurrent signal associated with a fiber-optic OCT system implemented using a superluminescent diode centered at 950nm+/-35nm, an FD-ODL, and a mirror and a layered LiTaO3 which owns suitable dispersion characteristics to model a skin specimen. We present a practically useful method associated with FD-ODL to minimize the effect of dispersion through the OCT system and the specimen combined, and quantify the results using two general metrics for axial resolution.

Akcay, Avni C.; Lee, Kye; Rolland, Jannick P.

2005-04-01

175

Compact MEMS-based Adaptive Optics Optical Coherence Tomography for Clinical Use  

Energy Technology Data Exchange (ETDEWEB)

We describe a compact MEMS-based adaptive optics (AO) optical coherence tomography system with improved AO performance and ease of clinical use. A typical AO system consists of a Shack-Hartmann wavefront sensor and a deformable mirror that measures and corrects the ocular and system aberrations. Because of the limitation on the current deformable mirror technologies, the amount of real-time ocular-aberration compensation is restricted and small in the previous AO-OCT instruments. In this instrument, we proposed to add an optical apparatus to correct the spectacle aberrations of the patients such as myopia, hyperopia and astigmatism. This eliminated the tedious process of the trial lenses in clinical imaging. Different amount of spectacle aberration compensation was achieved by motorized stages and automated with the AO computer for ease of clinical use. In addition, the compact AO-OCT was optimized to have minimum system aberrations to reduce AO registration errors and improve AO performance.

Chen, D; Olivier, S; Jones, S; Zawadzki, R; Evans, J; Choi, S; Werner, J

2008-02-04

176

Wavefront sensorless adaptive optics optical coherence tomography for in vivo retinal imaging in mice.  

Science.gov (United States)

We present wavefront sensorless adaptive optics (WSAO) Fourier domain optical coherence tomography (FD-OCT) for in vivo small animal retinal imaging. WSAO is attractive especially for mouse retinal imaging because it simplifies optical design and eliminates the need for wavefront sensing, which is difficult in the small animal eye. GPU accelerated processing of the OCT data permitted real-time extraction of image quality metrics (intensity) for arbitrarily selected retinal layers to be optimized. Modal control of a commercially available segmented deformable mirror (IrisAO Inc.) provided rapid convergence using a sequential search algorithm. Image quality improvements with WSAO OCT are presented for both pigmented and albino mouse retinal data, acquired in vivo. PMID:24575347

Jian, Yifan; Xu, Jing; Gradowski, Martin A; Bonora, Stefano; Zawadzki, Robert J; Sarunic, Marinko V

2014-02-01

177

Towards spectral-domain optical coherence tomography on a silicon chip  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Optical coherence tomography (OCT) is a widely used optical imaging technology, particularly in the medical field, since it can provide non-invasive, sub-micrometer resolution diagnostic images of tissue. Current OCT systems contain optical fibers and free-space optical components which make these instruments bulky and costly. A significant decrease in the size and cost of an OCT system is possible through the use of integrated optics, allowing for compact and low-cost OCT systems, especially...

Akca, B. I.; Wo?rhoff, K.; Nguyen, V. D.; Kalkman, J.; Leeuwen, T. G.; Ridder, R. M.; Pollnau, M.

2011-01-01

178

Acoustic modulation and photon-phonon scattering in optical coherence tomography.  

Science.gov (United States)

Acousto-optic interactions allow the measurement of nonoptical material properties with high-resolution optical methods. We modulated a sample with ultrasound while simultaneously imaging with a traditional optical coherence tomography (OCT) system. The measured acousto-optic signal then depends on the mechanical response of the tissue to the applied modulation. The acquired acoustically enhanced OCT signals are consistent with established acousto-optic theory and provide enhanced contrast to OCT images. PMID:18364947

Edney, P A; Walsh, J T

2001-12-01

179

Clinical manifestations of optic pit maculopathy as demonstrated by spectral domain optical coherence tomography  

Directory of Open Access Journals (Sweden)

Full Text Available Jonathan H Tzu, Harry W Flynn Jr, Audina M Berrocal, William E Smiddy, Timothy G Murray, Yale L FisherDepartment of Ophthalmology, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL, USAPurpose: The purpose of this retrospective study was to evaluate the characteristic features, including spectral-domain optical coherence tomography (SD-OCT, clinical course, and outcome of treatment if given for patients with optic disc pit maculopathy.Methods: We investigated a consecutive series of patients with a diagnosis of optic pit maculopathy treated between 2001 and 2012 at the Bascom Palmer Eye Institute. Patients were divided into two main groups, ie, patients who were observed without surgery and patients who received surgical intervention. The main outcome measures were presenting and final visual acuity, and changes in SD-OCT imaging were recorded. Other data including age, gender, eye, age of onset, length of follow-up, location of optic pit, and location of fluid by OCT were also recorded.Results: On OCT, 67% (12/18 of the eyes showed schisis-like cavities, 22% (4/18 had only subretinal fluid, and 17% (3/18 had only a schisis-like cavity without subretinal fluid. In the patients managed by observation, visual acuity was ?20/200 in 6/8 eyes initially and 6/8 eyes at last follow-up. Ten of 18 patients received either focal laser, surgery or both. Six of 10 eyes undergoing surgery had initial visual acuity ? 20/200, and 8 of 10 eyes undergoing surgery had a visual acuity of ?20/200 at last follow-up.Conclusion: In this study, many eyes were observed and remained stable during follow-up. In eyes with reduced vision, surgical intervention produced variable outcomes, and persistent intraretinal/subretinal fluid was a common occurrence.Keywords: optic pit maculopathy, spectral-domain optical coherence tomography

Tzu JH

2013-01-01

180

Cystoid macular edema diagnosed with optical coherent tomography in patients operated on from cataract  

International Nuclear Information System (INIS)

Refers frequency of cystoid macular edema diagnosed with optical coherence tomography in patients operated on from senile cataract at 'Ramon Pando Ferrer' Cuban Institute of Ophthalmology in the period from December 2006 to February 2007

 
 
 
 
181

Technical Note: Wet validation of optical tomography for drinking water discolouration studies  

Directory of Open Access Journals (Sweden)

Full Text Available This paper presents a set of validation experiments for the reconstruction of a cross-sectional particle concentration field in a transparent pipe filled with a fluid using optical tomography.

R. Floris

2013-02-01

182

Technical Note: Wet validation of optical tomography for drinking water discolouration studies  

Directory of Open Access Journals (Sweden)

Full Text Available This paper presents a set of validation experiments for the reconstruction of a cross-sectional particle concentration field in a transparent pipe filled with a fluid using optical tomography.

R. Floris

2013-06-01

183

Optical coherence tomography monitoring of enhanced skin optical clearing in rats in vivo.  

Science.gov (United States)

A comparative study of physical, chemical, and combined enhancement of transdermal transport of optical clearing agents (OCAs) is presented. As a physical enhancer of diffusivity, ultrasound (US) with a frequency 1 MHz and a power 1.1 W in the continuous mode was used, and dimethyl sulfoxide (DMSO) was used as a chemical enhancer. OCA (glycerol and polyethylene glycol-400 in equal proportion) was topically applied to the rat skin in vivo as alone or as together with the enhancers. Monitoring of skin optical clearing was implemented using an optical coherence tomography. The results have shown that the attenuation coefficient of intact skin dermis after the application of US-DMSO-OCA, US-OCA (both for 4 min), and DMSO-OCA (for 20 min) combinations decreased approximately by 31%, 19%, and 5%, respectively, while OCA alone did not induce a noticeable clearing effect for 20 min. Control skin sites with removed epidermis were used for modeling the upper limit of dermis optical clearing, i.e., maximal degree of optical clearing, by using the studied enhancers. They demonstrated that the attenuation coefficient decreases by 32%, 30%, 17%, and 16% at the action of US-DMSO-OCA, US-OCA, DMSO-OCA, and OCA, respectively. It can be concluded that US-DMSO-OCA combination only allowed reaching the upper limit of skin optical clearing. PMID:24105426

Genina, Elina A; Bashkatov, Alexey N; Kolesnikova, Ekaterina A; Basko, Marina V; Terentyuk, Georgy S; Tuchin, Valery V

2014-02-01

184

Optic disc topography of normal Indian eyes: An assessment using optical coherence tomography  

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Full Text Available Purpose: To study the optic disc topographic measurements of normal Indian eyes using optical coherence tomography (OCT. Materials and Methods: One hundred and fifty eyes selected randomly from 150 normal Indian subjects of both sex and various age groups underwent optic disc imaging with the OCT using the fast optic disc protocol. Results: Mean ± standard deviation of the optic disc topographic measurements were: disc area 2.63 ± 0.55 mm 2 , cup area 0.87 ± 0.45 mm 2 , neuroretinal rim area 1.78 ± 0.55 mm 2 and cup to disc area ratio 0.33 ± 0.15. There was no significant difference in the measurements between males and females. There was no significant correlation with respect to age and refractive errors ranging from -5.0 to +3.0 diopters of spherical equivalent. Conclusion: Our study provides a normative database for the various optic disc topographic measurements and its variations with age, sex and refractive error in normal Indian eyes using OCT.

Dacosta Shaun

2008-01-01

185

Optical diffraction tomography: accuracy of an off-axis reconstruction  

Science.gov (United States)

Optical diffraction tomography is an increasingly popular method that allows for reconstruction of three-dimensional refractive index distribution of semi-transparent samples using multiple measurements of an optical field transmitted through the sample for various illumination directions. The process of assembly of the angular measurements is usually performed with one of two methods: filtered backprojection (FBPJ) or filtered backpropagation (FBPP) tomographic reconstruction algorithm. The former approach, although conceptually very simple, provides an accurate reconstruction for the object regions located close to the plane of focus. However, since FBPJ ignores diffraction, its use for spatially extended structures is arguable. According to the theory of scattering, more precise restoration of a 3D structure shall be achieved with the FBPP algorithm, which unlike the former approach incorporates diffraction. It is believed that with this method one is allowed to obtain a high accuracy reconstruction in a large measurement volume exceeding depth of focus of an imaging system. However, some studies have suggested that a considerable improvement of the FBPP results can be achieved with prior propagation of the transmitted fields back to the centre of the object. This, supposedly, enables reduction of errors due to approximated diffraction formulas used in FBPP. In our view this finding casts doubt on quality of the FBPP reconstruction in the regions far from the rotation axis. The objective of this paper is to investigate limitation of the FBPP algorithm in terms of an off-axis reconstruction and compare its performance with the FBPJ approach. Moreover, in this work we propose some modifications to the FBPP algorithm that allow for more precise restoration of a sample structure in off-axis locations. The research is based on extensive numerical simulations supported with wave-propagation method.

Kostencka, Julianna; Kozacki, Tomasz

2014-05-01

186

Magnetic induction tomography using an all-optical $^{87}$Rb atomic magnetometer  

CERN Document Server

We demonstrate Magnetic Induction Tomography (MIT) with an all-optical atomic magnetometer. Our instrument creates a conductivity map of conductive objects. Both shape and size of the imaged samples compare very well with the actual shape and size. Given the potential of all-optical atomic magnetometers for miniaturization and extreme sensitivity, the proof-of-principle presented here opens up promising avenues in the development of instrumentation for magnetic induction tomography.

Wickenbrock, Arne; Dow, Albert; Marmugi, Luca; Renzoni, Ferruccio

2014-01-01

187

CHOROIDAL THICKNESS IN PATIENTS WITH DIABETIC RETINOPATHY ANALYZED BY SPECTRAL-DOMAIN OPTICAL COHERENCE TOMOGRAPHY  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Purpose: This study was designed to examine choroidal thickness in patients with diabetes using spectral-domain optical coherence tomography. Methods: Forty-nine patients (49 eyes) with diabetes and 24 age-matched normal subjects underwent high-definition raster scanning using spectral-domain optical coherence tomography with frame enhancement software. Patients with diabetes were classified into 3 groups: 11 patients with mild or moderate nonproliferative diabetic retinopathy and no macul...

Regatieri, Caio V.; Branchini, Lauren; Carmody, Jill; Fujimoto, James G.; Duker, Jay S.

2012-01-01

188

Two cases of X-linked retinoschisis with different spectral domain optical coherence tomography findings  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Spectral domain optical coherence tomography was used to image the maculae of two brothers who had the diagnosis of X-linked retinoschisis maculopathy. One patient demonstrated a large foveal cyst in one eye and a lamellar macular hole in the fellow eye. The second patient demonstrated small retinal cysts in multiple layers of the retina. Spectral domain optical coherence tomography allowed high-resolution imaging and characterization of the features in X-linked retinoschisis in these patient...

2012-01-01

189

Retinal and choroidal intravascular spectral-domain optical coherence tomography  

DEFF Research Database (Denmark)

Purpose:? To examine retinal and choroidal blood vessels using spectral-domain optical coherence tomography (SD-OCT). Methods:? Retrospective case series. Results:? Scans through retinal blood vessels in healthy subjects demonstrated vessel wall reflexes and a tri-layer profile of the blood column on longitudinal scans and a figure-of-eight configuration on cross-sectional scans. Intravascular reflectivity decreased with increasingly oblique angles of observation and was absent when blood flow was parallel to the line of sight. The high blood flow in the choroidal vessels in healthy subjects and the low flow in the retinal vessels in patients with ocular ischaemic syndrome and central retinal artery occlusion were both associated with lower reflectivity of the blood and an unstructured intravascular SD-OCT profile. Discussion:? This qualitative in vivo study found a characteristically structured SD-OCT profile of the blood column in retinal vessels with normal blood flow. Both structure and total reflectivityfaded when blood flow was lower or higher than normal or at oblique angles to the line of sight. In conclusion, SD-OCT scans of the vessels in the posterior pole of the eye may assist the clinical assessment of gross abnormalities of ocular blood flow, e.g. in carotid artery stenosis.

Willerslev, Anne; Li, Xiao Q

2013-01-01

190

Polarization-sensitive optical coherence tomography of dental structures.  

Science.gov (United States)

Optical coherence tomography (OCT) has been developed during the last 10 years as a new noninvasive imaging tool and has been applied to diagnose different ocular and skin diseases. This technique has been modified for cross-sectional imaging of dental structures. In this first preliminary study the technique was applied to obtain tomographic images of extracted sound and decayed human teeth in order to evaluate its possible diagnostic potential for dental applications. Classical OCT images based on reflectivity measurements and phase retardation images using polarization-sensitive OCT were recorded. It was demonstrated that polarization-sensitive OCT can provide additional information which is probably related to the mineralization status and/or the scattering properties of the dental material. One of the attractive features of OCT is that it uses near-infrared light instead of ionizing radiation. Furthermore, high transversal and depth resolution on the order of 10 microm can be obtained. Present limitations, e.g. the limited penetration depth, and possible solutions are discussed. PMID:10601786

Baumgartner, A; Dichtl, S; Hitzenberger, C K; Sattmann, H; Robl, B; Moritz, A; Fercher, A F; Sperr, W

2000-01-01

191

Automatic segmentation of anterior segment optical coherence tomography images  

Science.gov (United States)

Optical coherence tomography (OCT) images can provide quantitative measurements of the eye's entire anterior segment. A new technique founded on a newly proposed level set-based shape prior segmentation model has been developed for automatic segmentation of the cornea's anterior and posterior boundaries. This technique comprises three major steps: removal of regions containing irrelevant structures and artifacts, estimation of the cornea's location using a thresholding technique, and application of the new level set-based shape prior segmentation model to improve segmentation. The performance of our technique is compared to previously developed methods for analysis of the cornea in 33 OCT images of normal eyes, whereby manual annotations are used as a reference standard. The new technique achieves much improved concordance than previous methods, with a mean Dice's similarity coefficient of >0.92. This demonstrates the technique's potential to provide accurate and reliable measurements of the anterior segment geometry, which is important for many applications, including the construction of representative numerical simulations of the eye's mechanical behavior.

Williams, Dominic; Zheng, Yalin; Bao, Fangjun; Elsheikh, Ahmed

2013-05-01

192

The potential of optical coherence tomography for diagnosing meniscal pathology  

International Nuclear Information System (INIS)

Meniscal tears are often associated with anterior cruciate ligament (ACL) injury and may lead to pain and discomfort in humans. Maximal preservation of meniscal tissue is highly desirable to mitigate the progression of osteoarthritis. Guidelines of which meniscal tears are amenable to repair and what part of damaged tissues should be removed are elusive and lacking consensus. Images of microstructural changes in meniscus would potentially guide the surgeons to manage the meniscal tears better, but the resolution of current diagnostic techniques is limited for this application. In this study, we demonstrated the feasibility of using optical coherence tomography (OCT) for the diagnosis of meniscal pathology. Torn medial menisci were collected from dogs with ACL insufficiency. The torn meniscus was divided into three tissue samples and scanned by OCT and scanning electron microscopy (SEM). OCT and SEM images of torn menisci were compared. Each sample was evaluated for gross and microstructural abnormalities and reduction or loss of birefringence from the OCT images. The abnormalities detected with OCT were described for each type of tear. OCT holds promise in non-destructive and fast assessment of microstructural changes and tissue birefringence of meniscal tears. Future development of intraoperative OCT may help surgeons in the decision making of meniscal treatment

193

Optical coherence tomography: A new strategy to image planarian regeneration  

Science.gov (United States)

The planarian is widely used as a model for studying tissue regeneration. In this study, we used optical coherence tomography (OCT) for the real-time, high-resolution imaging of planarian tissue regeneration. Five planaria were sliced transversely to produce 5 head and 5 tail fragments. During a 2-week regeneration period, OCT images of the planaria were acquired to analyze the signal attenuation rates, intensity ratios, and image texture features (including contrast, correlation, homogeneity, energy, and entropy) to compare the primitive and regenerated tissues. In the head and tail fragments, the signal attenuation rates of the regenerated fragments decreased from -0.2 dB/?m to -0.05 dB/?m, between Day 1 and Day 6, and then increased to -0.2 dB/?m on Day 14. The intensity ratios decreased to approximately 0.8 on Day 6, and increased to between 0.8 and 0.9 on Day 14. The texture parameters of contrast, correlation, and homogeneity exhibited trends similar to the signal attenuation rates and intensity ratios during the planarian regeneration. The proposed OCT parameters might provide biological information regarding cell apoptosis and the formation of a mass of new cells during planarian regeneration. Therefore, OCT imaging is a potentially effective method for planarian studies.

Lin, Yu-Sheng; Chu, Chin-Chou; Lin, Jen-Jen; Chang, Chien-Cheng; Wang, Chun-Chieh; Wang, Chiao-Yin; Tsui, Po-Hsiang

2014-09-01

194

Imaging cutaneous T-Cell lymphoma with optical coherence tomography  

DEFF Research Database (Denmark)

Aim: To investigate the presentation of a patch-stage cutaneous T-cell lymphoma (CTCL) using optical coherence tomography (OCT). Methods: A patient with a patch caused by CTCL was photographed digitally, OCT-scanned and biopsied. A normal skin area adjacent to the patch was OCT-scanned for comparison, but not biopsied. The OCT image and the histological image were compared. Results: The OCT images illustrated a thickened and hyperreflective stratum corneum. OCT also demonstrated several elongated hyporeflective structures in the dermis. The largest structure was measured to have a width of 0.13 mm. A good immediate correlation was found between histology and OCT imaging of the sample. Conclusion: The aetiology of the elongated structures is thought to be lymphomatous infiltrates. Similar findings have been described in ocular lymphoma and may therefore be an important characteristic of cutaneous lymphoma. It may further be speculated that the differences in OCT images may reflect the biological behaviour of the infiltrate. This observation therefore suggests that OCT imaging may be a relevant tool for the in vivo investigation of mycosis fungoides and other CTCLs, but in order to verify these observed patterns in OCT imaging, further investigations will be required. Copyright © 2012 S. Karger AG, Basel.

Ring, H.C.; Hansen Stamp, I.M.

2012-01-01

195

Left main dissection conservatively managed with optical coherence tomography guidance.  

Science.gov (United States)

Left main dissection (LMD) is a rare but feared complication of cardiac catheterization. It is usually managed by bailout stent implantation or coronary artery bypass surgery. We describe a case of iatrogenic, retrograde LMD during percutaneous coronary intervention. After covering the retrograde entry of the dissection in the ostial left anterior descending artery (LAD), optical coherence tomography (OCT) showed, that there was no antegrade entry in the left main and that the minimal true lumen area in the left main was 7.2 mm(2) . It was therefore decided to treat the LMD conservatively and reassess the results by angiography 6 months later. At follow-up angiography, no stenosis or residual dissection in the left main were noted. The patient was doing fine at 1-year follow-up. OCT is a valuable tool for assessing coronary artery dissections and may guide the decision, whether to stent or not to stent a dissection. In selected cases LMD may be managed conservatively. PMID:23613429

Binder, Ronald K; Boone, Robert H; Webb, John G

2014-01-01

196

Full-range spectral domain Doppler optical coherence tomography  

Science.gov (United States)

Spectral domain optical coherence tomography (SD-OCT) systems achieve higher sensitivities compared to time domain OCT systems. However, one of the main challenges in SD-OCT is the obscuring object structure called "ghost image" or "mirror image" that arises from the Fourier transform of a real function. We have designed and developed a phaseshifting- based full-range SD-OCT system that we refer to as the dual detection full range SD-OCT. The proposed technique simultaneously obtains the quadrature components of a complex spectral interference. Therefore, the technique enables full range imaging without any loss of speed and is intrinsically less sensitive to movements of the subject. In this paper, we demonstrate that the dual detection technique can be applied to Doppler imaging without loss in the velocity dynamic range since the phase information of the acquired spectra is preserved. The dual detection full range SD-OCT provides a superior signal-to-noise ratio over a conventional SD-OCT since the most sensitive region around the zero path delay is usable. This capability improves the image quality of not only the structural image but also the Doppler image.

Meemon, P.; Lee, K. S.; Rolland, J. P.

2010-02-01

197

Orthogonal dispersive spectral-domain optical coherence tomography.  

Science.gov (United States)

Ultrahigh depth range spectral domain optical coherence tomography (SDOCT) can be realized based on the orthogonal dispersive spectrometer consisted by a high spectral resolution virtually-imaged phased array (VIPA) and a low spectral resolution grating. However, two critical issues result in the challenge of obtaining desirable one-dimensional (1-D) spectra from the recorded two-dimensional (2-D) orthogonal spectra for high-quality OD-SDOCT imaging. One is the wavenumber mapping errors and the other is the periodic intensity modulations. The paper proposes a method for desirable reconstruction of 1-D spectra from the recorded 2-D orthogonal spectra. A sample etalon with identical parameters to the dispersive VIPA is used to determine the free spectrum range (FSR) of the VIPA, and spectral phases from two reflecting mirrors are further applied for broadband wavenumber calibration. The cascading of column spectra are performed from interval of four lines of column spectra, and four records of cascaded 1-D spectra are obtained and then averaged to alleviate the periodic intensity modulations. Broadband 1-D spectra are thus reconstructed with an ultrahigh spectral resolution. To demonstrate the feasibility of the proposed method, three typical samples are imaged by the OD-SDOCT system. PMID:24787889

Bao, Wen; Ding, Zhihua; Li, Peng; Chen, Zhiyan; Shen, Yi; Wang, Chuan

2014-04-21

198

[The theory and research of near-infrared optical tomography].  

Science.gov (United States)

The fundamental theory and new research of near-infrared optical tomography (NIR OT) were introduced. NIR OT can offer the functional as well as structural information of tissue, so its applications have emerged in areas such as functional imaging of the brain, breast cancer detection, continue monitoring of the brain in babies and any other medical applications. The paper broadly divides the types of NIR OT instruments into three groups: continuous intensity, intensity-modulated and time-resolved instruments. The diffuse function of light propagation through tissue was given, and emphasized on the two distinct solutions to image reconstruction: linear methods based on inverse scattering theory and non-linear methods based on model fitting. Give some advanced work we can do in the future, concurrent NIR OT and other conventional anatomical imaging techniques, such as MRI, CT, research on the presence of anisotropies, contrast agent in NIR OT, three-dimensional image reconstruction. At last enumerate some of the fundamental difficulties involved in NIR OT, such as the intensity matching problem between simulated and experiment data, the boundary effect problem. Although these are often acknowledged, they remain largely unexplored. PMID:18435292

Li, Weitao; Qian, Zhiyu; Wang, Huinan

2008-02-01

199

Optical coherence tomography as a guide for cochlear implant surgery?  

Science.gov (United States)

To assess the potential use of optical coherence tomography (OCT) in cochlear implant surgery, OCT was applied in human temporal bones before cochleostomy. The question was whether OCT might provide information about the cochlear topography, especially about the site of the scala tympani. OCT was carried out on human temporal bone preparations, in which the cochleostomy was performed leaving the membranous labyrinth and the fluid-filled inner ear intact. A specially equipped operating microscope with integrated OCT prototype was used. Spectral-domain (SD)-OCT was used for all investigations. On all scans, OCT supplied information about inner ear structures, such as scala tympani, scala vestibuli while the membranous labyrinth was still intact. In the fresh temporal bone the scala media, basilar membrane and the Reissner's membrane were identified. This OCT study clearly documents the possibility to identify inner ear structures, especially the scala tympani without opening its enveloping membranes. These findings may have an impact on cochlear implant surgery, especially as an orientation guide to localize the scala tympani precisely before opening the fluid filled inner ear.

Just, T.; Lankenau, E.; Hüttmann, G.; Pau, H. W.

2008-02-01

200

Evaluation of fingerprint deformation using optical coherence tomography  

Science.gov (United States)

Biometric identification systems have important applications to privacy and security. The most widely used of these, print identification, is based on imaging patterns present in the fingers, hands and feet that are formed by the ridges, valleys and pores of the skin. Most modern print sensors acquire images of the finger when pressed against a sensor surface. Unfortunately, this pressure may result in deformations, characterized by changes in the sizes and relative distances of the print patterns, and such changes have been shown to negatively affect the performance of fingerprint identification algorithms. Optical coherence tomography (OCT) is a novel imaging technique that is capable of imaging the subsurface of biological tissue. Hence, OCT may be used to obtain images of subdermal skin structures from which one can extract an internal fingerprint. The internal fingerprint is very similar in structure to the commonly used external fingerprint and is of increasing interest in investigations of identify fraud. We proposed and tested metrics based on measurements calculated from external and internal fingerprints to evaluate the amount of deformation of the skin. Such metrics were used to test hypotheses about the differences of deformation between the internal and external images, variations with the type of finger and location inside the fingerprint.

Gutierrez da Costa, Henrique S.; Maxey, Jessica R.; Silva, Luciano; Ellerbee, Audrey K.

2014-02-01

 
 
 
 
201

Application of anterior segment optical coherence tomography in glaucoma.  

Science.gov (United States)

Optical coherence tomography (OCT) is a cross-sectional, three-dimensional, high-resolution imaging modality that uses low coherence interferometry to achieve axial resolution in the range of 3-20 ?m. Two OCT platforms have been developed: time domain (TD-OCT) and spectral (or Fourier) domain (SD/FD-OCT). Visante anterior segment OCT (Carl Zeiss Meditec) is a TD-OCT widely used for anterior segment imaging. The SD-OCT systems with both posterior and anterior segment imaging capabilities include the RTVue, iVue (Optovue), the Cirrus (Carl Zeiss Meditec), and the Spectralis (Heidelberg Engineering, Inc.). Each of the SD-OCTs has a wavelength in the range of 820-879 nm. Anterior segment OCT is a non-contact method providing high resolution tomographic cross-sectional imaging of anterior segment structures. Anterior segment OCT provides qualitative and quantitative assessment of the anterior segment structures important to the pathogenesis and the anatomical variations of glaucoma, and the approach to and success of treatment. We summarize the clinical applications of anterior segment OCT in glaucoma. PMID:24138894

Sharma, Reetika; Sharma, Ajay; Arora, Tarun; Sharma, Sourabh; Sobti, Amit; Jha, Bhaskar; Chaturvedi, Neha; Dada, Tanuj

2014-01-01

202

Surface imaging of metallic material fractures using optical coherence tomography.  

Science.gov (United States)

We demonstrate the capability of optical coherence tomography (OCT) to perform topography of metallic surfaces after being subjected to ductile or brittle fracturing. Two steel samples, OL 37 and OL 52, and an antifriction Sn-Sb-Cu alloy were analyzed. Using an in-house-built swept source OCT system, height profiles were generated for the surfaces of the two samples. Based on such profiles, it can be concluded that the first two samples were subjected to ductile fracture, while the third one was subjected to brittle fracture. The OCT potential for assessing the surface state of materials after fracture was evaluated by comparing OCT images with images generated using an established method for such investigations, scanning electron microscopy (SEM). Analysis of cause of fracture is essential in response to damage of machinery parts during various accidents. Currently the analysis is performed using SEM, on samples removed from the metallic parts, while OCT would allow in situ imaging using mobile units. To the best of our knowledge, this is the first time that the OCT capability to replace SEM has been demonstrated. SEM is a more costly and time-consuming method to use in the investigation of surfaces of microstructures of metallic materials. PMID:25321671

Hutiu, Gheorghe; Duma, Virgil-Florin; Demian, Dorin; Bradu, Adrian; Podoleanu, Adrian Gh

2014-09-10

203

OCT y fototoxicidad macular Optical coherence tomography and macular phototoxicity  

Directory of Open Access Journals (Sweden)

Full Text Available Caso clínico: Se realiza una exploración ocular y tomografía de coherencia óptica (OCT en tres pacientes con lesiones fototóxicas retinianas. Las angiografías fluoresceínicas muestran un defecto ventana. La OCT muestra hiporreflectividad en la porción externa de la fóvea y fragmentación de las capas más internas entre la porción interna de los fotorreceptores y los segmentos externos. Discusión: Las lesiones retinianas tras exposición a la luz aparecen precozmente mostrando diferentes patrones en la OCT. La OCT sugiere que la disminución de visión asocia una lesión de fotorreceptores y epitelio pigmentario retiniano (EPR. La OCT es útil para objetivar la retinopatía fototóxica donde los cambios oftalmoscópicos pueden estar ausentes o ser mínimos.Case report: Ocular examinations and optical coherence tomography (OCT were performed in three patients with retinal phototoxicity lesions. Fluorescein angiography depicted a window defect. OCT exhibited hyporeflectivity at the outer foveal retina and fragmentation of the inner reflective layers, corresponding to the junction between the inner and outer photoreceptor segments. Discussion: Retinal damage after light exposure has a rapid onset and shows different patterns in OCT examination. OCT findings suggest that decreased visual acuity may be associated with full-thickness photoreceptors and retinal pigment epithelium (RPE involvement. OCT is a useful tool for objective assessment of retinal pathology in phototoxicity cases where fundus changes may be minimal or absent.

N.A. Rodríguez-Marco

2008-04-01

204

OCT y fototoxicidad macular / Optical coherence tomography and macular phototoxicity  

Scientific Electronic Library Online (English)

Full Text Available SciELO Spain | Language: Spanish Abstract in spanish Caso clínico: Se realiza una exploración ocular y tomografía de coherencia óptica (OCT) en tres pacientes con lesiones fototóxicas retinianas. Las angiografías fluoresceínicas muestran un defecto ventana. La OCT muestra hiporreflectividad en la porción externa de la fóvea y fragmentación de las capa [...] s más internas entre la porción interna de los fotorreceptores y los segmentos externos. Discusión: Las lesiones retinianas tras exposición a la luz aparecen precozmente mostrando diferentes patrones en la OCT. La OCT sugiere que la disminución de visión asocia una lesión de fotorreceptores y epitelio pigmentario retiniano (EPR). La OCT es útil para objetivar la retinopatía fototóxica donde los cambios oftalmoscópicos pueden estar ausentes o ser mínimos. Abstract in english Case report: Ocular examinations and optical coherence tomography (OCT) were performed in three patients with retinal phototoxicity lesions. Fluorescein angiography depicted a window defect. OCT exhibited hyporeflectivity at the outer foveal retina and fragmentation of the inner reflective layers, c [...] orresponding to the junction between the inner and outer photoreceptor segments. Discussion: Retinal damage after light exposure has a rapid onset and shows different patterns in OCT examination. OCT findings suggest that decreased visual acuity may be associated with full-thickness photoreceptors and retinal pigment epithelium (RPE) involvement. OCT is a useful tool for objective assessment of retinal pathology in phototoxicity cases where fundus changes may be minimal or absent.

N.A., Rodríguez-Marco; J., Andonegui-Navarro; E., Compains-Silva; A., Rebollo-Aguayo; D., Aliseda-Pérez-de-Madrid; M., Aranguren-Laflin.

205

Optical coherence tomography for visualization of plant tissues  

Science.gov (United States)

First experimental results on optical coherence tomography (OCT) imaging of internal structure of plant tissues and in situ OCT monitoring of plant tissue regeneration at different water supply are reported. The OCT images are a map of backscattering coefficient 200 x 200 pixels, 1.5 mm along plant surface and up to 2 mm in depth (by analogy with ultrasound B-scan). Experiments for evaluating OCT capabilities were performed on Tradescantia blossfeldiana Mild. Using OCT device, in vivo images of plant tissues were acquired with a spatial resolution of 15 ?m. These OCT images correlate with standard microscopy data from the same tissue regions. Since incident light power at a wavelength of 1.3 ?m is as low as 0.5 mW, two-dimensional OCT images can be obtained directly on an intact plant not damaging it. Acquisition time for a 2D image is 1-3 s. OCT enables effective monitoring of fast reactions in plants at different water supply.

Sapozhnikova, Veronika V.; Kamensky, Vladislav A.; Kuranov, Roman V.

2003-09-01

206

Optical coherence tomography and confocal microscopy investigations of dental prostheses  

Science.gov (United States)

Dental prostheses are very complex systems, heterogenous in structure, made up from various materials, with different physical properties. An essential question mark is on the physical, chemical and mechanical compatibility between these materials. They have to satisfy high stress requirements as well as esthetic challenges. The masticatory stress may induce fractures of the prostheses, which may be triggered by initial materials defects or by alterations of the technological process. The failures of dental prostheses lead to functional, esthetic and phonetic disturbances which finally render the prosthetic treatment inefficient. The purpose of this study is to evaluate the capability of en-face optical coherence tomography as a possible non-invasive high resolution method in supplying the necessary information on the material defects of dental prostheses and microleakage at prosthetic interfaces. C-scan and B-scan OCT images as well as confocal images are acquired from a large range of samples. Gaps between the dental interfaces and material defects are clearly exposed. We conclude that OCT can successfully be used as a noninvasive analysis method.

Negrutiu, Meda L.; Sinescu, Cosmin; Hughes, Michael; Bradu, Adrian; Rominu, Mihai; Todea, Carmen; Dobre, George; Podoleanu, Adrian

2008-09-01

207

Fixed partial dentures investigated by optical coherent tomography  

Science.gov (United States)

Fixed partial prostheses as integral ceramics, integral polymers, metal ceramics or metal polymers bridges, are mainly used in the frontal part of the dental arch (especially the integral bridges). They have to satisfy high stress requirements as well as esthetic. The masticatory stress may induce fractures of the bridges. These may be triggered by initial materials defects or by alterations of the technological process. The fractures of these bridges lead to functional, esthetic and phonetic disturbances which finally render the prosthetic treatment inefficient. The purpose of this study is to evaluate the capability of en-face optical coherence tomography (OCT) in detection and analysis of possible fractures in several integral fixed partial dentures. The materials used were represented by several fixed partial prostheses, integral ceramics, integral polymers, metal ceramics and metal polymers bridges. In order to discover the defects, scanning was performed from incisal, vestibular, oral and cervical directions material defects such as fractures and pores were investigated using OCT. In conclusion, en-face OCT has proven as a valuable non invasive method to investigate fixed partial prostheses before their insertion in the oral cavity.

Sinescu, Cosmin; Negrutiu, Meda; Todea, Carmen; Hughes, Mike; Tudorache, Florin; Podoleanu, Adrian G.

2008-02-01

208

Morphological characterization of dental prostheses interfaces using optical coherence tomography  

Science.gov (United States)

Fixed partial prostheses as integral ceramic, polymers, metal-ceramic or metal-polymers bridges are mainly used in the frontal part of the dental arch (especially the integral bridges). They have to satisfy high stress as well as esthetic requirements. The masticatory stress may induce fractures of the bridges. These may be triggered by initial materials defects or by alterations of the technological process. The fractures of these bridges lead to functional, esthetic and phonetic disturbances which finally render the prosthetic treatment inefficient. Dental interfaces represent one of the most significant aspects in the strength of the dental prostheses under the masticatory load. The purpose of this study is to evaluate the capability of optical coherence tomography (OCT) to characterize the dental prostheses interfaces. The materials used were several fixed partial prostheses integral ceramic, polymers, metal-ceramic and metal-polymers bridges. It is important to produce both C-scans and B-scans of the defects in order to differentiate morphological aspects of the bridge infrastructures. The material defects observed with OCT were investigated with micro-CT in order to prove their existence and positions. In conclusion, it is important to have a non invasive method to investigate dental prostheses interfaces before the insertion of prostheses in the oral cavity.

Sinescu, Cosmin; Negrutiu, Meda L.; Ionita, Ciprian; Marsavina, Liviu; Negru, Radu; Caplescu, Cristiana; Bradu, Adrian; Topala, Florin; Rominu, Roxana O.; Petrescu, Emanuela; Leretter, Marius; Rominu, Mihai; Podoleanu, Adrian G.

2010-03-01

209

High-resolution optical tomographic imaging of human gastrointestinal tissue in vitro with optical coherence tomography  

Science.gov (United States)

Optical Coherence tomography is a recently developed imaging technique that has potential to improve the diagnostic limits of the currently available imaging techniques, allowing wide range of clinical disorders to be addressed at an early stage. To assess the clinical applicability of OCT, both the normal and pathological specimens from the G.I. tract were imaged, including oesophagus, oesophago- gastric junction, stomach and colon. Sharp differentiation of structures and features was observed between different stages of tissue. The images acquired in this study provide information on tissue microstructure that could only previously be obtained with conventional excisional biopsy.

Wang, Ruikang K.; Elder, James B.; Smith, Victoria

2000-10-01

210

Optical Projection Tomography as a Tool for 3D Microscopy and Gene Expression Studies  

Science.gov (United States)

Current techniques for three-dimensional (3D) optical microscopy (deconvolution, confocal microscopy, and optical coherence tomography) generate 3D data by ``optically sectioning'' the specimen. This places severe constraints on the maximum thickness of a specimen that can be imaged. We have developed a microscopy technique that uses optical projection tomography (OPT) to produce high-resolution 3D images of both fluorescent and nonfluorescent biological specimens with a thickness of up to 15 millimeters. OPT microscopy allows the rapid mapping of the tissue distribution of RNA and protein expression in intact embryos or organ systems and can therefore be instrumental in studies of developmental biology or gene function.

Sharpe, James; Ahlgren, Ulf; Perry, Paul; Hill, Bill; Ross, Allyson; Hecksher-Sørensen, Jacob; Baldock, Richard; Davidson, Duncan

2002-04-01

211

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

Science.gov (United States)

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 coil actuator as an alternative to a PZT-based optical delay. Voice coil actuators are light in weight, inexpensive and offer other advantages such as zero hysteresis, low operational voltage and a long life. We demonstrate a voice coil actuator as a feasible alternative to PZT-based actuators for the purpose of creating an optical delay, which can provide fast and precise axial displacements at high scanning rates.

Dsouza, Roshan; Subhash, Hrebesh; Neuhaus, Kai; Hogan, Josh; Wilson, Carol; Leahy, Martin

2014-02-01

212

All fiber optics circular-state swept source polarization-sensitive optical coherence tomography.  

Science.gov (United States)

A swept source (SS)-based circular-state (CS) polarization-sensitive optical coherence tomography (PS-OCT) constructed entirely with polarization-maintaining fiber optics components is proposed with the experimental verification. By means of the proposed calibration scheme, bulk quarter-wave plates can be replaced by fiber optics polarization controllers to, therefore, realize an all-fiber optics CS SSPS-OCT. We also present a numerical dispersion compensation method, which can not only enhance the axial resolution, but also improve the signal-to-noise ratio of the images. We demonstrate that this compact and portable CS SSPS-OCT system with an accuracy comparable to bulk optics systems requires less stringent lens alignment and can possibly serve as a technology to realize PS-OCT instrument for clinical applications (e.g., endoscopy). The largest deviations in the phase retardation (PR) and fast-axis (FA) angle due to sample probe in the linear scanning and a rotation angle smaller than 65 deg were of the same order as those in stationary probe setups. The influence of fiber bending on the measured PR and FA is also investigated. The largest deviations of the PR were 3.5 deg and the measured FA change by ~12 to 21 deg. Finally, in vivo imaging of the human fingertip and nail was successfully demonstrated with a linear scanning probe. PMID:24084890

Lin, Hermann; Kao, Meng-Chun; Lai, Chih-Ming; Huang, Jyun-Cin; Kuo, Wen-Chuan

2014-02-01

213

Platinum microheater integrated silicon optical bench assembly for endoscopic optical coherence tomography  

Science.gov (United States)

A novel platinum microheater and comb isolator integrated silicon optical bench (SiOB) assembly method has been successfully demonstrated to provide electrical connection and high precision alignment for a two-axis gimbal-less micromirror. Localized heating and wetting of plastic core micro solder balls is achieved by the integrated platinum heater, and the maximum measured temperature of the platinum heater is about 250 °C. In addition, assembly procedures are significantly simplified by involving a comb isolator made by deep reactive ion etching (DRIE) in comparison with our previously reported design. DRIE is also applied to form a 45° trench on the lower silicon substrate with a nearly vertical sidewall for the micromirror. Hence, the overall dimensions of the SiOB assembly can be reduced further to meet the requirements of endoscopic optical coherence tomography (EOCT) for miniaturization.

Xu, Y.; Wang, M. F.; Premachandran, C. S.; Chen, K. W. S.; Chen, N.; Olivo, M.

2010-01-01

214

Optical sensing method for screening disease in melon seeds by using optical coherence tomography.  

Science.gov (United States)

We report a noble optical sensing method to diagnose seed abnormalities using optical coherence tomography (OCT). Melon seeds infected with Cucumber green mottle mosaic virus (CGMMV) were scanned by OCT. The cross-sectional sensed area of the abnormal seeds showed an additional subsurface layer under the surface which is not found in normal seeds. The presence of CGMMV in the sample was examined by a blind test (n = 140) and compared by the reverse transcription-polymerase chain reaction. The abnormal layers (n = 40) were quantitatively investigated using A-scan sensing analysis and statistical method. By utilizing 3D OCT image reconstruction, we confirmed the distinctive layers on the whole seeds. These results show that OCT with the proposed data processing method can systemically pick up morphological modification induced by viral infection in seeds, and, furthermore, OCT can play an important role in automatic screening of viral infections in seeds. PMID:22163706

Lee, Changho; Lee, Seung-Yeol; Kim, Jeong-Yeon; Jung, Hee-Young; Kim, Jeehyun

2011-01-01

215

Optical Sensing Method for Screening Disease in Melon Seeds by Using Optical Coherence Tomography  

Directory of Open Access Journals (Sweden)

Full Text Available We report a noble optical sensing method to diagnose seed abnormalities using optical coherence tomography (OCT. Melon seeds infected with Cucumber green mottle mosaic virus (CGMMV were scanned by OCT. The cross-sectional sensed area of the abnormal seeds showed an additional subsurface layer under the surface which is not found in normal seeds. The presence of CGMMV in the sample was examined by a blind test (n = 140 and compared by the reverse transcription-polymerase chain reaction. The abnormal layers (n = 40 were quantitatively investigated using A-scan sensing analysis and statistical method. By utilizing 3D OCT image reconstruction, we confirmed the distinctive layers on the whole seeds. These results show that OCT with the proposed data processing method can systemically pick up morphological modification induced by viral infection in seeds, and, furthermore, OCT can play an important role in automatic screening of viral infections in seeds.

Jeehyun Kim

2011-10-01

216

«Optical Coherence Tomography» en desgarro del epitelio pigmentario retiniano / «Optical Coherence Tomography» of retinal pigment epithelial tears  

Scientific Electronic Library Online (English)

Full Text Available SciELO Spain | Language: Spanish Abstract in spanish Casos clínicos: Se presentan 3 pacientes con desgarro de epitelio pigmentario retiniano (EPR). En dos de ellos, éste se produjo de manera espontánea, estando el tercero en relación con la fotocoagulación de una neovascularización extrafoveal. Se realizaron angiografías (AGF) y estudio con tomografia [...] óptica de coherencia (OCT) que confirmaron el diagnóstico. Discusión: Existen pocos estudios sobre OCT en desgarro del EPR. Las principales características son: interrupción de la línea hiperreflectante del EPR, hiperreflectividad de la coroides en la zona de ausencia de EPR y doble capa de EPR donde éste está replegado. Es frecuente el desprendimiento de EPR y neurosensorial asociado. Abstract in english Case reports: Three cases of pigmentary epithelial tears are described in this study. One of them was related to previous extrafoveal photocoagulation, whereas the other two were idiopathic. Fluorescein angiography (FA) and optical coherence tomography (OCT) were performed to confirm the clinical di [...] agnosis. Discussion: Few studies using OCT to assess pigmentary retinal epithelial (RPE) tears have been published in the world literature. The main findings of our study included hyper-reflectant line breaks, choroidal hyper-reflectance due to the lack of RPE and RPE double layering where it was folded. Images were frequently associated with RPE tears and neurosensorial retinal detachment.

C., Torrón-Fernández-Blanco; E., Ferrer-Novella; O., Ruiz-Moreno; F.M., Honrubia-López.

217

«Optical Coherence Tomography» en desgarro del epitelio pigmentario retiniano «Optical Coherence Tomography» of retinal pigment epithelial tears  

Directory of Open Access Journals (Sweden)

Full Text Available Casos clínicos: Se presentan 3 pacientes con desgarro de epitelio pigmentario retiniano (EPR. En dos de ellos, éste se produjo de manera espontánea, estando el tercero en relación con la fotocoagulación de una neovascularización extrafoveal. Se realizaron angiografías (AGF y estudio con tomografia óptica de coherencia (OCT que confirmaron el diagnóstico. Discusión: Existen pocos estudios sobre OCT en desgarro del EPR. Las principales características son: interrupción de la línea hiperreflectante del EPR, hiperreflectividad de la coroides en la zona de ausencia de EPR y doble capa de EPR donde éste está replegado. Es frecuente el desprendimiento de EPR y neurosensorial asociado.Case reports: Three cases of pigmentary epithelial tears are described in this study. One of them was related to previous extrafoveal photocoagulation, whereas the other two were idiopathic. Fluorescein angiography (FA and optical coherence tomography (OCT were performed to confirm the clinical diagnosis. Discussion: Few studies using OCT to assess pigmentary retinal epithelial (RPE tears have been published in the world literature. The main findings of our study included hyper-reflectant line breaks, choroidal hyper-reflectance due to the lack of RPE and RPE double layering where it was folded. Images were frequently associated with RPE tears and neurosensorial retinal detachment.

C. Torrón-Fernández-Blanco

2007-04-01

218

Image reconstruction in optical tomography using Radon transform and its inverse  

Science.gov (United States)

Optical tomography is a new medical imaging modality that is at the threshold of realization. A large amount of clinical work has shown the very real benefits that such a method could provide. At the same time a considerable effort has been put into theoretical studies of its probable success. At present there exist gaps between these two realms. In this paper we review some general approaches to inverse problems to set the context for optical tomography. An essential requirement is to treat the problem in a nonlinear fashion, by using an iterative method. The inverse problem is approached by numerical solutions methods using MathCad program. The Radon transform is the basic tool of the computerized tomography. In the sequel we introduce this transform, review some properties and present a numerical program for its inversion. We show some results that represent the most complex and realistic simulations of optical tomography yet developed.

Petrehus, Viorel; Gavrila, Camelia; Gruia, Ion

2009-10-01

219

Common path optical coherence tomography based on fiber bundle imager  

Science.gov (United States)

Optical coherence tomography (OCT) has emerged as a promising medical imaging modality that can provide non-invasive high-resolution tomographic imaging in real-time. Generating high-resolution OCT images in real-time requires a complicated and costly system design. Therefore, there has been an interest in the development of a common-path (CP) approach to OCT which utilizes a simple interferometer where the sample and reference arms share a common optical path. This configuration allows a much simpler system design, lower associated costs, and the ability to use interchangeable probes as well as the freedom to use any arbitrary probe arm length. In this thesis, novel CP optic probes and image processing methods that could make the CP-OCT a practical system for a high-resolution endoscopic imaging have been developed and investigated. Despite the advantages of CP based OCT configurations, CP-OCT have had limited applications since the reference signal is usually obtained from the Fresnel reflection from the distal end of the optical fiber probe. Thus, when the probe is submerged in an aqueous medium or in contact with a target, the magnitude of the reflected power decreases due to the reduced index difference at the fiber probe reference plane. To solve this problem, gold-plated fiber probes were investigated for in situ imaging of retina and surrounding tissues. The probe operating in an aqueous medium was able to provide OCT images that can differentiate various retinal layers. To obtain 2D images, OCT requires a series of axial scans performed by mechanical spatial translation of the probe or the beam. Most current OCT systems use various miniaturized scanning probes in order to obtain lateral scanning. Alternatively, fiber bundle imagers have recently been suggested. However, the results so far have not been promising due to the inefficient coupling of light into the cores and the non-uniformity of the fiber array. Since CP-OCT obtains the reference at the distal end of the probe, it can overcome the difference between the optical properties between the fiber bundle pixels. In this work, the feasibility of pseudo-scanningless probe has been explored based on fiber bundle imager in the CP-OCT. The mechanical lateral scans are accomplished outside the specimen at the proximal entrance of the fiber bundle. This eliminated the need for moving parts in the distal end of the probe. Finally, to enhance the quality of OCT images obtained using a fiber bundle imager. An image processing method that can remove the fiber bundle's pixelation artifact due to the inherent arrangement of the fiber core arrays is proposed and studied. This method of eliminating pixelization effect from en face OCT image is based on applying a histogram equalization process followed by a weighted-averaged Gaussian smoothing filtering to not only remove the structural artifact of the bundle but also to enhances the image quality with minimum blurring of object's image features.

Han, Jae Ho

220

Consensus standards for acquisition, measurement, and reporting of intravascular optical coherence tomography studies : a report from the international working group for intravascular optical coherence tomography standardization and validation  

DEFF Research Database (Denmark)

The purpose of this document is to make the output of the International Working Group for Intravascular Optical Coherence Tomography (IWG-IVOCT) Standardization and Validation available to medical and scientific communities, through a peer-reviewed publication, in the interest of improving the diagnosis and treatment of patients with atherosclerosis, including coronary artery disease.

Tearney, Guillermo J; Regar, Evelyn

2012-01-01

 
 
 
 
221

A proposed fibre optic time domain optical coherence tomography system using a micro-photonic stationary optical delay line  

Science.gov (United States)

Conventional time domain Optical Coherence Tomography (OCT) relies on a reference Optical Delay Line (ODL). These reference ODLs require the physical movement of a mirror to scan a given depth range. This movement results in instrument degradation. We propose a new optical fibre based time domain OCT system that makes use of a micro-photonic structure as a stationary ODL. The proposed system uses an in-fibre interferometer, either a Michelson or a Mach-Zhender. The reference ODL makes use of a collimator to expand the light from the optical fibre. This is them expanded in one dimension via planar optics, that is, a cylindrical lens based telescope, using a concave and convex lens. The expanded beam is them passed through a transmissive Spatial Light Modulator (SLM), specifically a liquid crystal light valve used as an optical switch. Light is then reflected back through the system off the micro-photonic structure. The micro-photonic structure is a one dimensional array of stagged mirror steps, called a Stepped Mirror Structure (SMS). The system enables the selection of discrete optical delay lengths. The proposed ODL is capable of depth hoping and multicasting. We discuss the fabrication of the SMS, which consists of eight steps, each approximately 150 ?m high. A change in notch frequency using an in-fibre Mach Zhender interferometer was used to gauge the average step height. The results gave an average step height of 146 ?m.

Jansz, Paul Vernon; Wild, Graham; Hinckley, Steven

2008-04-01

222

Evaluation of caries-affected dentin with optical coherence tomography  

Directory of Open Access Journals (Sweden)

Full Text Available The purpose of this study was to evaluate the degree of demineralization of artificially induced caries-affected human dentin by an in vitro microbiological method. The occlusal surfaces of 6 human molar teeth were abraded until a flat surface was obtained, and the enamel was removed to expose the occlusal dentin surface. These teeth were sectioned in 12 halves in the vestibular-lingual direction and divided into 3 groups according to the period length of the microbiological essay (n = 4: G1, 7 days; G2, 14 days; and G3, 21 days. The surfaces of all specimens were protected by an acid-resistant nail varnish, except for a window where the caries lesion was induced by a Streptoccocus mutans biofilm in a batch-culture model supplemented with 5% sucrose. The specimens were then analyzed by optical coherence tomography (OCT with a super-luminescent light diode (? = 930 nm with 6.0-µm lateral and longitudinal resolution (in the air. Qualitative and quantitative results (images and average dentin demineralization, respectively were obtained. The mean demineralization depths were (µm 235 ± 31.4, 279 ± 14, and 271 ± 8.3 in groups 1, 2, and 3, respectively. In addition, no significant change was observed in the lesion mean depth from 7 days of cariogenic challenge on. In conclusion, OCT was shown to be an efficient and non-invasive method to detect the depths of lesions caused by demineralization. Further, a seven-day demineralization time was considered sufficient for caries-affected dentin to be obtained.

Cynthia Soares de Azevedo

2011-10-01

223

Efficient reduction of speckle noise in Optical Coherence Tomography.  

Science.gov (United States)

Speckle pattern, which is inherent in coherence imaging, influences significantly axial and transversal resolution of Optical Coherence Tomography (OCT) instruments. The well known speckle removal techniques are either sensitive to sample motion, require sophisticated and expensive sample tracking systems, or involve sophisticated numerical procedures. As a result, their applicability to in vivo real-time imaging is limited. In this work, we propose to average multiple A-scans collected in a fully controlled way to reduce the speckle contrast. This procedure involves non-coherent averaging of OCT A-scans acquired from adjacent locations on the sample. The technique exploits scanning protocol with fast beam deflection in the direction perpendicular to lateral dimension of the cross-sectional image. Such scanning protocol reduces the time interval between A-scans to be averaged to the repetition time of the acquisition system. Consequently, the averaging algorithm is immune to bulk motion of an investigated sample, does not require any sophisticated data processing to align cross-sectional images, and allows for precise control of lateral shift of the scanning beam on the object. The technique is tested with standard Spectral OCT system with an extra resonant scanner used for rapid beam deflection in the lateral direction. Ultrahigh speed CMOS camera serves as a detector and acquires 200,000 spectra per second. A dedicated A-scan generation algorithm allows for real-time display of images with reduced speckle contrast at 6 frames/second. This technique is applied to in vivo imaging of anterior and posterior segments of the human eye and human skin. PMID:22274479

Szkulmowski, Maciej; Gorczynska, Iwona; Szlag, Daniel; Sylwestrzak, Marcin; Kowalczyk, Andrzej; Wojtkowski, Maciej

2012-01-16

224

Performance comparison of different metrics for spectroscopic optical coherence tomography  

Science.gov (United States)

When light interacts with a scattering medium, the spectrum of the incident light undergoes changes that are dependent on the size of the scatterers in the medium. Spectroscopic Optical Coherence Tomography (S-OCT) is a method that can be used to ascertain the resulting spatially-dependent spectral information. In fact, S-OCT is sensitive to structures that are below the spatial resolution of the system, making S-OCT a promising tool for diagnosing many diseases and biological processes that change tissue structure, like cancer. The most important signal processing steps for S-OCT are the depth-resolved spectral analysis and the calculation of a spectroscopic metric. While the former calculates the spectra from the raw OCT data, the latter analyzes the information content of the processed depth-resolved spectra. We combine the Dual Window spectral analysis with different spectroscopic metrics, which are used as an input to colorize intensity based images. These metrics include the spectral center of mass method, principal component (PCA) and phasor analysis. To compare the performance of the metrics in a quantitative manner, we use a cluster algorithm to calculate efficiencies for all methods. For this purpose we use phantom samples which contain areas of microspheres of different sizes. Our results demonstrate that PCA and phasor analysis have the highest efficiencies, and can clearly separate these areas. Finally we will present data from cartilage tissue under static load in vitro. These preliminary results show that S-OCT can generate additional contrast in biological tissue in comparison to the pure intensity based images.

Jaedicke, Volker; Agcaer, Semih; Robles, Francisco E.; Steinert, Marian; Jones, David; Goebel, Sebastian; Gerhardt, Nils C.; Welp, Hubert; Hofmann, Martin R.

2014-03-01

225

Evaluation of caries-affected dentin with optical coherence tomography  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english The purpose of this study was to evaluate the degree of demineralization of artificially induced caries-affected human dentin by an in vitro microbiological method. The occlusal surfaces of 6 human molar teeth were abraded until a flat surface was obtained, and the enamel was removed to expose the o [...] cclusal dentin surface. These teeth were sectioned in 12 halves in the vestibular-lingual direction and divided into 3 groups according to the period length of the microbiological essay (n = 4): G1, 7 days; G2, 14 days; and G3, 21 days. The surfaces of all specimens were protected by an acid-resistant nail varnish, except for a window where the caries lesion was induced by a Streptoccocus mutans biofilm in a batch-culture model supplemented with 5% sucrose. The specimens were then analyzed by optical coherence tomography (OCT) with a super-luminescent light diode (? = 930 nm) with 6.0-µm lateral and longitudinal resolution (in the air). Qualitative and quantitative results (images and average dentin demineralization, respectively) were obtained. The mean demineralization depths were (µm) 235 ± 31.4, 279 ± 14, and 271 ± 8.3 in groups 1, 2, and 3, respectively. In addition, no significant change was observed in the lesion mean depth from 7 days of cariogenic challenge on. In conclusion, OCT was shown to be an efficient and non-invasive method to detect the depths of lesions caused by demineralization. Further, a seven-day demineralization time was considered sufficient for caries-affected dentin to be obtained.

Cynthia Soares de, Azevedo; Luciana Cardoso Espejo, Trung; Maria Regina Lorenzetti, Simionato; Anderson Zanardi de, Freitas; Adriana Bona, Matos.

226

Statistical analysis of high density diffuse optical tomography.  

Science.gov (United States)

High density diffuse optical tomography (HD-DOT) is a noninvasive neuroimaging modality with moderate spatial resolution and localization accuracy. Due to portability and wear-ability advantages, HD-DOT has the potential to be used in populations that are not amenable to functional magnetic resonance imaging (fMRI), such as hospitalized patients and young children. However, whereas the use of event-related stimuli designs, general linear model (GLM) analysis, and imaging statistics are standardized and routine with fMRI, such tools are not yet common practice in HD-DOT. In this paper we adapt and optimize fundamental elements of fMRI analysis for application to HD-DOT. We show the use of event-related protocols and GLM de-convolution analysis in un-mixing multi-stimuli event-related HD-DOT data. Statistical parametric mapping (SPM) in the framework of a general linear model is developed considering the temporal and spatial characteristics of HD-DOT data. The statistical analysis utilizes a random field noise model that incorporates estimates of the local temporal and spatial correlations of the GLM residuals. The multiple-comparison problem is addressed using a cluster analysis based on non-stationary Gaussian random field theory. These analysis tools provide access to a wide range of experimental designs necessary for the study of the complex brain functions. In addition, they provide a foundation for understanding and interpreting HD-DOT results with quantitative estimates for the statistical significance of detected activation foci. PMID:23732886

Hassanpour, Mahlega S; White, Brian R; Eggebrecht, Adam T; Ferradal, Silvina L; Snyder, Abraham Z; Culver, Joseph P

2014-01-15

227

Mechanical tissue optical clearing devices: evaluation of enhanced light penetration in skin using optical coherence tomography  

Science.gov (United States)

We report results of a study to evaluate effectiveness of a mechanical tissue optical clearing device (TOCD) using optical coherence tomography (OCT). The TOCD uses a pin array and vacuum pressure source to compress localized regions of the skin surface. OCT images (850 and 1310 nm) of in vivo human skin indicate application of the TOCD provides an up to threefold increased light penetration depth at spatial positions correlated with pin indentations. Increased contrast of the epidermal-dermal junction in OCT images spatially correlates with indented zones. OCT M-scans recorded while applying the TOCD indicate optical penetration depth monotonically increased, with most improvement at early times (5 to 10 s) of TOCD vacuum application. OCT M-scans of ex vivo porcine skin compressed using the TOCD suggest average group refractive index of the tissue increased, corresponding to a decrease in water concentration. Results of our study indicate that mechanical optical clearing of skin may provide an effective and efficient means to deliver increased light fluence to dermal and subdermal regions.

Drew, Christopher; Milner, Thomas E.; Rylander, Christopher G.

2009-11-01

228

Changes in retinal nerve fiber layer and optic disc algorithms by optical coherence tomography in glaucomatous Arab subjects  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Ferial M Zeried, Uchechukwu L Osuagwu Department of Optometry and Vision Sciences College of Applied Medical Sciences, King Saud University, Riyadh, Kingdom of Saudi Arabia Purpose: To assess the difference in retinal nerve fiber layer (RNFL) and optic disc algorithms between glaucomatous and normal Arab subjects using optical coherence tomography (OCT). Methods: RNFL thickness and optic disc parameters were obtained in 65 patients aged 50.1 ± 7.7 years. Percentage differences in all p...

Fm, Zeried; Ul, Osuagwu

2013-01-01

229

The collagen structure of equine articular cartilage, characterized using polarization-sensitive optical coherence tomography  

International Nuclear Information System (INIS)

Optical coherence tomography and polarization-sensitive optical coherence tomography images of equine articular cartilage are presented. Measurements were made on intact joint surfaces. Significant (e.g. x 2) variations in the intrinsic birefringence were found over spatial scales of a few millimetres, even on samples taken from young (18 month) animals that appeared visually homogeneous. A comparison of data obtained on a control tissue (equine flexor tendon) further suggests that significant variations in the orientation of the collagen fibres relative to the plane of the joint surface exist. Images of visually damaged cartilage tissue show characteristic features both in terms of the distribution of optical scatterers and of the birefringent components

230

Quantitative evaluation of systematic imaging error due to uncertainty in tissue optical properties in high-density diffuse optical tomography  

Science.gov (United States)

In MRI-guided diffuse optical tomography of the human brain function, three-dimensional anatomical head model consisting of up to five segmented tissue types can be specified. With disregard to misclassification between different tissues, uncertainty in the optical properties of each tissue type becomes the dominant cause of systematic error in image reconstruction. In this study we present a quantitative evaluation of image resolution dependence due to such uncertainty. Our results show that given a head model which provides a realistic description of its tissue optical property distribution, high-density diffuse optical tomography with cortically constrained image reconstruction are capable of detecting focal activation up to 21.81 mm below the human scalp at an imaging quality better than or equal to 1.0 cm in localization error and 1.0 cm3 in FVHM with a tolerance of uncertainty in tissue optical properties between +15% and -20%.

Zhan, Yuxuan; Eggebrecht, Adam; Dehghani, Hamid; Culver, Joseph

2011-02-01

231

Optical scattering coefficient estimated by optical coherence tomography correlates with collagen content in ovarian tissue  

Science.gov (United States)

Optical scattering coefficient from ex vivo unfixed normal and malignant ovarian tissue was quantitatively extracted by fitting optical coherence tomography (OCT) A-line signals to a single scattering model. 1097 average A-line measurements at a wavelength of 1310 nm were performed at 108 sites obtained from 18 ovaries. The average scattering coefficient obtained from the normal tissue group consisted of 833 measurements from 88 sites was 2.41 mm-1 (+/-0.59), while the average coefficient obtained from the malignant tissue group consisted of 264 measurements from 20 sites was 1.55 mm-1 (+/-0.46). The malignant ovarian tissue showed significant lower scattering than the normal group (p CAF) obtained from the normal tissue group was 48.4% (+/-12.3%), while the average CAF obtained from the malignant tissue group was 11.4% (+/-4.7%). A statistical significance of the collagen content was found between the two groups (p < 0.001). These results demonstrated that quantitative measurements of optical scattering coefficient from OCT images could be a potential powerful method for ovarian cancer detection.

Yang, Yi; Wang, Tianheng; Biswal, Nrusingh C.; Wang, Xiaohong; Sanders, Melinda; Brewer, Molly; Zhu, Quing

2011-09-01

232

Crystal Optical Properties of Inhomogeneous Plates and the Problems of Polarization Tomography of Photoelastic Materials  

Directory of Open Access Journals (Sweden)

Full Text Available Using the Jones matrix formalism, crystal optical properties of inhomogeneous material consisting of a pile of weakly birefringent plates are analysed in relation to the cell model adopted in polarization tomography of 3D dielectric tensor field in photoelastic media. It is shown that the material manifests in general an “apparent” optical gyration caused by different orientations of the plates. Relations between the polarimetric parameters and the dielectric tensor components are ascertained for the case of weak optical anisotropy.

Kushnir O.

2005-09-01

233

Optical Coherence Tomography (OCT): Imaging the Visual Pathway as a Model for Neurodegeneration  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Axonal and neuronal degeneration are important features of multiple sclerosis (MS) and other neurologic disorders that affect the anterior visual pathway. Optical coherence tomography (OCT) is a non-invasive technique that allows imaging of the retinal nerve fiber layer (RNFL), a structure which is principally composed of ganglion cell axons that form the optic nerves, chiasm, and optic tracts. Since retinal axons are nonmyelinated until they penetrate the lamina cribrosa, the RNFL is an idea...

Galetta, Kristin M.; Calabresi, Peter A.; Frohman, Elliot M.; Balcer, Laura J.

2011-01-01

234

Optical coherence tomography: technology and applications (biological and medical physics, biomedical engineering)  

CERN Document Server

Optical coherence tomography (OCT) is the optical analog of ultrasound imaging and is emerging as a powerful imaging technique that enables non-invasive, in vivo, high resolution, cross-sectional imaging in biological tissue. This book introduces OCT technology and applications not only from an optical and technological viewpoint, but also from biomedical and clinical perspectives. The chapters are written by leading research groups, in a style comprehensible to a broad audience.

2013-01-01

235

Patency of small laser iridotomy evaluated using anterior-segment optical coherence tomography  

Directory of Open Access Journals (Sweden)

Full Text Available Seigo Nakabayashi, Motofumi Kawai, Toru Yamaguchi, Akitoshi Yoshida Department of Ophthalmology, Asahikawa Medical University, Asahikawa, Japan Abstract: We report the case of a patient with recurrent acute angle-closure glaucoma who had undergone a previous laser iridotomy. Because the initial iridotomy was small, patency could not be determined by slit-lamp examination. Therefore, anterior-segment optical coherence tomography was used to evaluate the patency. Cross-sectional images showed the presence of a membrane with an anterior bowing configuration at the base of the iridotomy, suggesting that recurrent pupillary block was the causative mechanism. A repeat laser iridotomy was performed, with a resultant decrease in the intraocular pressure and widening of the anterior chamber angle. Anterior-segment optical coherence tomography may be helpful to confirm the status of a laser iridotomy, especially when the iridotomy is small. Keywords: anterior-segment optical coherence tomography, laser iridotomy, acute angle-closure glaucoma

Nakabayashi S

2014-03-01

236

Functional imaging in bulk tissue specimens using optical emission tomography: fluorescence preservation during optical clearing  

Science.gov (United States)

Optical emission computed tomography (optical-ECT) is a technique for imaging the three-dimensional (3D) distribution of fluorescent probes in biological tissue specimens with high contrast and spatial resolution. In optical-ECT, functional information can be imaged by (i) systemic application of functional labels (e.g. fluorophore labelled proteins) and/or (ii) endogenous expression of fluorescent reporter proteins (e.g. red fluorescent protein (RFP), green fluorescent protein (GFP)) in vivo. An essential prerequisite for optical-ECT is optical clearing, a procedure where tissue specimens are made transparent to light by sequential perfusion with fixing, dehydrating and clearing agents. In this study, we investigate clearing protocols involving a selection of common fixing (4% buffered paraformaldehyde (PFA), methanol and ethanol), dehydrating (methanol and ethanol) and clearing agents (methyl salicylate and benzyl-alcohol-benzyl-benzoate (BABB)) in order to determine a 'fluorescence friendly' clearing procedure. Cell culture experiments were employed to optimize the sequence of chemical treatments that best preserve fluorescence. Texas red (TxRed), fluorescein isothiocyanate (FITC), RFP and GFP were tested as fluorophores and fluorescent reporter proteins of interest. Fluorescent and control cells were imaged on a microscope using a DSred2 and FITC filter set. The most promising clearing protocols of cell culture experiments were applied to whole xenograft tumour specimens, to test their effectiveness in large unsectioned samples. Fluorescence of TxRed/FITC fluorophores was not found to be significantly affected by any of the test clearing protocols. RFP and GFP fluorescence, however, was found to be significantly greater when cell fixation was in ethanol. Fixation in either PFA or methanol resulted in diminished fluorescence. After ethanol fixation, the RFP and GFP fluorescence proved remarkably robust to subsequent exposure to either methyl salicylate or BABB. The optimized optical clearing procedure of ethanol fixation followed by methyl salicylate clearing preserved the fluorescence of constitutive RFP in whole xenograft tumour specimens, about 1 cc in dimension, indicating successful extension from cell plating experiments to whole tissue samples. Finally, the feasibility of imaging the 3D distribution of viable tumour cells (as indicated by the RFP emission) is demonstrated by optical-ECT imaging of cleared xenograft tumours using an in-house system.

Sakhalkar, H. S.; Dewhirst, M.; Oliver, T.; Cao, Y.; Oldham, M.

2007-04-01

237

Functional imaging in bulk tissue specimens using optical emission tomography: fluorescence preservation during optical clearing  

Energy Technology Data Exchange (ETDEWEB)

Optical emission computed tomography (optical-ECT) is a technique for imaging the three-dimensional (3D) distribution of fluorescent probes in biological tissue specimens with high contrast and spatial resolution. In optical-ECT, functional information can be imaged by (i) systemic application of functional labels (e.g. fluorophore labelled proteins) and/or (ii) endogenous expression of fluorescent reporter proteins (e.g. red fluorescent protein (RFP), green fluorescent protein (GFP)) in vivo. An essential prerequisite for optical-ECT is optical clearing, a procedure where tissue specimens are made transparent to light by sequential perfusion with fixing, dehydrating and clearing agents. In this study, we investigate clearing protocols involving a selection of common fixing (4% buffered paraformaldehyde (PFA), methanol and ethanol), dehydrating (methanol and ethanol) and clearing agents (methyl salicylate and benzyl-alcohol-benzyl-benzoate (BABB)) in order to determine a 'fluorescence friendly' clearing procedure. Cell culture experiments were employed to optimize the sequence of chemical treatments that best preserve fluorescence. Texas red (TxRed), fluorescein isothiocyanate (FITC), RFP and GFP were tested as fluorophores and fluorescent reporter proteins of interest. Fluorescent and control cells were imaged on a microscope using a DSred2 and FITC filter set. The most promising clearing protocols of cell culture experiments were applied to whole xenograft tumour specimens, to test their effectiveness in large unsectioned samples. Fluorescence of TxRed/FITC fluorophores was not found to be significantly affected by any of the test clearing protocols. RFP and GFP fluorescence, however, was found to be significantly greater when cell fixation was in ethanol. Fixation in either PFA or methanol resulted in diminished fluorescence. After ethanol fixation, the RFP and GFP fluorescence proved remarkably robust to subsequent exposure to either methyl salicylate or BABB. The optimized optical clearing procedure of ethanol fixation followed by methyl salicylate clearing preserved the fluorescence of constitutive RFP in whole xenograft tumour specimens, about 1 cc in dimension, indicating successful extension from cell plating experiments to whole tissue samples. Finally, the feasibility of imaging the 3D distribution of viable tumour cells (as indicated by the RFP emission) is demonstrated by optical-ECT imaging of cleared xenograft tumours using an in-house system.

Sakhalkar, H S [Department of Radiation Oncology, Duke University Medical Center, Durham, NC 27710 (United States); Dewhirst, M [Department of Radiation Oncology, Duke University Medical Center, Durham, NC 27710 (United States); Oliver, T [Department of Cell Biology, Duke University Medical Center, Durham, NC 27710 (United States); Cao, Y [Department of Radiation Oncology, Duke University Medical Center, Durham, NC 27710 (United States); Oldham, M [Department of Radiation Oncology Physics, and Biomedical Engineering, Duke University Medical Center, Durham, NC 27710 (United States)

2007-04-21

238

Optic nerve head analysis of superior segmental optic hypoplasia using Heidelberg retina tomography  

Directory of Open Access Journals (Sweden)

Full Text Available Atsushi Miki1,2, Motohiro Shirakashi1, Kiyoshi Yaoeda1, Atsushi Fukushima1, Mineo Takagi1, Haruki Abe11Division of Ophthalmology and Visual Sciences, Niigata University Graduate School of Medical and Dental Sciences, Niigata, 2Department of Ophthalmology, Kawasaki Medical School, Okayama, JapanPurpose: To evaluate the optic disc characteristics of eyes with superior segmental optic hypoplasia (SSOH using the Heidelberg retina tomograph (HRT.Patients and methods: Thirteen eyes of 13 Japanese patients with SSOH were studied with the HRT (software version: 3.0. The group included six males and seven females, with a mean age of 34.7 years. Six optic disc parameters in the six sectors derived from the patients with SSOH were compared with those of 13 eyes of 13 normal controls. In addition, the diagnostic classification performance of the Frederick S Mikelberg (FSM discriminant function, glaucoma probability score (GPS, and Moorfields regression analysis (MRA were assessed.Results: When compared with normal subjects, many of the optic disc parameters were significantly altered in SSOH in the superior sectors. The area under the curve (AUC for the receiver operating characteristic was 0.932 for the rim area, 0.926 for the cup-to-disc area ratio, and 0.882 for the cup shape measure. Among the HRT parameters, the largest AUC (0.988 was found for the cup shape measure in the nasal superior segment. The proportion classified as outside normal limits by the FSM discriminant function was 92.3% (12 eyes. For GPS, six eyes (46.2% were classified as outside normal limits. For MRA, when borderline cases were considered test-negative or test-positive, 10 eyes (76.9% or 11 eyes (84.6% were classified as outside normal limits, respectively. The AUCs were 0.976 for the FSM discriminant function, 0.914 for the MRA overall classification, and 0.710 for the GPS overall classification.Conclusions: In eyes with SSOH, there is a significant thinning of the rim, especially in the nasal superior sector. Approximately half of the eyes with SSOH were classified as abnormal using indices developed for detecting glaucoma, but the sectorial analysis revealed that the affected sectors were different from those of glaucoma. Optic nerve head measurements using the HRT may be useful in evaluating the optic disc characteristics in eyes with SSOH.Keywords: superior segmental optic hypoplasia, Heidelberg retina tomography

Atsushi Miki

2010-10-01

239

Functional imaging in bulk tissue specimens using optical emission tomography: fluorescence preservation during optical clearing  

International Nuclear Information System (INIS)

Optical emission computed tomography (optical-ECT) is a technique for imaging the three-dimensional (3D) distribution of fluorescent probes in biological tissue specimens with high contrast and spatial resolution. In optical-ECT, functional information can be imaged by (i) systemic application of functional labels (e.g. fluorophore labelled proteins) and/or (ii) endogenous expression of fluorescent reporter proteins (e.g. red fluorescent protein (RFP), green fluorescent protein (GFP)) in vivo. An essential prerequisite for optical-ECT is optical clearing, a procedure where tissue specimens are made transparent to light by sequential perfusion with fixing, dehydrating and clearing agents. In this study, we investigate clearing protocols involving a selection of common fixing (4% buffered paraformaldehyde (PFA), methanol and ethanol), dehydrating (methanol and ethanol) and clearing agents (methyl salicylate and benzyl-alcohol-benzyl-benzoate (BABB)) in order to determine a 'fluorescence friendly' clearing procedure. Cell culture experiments were employed to optimize the sequence of chemical treatments that best preserve fluorescence. Texas red (TxRed), fluorescein isothiocyanate (FITC), RFP and GFP were tested as fluorophores and fluorescent reporter proteins of interest. Fluorescent and control cells were imaged on a microscope using a DSred2 and FITC filter set. The most promising clearing protocols of cell culture experiments were applied to whole xenograft tumour sp were applied to whole xenograft tumour specimens, to test their effectiveness in large unsectioned samples. Fluorescence of TxRed/FITC fluorophores was not found to be significantly affected by any of the test clearing protocols. RFP and GFP fluorescence, however, was found to be significantly greater when cell fixation was in ethanol. Fixation in either PFA or methanol resulted in diminished fluorescence. After ethanol fixation, the RFP and GFP fluorescence proved remarkably robust to subsequent exposure to either methyl salicylate or BABB. The optimized optical clearing procedure of ethanol fixation followed by methyl salicylate clearing preserved the fluorescence of constitutive RFP in whole xenograft tumour specimens, about 1 cc in dimension, indicating successful extension from cell plating experiments to whole tissue samples. Finally, the feasibility of imaging the 3D distribution of viable tumour cells (as indicated by the RFP emission) is demonstrated by optical-ECT imaging of cleared xenograft tumours using an in-house system

240

Diagnostic ability of barrett's index to detect dysthyroid optic neuropathy using multidetector computed tomography  

Directory of Open Access Journals (Sweden)

Full Text Available OBJECTIVES: The objective of this study was to evaluate the ability of a muscular index (Barrett's Index, calculated with multidetector computed tomography, to detect dysthyroid optic neuropathy in patients with Graves' orbitopathy. METHODS: Thirty-six patients with Graves' orbitopathy were prospectively studied and submitted to neuro-ophthalmic evaluation and multidetector computed tomography scans of the orbits. Orbits were divided into two groups: those with and without dysthyroid optic neuropathy. Barrett's index was calculated as the percentage of the orbit occupied by muscles. Sensitivity and specificity were determined for several index values. RESULTS: Sixty-four orbits (19 with and 45 without dysthyroid optic neuropathy met the inclusion criteria for the study. The mean Barrett's index values (± SD were 64.47% ± 6.06% and 49.44% ± 10.94%in the groups with and without dysthyroid optic neuropathy, respectively (p60% should be carefully examined and followed for the development of dysthyroid optic neuropathy.

Mário L. R. Monteiro

2008-01-01

 
 
 
 
241

Coronary optical coherence tomography: minimally invasive virtual histology as part of targeted post-mortem computed tomography angiography.  

Science.gov (United States)

Social, cultural and practical barriers to conventional invasive autopsy have led to considerable interest in the development of minimally invasive radiological techniques as an alternative to the invasive autopsy for determining the cause of death. Critical to accurate diagnosis in this context is detailed examination of coronary anatomy and pathology. Current computed tomography and magnetic resonance imaging approaches have significantly advanced minimally invasive autopsy practice but have limited spatial resolution. This prohibits assessment at a microscopic level, meaning that histological assessment is still required for detailed analysis of, for example, coronary plaque rupture or dissection. Coronary optical coherence tomography (OCT) is used in the living during percutaneous coronary interventions to provide high-resolution coronary imaging, but this technique for obtaining virtual histology has not, to date, been translated into minimally invasive autopsy practice. We present a first description of minimally invasive post-mortem coronary OCT and discuss the potential for this technique to advance current practice. PMID:23455719

Adlam, David; Joseph, Shiju; Robinson, Claire; Rousseau, Clement; Barber, Jade; Biggs, Mike; Morgan, Bruno; Rutty, Guy

2013-09-01

242

Effects of Age on Optical Coherence Tomography Measurements of Healthy Retinal Nerve Fiber Layer, Macula, and Optic Nerve Head  

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Purpose—To determine the effects of age on global and sectoral peripapillary retinal nerve fiber layer (RNFL), macular thicknesses and optic nerve head (ONH) parameters in healthy subjects using optical coherence tomography (OCT). Design—Retrospective, cross-sectional observational study. Participants—226 eyes from 124 healthy subjects were included. Methods—Healthy subjects were scanned using the Fast RNFL, Fast Macula, and Fast ONH scan patterns on a Stratus OCT. A...

Sung, Kyung Rim; Wollstein, Gadi; Bilonick, Richard A.; Townsend, Kelly A.; Ishikawa, Hiroshi; Kagemann, Larry; Noecker, Robert J.; Fujimoto, James G.; Schuman, Joel S.

2009-01-01

243

Review of tissue simulating phantoms with controllable optical, mechanical and structural properties for use in optical coherence tomography  

Science.gov (United States)

We review the development of phantoms for optical coherence tomography (OCT) designed to replicate the optical, mechanical and structural properties of a range of tissues. Such phantoms are a key requirement for the continued development of OCT techniques and applications. We focus on phantoms based on silicone, fibrin and poly(vinyl alcohol) cryogels (PVA-C), as we believe these materials hold the most promise for durable and accurate replication of tissue properties. PMID:22741083

Lamouche, Guy; Kennedy, Brendan F.; Kennedy, Kelsey M.; Bisaillon, Charles-Etienne; Curatolo, Andrea; Campbell, Gord; Pazos, Valerie; Sampson, David D.

2012-01-01

244

Two cases of X-linked retinoschisis with different spectral domain optical coherence tomography findings.  

Science.gov (United States)

Spectral domain optical coherence tomography was used to image the maculae of two brothers who had the diagnosis of X-linked retinoschisis maculopathy. One patient demonstrated a large foveal cyst in one eye and a lamellar macular hole in the fellow eye. The second patient demonstrated small retinal cysts in multiple layers of the retina. Spectral domain optical coherence tomography allowed high-resolution imaging and characterization of the features in X-linked retinoschisis in these patients, and it highlighted the variability of the same genetic disease, even in one family. PMID:23055679

Leng, Theodore

2012-01-01

245

Megahertz all-optical swept-source optical coherence tomography based on broadband amplified optical time-stretch.  

Science.gov (United States)

We demonstrate all-optical ultrahigh-speed swept-source optical coherence tomography (OCT) based on amplified optical time-stretch (AOT). Such an inertia-free wavelength-swept mechanism, via group velocity dispersion, enables us to realize OCT with an A-scan rate well above MHz. More importantly, the key significance of AOT-OCT is its simultaneous broadband Raman amplification during the time-stretch process-greatly enhancing the detection sensitivity compared with prior attempts to apply optical time-stretch to OCT. Here, we report on an AOT-OCT system which is operated at an A-scan rate of 7.14 MHz, a superior roll-off performance (>2 mm/dB), a record-high sensitivity of time-stretch-based OCT (>80 dB) with a broadband gain bandwidth of 80 nm, which results in an axial resolution of ?15 ?m. Our AOT-OCT system is thus able to, for the first time to the best of our knowledge, perform time-stretch-based OCT of biological tissue in vivo. It represents a major step forward in utilizing AOT as an alternative for achieving practical MHz OCT, without any long-term mechanical stability concerns as in typical swept-source OCT or bypassing the speed limitation of the image sensor employed in spectral-domain OCT. PMID:24487881

Xu, Jingjiang; Zhang, Chi; Xu, Jianbing; Wong, K K Y; Tsia, K K

2014-02-01

246

Integrated optical coherence tomography and optical coherence microscopy imaging of human pathology  

Science.gov (United States)

Excisional biopsy is the current gold standard for disease diagnosis; however, it requires a relatively long processing time and it may also suffer from unacceptable false negative rates due to sampling errors. Optical coherence tomography (OCT) is a promising imaging technique that provide real-time, high resolution and three-dimensional (3D) images of tissue morphology. Optical coherence microscopy (OCM) is an extension of OCT, combining both the coherence gating and the confocal gating techniques. OCM imaging achieves cellular resolution with deeper imaging depth compared to confocal microscopy. An integrated OCT/OCM imaging system can provide co-registered multiscale imaging of tissue morphology. 3D-OCT provides architectural information with a large field of view and can be used to find regions of interest; while OCM provides high magnification to enable cellular imaging. The integrated OCT/OCM system has an axial resolution of specimens, including colon (58), thyroid (43), breast (34), and kidney (19), were imaged with OCT and OCM within 2 to 6 hours after excision. The images were compared with H & E histology to identify characteristic features useful for disease diagnosis. The feasibility of visualizing human pathology using integrated OCT/OCM was demonstrated in the pathology laboratory settings.

Lee, Hsiang-Chieh; Zhou, Chao; Wang, Yihong; Aquirre, Aaron D.; Tsai, Tsung-Han; Cohen, David W.; Connolly, James L.; Fujimoto, James G.

2010-02-01

247

Adaptive optics-assisted optical coherence tomography for imaging of patients with age related macular degeneration  

Science.gov (United States)

We developed an optical coherence tomography (OCT) prototype with a sample arm that uses a 3.4 mm beam, which is considerably larger than the 1.2 to 1.5 mm beam that is used in commercialized OCT systems. The system is equipped with adaptive optics (AO), and to distinguish it from traditional AO-OCT systems with a larger 6 mm beam we have coined this concept AO-assisted OCT. Compared to commercialized OCT systems, the 3.4 mm aperture combined with AO improves light collection efficiency and imaging lateral resolution. In this paper, the performance of the AOa-OCT system was compared to a standard OCT system and demonstrated for imaging of age-related macular degeneration (AMD). Measurements were performed on the retinas of three human volunteers with healthy eyes and on one eye of a patient diagnosed with AMD. The AO-assisted OCT system imaged retinal structures of healthy human eyes and a patient eye affected by AMD with higher lateral resolution and a 9° by 9° field of view. This combination of a large isoplanatic patch and high lateral resolution can be expected to fill a gap between standard OCT with a 1.2 mm beam and conventional AO-OCT with a 6 mm beam and a 1.5° by 1.5° isoplanatic patch.

Sudo, Kenta; Cense, Barry

2013-03-01

248

Simultaneous topography and tomography of latent fingerprints using full-field swept-source optical coherence tomography  

Science.gov (United States)

We demonstrate simultaneous topography and tomography of latent fingerprints using full-field swept-source optical coherence tomography (OCT). The swept-source OCT system comprises a superluminescent diode (SLD) as broad-band light source, an acousto-optic tunable filter (AOTF) as frequency tuning device, and a compact, nearly common-path interferometer. Both the amplitude and the phase map of the interference fringe signal are reconstructed. Optical sectioning of the latent fingerprint sample is obtained by selective Fourier filtering and the topography is retrieved from the phase map. Interferometry, selective filtering, low coherence and hence better resolution are some of the advantages of the proposed system over the conventional fingerprint detection techniques. The present technique is non-invasive in nature and does not require any physical or chemical processing. Therefore, the quality of the sample does not alter and hence the same fingerprint can be used for other types of forensic test. Exploitation of low-coherence interferometry for fingerprint detection itself provides an edge over other existing techniques as fingerprints can even be lifted from low-reflecting surfaces. The proposed system is very economical and compact.

Dubey, Satish Kumar; Singh Mehta, Dalip; Anand, Arun; Shakher, Chandra

2008-01-01

249

Self optical motion-tracking for endoscopic optical coherence tomography probe using micro-beamsplitter probe  

Science.gov (United States)

Long range optical coherence tomography (OCT), with its high speed, high resolution, non-ionized properties and cross-sectional imaging capability, is suitable for upper airway lumen imaging. To render 2D OCT datasets to true 3D anatomy, additional tools are usually applied, such as X-ray guidance or a magnetic sensor. X-ray increases ionizing radiation. A magnetic sensor either increases probe size or requires an additional pull-back of the tracking sensor through the body cavity. In order to overcome these limitations, we present a novel tracking method using a 1.5 mm×1.5mm, 90/10-ratio micro-beamsplitter: 10% light through the beam-splitter is used for motion tracking and 90% light is used for regular OCT imaging and motion tracking. Two signals corresponding to these two split-beams that pass through different optical path length delays are obtained by the detector simultaneously. Using the two split beams' returned signals from the same marker line, the 2D inclination angle of each step is computed. By calculating the 2D inclination angle of each step and then connecting the translational displacements of each step, we can obtain the 2D motion trajectory of the probe. With two marker lines on the probe sheath, 3D inclination angles can be determined and then used for 3D trajectory reconstruction. We tested the accuracy of trajectory reconstruction using the probe and demonstrated the feasibility of the design for structure reconstruction of a biological sample using a porcine trachea specimen. This optical-tracking probe has the potential to be made as small as an outer diameter of 1.0mm, which is ideal for upper airway imaging.

Li, Jiawen; Zhang, Jun; Chou, Lidek; Wang, Alex; Jing, Joseph; Chen, Zhongping

2014-03-01

250

Tomography  

International Nuclear Information System (INIS)

Already widely accepted in medicine, tomography can also be useful in industry. The theory behind tomography and a demonstration of the technique to inspect a motorcycle carburetor is presented. To demonstrate the potential of computer assisted tomography (CAT) to accurately locate defects in three dimensions, a sectioned 5 cm gate valve with a shrink cavity made visible by the sectioning was tomographically imaged using a Co-60 source. The tomographic images revealed a larger cavity below the sectioned surface. The position of this cavity was located with an in-plane and axial precision of approximately +-1 mm. The volume of the cavity was estimated to be approximately 40 mm3

251

Optical coherence tomography: Monte Carlo simulation and improvement by optical amplification  

DEFF Research Database (Denmark)

An advanced novel Monte Carlo simulation model of the detection process of an optical coherence tomography (OCT) system is presented. For the first time it is shown analytically that the applicability of the incoherent Monte Carlo approach to model the heterodyne detection process of an OCT system is firmly justified. This is obtained by calculating the heterodyne mixing of the reference and sample beams in a plane conjugate to the discontinuity in the sample probed by the system. Using this approach, a novel expression for the OCT signal is derived, which only depends uopon the intensity distribution of the light from the sample and the reference beam. To adequately estimate the intensity distributions, a novel method of modeling a focused Gaussian beam using Monte Carlo simulation is developed. This method is then combined with the derived expression for the OCT signal into a new Monte Carlo model of the OCT signal. The OCT signal from a scattering medium are obtained for several beam and sample geometries using the new Monte Carlo model, and when comparing to results of an analytical model based on the extended Huygens-Fresnel principle excellent agreement is obtained. With the greater flexibility of Monte Carlo simulations, this new model is demonstrated to be excellent as a numerical phantom, i.e., as a substitute for otherwise difficult experiments. Finally, a new model of the signal-to-noise ratio (SNR) of an OCT system with optical amplification of the light reflected from the sample is derived, and discussed. Using this model, the conclusion is reached that an optical amplifier will enable substantial improvement of the SNR for OCT systems dominated by receiver noise. Receiver noise is of practical concern because of the (often) limited irradiance of suitable optical sources for OCT, and high insertion loss of the fast optical delay-line scanners that are necessary for fast imaging. Correspondingly, an increase in penetration depth of about 30-100% is demonstrated for OCT imaging in skin based on resultsobtained with the new Monte Carlo model. Accordingly, the two new models are demonstrated as valuable tools for future development and optimization of OCT systems to extend the applications of the system in biomedicine.

Tycho, Andreas

2002-01-01

252

Theoretical study of Acousto-optical coherence tomography using random phase jumps on US and light  

CERN Document Server

Acousto-optical coherence tomography (AOCT) is a variant of acousto-optic imaging (also called ultrasonic modulation imaging) that makes it possible to get the z resolution with acoustic and optic continuous wave beams. We describe here theoretically the AOCT effect, and we show that the acousto-optic "tagged photons" remain coherent if they are generated within a specific z region of the sample. We quantify the z selectivity for both the "tagged photon" field and for the Lesaffre et al. [Opt. Express 17, 18211 (2009)] photorefractive signal.

Gross, Michel; Ramaz, François; Farahi, Salma; Boccara, A C

2011-01-01

253

Computed tomography of the optic nerve with special reference to the attenuation values  

International Nuclear Information System (INIS)

The value of computed tomography (CT) for ophthalmology needs no longer to be emphasized. Everything, however, has its limitations. In this article, the limitations of CT for the diagnosis of the optic nerve diameter were studied in an orbit-optic nerve model. The difference of 15 Hounsfield units between two scans which demonstrated the optic nerve having almost the same diameter, as a result of the partial volume effect, was obtained. This suggested that the attenuation values of the optic nerve are markedly influenced by the partial volume effect, and that they require further investigation for clinical use. (author)

254

Multi-parametric imaging of murine brain using spectral and time domain optical coherence tomography.  

Science.gov (United States)

Examination of brain functions in small animal models may help improve the diagnosis and treatment of neurological conditions. Transcranial imaging of small rodents' brains poses a major challenge for optical microscopy. Another challenge is to reduce the measurement time. We describe methods and algorithms for three-dimensional assessment of blood flow in the brains of small animals, through the intact skull, using spectral and time domain optical coherence tomography. By introducing a resonant scanner to the optical setup of the optical coherence tomography (OCT) system, we have developed and applied a high-speed spectral OCT technique that allows us to vary the imaging range of flow and to shorten measurement time. Multi-parameter signal analysis enables us to obtain both qualitative and quantitative information about flow velocity from the same set of data. PMID:23223991

Bukowska, Danuta; Ruminski, Daniel; Szlag, Daniel; Grulkowski, Ireneusz; Wlodarczyk, Jakub; Szkulmowski, Maciej; Wilczynski, Grzegorz; Gorczynska, Iwona; Wojtkowski, Maciej

2012-10-01

255

Optical Coherence Tomography Imaging: Novel Insights into the Vascular Response After Coronary Stent Implantation  

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Optical coherence tomography (OCT) is a high-resolution imaging technique that is increasingly used for intracoronary imaging to characterize coronary atherosclerotic plaques and vascular responses after coronary stent implantation. Introduction of optical frequency-domain imaging (OFDI; second generation OCT) has simplified practical use of this novel imaging modality resulting in a more widespread availability in interventional cardiology. Here we highlight recent insights into the acute an...

Jaguszewski, Milosz; Landmesser, Ulf

2012-01-01

256

Coherent noise-free ophthalmic imaging by spectral optical coherence tomography  

International Nuclear Information System (INIS)

In this contribution we examine a methodology to avoid parasitic cross-correlation terms in spectral optical coherence tomography (SOCT) images. The optimal conditions of optical power and exposure time are found theoretically and confirmed experimentally to ensure that parasitic images are hidden under the shot noise. An upper limit on useful exposures may then be estimated. In a case of SOCT imaging of the retina this limit is below the ANSI safety limit

257

Effect of tissue preservation on imaging using ultrahigh resolution optical coherence tomography  

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Ultrahigh resolution optical coherence tomography (OCT) is an emerging imaging modality that enables noninvasive imaging of tissue with 1- to 3-?m resolutions. Initial OCT studies have typically been performed using harvested tissue specimens (ex vivo). No reports have investigated postexcision tissue degradation on OCT image quality. We investigate the effects of formalin fixation and commonly used cell culture media on tissue optical scattering characteristics in OCT images at different ti...

Hsiung, Pei-lin; Nambiar, Prashant R.; Fujimoto, James G.

2005-01-01

258

Two cases of X-linked retinoschisis with different spectral domain optical coherence tomography findings  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Theodore LengByers Eye Institute at Stanford, Stanford University School of Medicine, Palo Alto, CA, USAAbstract: Spectral domain optical coherence tomography was used to image the maculae of two brothers who had the diagnosis of X-linked retinoschisis maculopathy. One patient demonstrated a large foveal cyst in one eye and a lamellar macular hole in the fellow eye. The second patient demonstrated small retinal cysts in multiple layers of the retina. Spectral domain optical coherence tomograp...

Leng T

2012-01-01

259

In-situ monitoring of surface post-processing in large aperture fused silica optics with Optical Coherence Tomography  

Energy Technology Data Exchange (ETDEWEB)

Optical Coherence Tomography is explored as a method to image laser-damage sites located on the surface of large aperture fused silica optics during post-processing via CO{sub 2} laser ablation. The signal analysis for image acquisition was adapted to meet the sensitivity requirements for this application. A long-working distance geometry was employed to allow imaging through the opposite surface of the 5-cm thick optic. The experimental results demonstrate the potential of OCT for remote monitoring of transparent material processing applications.

Guss, G M; Bass, I l; Hackel, R P; Mailhiot, C; Demos, S G

2008-02-08

260

SIMULATION STUDY FOR GASEOUS FLUXES FROM AN AREA SOURCE USING COMPUTED TOMOGRAPHY AND OPTICAL REMOTE SENSING  

Science.gov (United States)

The paper presents a new approach to quantifying emissions from fugitive gaseous air pollution sources. Computed tomography (CT) and path-integrated optical remote sensing (PI-ORS) concentration data are combined in a new field beam geometry. Path-integrated concentrations are ...

 
 
 
 
261

Optical Coherence Tomography and Biomolecular Imaging with Coherent Raman Scattering Microscopy  

DEFF Research Database (Denmark)

The Special Section on Selected Topics in Biophotonics: Optical Coherence Tomography and Biomolecular Imaging with Coherent Raman Scattering Microscopy comprises two invited review papers and several contributed papers from the summer school Biophotonics ’13, as well as contributed papers within this general scope.

Andersson-Engels, Stefan; Andersen, Peter E.

2014-01-01

262

Autocorrelation artifacts in optical coherence tomography and interferometric synthetic aperture microscopy  

Science.gov (United States)

Interferometric synthetic aperture microscopy processing of optical coherence tomography data has been shown to allow computational focusing of en face planes that have traditionally been regarded as out of focus. It is shown that this focusing of the image also produces a defocusing effect in autocorrelation artifacts resulting from Fourier-domain data collection. This effect is verified experimentally and through simulation.

Davis, Brynmor J.; Ralston, Tyler S.; Marks, Daniel L.; Boppart, Stephen A.; Carney, P. Scott

2007-06-01

263

Measurement of tissue optical properties with optical coherence tomography: Implication for noninvasive blood glucose concentration monitoring  

Science.gov (United States)

Approximately 14 million people in the USA and more than 140 million people worldwide suffer from diabetes mellitus. The current glucose sensing technique involves a finger puncture several times a day to obtain a droplet of blood for analysis. There have been enormous efforts by many scientific groups and companies to quantify glucose concentration noninvasively using different optical techniques. However, these techniques face limitations associated with low sensitivity, accuracy, and insufficient specificity of glucose concentrations over a physiological range. Optical coherence tomography (OCT), a new technology, is being applied for noninvasive imaging in tissues with high resolution. OCT utilizes sensitive detection of photons coherently scattered from tissue. The high resolution of this technique allows for exceptionally accurate measurement of tissue scattering from a specific layer of skin compared with other optical techniques and, therefore, may provide noninvasive and continuous monitoring of blood glucose concentration with high accuracy. In this dissertation work I experimentally and theoretically investigate feasibility of noninvasive, real-time, sensitive, and specific monitoring of blood glucose concentration using an OCT-based biosensor. The studies were performed in scattering media with stable optical properties (aqueous suspensions of polystyrene microspheres and milk), animals (New Zealand white rabbits and Yucatan micropigs), and normal subjects (during oral glucose tolerance tests). The results of these studies demonstrated: (1) capability of the OCT technique to detect changes in scattering coefficient with the accuracy of about 1.5%; (2) a sharp and linear decrease of the OCT signal slope in the dermis with the increase of blood glucose concentration; (3) the change in the OCT signal slope measured during bolus glucose injection experiments (characterized by a sharp increase of blood glucose concentration) is higher than that measured in the glucose clamping experiments (characterized by slow, controlled increase of the blood glucose concentration); and (4) the accuracy of glucose concentration monitoring may substantially be improved if optimal dimensions of the probed skin area are used. The results suggest that high-resolution OCT technique has a potential for noninvasive, accurate, and continuous glucose monitoring with high sensitivity.

Larin, Kirill V.

264

Edema macular quístico pseudofáquico: Detección mediante «optical coherence tomography» Pseudophakic cystoid macular edema: Assesment with optical coherence tomography  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Objetivo: Detectar la incidencia de edema macular quístico (EMQ) tras cirugía de catarata tanto clínico como subclínico, mediante «ocular coherence tomography» (OCT) y comparar dicha incidencia entre un grupo de pacientes diabéticos y otro de no diabéticos. Material y métodos: Estudio prospectivo de 260 ojos intervenidos de forma consecutiva de catarata mediante facoemulsificación con implante de lente intraocular acrílica, desde septiembre de 2004 a marzo de 2005. Grupo A: 208 ojo...

Torro?n-ferna?ndez-blanco, C.; Ruiz-moreno, O.; Ferrer-novella, E.; Sa?nchez-cano, A.; Honrubia-lo?pez, F. M.

2006-01-01

265

A combined time-domain diffuse fluorescence and optical tomography system for breast tumor detection  

Science.gov (United States)

A combined time-domain diffuse fluorescence and optical tomographic system is proposed based on the multi-channel time-correlated single-photon counting (TCSPC) technique, aiming at enhancing the reliability of breast diffuse optical tomography. The system equipped with two pulsed laser diodes at wavelengths of 780 nm and 830 nm that are specific to the maximal excitation and emission of the FDA-approved ICG dye, and works with a 4-channel TCSPC module to acquire the temporal distributions of the light re-emissions 32 boundary sites of tissues in a tandem serial-to-parallel mode. The performance and efficacy of the system are investigated with phantom experiments for diffuse optical tomography (DOT), as well as fluorescence-guided DOT.

Zhang, Wei; Gao, Feng; Wu, Linhui; Ma, Wenjuan; Lu, Yiming; Zhou, Zhongxing

2012-03-01

266

Photons-based medical imaging - Radiology, X-ray tomography, gamma and positrons tomography, optical imaging; Imagerie medicale a base de photons - Radiologie, tomographie X, tomographie gamma et positons, imagerie optique  

Energy Technology Data Exchange (ETDEWEB)

This book describes the different principles used in medical imaging. The detection aspects, the processing electronics and algorithms are detailed for the different techniques. This first tome analyses the photons-based techniques (X-rays, gamma rays and visible light). Content: 1 - physical background: radiation-matter interaction, consequences on detection and medical imaging; 2 - detectors for medical imaging; 3 - processing of numerical radiography images for quantization; 4 - X-ray tomography; 5 - positrons emission tomography: principles and applications; 6 - mono-photonic imaging; 7 - optical imaging; Index. (J.S.)

Fanet, H.; Dinten, J.M.; Moy, J.P.; Rinkel, J. [CEA Leti, Grenoble (France); Buvat, I. [IMNC - CNRS, Orsay (France); Da Silva, A. [Institut Fresnel, Marseille (France); Douek, P.; Peyrin, F. [INSA Lyon, Lyon Univ. (France); Frija, G. [Hopital Europeen George Pompidou, Paris (France); Trebossen, R. [CEA-Service hospitalier Frederic Joliot, Orsay (France)

2010-07-01

267

Passive component based multifunctional Jones matrix swept source optical coherence tomography for Doppler and polarization imaging.  

Science.gov (United States)

We present a fiber based multifunctional Jones matrix swept source optical coherence tomography (SS-OCT) system for Doppler and polarization imaging. Jones matrix measurement without using active components such as electro-optic modulators is realized by incident polarization multiplexing based on independent delay of two orthogonal polarization states and polarization diversity detection. In addition to polarization sensitivity, this system measures Doppler flow without extra hardware for phase stabilized SS-OCT detection. An eighth-wave plate was measured to demonstrate the polarization detection accuracy. The optic nerve head of a retina was measured in vivo. Detailed vasculature and birefringent structures were investigated simultaneously. PMID:22660086

Lim, Yiheng; Hong, Young-Joo; Duan, Lian; Yamanari, Masahiro; Yasuno, Yoshiaki

2012-06-01

268

Low-voltage polymer-based scanning cantilever for in vivo optical coherence tomography  

Science.gov (United States)

Novel hand-held optical coherence tomography (OCT) probes with polymer cantilevers have been developed for clinical oral and skin imaging. An electroactive ionic polymer-metal composite cantilever was used to generate 3-mm transverse scanning movement of an optical fiber with applied 2-V linear alternating voltage at 1Hz. Low driving voltage ensures safety. Two different optical designs achieve both forward and sidewise scanning and make it possible to image everywhere within the human oral cavity. In vivo OCT imaging of the human tongue is demonstrated.

Wang, Yuli; Bachman, Mark; Li, Guann-Pyng; Guo, Shuguang; Wong, Brian J. F.; Chen, Zhongping

2005-01-01

269

Flexible miniature compound lens design for high-resolution optical coherence tomography balloon imaging catheter.  

Science.gov (United States)

We report on a new optics design for an optical coherence tomography (OCT) balloon imaging catheter. The design involves a miniature compound gradient-index (GRIN) rod lens, which consists of a fiber optic mode-field reducer and relay rod lenses to achieve predictable high lateral resolution at a desired large working distance. The compound lens design significantly simplifies the engineering process for an OCT catheter and enables 3-D full circumferential cross sectional imaging of large luminal organs such as human esophagus. An as-designed OCT catheter is developed and demonstrated for real-time in vivo swine esophagus imaging in a 3-D spiral fashion. PMID:19123643

Fu, Henry L; Leng, Yuxin; Cobb, Michael J; Hsu, Kevin; Hwang, Joo Ha; Li, Xingde

2008-01-01

270

Analysis and optimization of a diffuse photon optical tomography of turbid media  

International Nuclear Information System (INIS)

In a numerical study, we investigate a diffuse-photon computed tomography of a turbid medium. Using a perturbation approach, we relate through a matrix K a bulk heterogeneous distribution of the optical absorption coefficient ?a that characterizes the heterogeneity in an otherwise homogeneous turbid medium to the diffuse photon flux that emerges from its surface. By studying the condition number (NC) of the matrix K as a function of illumination-detection schemes and choices of reconstruction grids, we explore strategies that optimize the fidelity and spatial resolution of the computed tomography. (c) 2000 The American Physical Society

271

Tomography  

International Nuclear Information System (INIS)

Tomography is a non-invasive technique now being developed as an industrial tool. It will be most useful for studying complex geometries where other NDT techniques provide ambiguous information, and complex processes where the quantitative data obtained can be used to rigorously test our understanding of the process. An overview of the CRNL program is presented

272

Sagittal laser optical tomography for imaging of rheumatoid finger joints  

Energy Technology Data Exchange (ETDEWEB)

We present a novel optical tomographic imaging system that was designed to determine two-dimensional spatial distribution of optical properties in a sagittal plane through finger joints. The system incorporates a single laser diode and a single silicon photodetector into a scanning device that records spatially resolved light intensities as they are transmitted through a finger. These data are input to a model-based iterative image reconstruction (MOBIIR) scheme, which uses the equation of radiative transfer (ERT) as a forward model for light propagation through tissue. We have used this system to obtain tomographic images of six proximal interphalangeal finger joints from two patients with rheumatoid arthritis. The optical images were compared to clinical symptoms and ultrasound images.

Hielscher, Andreas H [Departments of Biomedical Engineering and Radiology, Columbia University, New York, NY 10027 (United States); Klose, Alexander D [Departments of Biomedical Engineering and Radiology, Columbia University, New York, NY 10027 (United States); Scheel, Alexander K [Department of Nephrology and Rheumatology, Georg-August University, Goettingen (Germany); Moa-Anderson, Bryte [Departments of Biomedical Engineering and Radiology, Columbia University, New York, NY 10027 (United States); Backhaus, Marina [Department of Rheumatology and Clinical Immunology, Charite University Hospital, Berlin (Germany); Netz, Uwe [Institute for Medical Physics and Laser Medicine, Free University of Berlin, Berlin (Germany); Beuthan, Juergen [Institute for Medical Physics and Laser Medicine, Free University of Berlin, Berlin (Germany)

2004-04-07

273

Relation between quantum tomography and optical Fresnel transform  

CERN Document Server

Corresponding to optical Fresnel transformation characteristic of ray transfer matrix elements (A;B;C;D); AD-BC = 1, there exists Fresnel operator F(A;B;C;D) in quantum optics, we show that under the Fresnel transformation the pure position density |x>_rs,rs__rs,rs_ is just the wave function of its Fresnel transformed state F|phi>, i.e. rs_= . Similarly, we find F|p>_rs,rs_

Fan, Hong-yi

2008-01-01

274

Complete complex conjugate resolved heterodyne swept-source optical coherence tomography using a dispersive optical delay line  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Swept-source optical coherence tomography (SSOCT) provides a substantial sensitivity advantage over its time-domain counterpart, but suffers from a reduced imaging depth range due to sensitivity falloff and complex conjugate ambiguity. Heterodyne complex conjugate-resolved SSOCT (HCCR-SSOCT) has been previously demonstrated as a technique to completely resolve the complex conjugate ambiguity, effectively doubling the falloff limited imaging depth, without the reduction in imaging speed associ...

Dhalla, Al-hafeez; Izatt, Joseph A.

2011-01-01

275

Noise statistics of phase-resolved optical coherence tomography imaging: single-and dual-beam-scan Doppler optical coherence tomography.  

Science.gov (United States)

Noise statistics of phase-resolved optical coherence tomography (OCT) imaging are complicated and involve noises of OCT, correlation of signals, and speckles. In this paper, the statistical properties of phase shift between two OCT signals that contain additive random noises and speckle noises are presented. Experimental results obtained with a scattering tissue phantom are in good agreement with theoretical predictions. The performances of the dual-beam method and conventional single-beam method are compared. As expected, phase shift noise in the case of the dual-beam-scan method is less than that for the single-beam method when the transversal sampling step is large. PMID:24663800

Makita, Shuichi; Jaillon, Franck; Jahan, Israt; Yasuno, Yoshiaki

2014-02-24

276

Optical Effects at projection measurements for Terahertz tomography  

Science.gov (United States)

Optical effects like refraction, diffraction and edge effects have an influence on Terahertz measurements. They can result in image artifacts which makes it difficult to detect and resolve material defects inside the samples. We used a geometrical optical ray tracing approach to analyze the optical effects at Terahertz projection measurements which can be used to perform 2D or 3D THz images. We measured rectangular and cylindrical samples made of PEEK (Polyetheretherketon), POM (Polyoxymethylen), and PMMA (Polymethylmethacrylat) and compared the results to simulations that are realized with the software ZEMAX. We were able to simulate the measured Fresnel refraction and transmission behavior for rectangular cuboids with a length of 25 mm and cylinders with diameter of 25 mm. We showed the influence of diffraction and edge effects at samples with different sizes made of PMMA. Thus, the optical effect of refraction was significant and observable for cylinders with diameters greater than 1.5 mm and holes with diameter greater than 2.5 mm.

Brahm, A.; Wilms, A.; Tymoshchuk, M.; Grossmann, C.; Notni, G.; Tünnermann, A.

2014-10-01

277

Full range spectral domain optical coherence tomography using a fiber-optic probe as a self-phase shifter.  

Science.gov (United States)

We present a full range handheld probe type spectral domain optical coherence tomography (SD-OCT) method. Here, the sample arm is composed of a tilted fiber-optic cantilever scanner; thus, the phase shift concurrently occurs while sample scanning. With the phase shift, we could achieve a full range complex-conjugate-free OCT image with no additional phase shifters in the reference arm. To realize this technique, a magnetically actuated probe was adopted. Full range SD-OCT images of a pearl, human fingernail, and human tooth were subsequently obtained using this suggested probe. The scanning range and acquisition speed were 3 mm and 20 frames/s, respectively. PMID:22859100

Min, Eun Jung; Shin, Jun Geun; Lee, Jae Hwi; Yasuno, Yoshiaki; Lee, Byeong Ha

2012-08-01

278

Images of arterial tissues using catheter swept source optical coherence tomography  

Science.gov (United States)

Optical coherence tomography images of arterial samples harvested from asymptomatic pigs and from lipid-rich Watanabe heritable hyperlipidemic rabbits were acquired using a fiber catheter-based swept-source optical coherence tomography system (OCT). A quadrature Mach-Zehnder interferometer based on multi-port fiber couplers and a semiconductor optical amplifier (SOA) were employed in the swept-source optical coherence tomography system. The improvement of signal to noise ratio as a result of incorporating the SOA into the configuration translated in an increase of the penetration depth. A fiber probe ending in a fiber ball lens was developed for the arterial imaging. The images acquired by this system offer the possibility to investigate anatomical details located under the surface of the artery such as the intima, media, and adventitia layers (from lumen side) of the blood vessel wall , as well as morphological features specific to artherosclerotic plaques such as lipid pools, fibrous caps, macrophage accumulations and calcified. This report indicates that our improved catheter-based swept source OCT is a potential tool for in vivo intravascular imaging.

Mao, Youxin; Flueraru, Costel; Chang, Shoude; Popescu, Dan P.; Sowa, M. G.

2010-06-01

279

Normal distributions transform in multi-modal image registration of optical coherence tomography and computed tomography datasets  

Science.gov (United States)

In recent years, optical coherence tomography (OCT) has gained increasing attention not only as an imaging device, but also as a navigation system for surgical interventions. This approach demands to register intraoperative OCT to pre-operative computed tomography (CT) data. In this study, we evaluate algorithms for multi-modal image registration of OCT and CT data of a human temporal bone specimen. We focus on similarity measures that are common in this field, e.g., normalized mutual information, normalized cross correlation, and iterative closest point. We evaluate and compare their accuracies to the relatively new normal distribution transform (NDT), that is very common in simultaneous localization and mapping applications, but is not widely used in image registration. Matching is realized considering appropriate image pre-processing, the aforementioned similarity measures, and local optimization algorithms, as well as line search optimization. For evaluation purpose, the results of a point-based registration with fiducial landmarks are regarded as ground truth. First results indicate that state of the art similarity functions do not perform with the desired accuracy, when applied to unprocessed image data. In contrast, NDT seems to achieve higher registration accuracy.

Díaz Díaz, Jesús; Riva, Mauro H.; Majdani, Omid; Ortmaier, Tobias

2014-03-01

280

Tomography  

International Nuclear Information System (INIS)

Tomography is a non-intrusive imaging technique being developed at CRNL as an industrial tool for generating quantitative cross-sectional density maps of objects. Of most interest is tomography's ability to: distinguish features within complex geometries where other NDT techniques fail because of the complexity of the geometry; detect/locate small density changes/defects within objects, e.g. void fraction measurements within thick-walled vessels, shrink cavities in castings, etc.; provide quantitative data that can be used in analyses, e.g. of complex processes, or fracture mechanics; and provide objective quantitative data that can be used for (computer-based) quality assurance decisions, thereby reducing and in some cases eliminating the present subjectivity often encountered in NDT. The CRNL program is reviewed and examples are presented to illustrate the potential and the limitations of the technology

 
 
 
 
281

Breast cancer imaging and tomography using a hand-held optical imager  

Science.gov (United States)

Hand-held optical imaging devices are currently developed by several research groups as a noninvasive and non-ionizing method towards clinical imaging of breast cancer. The devices developed to date are typically utilized towards spectroscopic imaging via reflectance-based measurements. Additionally, a couple of devices have been used to perform 3D tomography with the addition of a second modality (e.g. ultrasound). A hand-held optical device that is unique in its ability to perform rapid 2D imaging and 3D tomography (without the use of a second modality) has been developed in our Optical Imaging laboratory. Herein, diffuse optical imaging studies are performed in breast cancer subjects. For these studies, the subject lay in a recliner chair and both breast tissues were imaged with the hand-held optical device which uses 785 nm laser source and an intensified CCD camera-based detector. Preliminary results demonstrate the ability to image invasive ductal carcinoma and lymphatic spread, as compared to the patient's medical records (e.g. xray, ultrasound, MRI). Multiple imaging studies with a subject undergoing chemotherapy demonstrated the potential to monitor response to treatment. Currently, studies are carried out to tomographically determine the 3D location of the tumor(s) in breast cancer subjects using the hand-held optical device.

Erickson, Sarah J.; Roman, Manuela; Gonzalez, Jean; Kiszonas, Richard; Lopez-Penalver, Cristina; Godavarty, Anuradha

2012-03-01

282

Finite elements parameterization of optical tomography with the radiative transfer equation in frequency domain  

International Nuclear Information System (INIS)

Optical tomography is a technique of probing semi-transparent media with the help of light sources. In this method, the spatial distribution of the optical properties inside the probed medium is reconstructed by minimizing a cost function based on the errors between the measurements and the predictions of a numerical model of light transport (also called forward/direct model) within the medium at the detectors locations. Optical tomography with finite elements methods involves generally continuous formulations where the optical properties are constant per mesh elements. This study proposes a numerical analysis in the parameterization of the finite elements space of the optical properties in order to improve the accuracy and the contrast of the reconstruction. Numerical tests with noised data using the same algorithm show that continuous finite elements spaces give better results than discontinuous ones by allowing a better transfer of the information between the whole computational nodes of the inversion. It is seen that the results are more accurate when the number of degrees of freedom of the finite element space of the optical properties (number of unknowns) is lowered. This shows that reducing the number of unknowns decreases the ill-posed nature of the inverse problem, thus it is a promising way of regularizing the inversion.

283

Block matching 3D random noise filtering for absorption optical projection tomography  

Energy Technology Data Exchange (ETDEWEB)

Absorption and emission optical projection tomography (OPT), alternatively referred to as optical computed tomography (optical-CT) and optical-emission computed tomography (optical-ECT), are recently developed three-dimensional imaging techniques with value for developmental biology and ex vivo gene expression studies. The techniques' principles are similar to the ones used for x-ray computed tomography and are based on the approximation of negligible light scattering in optically cleared samples. The optical clearing is achieved by a chemical procedure which aims at substituting the cellular fluids within the sample with a cell membranes' index matching solution. Once cleared the sample presents very low scattering and is then illuminated with a light collimated beam whose intensity is captured in transillumination mode by a CCD camera. Different projection images of the sample are subsequently obtained over a 360{sup 0} full rotation, and a standard backprojection algorithm can be used in a similar fashion as for x-ray tomography in order to obtain absorption maps. Because not all biological samples present significant absorption contrast, it is not always possible to obtain projections with a good signal-to-noise ratio, a condition necessary to achieve high-quality tomographic reconstructions. Such is the case for example, for early stage's embryos. In this work we demonstrate how, through the use of a random noise removal algorithm, the image quality of the reconstructions can be considerably improved even when the noise is strongly present in the acquired projections. Specifically, we implemented a block matching 3D (BM3D) filter applying it separately on each acquired transillumination projection before performing a complete three-dimensional tomographical reconstruction. To test the efficiency of the adopted filtering scheme, a phantom and a real biological sample were processed. In both cases, the BM3D filter led to a signal-to-noise ratio increment of over 30 dB on severe noise-affected reconstructions revealing original-noise-hidden-image details. These results show the utility of the BM3D approach for OPT under typical conditions of very low light absorption, suggesting its implementation as an efficient alternative to other filtering schemes such as for example the median filter.

Fumene Feruglio, P; Vinegoni, C; Weissleder, R [Center for Systems Biology, Massachusetts General Hospital, Harvard Medical School, 185 Cambridge Street, Boston, MA 02114 (United States); Gros, J [Department of Genetics, Harvard Medical School, 77 Avenue Louis Pasteur, Boston MA 02115 (United States); Sbarbati, A, E-mail: cvinegoni@mgh.harvard.ed [Department of Morphological and Biomedical Sciences, University of Verona, Strada Le Grazie 8, 37134 Verona (Italy)

2010-09-21

284

Block matching 3D random noise filtering for absorption optical projection tomography  

International Nuclear Information System (INIS)

Absorption and emission optical projection tomography (OPT), alternatively referred to as optical computed tomography (optical-CT) and optical-emission computed tomography (optical-ECT), are recently developed three-dimensional imaging techniques with value for developmental biology and ex vivo gene expression studies. The techniques' principles are similar to the ones used for x-ray computed tomography and are based on the approximation of negligible light scattering in optically cleared samples. The optical clearing is achieved by a chemical procedure which aims at substituting the cellular fluids within the sample with a cell membranes' index matching solution. Once cleared the sample presents very low scattering and is then illuminated with a light collimated beam whose intensity is captured in transillumination mode by a CCD camera. Different projection images of the sample are subsequently obtained over a 3600 full rotation, and a standard backprojection algorithm can be used in a similar fashion as for x-ray tomography in order to obtain absorption maps. Because not all biological samples present significant absorption contrast, it is not always possible to obtain projections with a good signal-to-noise ratio, a condition necessary to achieve high-quality tomographic reconstructions. Such is the case for example, for early stage's embryos. In this work we demonstrate how, through the use of a random noise removal algorithm, the image quality of the reconstructions can be considerably improved even when the noise is strongly present in the acquired projections. Specifically, we implemented a block matching 3D (BM3D) filter applying it separately on each acquired transillumination projection before performing a complete three-dimensional tomographical reconstruction. To test the efficiency of the adopted filtering scheme, a phantom and a real biological sample were processed. In both cases, the BM3D filter led to a signal-to-noise ratio increment of over 30 dB on severe noise-affected reconstructions revealing original-noise-hidden-image details. These results show the utility of the BM3D approach for OPT under typical conditions of very low light absorption, suggesting its implementation as an efficient alternative to other filtering schemes such as for example the median filter.

285

Image reconstruction for optical tomography using photon density waves  

Energy Technology Data Exchange (ETDEWEB)

Diagnostic imaging makes use of different kinds of radiation. A recent type of imaging using near-infrared light is thought to be a safer and less-expensive method of in-vivo imaging. Near infra-red light can penetrate biological tissue to certain depths. The problem of using near infrared light for imaging, is that the scattering of the photons dominates absorption, causing difficulties in the reconstruction model on which biomedical optical imaging depends crucially. The aim of this thesis is to develop and investigate the performance of a reconstruction algorithm in the frequency domain which allows fast and efficient reconstruction of the image of a limb, or an optical phantom. The forward problem of the propagation of photons inside biological tissue is modelled using the Diffusion Approximation theory solved by the finite element method. Values of DC intensity, phase shift and modulation depth at the boundary as functions of the diffusion and absorption coefficients are given. The inverse model is formulated as a nonlinear least-squares optimisation problem. The Truncated Newton method with Trust region is used to determine the optical properties. Reverse differentiation is used to calculate the error function because of its speed advantage over forward differentiation. A sensitivity analysis is performed to investigate the simultaneous reconstruction of the diffusion and absorption coefficients. The use of a combined error function of DC intensity, phase and modulation prove to be the most successful at recovering the optical parameters. The ability to distinguish between object size and size of optical parameter is also investigated. Contrast, mean and standard deviation are used as measures of the performance of the reconstruction algorithm. A Tikhonov regularisation method was used to improve ill-conditioning and behaviour in the presence of noise. An investigation of the optimal regularisation parameter is undertaken with the addition of noise to the measured data. Use of the L-curve method is investigated. This work has resulted in an efficient and functional reconstruction algorithm and program for the image reconstruction in the frequency domain. (author)

Khalaf, R

1999-08-01

286

New developments in frequency domain optical tomography. Part I: Forward model and gradient computation  

International Nuclear Information System (INIS)

This two part study introduces new developments in frequency domain optical tomography to take into account the collimated source direction in the computation of both the forward and the adjoint models. The solution method is based on the least square finite element method associated to the discrete ordinates method where no empirical stabilization is needed. In this first part of the study, the solution method of the forward model is highlighted with an easy handling of complex boundary condition through a penalization method. Gradient computation from an adjoint method is developed rigorously in a continuous manner through a lagrangian formalism for the deduction of the adjoint equation and the gradient of the objective function. The proposed formulation can be easily generalized to stationary and time domain optical tomography by keeping the same expressions.

287

Utilizing optical coherence tomography in the nondestructive and noncontact measurement of egg shell thickness.  

Science.gov (United States)

The goal of this study was to measure the thickness of egg shells without any contact and by utilizing a nondestructive method that sends infrared light beam on the egg. We obtain measurement resolutions on the order of 7 ?m up to a penetration depth of 1.7 mm from the actual surface of the egg shell. The measurement results we obtained show that optical coherence tomography can be used to accurately determine the egg shell thickness. Scanning the light beam over the surface allows for measuring the egg profile and monitoring the variations of shell thickness. Since this information gives a quantitative value for the uniformity of the egg shell structure, we anticipate that optical coherence tomography may be used in the quantitative evaluation of egg quality in in-line automated inspection systems. PMID:25133208

Sabuncu, Metin; Akdo?an, Mete

2014-01-01

288

Differentiation of ex vivo human breast tissue using polarization-sensitive optical coherence tomography  

Science.gov (United States)

Successful treatment of breast cancer typically requires surgical removal of the tumor. Optical coherence tomography (OCT) has been previously developed for real-time imaging of the surgical margin. However, it can be difficult to distinguish between normal stromal tissue and cancer tissue based on scattering intensity and structure alone. Polarization-sensitive optical coherence tomography (PS-OCT) is sensitive to form birefringence of biological tissue. We report on the development of a high-speed PS-OCT system and imaging of ex vivo human breast tissue, showing enhanced contrast between healthy and cancerous tissues based upon collagen content confirmed with corresponding histology. These results demonstrate the feasibility of using PS-OCT to supplement structural OCT as a possible method for intraoperative tumor margin evaluation. PMID:25360360

South, Fredrick A.; Chaney, Eric J.; Marjanovic, Marina; Adie, Steven G.; Boppart, Stephen A.

2014-01-01

289

Macular edema in the era of spectral-domain optical coherence tomography  

Directory of Open Access Journals (Sweden)

Full Text Available Allan Hunter,1 Eric K Chin,1 David G Telander,21Department of Ophthalmology, University of California, Davis, 2Department of Ophthalmology, Retinal Consultants, Sacramento, CA, USAAbstract: The development of spectral-domain optical coherence tomography (OCT allows for the highest commercially available resolution of in vivo retinal anatomic details to date. The ability to see the macula with ever increasing detail is dramatically improving our understanding of the pathogenesis of retinal disease. However, the only prospective study that partially evaluated spectral-domain OCT versus time-domain OCT failed to show any clinical benefit of increased OCT resolution. Clinical outcomes, eg, best-corrected visual acuity, central macular thickness and number of injections, with “newer” OCT technologies remain an unproven advantage.Keywords: retina, macular edema, optical coherence tomography, fluorescein angiography, indocyanine green angiography

Hunter A

2013-10-01

290

Influence of excitation light rejection on forward model mismatch in optical tomography  

International Nuclear Information System (INIS)

Fluorescence enhanced tomography for molecular imaging requires low background for detection and accurate image reconstruction. In this contribution, we show that excitation light leakage is responsible for elevated background and can be minimized with the use of gradient index (GRIN) lenses when using fibre optics to collect propagated fluorescence light from tissue or other biological media. We show that the model mismatch between frequency-domain photon migration (FDPM) measurements and the diffusion approximation prediction is decreased when GRIN lenses are placed prior to the interference filters to provide efficient excitation light rejection. Furthermore, model mismatch is correlated to the degree of excitation light leakage. This work demonstrates the importance of proper light filtering when designing fluorescence optical imaging and tomography

291

Two cases of X-linked retinoschisis with different spectral domain optical coherence tomography findings  

Directory of Open Access Journals (Sweden)

Full Text Available Theodore LengByers Eye Institute at Stanford, Stanford University School of Medicine, Palo Alto, CA, USAAbstract: Spectral domain optical coherence tomography was used to image the maculae of two brothers who had the diagnosis of X-linked retinoschisis maculopathy. One patient demonstrated a large foveal cyst in one eye and a lamellar macular hole in the fellow eye. The second patient demonstrated small retinal cysts in multiple layers of the retina. Spectral domain optical coherence tomography allowed high-resolution imaging and characterization of the features in X-linked retinoschisis in these patients, and it highlighted the variability of the same genetic disease, even in one family.Keywords: SD-OCT, XLRS, retina, imaging, maculopathy

Leng T

2012-09-01

292

A haemodynamic response function model in spatio-temporal diffuse optical tomography  

Energy Technology Data Exchange (ETDEWEB)

Diffuse optical tomography (DOT) is a new and effective technique for functional brain imaging. It can detect local changes in both oxygenated and deoxygenated haemoglobin concentrations in tissue based on differential absorption at multiple wavelengths. Traditional methods in spatio-temporal analysis of haemoglobin concentrations in diffuse optical tomography first reconstruct the spatial distribution at different time instants independently, then look at the temporal dynamics on each pixel, without incorporating any temporal information as a prior in the image reconstruction. In this work, we present a temporal haemodynamic response function model described by a basis function expansion, in a joint spatio-temporal DOT reconstruction of haemoglobin concentration changes during simulated brain activation. In this joint framework, we simultaneously employ spatial regularization, spectral information and temporal assumptions. We also present an efficient algorithm for solving the associated large-scale systems. The expected improvements in spatial resolution and contrast-to-noise ratio are illustrated with simulations of human brain activation.

Zhang Yiheng [Department of Radiology, University of Michigan Hospital, 1500 E Medical Center Drive, CGC B2109, Ann Arbor, MI 48109 (United States); Brooks, Dana H [Electrical and Computer Engineering Department, 442 DANA, Northeastern University, 360 Huntington Avenue, Boston, MA 02115 (United States); Boas, David A [Athinoula A Martinos Center, Massachusetts General Hospital, Harvard Medical School, 149 13th Street, Room 2301, Charlestown, MA 02129 (United States)

2005-10-07

293

A haemodynamic response function model in spatio-temporal diffuse optical tomography  

International Nuclear Information System (INIS)

Diffuse optical tomography (DOT) is a new and effective technique for functional brain imaging. It can detect local changes in both oxygenated and deoxygenated haemoglobin concentrations in tissue based on differential absorption at multiple wavelengths. Traditional methods in spatio-temporal analysis of haemoglobin concentrations in diffuse optical tomography first reconstruct the spatial distribution at different time instants independently, then look at the temporal dynamics on each pixel, without incorporating any temporal information as a prior in the image reconstruction. In this work, we present a temporal haemodynamic response function model described by a basis function expansion, in a joint spatio-temporal DOT reconstruction of haemoglobin concentration changes during simulated brain activation. In this joint framework, we simultaneously employ spatial regularization, spectral information and temporal assumptions. We also present an efficient algorithm for solving the associated large-scale systems. The expected improvements in spatial resolution and contrast-to-noise ratio are illustrated with simulations of human brain activation

294

High resolution 3D image reconstruction in laminar optical tomography based on compressive sensing  

Science.gov (United States)

Laminar optical tomography (LOT) combines the advantages of diffuse optical tomography image reconstruction and a microscopy-based setup to allow non-contact imaging at depth up to a few millimeters. However, LOT image reconstruction paradigm is inherently an ill-posed and computationally expensive inverse problem. Herein, we cast the LOT inverse problem in the compressive sensing (CS) framework to exploit the sparsity of the fluorophore yield in the image domain and to address the ill-posedness of the LOT inverse problem. We apply this new approach to thick tissue engineering applications. We demonstrate the enhanced resolution of our method in 3-D numerical simulations of anatomically accurate microvasculature and using real data obtained from phantom experiments. Furthermore, CS is shown to be more robust against the reduction of measurements in comparison to the classic methods for such application. Potential benefits and shortcomings of the CS approach in the context of LOT are discussed.

Yang, Fugang; Ozturk, Mehmet S.; Cong, Wenxiang; Wang, Ge; Intes, Xavier

2014-02-01

295

Patency of small laser iridotomy evaluated using anterior-segment optical coherence tomography.  

Science.gov (United States)

We report the case of a patient with recurrent acute angle-closure glaucoma who had undergone a previous laser iridotomy. Because the initial iridotomy was small, patency could not be determined by slit-lamp examination. Therefore, anterior-segment optical coherence tomography was used to evaluate the patency. Cross-sectional images showed the presence of a membrane with an anterior bowing configuration at the base of the iridotomy, suggesting that recurrent pupillary block was the causative mechanism. A repeat laser iridotomy was performed, with a resultant decrease in the intraocular pressure and widening of the anterior chamber angle. Anterior-segment optical coherence tomography may be helpful to confirm the status of a laser iridotomy, especially when the iridotomy is small. PMID:24711692

Nakabayashi, Seigo; Kawai, Motofumi; Yamaguchi, Toru; Yoshida, Akitoshi

2014-01-01

296

Evaluation of the macular architecture of patients operated on from macula-off rhegmatogenous retinal detachment using optical coherence tomography  

International Nuclear Information System (INIS)

With the support of optical coherence tomography, to evaluate the macular condition of the patients operated on from rhegmatogenous retinal detachment, with detached macula, who underwent buckling surgery and pars plana vitrectomy

297

Retinal nerve fiber layer evaluation in multiple sclerosis with spectral domain optical coherence tomography  

Directory of Open Access Journals (Sweden)

Full Text Available Aziz A Khanifar1, George J Parlitsis1, Joshua R Ehrlich1, Grant D Aaker1, Donald J D’Amico1, Susan A Gauthier2, Szilárd Kiss11Departments of Ophthalmology, 2Neurology, Judith Jaffe Multiple Sclerosis Center, Weill Cornell Medical College, New York, USAPurpose: Histopathologic studies have reported retinal nerve fiber layer (RNFL thinning in various neurodegenerative diseases. Attempts to quantify this loss in vivo have relied on ­time-domain optical coherence tomography (TDOCT, which has low resolution and requires substantial interpolation of data for volume measurements. We hypothesized that the significantly higher resolution of spectral-domain optical coherence tomography (SDOCT would better detect RNFL changes in patients with multiple sclerosis, and that RNFL thickness differences between eyes with and without optic neuritis might be identified more accurately.Methods: In this retrospective case series, patients with multiple sclerosis were recruited from the Judith Jaffe Multiple Sclerosis Center at Weill Cornell Medical College in New York. Patients with a recent clinical diagnosis of optic neuritis (less than three months were excluded. Eyes with a history of glaucoma, optic neuropathy (other than multiple sclerosis-related optic neuritis, age-related macular degeneration, or other relevant retinal and/or optic nerve disease were excluded. Both eyes of each patient were imaged with the Heidelberg Spectralis® HRA + OCT. RNFL and macular thickness were measured for each eye using the Heidelberg OCT software. These measurements were compared with validated published normal values, and were modeled as linear functions of duration of disease. The odds of an optic neuritis diagnosis as a function of RNFL and macular thickness were calculated.Results: Ninety-four eyes were prospectively evaluated using OCT. Ages of patients ranged from 26 to 69 years, with an average age of 39 years. Peripapillary RNFL thinning was demonstrated in multiple sclerosis patients; mean RNFL thickness was 88.5 µm for individuals with multiple sclerosis compared with a reported normal value of 97 µm (P < 0.001. Eyes with a history of optic neuritis had more thinning compared with those without optic neuritis (83.0 µm versus 90.5 µm, respectively, P = 0.02. No significant differences were observed in macular thickness measurements between eyes with and without optic neuritis, nor were macular thickness measurements significantly different from normal values. As a function of multiple sclerosis duration and controlling for age, RNFL thickness was decreased in patients with a duration of multiple sclerosis greater than five years compared with those with a duration less than or equal to one year (P = 0.008.Conclusions: Patients with a history of multiple sclerosis had RNFL thinning that was detectable on SDOCT. Decreasing RNFL thickness in eyes with optic neuritis was found, and the odds of having optic neuritis were increased significantly with decreasing RNFL thickness. Average RNFL thinning with increasing duration of disease was an excellent predictor of a reported history of optic neuritis. SDOCT retinal imaging may represent a high-resolution, objective, noninvasive, and easily quantifiable in vivo biomarker of the presence of optic neuritis and severity of multiple sclerosis.Keywords: multiple sclerosis, spectral-domain optical coherence tomography, optical ­coherence tomography, nerve fiber layer, nerve fiber layer thickness, optic neuritis

Aziz A Khanifar

2010-09-01

298

Femtosecond laser micro-inscription of optical coherence tomography resolution test artifacts  

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Optical coherence tomography (OCT) systems are becoming more commonly used in biomedical imaging and, to enable continued uptake, a reliable method of characterizing their performance and validating their operation is required. This paper outlines the use of femtosecond laser subsurface micro-inscription techniques to fabricate an OCT test artifact for validating the resolution performance of a commercial OCT system. The key advantage of this approach is that by utilizing the nonlinear absorp...

Tomlins, Peter H.; Smith, Graham N.; Woolliams, Peter D.; Rasakanthan, Janarthanan; Sugden, Kate

2011-01-01

299

Imaging actinic keratosis by high-definition optical coherence tomography. Histomorphologic correlation : a pilot study  

DEFF Research Database (Denmark)

With the continued development of non-invasive therapies for actinic keratosis such as PDT and immune therapies, the non-invasive diagnosis and monitoring become increasingly relevant. High-definition optical coherence tomography is a high-resolution imaging tool, with micrometre resolution in both transversal and axial directions, enable to visualize individual cells up to a depth of around 570 ?m filling the imaging gap between conventional optical coherence tomography and reflectance confocal microscopy. We sought to determine the feasibility of detecting and grading of actinic keratosis by this technique using criteria defined for reflectance confocal microscopy compared to histology. In this pilot study, skin lesions of 17 patients with a histologically proven actinic keratosis were imaged by high-definition optical coherence tomography just before excision and images analysed qualitatively. The surrounding normal looking skin has been used as control group. In lesional skin, dyskeratotic and atypical keratinocytes could be noticed with this new technique. An atypical honeycomb pattern in variable degree or a disarranged epidermal pattern could be observed. A good correlation between the dimension of atypia and/or disarrangement of the spinous-granular layer on en face images and the histopathological grading could be demonstrated. Relevant cross-sectional imaging criteria could be defined for the different histopathological variants of actinic keratoses. The surrounding skin displayed features of photodamage. Using features already suggested by reflectance confocal microscopy, the study implies that high-definition optical coherence tomography facilitates in vivo diagnosis of actinic keratosis and allows the grading of different actinic keratosis lesions for increased clinical utility.

Boone, Marc A L M; Norrenberg, Sarah

2013-01-01

300

Ultrasound-modulated optical tomography in reflection-mode with ring-shaped light illumination  

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We have succeeded in implementing ring-shaped light illumination ultrasound-modulated optical tomography (UOT) in reflection mode. The system used intense acoustic bursts and a charge-coupled device camera-based speckle contrast detection method. In addition, the implementation allows placing the tissue sample below (not within) an acoustic coupling water tank and scanning the tissue without moving the sample. Thus, the UOT system is more clinically applicable than previous transmission-mode ...

Kim, Chulhong; Song, Kwang Hyun; Maslov, Konstantin; Wang, Lihong V.

2009-01-01

 
 
 
 
301

Optical Coherence Tomography for the Assessment of Coronary Atherosclerosis and Vessel Response after Stent Implantation  

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Optical Coherence Tomography (OCT) is a light-based imaging modality that can provide in vivo high-resolution images of the coronary artery with a level of resolution (axial 10-20 µm) ten times higher than intravascular ultrasound. The technique, uses low-coherent near infrarred light to create high-resolution cross sectional images of the vessel. The technology refinement achieved in the last years has made this imaging modality less procedurally demanding opening its possibilities for cli...

Gonzalo, N.

2010-01-01

302

Modelling the normal retinal nerve fibre layer thickness as measured by Stratus optical coherence tomography.  

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Background: The variation in retinal nerve fibre layer thickness (RNFLT) as measured by Stratus optical coherence tomography (OCT) in healthy subjects may be reduced when the effect on RNFLT measurements of factors other than disease is corrected for, and this may improve the diagnostic accuracy in glaucoma. With this perspective we evaluated the isolated and combined effects of factors potentially affecting the Stratus OCT RNFLT measurements in healthy subjects. Methods: We included 178 heal...

Hougaard, Jesper; Ostenfeld, Carl; Heijl, Anders; Bengtsson, Boel

2006-01-01

303

Relation between Optical Fresnel transformation and quantum tomography in two-mode entangled case  

CERN Document Server

Similar in spirit to the preceding work [Opt. Commun. 282 (2009) 3734] where the relation between optical Fresnel transformation and quantum tomography is revealed, we study this kind of relationship in the two-mode entangled case. We show that under the two-mode Fresnel transformation the bipartite entangled state density |eta>_{r,s}=. Similarly, we find a simial conclusion in the `frequency` domain.

Fan, Hong-yi

2009-01-01

304

GPU-Accelerated Finite Element Method for Modelling Light Transport in Diffuse Optical Tomography  

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We introduce a GPU-accelerated finite element forward solver for the computation of light transport in scattering media. The forward model is the computationally most expensive component of iterative methods for image reconstruction in diffuse optical tomography, and performance optimisation of the forward solver is therefore crucial for improving the efficiency of the solution of the inverse problem. The GPU forward solver uses a CUDA implementation that evaluates on the graphics hardware th...

Martin Schweiger

2011-01-01

305

Lamin B distribution and association with peripheral chromatin revealed by optical sectioning and electron microscopy tomography  

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We have used a combination of immunogold staining, optical sectioning light microscopy, intermediate voltage electron microscopy, and EM tomography to examine the distribution of lamin B over the nuclear envelope of CHO cells. Apparent inconsistencies between previously published light and electron microscopy studies of nuclear lamin staining were resolved. At light microscopy resolution, an apparent open fibrillar network is visualized. Colocalization of lamin B and nuclear pores demonstrate...

1993-01-01

306

Thinking inside the graft: Applications of optical coherence tomography in coronary artery bypass grafting  

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Recent advances in catheter-based optical coherence tomography (OCT) have provided the necessary resolution and acquisition speed for high-quality intravascular imaging. Complications associated with clearing blood from the vessel of a living patient have prevented its wider acceptance. We identify a surgical application that takes advantage of the vascular imaging powers of OCT but that circumvents the difficulties. Coronary artery bypass grafting (CABG) is the most commonly performed major ...

Brown, Emile N.; Burris, Nicholas S.; Gu, Junyan; Kon, Zachary N.; Laird, Patrick; Kallam, Seeta; Tang, Cha-min; Schmitt, Joseph M.; Poston, Robert S.

2007-01-01

307

IN VIVO FIBER BASED HIGH SPEED OPTICAL COHERENCE TOMOGRAPHY IMAGES OF HUMAN FINGER  

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Full Text Available A High Speed Optical Coherence Tomography (OCT system based on single mode fiber which can capture eight images per second was used to acquire real time OCT images of human finger in vivo. The axial resolution of the set up was estimated to be 18 ?m. With this OCT images, the thickness of stratum corneum of the fingertip, finger pad and finger nail is evaluated.

S. Kumari

2011-08-01

308

Fluorescence diffuse optical tomography: Time-resolved versus continuous-wave in the reflectance configuration  

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Context and objectives In the context of fluorescence diffuse optical tomography, the time-resolved approach was shown to improve the reconstruction quality compared to the continuous-wave approach when adopting the transmittance configuration. However, the improvement seriously decreases in the presence of noise. The scope of this paper is to investigate the additional value of the time-resolved approach in the reflectance configuration. Material and methods A comparative study between time-...

Ducros, Nicolas; D Andrea, Cosimo; Bassi, Andrea; Peyrin, Franc?oise

2011-01-01

309

Experimental demonstration of quantitative imaging beyond Abbe's limit with optical diffraction tomography.  

Science.gov (United States)

Optical diffraction tomography (ODT) is a recent imaging technique that combines the experimental methods of phase microscopy and synthetic aperture with the mathematical tools of inverse scattering theory. We show experimentally that this approach permits us to obtain the map of permittivity of highly scattering samples with axial and transverse resolutions that are much better than that of a microscope with the same numerical aperture. PMID:19519110

Maire, Guillaume; Drsek, Filip; Girard, Jules; Giovannini, Hugues; Talneau, Anne; Konan, Denis; Belkebir, Kamal; Chaumet, Patrick C; Sentenac, Anne

2009-05-29

310

Can normal lymph node architecture be characterised by optical coherence tomography?  

Science.gov (United States)

Assessment of lymph node involvement is a key prognostic marker in early breast cancer. This paper demonstrates the ability of optical coherence tomography (OCT) to characterise the micro-architecture of healthy, non-cancerous lymph nodes. OCT is shown to differentiate stroma, cortex and adipose tissue. Characteristic patterns are also identified for germinal centres and blood vessels within the node. Results are correlated against a histopathological gold standard.

McLaughlin, R. A.; Scolaro, L.; Klyen, B. R.; Hamza, S.; Robbins, P.; Saunders, C.; Sampson, D. D.

2008-12-01

311

Comparison of central corneal thickness measured by anterior segment optical coherence tomography, pentacam and ultrasonic pachymetry  

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AIM: To investigate and analyze the differences in central corneal thickness(CCT)measurement by anterior segment optical coherence tomography(AS-OCT), pentacam rotating Scheimpflug camera and ultrasonic pachymetry(USP). METHODS: The retrospective study measured CCT of 43 patients(86 eyes)performed excimer laser myopia corrective surgery by the same examiner using RTVue AS-OCT with an anterior segment adaptor, pentacam rotating Scheimpflug camera, and PACSCAN300P USP. Data of three groups w...

Wei Zhao; Ting Wu; Ze-Hong Dong; Jie Feng; Yu-Feng Ren; Yu-Sheng Wang

2013-01-01

312

Central corneal thickness determined with optical coherence tomography in various types of glaucoma  

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AIMS—To evaluate central corneal thickness determined by optical coherence tomography (OCT) in various types of glaucoma, and its influence on intraocular pressure (IOP) measurement.?METHODS—Central corneal thickness (CCT) was determined by using OCT in 167 subjects (167 eyes). 20 had primary open angle glaucoma (POAG), 42 had low tension glaucoma (LTG), 22 had ocular hypertension (OHT), 10 had primary angle closure glaucoma (AC), 24 had pseudoexfoliation glaucoma (PEX), 13 had ...

Bechmann, M.; Thiel, M.; Roesen, B.; Ullrich, S.; Ulbig, M.; Ludwig, K.

2000-01-01

313

Correlation of spectral domain optical coherence tomography findings in acute central serous chorioretinopathy with visual acuity  

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Unnikrishnan Nair,1 Sunil Ganekal,2 Manoj Soman,1 KGR Nair11Chaithanya Eye Hospital and Research Institute, Trivandrum, Kerala, India; 2Nayana Super Specialty Eye Hospital and Research Center, Davangere, Karnataka, IndiaPurpose: To evaluate the structural changes in the acute phase of central serous chorioretinopathy and after its resolution, using spectral domain optical coherence tomography, to correlate these tomographic changes with visual acuity (VA).Method: This was a prospective study ...

Nair U; Ganekal S; Soman M; Kg, Nair

2012-01-01

314

Blunt ocular trauma at the posterior pole in optical coherence tomography and fluorescein angiography  

International Nuclear Information System (INIS)

Blunt ocular trauma at the posterior pole may involve a variety of retinal structures. We examined the most frequent retinal trauma (choroidal folds, commotion retinae, choroidal rupture, valsalva retinopathy, PPE-tears, Purtscher's Retinopathy etc.) by optical coherence tomography (OCT). The damaged pre-, intra- or subretinal structures were clearly visible. The OCT is during acute and chronic phases of different traumatic events an important diagnostic tool. (author)

315

Optical coherence tomography of the vitreoretinal interface in macular hole formation  

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AIMS—To image the vitreoretinal interface and provide further information on the pathogenesis of idiopathic macular hole formation.?METHODS—Prospective recruitment of 80 eyes of 41 consecutive patients referred with a diagnosis of idiopathic full thickness macular hole (FTMH) to a teaching hospital retinal clinic. Both eyes of each patient underwent optical coherence tomography (OCT) imaging with vertical and horizontal scans centred on the fovea.?RESULTS—A total of 30 eyes had s...

Tanner, V.; Chauhan, D.; Jackson, T.; Williamson, T.

2001-01-01

316

Endovascular optical coherence tomography intensity kurtosis: visualization of vasa vasorum in porcine carotid artery  

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Application of speckle variance optical coherence tomography (OCT) to endovascular imaging faces difficulty of extensive motion artifacts inherently associated with arterial pulsations in addition to other physiological movements. In this study, we employed a technique involving a fourth order statistical method, kurtosis, operating on the endovascular OCT intensity images to visualize the vasa vasorum of carotid artery in vivo and identify its flow dynamic in a porcine model. The intensity k...

Cheng, Kyle H. Y.; Sun, Cuiru; Vuong, Barry; Lee, Kenneth K. C.; Mariampillai, Adrian; Marotta, Thomas R.; Spears, Julian; Montanera, Walter J.; Herman, Peter R.; Kiehl, Tim-rasmus; Standish, Beau A.; Yang, Victor X. D.

2012-01-01

317

An active contour approach for segmentation of intra-retinal layers in optical coherence tomography images  

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Optical Coherence Tomography (OCT) is a non-invasive, depth-resolved imaging modality that has become a prominent ophthalmic diagnostic technique. We present a novel segmentation algorithm based on Chan-Vese's energy-minimizing active contours to detect intra-retinal layers in OCT images. A multi-phase framework with a circular shape prior is adopted to model the boundaries of retinal layers and estimate shape parameters using least squares. We use a contextual scheme to balance the weight of...

Yazdan Panah Gohar Rizi, Azadeh

2010-01-01

318

Large-volume optical coherence tomography with real-time correction of geometric distortion artifacts  

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Large-volume optical coherence tomography (OCT)-setups employ scanning mirrors and suffer from non-linear geometric distortion artifacts in which the degree of distortion is determined by the maximum angles over which the mirrors rotate. In this chapter, we describe a straightforward approach to correct for these distortion artifacts, creating an alternative to previously reported ray-tracing schemes that are unable to apply these corrections in real-time. By implementing th...

Jeught, Sam; Buytaert, Jan A. N.; Bradu, Adrian; Podoleanu, Adrian Gh; Dirckx, Joris J. J.

2012-01-01

319

Hemorrhagic Retinoschisis in Shaken Baby Syndrome Imaged with Spectral Domain Optical Coherence Tomography  

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Spectral domain optical coherence tomography (SD-OCT) images from an infant victim of shaken baby syndrome who presented with vitreous hemorrhage in the left eye and bilateral, large hemorrhages over both maculae. Both RetCam and SD-OCT images were obtained, demonstrating the position of the blood beneath the internal limiting membrane of the right macula. Image registration software was used to register the photographic images with the surface projection images obtained by the SD-OCT. In the...

Koozekanani, Dara D.; Weinberg, David V.; Dubis, Adam M.; Beringer, Joseph; Carroll, Joseph

2010-01-01

320

Optical coherence tomography imaging in asymptomatic patients with carotid artery stenosis  

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Assessment and treatment plan for asymptomatic patients with carotid stenosis are based on angiography at the present time. However, angiography or other imaging modalities are limited with their resolution to detect high-risk plaque features. Intravascular optical coherence tomography (IVOCT) recently emerged as a novel imaging modality with a unique resolution to identify vulnerable plaque characteristics. We report use of IVOCT in two separate asymptomatic patients with carotid stenosis with two different plaque types.

Cilingiroglu, Mehmet, E-mail: Mcilingiroglu@yahoo.com [University of Pittsburgh Heart and Vascular Institute, Pittsburgh, PA (United States); Hakeem, Abdul [William Beaumont Hospital, Royal Oak, MI (United States); Feldman, Marc [University of Texas Health Sciences Center at San Antonio, San Antonio, TX (United States); Wholey, Mark [University of Pittsburgh Heart and Vascular Institute, Pittsburgh, PA (United States)

2013-01-15

 
 
 
 
321

Multiple Fan-Beam Optical Tomography: Modelling Techniques  

Directory of Open Access Journals (Sweden)

Full Text Available This paper explains in detail the solution to the forward and inverse problem faced in this research. In the forward problem section, the projection geometry and the sensor modelling are discussed. The dimensions, distributions and arrangements of the optical fibre sensors are determined based on the real hardware constructed and these are explained in the projection geometry section. The general idea in sensor modelling is to simulate an artificial environment, but with similar system properties, to predict the actual sensor values for various flow models in the hardware system. The sensitivity maps produced from the solution of the forward problems are important in reconstructing the tomographic image.

Pang Jon Fea

2009-10-01

322

Real-time three-dimensional optical coherence tomography image-guided core-needle biopsy system  

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Advances in optical imaging modalities, such as optical coherence tomography (OCT), enable us to observe tissue microstructure at high resolution and in real time. Currently, core-needle biopsies are guided by external imaging modalities such as ultrasound imaging and x-ray computed tomography (CT) for breast and lung masses, respectively. These image-guided procedures are frequently limited by spatial resolution when using ultrasound imaging, or by temporal resolution (rapid real-time feedba...

Kuo, Wei-cheng; Kim, Jongsik; Shemonski, Nathan D.; Chaney, Eric J.; Spillman, Darold R.; Boppart, Stephen A.

2012-01-01

323

Imaging of basal cell carcinoma by high-definition optical coherence tomography : histomorphological correlation. A pilot study  

DEFF Research Database (Denmark)

With the continued development of noninvasive therapies for basal cell carcinoma (BCC) such as photodynamic therapy and immune therapies, noninvasive diagnosis and monitoring become increasingly relevant. High-definition optical coherence tomography (HD-OCT) is a high-resolution imaging tool, with micrometre resolution in both transversal and axial directions, enabling visualization of individual cells up to a depth of around 570 ?m, and filling the imaging gap between conventional optical coherence tomography (OCT) and reflectance confocal microscopy (RCM).

Boone, M A L M; Norrenberg, S

2012-01-01

324

Intravascular atherosclerotic imaging with combined fluorescence and optical coherence tomography probe based on a double-clad fiber combiner  

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We developed a multimodality fluorescence and optical coherence tomography probe based on a double-clad fiber (DCF) combiner. The probe is composed of a DCF combiner, grin lens, and micromotor in the distal end. An integrated swept-source optical coherence tomography and fluorescence intensity imaging system was developed based on the combined probe for the early diagnoses of atherosclerosis. This system is capable of real-time data acquisition and processing as well as image display. For flu...

Liang, Shanshan; Saidi, Arya; Jing, Joe; Liu, Gangjun; Li, Jiawen; Zhang, Jun; Sun, Changsen; Narula, Jagat; Chen, Zhongping

2012-01-01

325

Nonangiographic assessment of coronary artery disease: a practical approach to optical coherence tomography and fractional flow reserve.  

Science.gov (United States)

In an era of increased scrutiny of the appropriateness and safety of revascularization, interventional cardiologists must evolve by adding key tools to their armamentarium. This review highlights the utility of optical coherence tomography and fractional flow reserve in the catheterization lab and provides a practical guide for using these technologies during coronary intervention in various lesion subsets. We propose that fractional flow reserve informs the decision to intervene and optical coherence tomography guides the optimization of the outcome. PMID:25203101

Rassi, Andrew N; O'Dea, John A; Jia, Haibo; Seto, Arnold H; Jang, Ik-Kyung

2014-11-01

326

Mid-ventricular Tako-Tsubo cardiomyopathy with structurally normal coronary arteries confirmed by optical coherence tomography.  

Science.gov (United States)

Tako-Tsubo cardiomyopathy is an entity of unknown etiology characterized by transient apical dyskinesia in patients with angiographically normal coronary arteries. However, atypical forms of Tako-Tsubo cardiomyopathy may also occur, affecting other myocardial segments. Optical coherence tomography has a unique resolution and may detect angiographically silent atherosclerotic coronary artery disease. In this report, we describe optical coherence tomography findings in a patient with atypical Tako-Tsubo cardiomyopathy presenting as transient mid-ventricular ballooning. PMID:24296394

Alfonso, Fernando; Cárdenas, Alberto; Ibáñez, Borja

2013-12-01

327

In vivo lung microvasculature visualized in three dimensions using fiber-optic color Doppler optical coherence tomography  

Science.gov (United States)

For the first time, the use of fiber-optic color Doppler optical coherence tomography (CDOCT) to map in vivo the three-dimensional (3-D) vascular network of airway segments in human lungs is demonstrated. Visualizing the 3-D vascular network in the lungs may provide new opportunities for detecting and monitoring lung diseases such as asthma, chronic obstructive pulmonary disease, and lung cancer. Our CDOCT instrument employs a rotary fiber-optic probe that provides simultaneous two-dimensional (2-D) real-time structural optical coherence tomography (OCT) and CDOCT imaging at frame rates up to 12.5 frames per second. Controlled pullback of the probe allows 3-D vascular mapping in airway segments up to 50 mm in length in a single acquisition. We demonstrate the ability of CDOCT to map both small and large vessels. In one example, CDOCT imaging allows assignment of a feature in the structural OCT image as a large (˜1 mm diameter) blood vessel. In a second example, a smaller vessel (˜80 ?m diameter) that is indistinguishable in the structural OCT image is fully visualized in 3-D using CDOCT.

Lee, Anthony M. D.; Ohtani, Keishi; MacAulay, Calum; McWilliams, Annette; Shaipanich, Tawimas; Yang, Victor X. D.; Lam, Stephen; Lane, Pierre

2013-05-01

328

Imaging cone photoreceptors in three dimensions and in time using ultrahigh resolution optical coherence tomography with adaptive optics.  

Science.gov (United States)

Cone photoreceptors in the living human eye have recently been imaged with micron-scale resolution in all three spatial dimensions using adaptive optics optical coherence tomography. While these advances have allowed non-invasive study of the three-dimensional structure of living human cones, studies of their function and physiology are still hampered by the difficulties to monitor the same cells over time. The purpose of this study is to demonstrate the feasibility of cone monitoring using ultrahigh-resolution adaptive optics optical coherence tomography. Critical to this is incorporation of a high speed CMOS camera (125 KHz) and a novel feature-based, image registration/dewarping algorithm for reducing the deleterious effects of eye motion on volume images. Volume movies were acquired on three healthy subjects at retinal eccentricities from 0.5° to 6°. Image registration/dewarping reduced motion artifacts in the movies from 15 ?m to 1.3 ?m root mean square, the latter sufficient for identifying and tracking cones. Cone row-to-row spacing and outer segment lengths were consistent with that reported in the literature. Cone length analysis demonstrates that UHR-AO-OCT is sufficiently sensitive to measure real length differences between cones in the same 0.5° retinal patch, and requires no more than five measurements of OS length to achieve 95% confidence. We know of no other imaging modality that can monitor foveal or parafoveal cones over time with comparable resolution in all three dimensions. PMID:21483600

Kocaoglu, Omer P; Lee, Sangyeol; Jonnal, Ravi S; Wang, Qiang; Herde, Ashley E; Derby, Jack C; Gao, Weihua; Miller, Donald T

2011-01-01

329

Stellate figure in the macula: visualization in the Henle fiber layer on optical coherence tomography  

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Full Text Available Shinji Makino, Meri Watanabe, Hironobu TampoDepartment of Ophthalmology, Jichi Medical University, Shimotsuke, Tochigi, JapanAbstract: A 21-year-old woman complaining of a sudden visual disturbance in her left eye was referred to our hospital. The best-corrected visual acuity (BCVA in the left eye was 0.3. Fundus examination revealed tortuous retinal veins, soft exudates, and retinal edema. Optical coherence tomography showed that the macular thickness was increased to 685 µm. We diagnosed the condition as a central retinal vein occlusion. Systemic administration of an antiplatelet agent was initiated. The BCVA improved to 0.6, the retinal edema dramatically resolved, and the macular thickness was reduced to 318 µm 1 week later. Furthermore, the reduced retinal edema had transformed to many spokes in a wheel of exudates, a so-called “stellate figure”s, in the macula. On optical coherence tomography, hyper-reflective substances were detected in the Henle fiber layer. One month later, the BCVA improved to 1.0. Changes in microstructural findings and visual acuity were analogous during the recovery of macular edema in our patient.Keywords: stellate figure in the macula, Henle fiber layer, central retinal vein occlusion, macular edema, optical coherence tomography

Makino S

2014-01-01

330

Characteristics of polyacrylamide gel with THPC and Turnbull Blue gel dosimeters evaluated using optical tomography  

Science.gov (United States)

The purpose of this study was to compare characteristics of radiochromic gel - Turnbull Blue gel (TB gel) with polymer gel - polyacrylamide gel and tetrakis hydroxymethyl phosphonium chloride (PAGAT) using optical tomography. Both types of gels were examined in terms of dose sensitivity, dose response linearity and background value of spectrophotometric absorbance. The calibration curve was obtained for 60Co irradiation performed on Gammacell 220 at predefined gamma dose levels between 0 and 140 Gy for TBG and 0-15 Gy for PAGAT. To measure relative dose distributions from stereotactic irradiation, dosimeters were irradiated on Leksell Gamma Knife Perfexion. The cylindrical glass housings filled with gel were attached to the stereotactic frame. They were exposed with single shot and 16 mm collimator by 65 Gy to a 50% prescription isodose for TB gel and 4 Gy to a 50% prescription isodose for PAGAT. Evaluations of dosimeters were performed on an UV-vis Spectrophotometer Helios ? and an optical cone beam homemade tomography scanner with a 16-bit astronomy CCD camera with a set of color filters. The advantages and potential disadvantages for both types of gel dosimeters were summarized. Dose distribution in central slice and measured profiles of 16 mm shot shows excellent correspondence with treatment planning system Leksell GammaPlan® for both PAGAT and Turnbull Blue gels. Gel dosimeters are suitable for steep dose gradient verification. An optical tomography evaluation method is successful. Dose response characteristics of TB gel and PAGAT gel are presented.

Pila?ová (Vávr?), Kate?ina; Kozubíková, Petra; Šolc, Jaroslav; Sp?vá?ek, Václav

2014-11-01

331

The complementary benefit of anterior segment optical coherence tomography in penetrating keratoplasty  

Directory of Open Access Journals (Sweden)

Full Text Available Nursal Melda Yenerel,1 Raciha Beril Kucumen,2 Ebru Gorgun3 1Haydarpasa Numune Research and Training Hospital, Istanbul, Turkey; 2Yeditepe University Medical Faculty, Department of Ophthalmology, Istanbul, Turkey; 3Dunya Goz Eye Hospital, Istanbul, Turkey Purpose: To evaluate the utility of anterior segment optical coherence tomography (AS-OCT assessment in the pre- and postsurgical management of full-thickness corneal grafts. Methods: Seventy eyes of 58 patients who had penetrating keratoplasty were included in the study. High resolution AS-OCT scans of the cornea and the anterior segment were performed before and after transplantation in 17 eyes with the VisanteTM optical coherence tomography. Fifty-three eyes were examined in the late postoperative period. Results: The mean follow-up was 4.3 years (range, 1–15 years. Six different graft–host junctions were identified. Three patients with graft rejection, four patients with anterior synechia, and three patients with corneal ulcer were evaluated. Preoperative evaluation of eyes with semiopaque and totally opaque corneas revealed important information about anterior segment structures additional to slit-lamp findings. Conclusion: AS-OCT is a useful complementary tool for the evaluation of penetrating corneal transplantation surgery and in the management of its postoperative complications. Keywords: anterior segment optical coherence tomography, imaging techniques, penetrating keratoplasty

Yenerel NM

2013-07-01

332

Edema macular quístico pseudofáquico: Detección mediante «optical coherence tomography» / Pseudophakic cystoid macular edema: Assesment with optical coherence tomography  

Scientific Electronic Library Online (English)

Full Text Available SciELO Spain | Language: Spanish Abstract in spanish Objetivo: Detectar la incidencia de edema macular quístico (EMQ) tras cirugía de catarata tanto clínico como subclínico, mediante «ocular coherence tomography» (OCT) y comparar dicha incidencia entre un grupo de pacientes diabéticos y otro de no diabéticos. Material y métodos: Estudio prospectivo de [...] 260 ojos intervenidos de forma consecutiva de catarata mediante facoemulsificación con implante de lente intraocular acrílica, desde septiembre de 2004 a marzo de 2005. Grupo A: 208 ojos de pacientes no diabéticos, grupo B: 42 ojos de pacientes diabéticos, grupo C: 10 ojos de pacientes diabéticos con edema macular y que recibieron triamcinolona intravítrea (TAIV) al finalizar la cirugía. En cada revisión efectuada a los 6 días (basal), 5 semanas y 12 semanas se realizó biomicroscopía de polo posterior y OCT. Resultados: El espesor macular en la OCT, fue significativamente superior en el grupo B que en el grupo A (241,6 versus 204,6 µm p- 43,74 µm (2 DE del valor basal del grupo A). En el grupo B, seis ojos presentaron EMQ clínicamente significativo, con disminución de agudeza visual (14,2%), en 12 ojos detectamos aumento del espesor macular (28,5%). Las diferencias entre grupos fueron significativas (p Abstract in english Purpose: To determine the incidence of cystoid macular edema (CME) by means of clinical evaluation and subclinical assessment by means of ocular coherence tomography (OCT), and to compare the incidence between diabetic and non-diabetic groups of patients. Methods: Prospective study of 260 consecutiv [...] e cataract surgeries operated from September 2004 to March 2005. The procedures were performed by means of phacoemulsification plus intraocular acrylic lens implantation. Group A: 208 eyes of non-diabetic patients; Group B: 42 eyes of patients with diabetes and Group C: 10 eyes of diabetic patients with macular edema that received an intravitreal injection of triamcinolone at the end of surgery. Postoperative follow-up visits were performed 6 days (basal visit), 5 weeks and 12 weeks after surgery. Each visit included posterior pole biomicroscopy and OCT. Results: Central macular thickness measured by OCT was significantly increased in group B compared with group A (241.6 versus 204.6 µm; p

C., Torrón-Fernández-Blanco; O., Ruiz-Moreno; E., Ferrer-Novella; A., Sánchez-Cano; F.M., Honrubia-López.

2006-03-01

333

Automatic Detection of Glaucoma Using Optical Coherence Tomography Image  

Directory of Open Access Journals (Sweden)

Full Text Available Glaucoma is an eye disorder in which the optic nerve suffers damage, leading to vision defect in the affected eye(s and rolling to complete blindness if untreated. It is frequently associated with increased pressure in the fluid of the eye; aqueous humour. Glaucoma often goes undetected until significant damage to the subject’s visual field has occurred. As glaucoma progresses, neural tissues die, the nerve fiber layer thins and the cup-to-disk ratio increases. The conventional techniques typically used for this measurement are unreliable and creates intricacies while measuring considerably small changes in the nerve head geometry. In this study, an algorithm is proposed that facilitates segmentation of the retinal-nerve head vitreal boundary, choroid-nerve head boundary identification and determination of the extent of the optic cup and disk. This algorithm is assessed and evaluated with many samples of OCT images from both normal and pathological eyes. Subsequently, the results are validated with the available documents from expert ophthalmologist reporting the correlation coefficient for cup to disk ratio.

Rengaraj Venkatesh

2012-01-01

334

Scatter measurements for optical cone-beam computed tomography  

International Nuclear Information System (INIS)

Both x-ray and optical cone-beam CT (CBCT) scanners are limited by scattered photons that contaminate the primary images. Transparent radiochromic gels and plastics are anticipated to produce less scattering than polymerization gels and hence result in reconstructed dose distributions with greater contrast and dynamic range. Four methods of scatter measurement were investigated to quantify scatter fractions using an in-house optical CBCT scanner. The methods consisted of generating either 'coin' shadows or primary beamlets in transmission images. The four methods generated similar results of 10% scatter fractions in gel transmission images for this particular scanner configuration with both leuco crystal violet and carbon black micelle gels. The scatter contributions were distributed as 5% from micelle gel, 2% from Teflon wall, 2% from refractive index matching liquid and 1% other sources. Applying a uniform background subtraction of 2% of open field intensity resulted in 0.2% difference between laser CT and cone-beam CT reconstructed attenuation coefficients for a black micelle gel finger phantom.

335

Optical coherence tomography technologies: which machine do you want to own?  

Science.gov (United States)

Optical coherence tomography (OCT) has evolved over the past decade to become one of the most important ancillary tests in ophthalmic practice. This noninvasive ocular imaging technique provides high-resolution, cross-sectional images of the retinal nerve fiber layer (RNFL), macular region, ganglion cell layer, and optic nerve head. With OCT, we can learn much about axonal-neuronal integrity in the anterior aspect of the afferent visual pathway and gain insights about mechanisms of brain injury in various central nervous system disorders. PMID:25133968

Costello, Fiona E

2014-09-01

336

Enhancement of the signal-to-noise ratio at depths in Fourier domain optical coherence tomography  

Science.gov (United States)

We present a Fourier domain optical coherence tomography set-up built around an optical configuration that exhibits Talbot bands. To produce Talbot bands, the two interferometer beams, object and reference are laterally shifted in their way towards the diffraction grating. This allows attenuation of mirror terms and optimisation of the sensitivity profile. We imaged the human skin in-vivo, and quantified the profile of the sensitivity profile in tissue by measuring the ratio between the strengths of signals originating in the reticular dermis and in the stratum corneum for different values of the lateral shift of the two interfering beams.

Bradu, Adrian; Bouchal, Petr; Podoleanu, Adrian Gh.

2012-01-01

337

Optical coherence tomography use in evaluation of the vitreoretinal interface: a review.  

Science.gov (United States)

Optical coherence tomography (OCT) is a valuable tool for assessment of the vitreoretinal interface. This article reviews the normal process of age-related posterior vitreous detachment as viewed by OCT. Abnormalities of the vitreoretinal interface as imaged by OCT are described including vitreomacular traction syndrome, cystoid macular edema/ diabetic macular edema, epiretinal membranes, full thickness macular holes, lamellar holes, pseudoholes, microholes, and schisis from myopia or optic pits/colobomas. This tool has given us new insights into the pathogenesis of these retinal abnormalities. PMID:17574065

Mirza, Rukhsana G; Johnson, Mark W; Jampol, Lee M

2007-01-01

338

An all-at-once reduced Hessian SQP algorithm for frequency domain optical tomography  

Science.gov (United States)

We introduce in this work a PDE-constrained approach to optical tomography that makes use of an all-atonce reduced Hessian Sequential Quadratic Programming (rSQP) scheme. The proposed scheme treats the forward and inverse variables independently, which makes it possible to update the radiation intensities and the optical coefficients simultaneously by solving the forward and inverse problems, all at once. We evaluate the performance of the proposed scheme with numerical and experimental data, and find that the rSQP scheme can reduce the computation time by a factor of 10 to 25, as compared to the commonly employed limited memory BFGS method.

Kim, Hyun Keol; Gu, Xuejun; Hielscher, Andreas H.

2009-02-01

339

Misguided progression analysis by optical coherence tomography: a report of two cases.  

Science.gov (United States)

Spectral domain optical coherence tomography (SOCT) is an important tool for the diagnosis and management of glaucoma. In an effort to help automate the detection of progressive structural glaucomatous optic nerve damage, Carl Zeiss Meditec has developed Guided Progression Analysis (GPA) software in conjunction with the Cirrus SOCT (Carl Zeiss Meditec, Dublin, Calif., USA). Here, we report a case in which the GPA merged information from 2 different patients, and another case in which data from alternate eyes was compared, making the final analysis invalid. PMID:25202265

Kennedy, Jeffrey B; SooHoo, Jeffrey R; Seibold, Leonard K; Kahook, Malik Y

2014-05-01

340

Quantitative upper airway endoscopy with swept-source anatomical optical coherence tomography.  

Science.gov (United States)

Minimally invasive imaging of upper airway obstructions in children and adults is needed to improve clinical decision-making. Toward this goal, we demonstrate an anatomical optical coherence tomography (aOCT) system delivered via a small-bore, flexible endoscope to quantify the upper airway lumen geometry. Helical scans were obtained from a proximally-scanned fiber-optic catheter of 820 ?m outer diameter and >2 mm focal length. Coupled with a long coherence length wavelength-swept light source, the system exhibited an SNR roll-off of decision making, and predictive modeling of upper airway obstructive disorders. PMID:24688814

Wijesundara, Kushal; Zdanski, Carlton; Kimbell, Julia; Price, Hillel; Iftimia, Nicusor; Oldenburg, Amy L

2014-03-01

 
 
 
 
341

Diagnostic ability of barrett's index to detect dysthyroid optic neuropathy using multidetector computed tomography  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english OBJECTIVES: The objective of this study was to evaluate the ability of a muscular index (Barrett's Index), calculated with multidetector computed tomography, to detect dysthyroid optic neuropathy in patients with Graves' orbitopathy. METHODS: Thirty-six patients with Graves' orbitopathy were prospec [...] tively studied and submitted to neuro-ophthalmic evaluation and multidetector computed tomography scans of the orbits. Orbits were divided into two groups: those with and without dysthyroid optic neuropathy. Barrett's index was calculated as the percentage of the orbit occupied by muscles. Sensitivity and specificity were determined for several index values. RESULTS: Sixty-four orbits (19 with and 45 without dysthyroid optic neuropathy) met the inclusion criteria for the study. The mean Barrett's index values (± SD) were 64.47% ± 6.06% and 49.44% ± 10.94%in the groups with and without dysthyroid optic neuropathy, respectively (p60% should be carefully examined and followed for the development of dysthyroid optic neuropathy.

Mário L. R., Monteiro; Allan C. P., Gonçalves; Carla T. M., Silva; Janete P., Moura; Carolina S., Ribeiro; Eloisa M.M.S., Gebrim.

342

Dual modality optical coherence and whole-body photoacoustic tomography imaging of chick embryos in multiple development stages.  

Science.gov (United States)

Chick embryos are an important animal model for biomedical studies. The visualization of chick embryos, however, is limited mostly to postmortem sectional imaging methods. In this work, we present a dual modality optical imaging system that combines swept-source optical coherence tomography and whole-body photoacoustic tomography, and apply it to image chick embryos at three different development stages. The explanted chick embryos were imaged in toto with complementary contrast from both optical scattering and optical absorption. The results serve as a prelude to the use of the dual modality system in longitudinal whole-body monitoring of chick embryos in ovo. PMID:25401028

Liu, Mengyang; Maurer, Barbara; Hermann, Boris; Zabihian, Behrooz; Sandrian, Michelle G; Unterhuber, Angelika; Baumann, Bernhard; Zhang, Edward Z; Beard, Paul C; Weninger, Wolfgang J; Drexler, Wolfgang

2014-09-01

343

Early clinical results of time-of-flight optical tomography in a neonatal intensive care unit  

Science.gov (United States)

Medical optical imaging (MOI) and spectroscopy (MOS) use light emitted into opaque tissues in order to determine the interior structure and chemical content. These optical techniques have been developed in an attempt to prospectively identify impending brain injuries before they become irreversible, thus allowing injury to be avoided or minimized. Optical imaging and spectroscopy center around the simple idea that light passes through the body in small amounts, and emerges bearing clues about tissues through which it passed. Images can be reconstructed from such data, and this is the basis of optical tomography. We have used a time-of-flight system reported earlier to monitor oxygenation and image hemorrahage in neonatal brain. This chapter summarizes our early results.

Benaron, David A.; Van Houten, John P.; Cheong, Wai-Fung; Kermit, Eben L.; King, Richard A.

1995-05-01

344

Time resolved optical tomography of the human forearm  

International Nuclear Information System (INIS)

A 32-channel time-resolved optical imaging instrument has been developed principally to study functional parameters of the new-born infant brain. As a prelude to studies on infants, the device and image reconstruction methodology have been evaluated on the adult human forearm. Cross-sectional images were generated using time-resolved measurements of transmitted light at two wavelengths. All data were acquired using a fully automated computer-controlled protocol. Images representing the internal scattering and absorbing properties of the arm are presented, as well as images that reveal physiological changes during a simple finger flexion exercise. The results presented in this paper represent the first simultaneous tomographic reconstruction of the internal scattering and absorbing properties of a clinical subject using purely temporal data, with additional co-registered difference images showing repeatable absorption changes at two wavelengths in response to exercise. (author)

345

Time resolved optical tomography of the human forearm  

Energy Technology Data Exchange (ETDEWEB)

A 32-channel time-resolved optical imaging instrument has been developed principally to study functional parameters of the new-born infant brain. As a prelude to studies on infants, the device and image reconstruction methodology have been evaluated on the adult human forearm. Cross-sectional images were generated using time-resolved measurements of transmitted light at two wavelengths. All data were acquired using a fully automated computer-controlled protocol. Images representing the internal scattering and absorbing properties of the arm are presented, as well as images that reveal physiological changes during a simple finger flexion exercise. The results presented in this paper represent the first simultaneous tomographic reconstruction of the internal scattering and absorbing properties of a clinical subject using purely temporal data, with additional co-registered difference images showing repeatable absorption changes at two wavelengths in response to exercise. (author)

Hillman, Elizabeth M.C.; Hebden, Jeremy C.; Schweiger, Martin; Dehghani, Hamid; Schmidt, Florian E.W.; Delpy, David T. [Department of Medical Physics and Bioengineering, University College London, 11-20 Capper Street, London WC1E 6JA (United Kingdom); Arridge, Simon R. [Department of Computer Science, University College London, Gower Street, London WC1E 6BT (United Kingdom)

2001-04-01

346

Specifying tissue optical properties using axial dependence of confocal reflectance images: confocal scanning laser microscopy and optical coherence tomography  

Science.gov (United States)

The optical properties of a tissue can be specified by the depth dependence of a reflectance-mode confocal measurement, as the focus is scanned down into a tissue. Reflectance-mode confocal scanning laser microscopy (rCSLM) and optical coherence tomography in focus tracking mode (OCT) are two examples of such confocal measurements. The measurement of reflected signal as a function of the depth of focus, R(z), is expressed as ?e -?z, where ? [dimensionless] is the local reflectivity from the focus within a tissue and ? [cm -1] is the attenuation of signal as a function of z. The reflectivity of a mirror defines ? = 1. This paper describes how the experimental ? and ? map into the optical properties of scattering coefficient, ?s [cm -1], and anisotropy of scattering, g [dimensionless]. Preliminary results on tissue for the rCSLM and OCT systems are reported.

Jacques, S.; Samatham, R.; Choudhury, N.; Gareau, D. S.

2007-02-01

347

Analysis of cracks and damages in optical elements by a swept-source optical coherence tomography technique  

Science.gov (United States)

Optical coherence tomography (OCT) is a non- invasive technique where a near-infrared laser beam penetrates a sample and through the analysis of its scattered light information about the internal structure of the sample is calculated. Although OCT is mainly used in medicine its application to areas of enginery has been increased recently. Important features of recent OCT systems allow us to determine accurately volumetric structure not only slices. In this works we report such volumetric analysis applied to the study of scratches and damages in optical elements in order to quantify not only the scratch sizes but also its depths. This study is compared with an Schlieren technique. Experimental results are presented. The finding reveals clearly the faults locations which may be an attractive results for the optical work shop and the application of norms.

Muñoz Moreno, Gilberto; Alcalá Ochoa, Noé

2011-08-01

348

Improvement of fluorescence-enhanced optical tomography with improved optical filtering and accurate model-based reconstruction algorithms.  

Science.gov (United States)

The goal of preclinical fluorescence-enhanced optical tomography (FEOT) is to provide three-dimensional fluorophore distribution for a myriad of drug and disease discovery studies in small animals. Effective measurements, as well as fast and robust image reconstruction, are necessary for extensive applications. Compared to bioluminescence tomography (BLT), FEOT may result in improved image quality through higher detected photon count rates. However, background signals that arise from excitation illumination affect the reconstruction quality, especially when tissue fluorophore concentration is low and/or fluorescent target is located deeply in tissues. We show that near-infrared fluorescence (NIRF) imaging with an optimized filter configuration significantly reduces the background noise. Model-based reconstruction with a high-order approximation to the radiative transfer equation further improves the reconstruction quality compared to the diffusion approximation. Improvements in FEOT are demonstrated experimentally using a mouse-shaped phantom with targets of pico- and subpico-mole NIR fluorescent dye. PMID:22191919

Lu, Yujie; Zhu, Banghe; Darne, Chinmay; Tan, I-Chih; Rasmussen, John C; Sevick-Muraca, Eva M

2011-12-01

349

Optical tomography reconstruction algorithm with the finite element method: An optimal approach with regularization tools  

International Nuclear Information System (INIS)

Highlights: •New strategies to improve the accuracy of the reconstruction through mesh and finite element parameterization. •Use of gradient filtering through an alternative inner product within the adjoint method. •An integral form of the cost function is used to make the reconstruction compatible with all finite element formulations, continuous and discontinuous. •Gradient-based algorithm with the adjoint method is used for the reconstruction. -- Abstract: Optical tomography is mathematically treated as a non-linear inverse problem where the optical properties of the probed medium are recovered through the minimization of the errors between the experimental measurements and their predictions with a numerical model at the locations of the detectors. According to the ill-posed behavior of the inverse problem, some regularization tools must be performed and the Tikhonov penalization type is the most commonly used in optical tomography applications. This paper introduces an optimized approach for optical tomography reconstruction with the finite element method. An integral form of the cost function is used to take into account the surfaces of the detectors and make the reconstruction compatible with all finite element formulations, continuous and discontinuous. Through a gradient-based algorithm where the adjoint method is used to compute the gradient of the cost function, an alternative inner product is employed for preconditioning the reconstruction algorithm. Moreover, appropriate re-parameterization of the optical properties is performed. These regularization strategies are compared with the classical Tikhonov penalization one. It is shown that both the re-parameterization and the use of the Sobolev cost function gradient are efficient for solving such an ill-posed inverse problem

350

Optical tomography reconstruction algorithm with the finite element method: An optimal approach with regularization tools  

Energy Technology Data Exchange (ETDEWEB)

Highlights: •New strategies to improve the accuracy of the reconstruction through mesh and finite element parameterization. •Use of gradient filtering through an alternative inner product within the adjoint method. •An integral form of the cost function is used to make the reconstruction compatible with all finite element formulations, continuous and discontinuous. •Gradient-based algorithm with the adjoint method is used for the reconstruction. -- Abstract: Optical tomography is mathematically treated as a non-linear inverse problem where the optical properties of the probed medium are recovered through the minimization of the errors between the experimental measurements and their predictions with a numerical model at the locations of the detectors. According to the ill-posed behavior of the inverse problem, some regularization tools must be performed and the Tikhonov penalization type is the most commonly used in optical tomography applications. This paper introduces an optimized approach for optical tomography reconstruction with the finite element method. An integral form of the cost function is used to take into account the surfaces of the detectors and make the reconstruction compatible with all finite element formulations, continuous and discontinuous. Through a gradient-based algorithm where the adjoint method is used to compute the gradient of the cost function, an alternative inner product is employed for preconditioning the reconstruction algorithm. Moreover, appropriate re-parameterization of the optical properties is performed. These regularization strategies are compared with the classical Tikhonov penalization one. It is shown that both the re-parameterization and the use of the Sobolev cost function gradient are efficient for solving such an ill-posed inverse problem.

Balima, O., E-mail: ofbalima@gmail.com [Département des Sciences Appliquées, Université du Québec à Chicoutimi, 555 bd de l’Université, Chicoutimi, QC, Canada G7H 2B1 (Canada); Favennec, Y. [LTN UMR CNRS 6607 – Polytech’ Nantes – La Chantrerie, Rue Christian Pauc, BP 50609 44 306 Nantes Cedex 3 (France); Rousse, D. [Chaire de recherche industrielle en technologies de l’énergie et en efficacité énergétique (t3e), École de technologie supérieure, 201 Boul. Mgr, Bourget Lévis, QC, Canada G6V 6Z3 (Canada)

2013-10-15

351

Edema macular quístico pseudofáquico: Detección mediante «optical coherence tomography» Pseudophakic cystoid macular edema: Assesment with optical coherence tomography  

Directory of Open Access Journals (Sweden)

Full Text Available Objetivo: Detectar la incidencia de edema macular quístico (EMQ tras cirugía de catarata tanto clínico como subclínico, mediante «ocular coherence tomography» (OCT y comparar dicha incidencia entre un grupo de pacientes diabéticos y otro de no diabéticos. Material y métodos: Estudio prospectivo de 260 ojos intervenidos de forma consecutiva de catarata mediante facoemulsificación con implante de lente intraocular acrílica, desde septiembre de 2004 a marzo de 2005. Grupo A: 208 ojos de pacientes no diabéticos, grupo B: 42 ojos de pacientes diabéticos, grupo C: 10 ojos de pacientes diabéticos con edema macular y que recibieron triamcinolona intravítrea (TAIV al finalizar la cirugía. En cada revisión efectuada a los 6 días (basal, 5 semanas y 12 semanas se realizó biomicroscopía de polo posterior y OCT. Resultados: El espesor macular en la OCT, fue significativamente superior en el grupo B que en el grupo A (241,6 versus 204,6 µm p- 43,74 µm (2 DE del valor basal del grupo A. En el grupo B, seis ojos presentaron EMQ clínicamente significativo, con disminución de agudeza visual (14,2%, en 12 ojos detectamos aumento del espesor macular (28,5%. Las diferencias entre grupos fueron significativas (pPurpose: To determine the incidence of cystoid macular edema (CME by means of clinical evaluation and subclinical assessment by means of ocular coherence tomography (OCT, and to compare the incidence between diabetic and non-diabetic groups of patients. Methods: Prospective study of 260 consecutive cataract surgeries operated from September 2004 to March 2005. The procedures were performed by means of phacoemulsification plus intraocular acrylic lens implantation. Group A: 208 eyes of non-diabetic patients; Group B: 42 eyes of patients with diabetes and Group C: 10 eyes of diabetic patients with macular edema that received an intravitreal injection of triamcinolone at the end of surgery. Postoperative follow-up visits were performed 6 days (basal visit, 5 weeks and 12 weeks after surgery. Each visit included posterior pole biomicroscopy and OCT. Results: Central macular thickness measured by OCT was significantly increased in group B compared with group A (241.6 versus 204.6 µm; p<0,001. No clinical evidence of CME was found in group A, although 4 eyes (1.92% showed macular thickness equal to or greater than 43.74 µm (2 standard deviations of the basal value for group A. In group B, clinical evidence of CME was found in 6 eyes, with decreased visual acuities (14.2%. The differences between these groups were statistically significant (p<0.001. The 10 eyes that received an intravitreal injection of triamcinolone after the surgical procedure showed a mean decrease in central retinal thickness of 77 µm after 12 weeks postoperative. Conclusions: This study has shown a low incidence of clinical CME. OCT showed increased macular thickness in both groups of patients in a small percentage of cases, and significantly increased macular thickness in diabetic patients.

C. Torrón-Fernández-Blanco

2006-03-01

352

Assessment of coronary arterial thrombus by optical coherence tomography.  

Science.gov (United States)

We analyzed optical coherence tomographic (OCT) characteristics of different types of coronary thrombi that had been confirmed at postmortem histologic examination. We examined 108 coronary arterial segments of 40 consecutive human cadavers. OCT images of red and white thrombi were obtained and the intensity property of these thrombi was analyzed. Red and white thrombi were found in 16 (17%) and 19 (18%) of the 108 arterial segments, respectively. Red thrombi were identified as high-backscattering protrusions inside the lumen of the artery, with signal-free shadowing in the OCT image. White thrombi were identified as low-backscattering projections in the OCT image. There were no significant differences in peak intensity of OCT signal between red and white thrombi (130+/-18 vs 145+/-34, p=0.12). However, the 1/2 attenuation width of the signal intensity curve, which was defined as the distance from peak intensity to its 1/2 intensity, was significantly different between red and white thrombi (324+/-50 vs 183+/- 42 microm, pus not only to estimate plaque morphology but also to distinguish red from white thrombi. PMID:16765119

Kume, Teruyoshi; Akasaka, Takashi; Kawamoto, Takahiro; Ogasawara, Yasuo; Watanabe, Nozomi; Toyota, Eiji; Neishi, Yoji; Sukmawan, Renan; Sadahira, Yoshito; Yoshida, Kiyoshi

2006-06-15

353

Versatile optical coherence tomography for imaging the human eye.  

Science.gov (United States)

We demonstrated the feasibility of a CMOS-based spectral domain OCT (SD-OCT) for versatile ophthalmic applications of imaging the corneal epithelium, limbus, ocular surface, contact lens, crystalline lens, retina, and full eye in vivo. The system was based on a single spectrometer and an alternating reference arm with four mirrors. A galvanometer scanner was used to switch the reference beam among the four mirrors, depending on the imaging application. An axial resolution of 7.7 ?m in air, a scan depth of up to 37.7 mm in air, and a scan speed of up to 70,000 A-lines per second were achieved. The approach has the capability to provide high-resolution imaging of the corneal epithelium, contact lens, ocular surface, and tear meniscus. Using two reference mirrors, the zero delay lines were alternatively placed on the front cornea or on the back lens. The entire ocular anterior segment was imaged by registering and overlapping the two images. The full eye through the pupil was measured when the reference arm was switched among the four reference mirrors. After mounting a 60 D lens in the sample arm, this SD-OCT was used to image the retina, including the macula and optical nerve head. This system demonstrates versatility and simplicity for multi-purpose ophthalmic applications. PMID:23847729

Tao, Aizhu; Shao, Yilei; Zhong, Jianguang; Jiang, Hong; Shen, Meixiao; Wang, Jianhua

2013-07-01

354

A small animal time-resolved optical tomography platform using wide-field excitation  

Science.gov (United States)

Small animal imaging plays a critical role in present day biomedical research by filling an important gap in the translation of research from the bench to the bedside. Optical techniques constitute an emerging imaging modality which have tremendous potential in preclinical applications. Optical imaging methods are capable of non-invasive assessment of the functional and molecular characteristics of biological tissue. The three-dimensional optical imaging technique, referred to as diffuse optical tomography, provides an approach for the whole-body imaging of small animal models and can provide volumetric maps of tissue functional parameters (e.g. blood volume, oxygen saturation etc.) and/or provide 3D localization and quantification of fluorescence-based molecular markers in vivo. However, the complex mathematical reconstruction problem associated with optical tomography and the cumbersome instrumental designs limits its adoption as a high-throughput quantitative whole-body imaging modality in current biomedical research. The development of new optical imaging paradigms is thus necessary for a wide-acceptance of this new technology. In this thesis, the design, development, characterization and optimization of a small animal optical tomography system is discussed. Specifically, the platform combines a highly sensitive time-resolved imaging paradigm with multi-spectral excitation capability and CCD-based detection to provide a system capable of generating spatially, spectrally and temporally dense measurement datasets. The acquisition of such data sets however can take long and translate to often unrealistic acquisition times when using the classical point source based excitation scheme. The novel approach in the design of this platform is the adoption of a wide-field excitation scheme which employs extended excitation sources and in the process allows an estimated ten-fold reduction in the acquisition time. The work described herein details the design of the imaging platform employing DLP-based excitation and time-gated intensified CCD detection and the optimal system operation parameters are determined. The feasibility this imaging approach and accuracy of the system in reconstructing functional parameters and fluorescence markers based on lifetime contrast is established through phantom studies. As a part of the system characterization, the effect of noise in time-resolved optical tomography is investigated and propagation of system noise in optical reconstructions is established. Furthermore, data processing and measurement calibration techniques aimed at reducing the effect of noise in reconstructions are defined. The optimization of excitation pattern selection is established through a novel measurement-guided iterative pattern correction scheme. This technique referred to as Adaptive Full-Field Optical Tomography was shown to improve reconstruction performances in murine models by reducing the dynamic range in photon flux measurements on the surface. Lastly, the application of the unique attributes of this platform to a biologically relevant imaging application, referred to as Forster Resonance Energy Transfer is described. The tomographic imaging of FRET interaction in vivo on a whole-body scale is achieved using the wide-field imaging approach based on lifetime contrast. This technique represents the first demonstration of tomographic FRET imaging in small animals and has significant potential in the development of optical imaging techniques in varied applications ranging from drug discovery to in vivo study of protein-protein interaction.

Venugopal, Vivek

355

Optical tomography with the discontinuous Galerkin formulation of the radiative transfer equation in frequency domain  

International Nuclear Information System (INIS)

Optical tomography is an inverse method of probing semi-transparent media with the help of light sources. The reconstruction of the optical properties usually employs finite volumes or continuous finite elements formulations of light transport as a forward model for the predictions. In a previous study, we have introduced a generalization of the inversion approach with finite elements formulations by using an integral form of the objective function. The novelty is that the surfaces of the detectors are taken into account in the reconstruction and compatibility is obtained for all finite element formulations. This present paper illustrates this new approach by developing a Discontinuous Galerkin formulation as a forward model for an optical tomography application in the frequency domain framework. Numerical tests are performed to gauge the accuracy of the method in recovering optical properties distribution with a gradient-based algorithm where the adjoint method is used to fastly compute the objective function gradient. It is seen that the reconstruction is accurate and can be affected by noise on the measurements as expected. Filtering of the gradient at each iteration of the reconstruction is used to cope with the ill-posed nature of the inverse problem and to improves the quality and accuracy of the reconstruction.

356

Predicting dysthyroid optic neuropathy using computed tomography volumetric analyses of orbital structures  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english OBJECTIVE: To evaluate the ability of orbital apex crowding volume measurements calculated with multidetector-computed tomography to detect dysthyroid optic neuropathy. METHODS: Ninety-three patients with Graves' orbitopathy were studied prospectively. All of the patients underwent a complete neuro- [...] ophthalmic examination and computed tomography scanning. Volumetric measurements were calculated from axial and coronal contiguous sections using a dedicated workstation. Orbital fat and muscle volume were estimated on the basis of their attenuation values (in Hounsfield units) using measurements from the anterior orbital rim to the optic foramen. Two indexes of orbital muscle crowding were calculated: i) the volumetric crowding index, which is the ratio between soft tissue (mainly extraocular muscles) and orbital fat volume and is based on axial scans of the entire orbit; and ii) the volumetric orbital apex crowding index, which is the ratio between the extraocular muscles and orbital fat volume and is based on coronal scans of the orbital apex. Two groups of orbits (with and without dysthyroid optic neuropathy) were compared. RESULTS: One hundred and two orbits of 61 patients with Graves' orbitopathy met the inclusion criteria and were analyzed. Forty-one orbits were diagnosed with Graves' orbitopathy, and 61 orbits did not have optic neuropathy. The two groups of orbits differed significantly with regard to both of the volumetric indexes (p

Allan C. Pieroni, Gonçalves; Lucas Nunes, Silva; Eloísa M. M. S., Gebrim; Suzana, Matayoshi; Mário Luiz Ribeiro, Monteiro.

2012-08-01

357

Relationship Between Optic Nerve Appearance and Retinal Nerve Fiber Layer Thickness as Explored with Spectral Domain Optical Coherence Tomography  

Science.gov (United States)

Purpose To study the relationship between the appearance of the optic nerve and the retinal nerve fiber layer (RNFL) thickness determined by spectral domain optical coherence tomography (OCT). Methods Records from patients with spectral domain-OCT imaging in a neuro-ophthalmology practice were reviewed. Eyes with glaucoma/glaucoma suspicion, macular/optic nerve edema, pseudophakia, and with refractive errors > 6D were excluded. Optic nerve appearance by slit lamp biomicroscopy was related to the RNFL thickness by spectral domain-OCT and to visual field results. Results Ninety-one patients (176 eyes; mean age: 49 ± 15 years) were included. Eighty-three eyes (47%) showed optic nerve pallor; 89 eyes (50.6%) showed RNFL thinning (sectoral or average peripapillary). Average peripapillary RNFL thickness in eyes with pallor (mean ± SD = 76 ± 17 ?m) was thinner compared to eyes without pallor (91 ± 14 ?m, P Optic nerve pallor predicted RNFL thinning with a sensitivity of 69% and a specificity of 75%. Optic nerve appearance predicted RNFL thinning (with a sensitivity and specificity of 81%) when RNFL had thinned by ? 40%. Most patients with pallor had RNFL thinning with (66%) or without (25%) visual field loss; the remainder had normal RNFL and fields (5%) or with visual field abnormalities (4%). Conclusions Optic nerve pallor as a predictor of RNFL thinning showed fair sensitivity and specificity, although it is optimally sensitive/specific only when substantial RNFL loss has occurred. Translational Relevance Finding an acceptable relationship between the optic nerve appearance by ophthalmoscopy and spectral domain-OCT RNFL measures will help the clinician's interpretation of the information provided by this technology, which is gaining momentum in neuro-ophthalmic research. PMID:25374773

Aleman, Tomas S.; Huang, Jiayan; Garrity, Sean T.; Carter, Stuart B.; Aleman, Wendy D.; Ying, Gui-shuang; Tamhankar, Madhura A.

2014-01-01

358

Light shadowing effect of large breast lesions imaged by optical tomography in reflection geometry  

Science.gov (United States)

When a large, highly absorbing breast lesion is imaged by optical tomography in reflection geometry, most of the photons are absorbed by the top portion of the lesion. As a result, the lower portion of the lesion is not quantified correctly. This posterior light shadowing effect is similar to the sound shadowing effect frequently seen in pulse-echo ultrasound images. The presence of significant posterior shadowing of a lesion in ultrasound images suggests malignance. The light shadowing effect due to optical contrast is characterized using a simple measure and validated by the Monte Carlo photon-tracking method and phantom experiments. Clinical examples of large malignant and benign lesions are presented to demonstrate the shadowing effect and the utility of the measure. Understanding and quantifying the shadowing effect due to optical contrast is important for characterizing larger malignant cancers from benign lesions.

Xu, Chen; Zhu, Quing

2010-05-01

359

Design and optimization of a spectrometer for spectral domain optical coherence tomography  

Science.gov (United States)

There are several factors such as the chosen optical source, central wavelength, spectral bandwidth, spectrometer optical components and the detector specifications that affect the overall performance of a spectral domain optical coherence tomography (SD-OCT) imaging system. Among these factors a good design and implementation of the spectrometer is of paramount importance as it directly affects the system resolution, sensitivity fall-off, maximum imaging depth, SNR and in general the system performance. This study demonstrates the design steps and some considerations during the design of a spectrometer. The imaging performance of this design is assessed. The obtained experimental results prove an improvement of the overall performance of the common path SD-OCT imaging system and agree with the expected outcome from the design stage.

Hosseiny, Hamid; Carmelo Rosa, Carla

2014-08-01

360

Imaging of subcutaneous blood vessels and flow velocity profiles by optical coherence tomography  

Science.gov (United States)

We have applied a compact low power rapid scanning Doppler Optical Coherence Tomography system to monitor multi-dimensional velocity profiles within the complex vessels and simultaneous real-time non-invasive imaging of skin tissues morphology in vivo, in the wavelength range of 1.3-1.5 nm. Optical clearing of skin tissues has been utilized to achieve depth of OCT images up to 1.7 mm. Current approach enables applying low-power (0.4-0.5 mW) and low-noise broadband near-infrared light sources and obtaining OCT images with down to 12 ?m spatial resolution. Two-dimensional time-domain OCT images of complex flow velocity profiles in blood vessel phantom and in vivo subcutaneous human skin tissues are presented. The effect of optical clearing on in vivo images is demonstrated and discussed.

Bonesi, M.; Proskurin, S. G.; Meglinski, I. V.

2010-04-01

 
 
 
 
361

Imaging osteoarthritis in the knee joints using x-ray guided diffuse optical tomography  

Science.gov (United States)

In our previous studies, near-infrared (NIR) diffuse optical tomography (DOT) had been successfully applied to imaging osteoarthritis (OA) in the finger joints where significant difference in optical properties of the joint tissues was evident between healthy and OA finger joints. Here we report for the first time that large joints such as the knee can also be optically imaged especially when DOT is combined with x-ray tomosynthesis where the 3D image of the bones from x-ray is incorporated into the DOT reconstruction as spatial a priori structural information. This study demonstrates that NIR light can image large joints such as the knee in addition to finger joints, which will drastically broaden the clinical utility of our x-ray guided DOT technique for OA diagnosis.

Zhang, Qizhi; Yuan, Zhen; Sobel, Eric S.; Jiang, Huabei

2010-02-01

362

Fiber-Based Polarization Diversity Detection for Polarization-Sensitive Optical Coherence Tomography  

Directory of Open Access Journals (Sweden)

Full Text Available We present a new fiber-based polarization diversity detection (PDD scheme for polarization sensitive optical coherence tomography (PSOCT. This implementation uses a new custom miniaturized polarization-maintaining fiber coupler with single mode (SM fiber inputs and polarization maintaining (PM fiber outputs. The SM fiber inputs obviate matching the optical lengths of the two orthogonal OCT polarization channels prior to interference while the PM fiber outputs ensure defined orthogonal axes after interference. Advantages of this detection scheme over those with bulk optics PDD include lower cost, easier miniaturization, and more relaxed alignment and handling issues. We incorporate this PDD scheme into a galvanometer-scanned OCT system to demonstrate system calibration and PSOCT imaging of an achromatic quarter-wave plate, fingernail in vivo, and chicken breast, salmon, cow leg, and basa fish muscle samples ex vivo.

Hamid Pahlevaninezhad

2014-09-01

363

Three-dimensional spectral domain optical coherence tomography in X linked foveal retinoschisis.  

Science.gov (United States)

Spectral domain optical coherence tomography (SD-OCT) was performed in two cases of bilateral X linked foveal retinoschisis of different age groups. On fundus examination spoke wheel and honeycomb pattern of cysts were observed along with retinal nerve fibre layer (RNFL) defects. On SD-OCT, schisis was observed in the outer plexiform layer. External limiting membrane disruption was observed in the subfoveal area, along with disruption of outer nuclear layer (ONL) and inner-outer segment junction. Elevation of ONL due to tractional pull of central palisade was a novel observation. Retinoschisis extended beyond the optic disc up to the nasal region. Extracted RNFL tomogram presented an unprecedented visualisation of schisis along 360° of the optic disc. Tractional elevation in the foveal area and schisis involving nasal region, not observed upon clinical examination, was highlighted on SD-OCT. This investigative modality is an important adjunct in the assessment of foveal retinoschisis. PMID:23563673

Saxena, Sandeep; Manisha; Meyer, Carsten H

2013-01-01

364

Identification of prefrontal cortex (BA10) activation while performing Stroop test using diffuse optical tomography  

Science.gov (United States)

Stroop test is commonly used as a behavior-testing tool for psychological examinations that are related to attention and cognitive control of the human brain. Studies have shown activations in Broadmann area 10 (BA10) of prefrontal cortex (PFC) during attention and cognitive process. The use of diffuse optical tomography (DOT) for human brain mapping is becoming more prevalent. In this study we expect to find neural correlates between the performed cognitive tasks and hemodynamic signals detected by a DOT system. Our initial observation showed activation of oxy-hemoglobin concentration in BA 10, which is consistent with some results seen by positron emission tomography (PET) and functional magnetic resonance imaging (fMRI). Our study demonstrates the possibility of combining DOT with Stroop test to quantitatively investigate cognitive functions of the human brain at the prefrontal cortex.

Khadka, Sabin; Chityala, Srujan R.; Tian, Fenghua; Liu, Hanli

2011-03-01

365

Tomography  

International Nuclear Information System (INIS)

Tomography images of a body are constructed by placing a plurality of surface electrodes at spaced intervals on the body, causing currents to flow in the body (e.g. by applying a potential between each pair of electrodes in turn, or by induction), and measuring the potential between pairs of electrodes, calculating the potential expected in each case on the assumption that the body consists of a medium of uniform impedance, plotting the isopotentials corresponding to the calculated results to create a uniform image of the body, obtaining the ratio between the measured potential and the calculated potential in each case, and modifying the image in accordance with the respective ratios by increasing the assumed impedance along an isopotential in proportion to a ratio greater than unity or decreasing the assumed impedance in proportion to a ratio less than unity. The modified impedances along the isopotentials for each pair of electrodes are superimposed. The calculations are carried out using a computer and the plotting is carried out by a visual display unit and/or a print-out unit. (author)

366

Three-dimensional correction of conduction velocity in the embryonic heart using integrated optical mapping and optical coherence tomography  

Science.gov (United States)

Optical mapping (OM) of cardiac electrical activity conventionally collects information from a three-dimensional (3-D) surface as a two-dimensional (2-D) projection map. When applied to measurements of the embryonic heart, this method ignores the substantial and complex curvature of the heart surface, resulting in significant errors when calculating conduction velocity, an important electrophysiological parameter. Optical coherence tomography (OCT) is capable of imaging the 3-D structure of the embryonic heart and accurately characterizing the surface topology. We demonstrate an integrated OCT/OM imaging system capable of simultaneous conduction mapping and 3-D structural imaging. From these multimodal data, we obtained 3-D activation maps and corrected conduction velocity maps of early embryonic quail hearts. 3-D correction eliminates underestimation bias in 2-D conduction velocity measurements, therefore enabling more accurate measurements with less experimental variability. The integrated system will also open the door to correlate the structure and electrophysiology, thereby improving our understanding of heart development.

Ma, Pei; Wang, Yves T.; Gu, Shi; Watanabe, Michiko; Jenkins, Michael W.; Rollins, Andrew M.

2014-07-01

367

Morphological changes in blood vessels produced by hyperosmotic agents and measured by optical coherence tomography.  

Science.gov (United States)

Optical tissue clearing by hyperosmotic chemical agents significantly increases light depth penetration in skin and may improve light-based therapeutics such as laser treatment of cutaneous vascular lesions. A feasibility study was conducted to evaluate the potential role of optical clearing by glycerol in laser treatment of cutaneous vessels. Optical imaging was performed to investigate the morphological effects of glycerol on blood vessels of skin. Blood vessels were imaged using Doppler optical coherence tomography in in vivo hamster skin treated with glycerol. Images were obtained from the subdermal side to assess morphological changes in the blood vessels caused by glycerol and from the epidermal side to assess enhanced Doppler imaging of blood vessels. Application of glycerol to the subdermis resulted in venule stasis and for prolonged treatment times, arteriole stasis. In cases where flow remained in arterioles, an improved Doppler signal was detected from blood vessels when imaging transepidermally compared with the native condition. Intensity images indicated changes in blood optical properties and improved contrast of skin cross sections after glycerol application. The observed optical and morphological effects were reversed upon hydration of the skin with phosphate-buffered saline. The combination of increased depth of light penetration and the temporary slowing or cessation of flow in blood vessels could mean improved laser treatment of vessels. PMID:12812298

Vargas, Gracie; Readinger, Allison; Dozier, Susan S; Welch, Ashley J

2003-05-01

368

Detecting glucose-induced changes in in vitro and in vivo experiments with optical coherence tomography.  

Science.gov (United States)

Optical clearing is a well-known phenomenon. It is based on the matching of refractive indices of a bulk material and scattering particles. The same principle is also used in scattering-based optical measurements of different constituents, such as glucose. By registering changes in scattering, it is possible to evaluate changes in the concentration of a solvent. This work describes the use of optical coherence tomography (OCT) to monitor glucose-induced changes in the optical properties of samples. Intralipid, mouse skin tissue, and mice (C57BL) are used as samples. Differences between in vitro and in vivo measurement conditions, the effect of glucose on the samples' optical properties, as well as possible problems in OCT experiments are discussed. A comparison of OCT signals from mouse skin samples and mice in vivo shows that the intensity of backscattered radiation is stronger in a living animal than in cultured tissue. Moreover, the effect of glucose on the scattering properties is larger in an in vivo case than in an in vitro case. In comparison with tissue, the effect of glucose is the smallest in Intralipid. The results increase the value of using cultured tissue in developing optical sensing techniques. PMID:18465960

Kinnunen, Matti; Myllylä, Risto; Vainio, Seppo

2008-01-01

369

Diagnosing breast cancer using independent diffuse optical tomography and x-ray mammography scans  

Science.gov (United States)

We have previously demonstrated the utilization of spatially co-registered diffuse optical tomography (DOT) and digital breast tomosynthesis (DBT) for joint breast cancer diagnosis. However, clinical implementation of such a multi-modality approach may require development of integrated DOT/DBT imaging scanners, which can be costly and time-consuming. Exploring effective image registration methods that combine the diagnostic information from a standalone DOT measurement and a separate mammogram can be a cost-effective solution, which may eventually enable adding functional optical assessment to all previously installed digital mammography systems. In this study, we investigate a contour-based image registration method to convert independent optical and x-ray scans into co-registered datasets that can benefit from a joint image analysis. The breast surface used in 3D optical DOT reconstruction is registered with the breast contour line extracted from an x-ray mammogram acquired separately. This allows us to map the 2D mammogram to the optical measurement space and build structural constraints for optical image reconstruction. A non-linear reconstruction utilizing structure-priors is then performed to produce hemoglobin maps with improved resolution. To validate this approach, we used a set of tumor patient measurements with simultaneous DOT/DBT and separate 2D mammographic scans. The images recovered from the registration procedure derived from DOT and 2D mammogram present similar image quality compared to those recovered from co-registered DOT/DBT measurements.

Fradkin, Maxim; Hofmann, Matthias C.; Rouet, Jean-Michel; Moore, Richard H.; Kopans, Daniel B.; Tipton, Keith; Suryanarayanan, Sankar; Boas, David A.; Fang, Qianqian

2013-03-01

370

Optical coherence tomography in the diagnosis and treatment of neurological disorders.  

Science.gov (United States)

Optical contrast is often the limiting factor in the imaging of live biological tissue. Studies were conducted in postmortem human brain to identify clinical applications where the structures of interest possess high intrinsic optical contrast and where the real-time, high-resolution imaging capabilities of optical coherence tomography (OCT) may be critical. Myelinated fiber tracts and blood vessels are two structures with high optical contrast. The ability to image these two structures in real time may improve the efficacy and safety of a neurosurgical procedure to treat Parkinson's disease called deep brain stimulation (DBS). OCT was evaluated as a potential optical guidance system for DBS in 25 human brains. The results suggest that catheter-based OCT has the resolution and contrast necessary for DBS targeting. The results also demonstrate the ability of OCT to detect blood vessels with high sensitivity, suggesting a possible means to avoid their laceration during DBS. Other microscopic structures in the human brain with high optical contrast are pathological vacuoles associated with transmissible spongiform encephalopathy (TSE). TSE include diseases such as Mad Cow disease and Creutzfeldt-Jakob disease (CJD) in humans. OCT performed on the brain from a woman who died of CJD was able to detect clearly the pathological vacuoles. PMID:16292951

Jafri, M Samir; Farhang, Suzanne; Tang, Rebecca S; Desai, Naman; Fishman, Paul S; Rohwer, Robert G; Tang, Cha-Min; Schmitt, Joseph M

2005-01-01

371

Study of continuous-wave domain fluorescence diffuse optical tomography for quality control on agricultural produce  

International Nuclear Information System (INIS)

The importance of monitoring the quality of vegetables and fruits is prosperity by giving a competitive advantage for producer and providing a more healthy food for consumer. Diffuse Optical Tomography (DOT) is offering the possibility to detect the internal defects of the agricultural produce quality. Fluorescence diffuse optical tomography (FDOT) is the development of DOT, offering the possibilities to improve spatial resolution and to contrast image. The purpose of this research is to compare FDOT and DOT in forward analysis with continuous wave approach. The scattering and absorbing parameters of potatoes are used to represent the real condition. The object was illuminated by the NIR source from some positions on the boundary of object. A set of NIR detector are placed on the peripheral position of the object to measure the intensity of propagated or emitted light. In the simulation, we varied a condition of object then we analyzed the sensitivity of forward problem. The result of this study shows that FDOT has a better sensitivity than DOT and a better potential to monitor internal defects of agricultural produce because of the contrast value between optical and fluorescence properties of agricultural produce normal tissue and defects

372

Study of continuous-wave domain fluorescence diffuse optical tomography for quality control on agricultural produce  

Energy Technology Data Exchange (ETDEWEB)

The importance of monitoring the quality of vegetables and fruits is prosperity by giving a competitive advantage for producer and providing a more healthy food for consumer. Diffuse Optical Tomography (DOT) is offering the possibility to detect the internal defects of the agricultural produce quality. Fluorescence diffuse optical tomography (FDOT) is the development of DOT, offering the possibilities to improve spatial resolution and to contrast image. The purpose of this research is to compare FDOT and DOT in forward analysis with continuous wave approach. The scattering and absorbing parameters of potatoes are used to represent the real condition. The object was illuminated by the NIR source from some positions on the boundary of object. A set of NIR detector are placed on the peripheral position of the object to measure the intensity of propagated or emitted light. In the simulation, we varied a condition of object then we analyzed the sensitivity of forward problem. The result of this study shows that FDOT has a better sensitivity than DOT and a better potential to monitor internal defects of agricultural produce because of the contrast value between optical and fluorescence properties of agricultural produce normal tissue and defects.

Nadhira, Vebi, E-mail: vebi@tf.itb.ac.id; Kurniadi, Deddy, E-mail: vebi@tf.itb.ac.id; Juliastuti, E., E-mail: vebi@tf.itb.ac.id; Sutiswan, Adeline, E-mail: vebi@tf.itb.ac.id [Instrumentation and Control Research Group, Faculty of Industrial Technology, Institute Technology of Bandung, Ganesha 10 40132 Bandung (Indonesia)

2014-03-24

373

Posterior segment laser scanning tomography: contour-line modulation in optic disk analysis  

Science.gov (United States)

Laser scanning tomography is a technique for obtaining three-dimensional morphometric measurements in vivo. Beside " volumetric" parameters for optic disk analysis eg excavation volume maximal excavation depth or third moment of frequency distribution of excavation depth readings the evaluation of a new parameter the contour-line modulation is of special interest. The contour-line defines the disk border. In laser scanning tomography each pixel of the contourline is defined three-dimensionally. The contour-line modulation is the difference in height readings between the mean height position of the contour-line in the segment under investigation and the mean height position of the contour-line of an optic disk. We analysed a series of 27 control group eyes of 27 patients (C no defects in computerized static 30 degree visual field test octopus program 32 or 38) and 38 glaucoma eyes of 38 patients (G at least three points with a relative scotoma of -1 0dB loss or greater). Within the temporal 1 800 of the optic nerve head the contour-line modulation values were +79 m for the temporal superior octant (G) and +40 m for the temporal inferior octant (G) compared to the temporal quadrant and +1 71 pm for the temporal superior octant (C) and +1 34 tm for the temporal inferior octant (C) respectively . These data suggest that contour-line modulation values may be a quantitative structural parameter for nerve fiber bundle defects. Further studies

Burk, Reinhard O. W.; Rohrschneider, Klaus; Voelcker, Hans E.

1990-11-01

374

Corneal imaging and refractive index measurement using a combined multiphoton microscopy and optical coherence tomography system  

Science.gov (United States)

Refractive index (RI) is the optical property of a medium that describes its ability to bend incident light. The corneal refractive index is an especially important measurement in corneal and intraocular refractive surgery where its precise estimation is necessary to obtain accurate surgical outcomes. In this study, we calculated the corneal RI using a combined multiphoton microscopy (MPM) and optical coherence tomography (OCT) system. MPM excites and detects nonlinear signals including two photon excitation fluorescence (TPEF) and second harmonic generation (SHG). TPEF signals are observed from NADH in the cytoplasm, allowing MPM to image the cellular structures in the corneal epithelium and endothelium. SHG signals are observed from collagen, an abundant connective tissue found in the stroma. Optical coherence tomography (OCT) produces cross-sectional, structural images based on the interference fringes created by the reflected light from the sample and reference arms. Our system uses a single sub-10 fs Ti: sapphire laser source which is good for both MPM excitation and OCT resolution. The MPM and OCT images are coregistered when they are taken successively because their axial resolutions are similar and the system shares the laser source and the scanning unit. We can calculate the RI by measuring the optical thickness and the optical path length of the cornea from the MPM and OCT images respectively. We have imaged and calculated the RI of murine and piscine corneas. We were able to see the epithelial, stromal, and endothelial layers and compare their relative thicknesses and the organization of the stromal collagen lamellae. Our results showed that our system can provide both functional and structural information about the cornea and measure the RI of multi-layered tissues.

Lai, Tom; Chong, Shau Poh; Zhou, Yifeng; Moloney, Gregory; Tang, Shuo

2013-02-01

375

Femtosecond laser micro-inscription of optical coherence tomography resolution test artifacts.  

Science.gov (United States)

Optical coherence tomography (OCT) systems are becoming more commonly used in biomedical imaging and, to enable continued uptake, a reliable method of characterizing their performance and validating their operation is required. This paper outlines the use of femtosecond laser subsurface micro-inscription techniques to fabricate an OCT test artifact for validating the resolution performance of a commercial OCT system. The key advantage of this approach is that by utilizing the nonlinear absorption a three dimensional grid of highly localized point and line defects can be written in clear fused silica substrates. PMID:21559143

Tomlins, Peter H; Smith, Graham N; Woolliams, Peter D; Rasakanthan, Janarthanan; Sugden, Kate

2011-01-01

376

Simultaneous dual wavelength eye-tracked ultrahigh resolution retinal and choroidal optical coherence tomography  

DEFF Research Database (Denmark)

We demonstrate an optical coherence tomography device that simultaneously combines different novel ultrabroad bandwidth light sources centered in the 800 and 1060 nm regions, operating at 66 kHz depth scan rate, and a confocal laser scanning ophthalmoscope-based eye tracker to permit motion-artifact-free, ultrahigh resolution and high contrast retinal and choroidal imaging. The two wavelengths of the device provide the complementary information needed for diagnosis of subtle retinal changes, while also increasing visibility of deeper-lying layers to image pathologies that include opaque media in the anterior eye segment or eyes with increased choroidal thickness.

Müller, André; Jensen, Ole Bjarlin

2013-01-01

377

Suppression of image autocorrelation artefacts in spectral domain optical coherence tomography and multiwave digital holography  

Energy Technology Data Exchange (ETDEWEB)

An improved method for suppressing image artefacts in spectral domain optical coherence tomography (SD OCT) and multiwave digital holography, caused by the influence of coherent noise in the course of successive registration of an autocorrelation component and informative signal is reported. The method allows complete suppression of all types of coherent noises, provided that the sample of values used to record the autocorrelation component satisfies the conditions of Kotelnikov's theorem: in SD OCT - for the transverse structure of the studied medium, in multiwave digital holography - for the envelop function of the radiation source frequency tuning spectrum.

Gelikonov, V M; Gelikonov, G V; Terpelov, D A; Shabanov, D V; Shilyagin, P A [Institute of Applied Physics, Russian Academy of Sciences, Nizhny Novgorod (Russian Federation)

2012-05-31

378

Imaging of human breast tissue using polarization sensitive optical coherence tomography  

Science.gov (United States)

We report a study on the use of polarization sensitive optical coherence tomography (PSOCT) for discriminating malignant (invasive ductal carcinoma), benign (fibroadenoma) and normal (adipocytes) breast tissue sites. The results show that while conventional OCT, that utilizes only the intensity of light back-scattered from tissue microstructures, is able to discriminate breast tissues as normal (adipocytes) and abnormal (malignant and benign) tissues, PS-OCT helps in discriminating between malignant and benign tissue sites also. The estimated values of birefringence obtained from the PSOCT imaging show that benign breast tissue samples have significantly higher birefringence as compared to the malignant tissue samples.

Verma, Y.; Gautam, M.; Divakar Rao, K.; Swami, M. K.; Gupta, P. K.

2011-12-01

379

A new algorithm for speckle reduction of optical coherence tomography images  

Science.gov (United States)

In this study, we present a new algorithm based on an artificial neural network (ANN) for reducing speckle noise from optical coherence tomography (OCT) images. The noise is modeled for different parts of the image using Rayleigh distribution with a noise parameter, sigma, estimated by the ANN. This is then used along with a numerical method to solve the inverse Rayleigh function to reduce the noise in the image. The algorithm is tested successfully on OCT images of retina, demonstrating a significant increase in the signal-to-noise ratio (SNR) and the contrast of the processed images.

Avanaki, Mohammadreza R. N.; Marques, Manuel J.; Bradu, Adrian; Hojjatoleslami, Ali; Podoleanu, Adrian G.

2014-03-01

380

Optical coherence tomography following percutaneous coronary intervention with Excimer laser coronary atherectomy  

Energy Technology Data Exchange (ETDEWEB)

The indications for Excimer laser coronary atherectomy (ELCA) have been refined in modern interventional practice. With the expanding role for optical coherence tomography (OCT) providing high-resolution intra-coronary imaging, this article examines the appearance of the coronary lumen after ELCA. Each indication for ELCA is discussed and illustrated with a clinical case, followed by detailed analysis of the OCT imaging pre and post ELCA. The aim of the article is to provide information to interventional cardiologists to facilitate decision making during PCI, when ELCA has been used as part of the interventional strategy.

Rawlins, John, E-mail: john.rawlins@doctors.net.uk; Talwar, Suneel; Green, Mark; O’Kane, Peter

2014-01-15

 
 
 
 
381

The use of optical coherence tomography for morphological study of scaffolds  

International Nuclear Information System (INIS)

Aimed at possible widening of the optical coherence tomography (OCT) field of application, an attempt is made to use OCT in tissue engineering and cell transplantology as a tool for morphological studies of substrate materials by the example of scaffolds. By means of the traditional fibreoptical OCT scheme the images of inner structure of scaffolds are obtained, and simultaneously the spatial distribution of the intralipid flow velocity is reconstructed using the Doppler OCT. It is shown that combined use of traditional OCT and Doppler OCT schemes allows revealing the regions of the scaffold demonstrating optimal effect of shear stress, which is a key factor of cell growth.

382

Quantum-state tomography of a single nuclear spin qubit of an optically manipulated ytterbium atom  

International Nuclear Information System (INIS)

A single Yb atom is loaded into a high-finesse optical cavity with a moving lattice, and its nuclear spin state is manipulated using a nuclear magnetic resonance technique. A highly reliable quantum state control with fidelity and purity greater than 0.98 and 0.96, respectively, is confirmed by the full quantum state tomography; a projective measurement with high speed (500 ?s) and high efficiency (0.98) is accomplished using the cavity QED technique. Because a hyperfine coupling is induced only when the projective measurement is operational, the long coherence times (T1=0.49 s and T2=0.10 s) are maintained.

383

Live Imaging of Early Developmental Processes in Mammalian Embryos with Optical Coherence Tomography  

Science.gov (United States)

Early embryonic imaging of cardiovascular development in mammalian models requires a method that can penetrate through and distinguish the many tissue layers with high spatial and temporal resolution. In this paper we evaluate the capability of Optical Coherence Tomography (OCT) technique for structural 3D embryonic imaging in mouse embryos at different stages of the developmental process ranging from 7.5 dpc up to 10.5 dpc. Obtained results suggest that the collected data is suitable for quantitative and qualitative measurements to assess cardiovascular function in mouse models, which is likely to expand our knowledge of the complexity of the embryonic heart, and its development into an adult heart. PMID:20582330

Larin, Kirill V.; Larina, Irina V.; Liebling, Michael; Dickinson, Mary E.

2010-01-01

384

Discrimination of conjunctiva and sclera using texture analysis of polarization sensitive optical coherence tomography images  

Science.gov (United States)

Conjunctiva and sclera are not always discriminated in anterior eye optical coherence tomography (OCT) images, although they have distinctive tissue properties. In contrast, characteristic pattern can be observed at the sclera in a phase retardation OCT image measured by polarization sensitive OCT (PS-OCT). This is because sclera consists of collagen and it has birefringence. We developped a new algorithm which discriminates conjunctiva and sclera based on the local statistics of intensity and phase retardation OCT images. In 4 of 4 cases, conjunctiva and sclera were discriminated. This new algorithm is useful to discriminate tissues of PS-OCT images not by anatomical tissue structures but by direct tissue properties.

Miyazawa, Arata; Yamanari, Masahiro; Yasuno, Yoshiaki

2009-02-01

385

Morphological characterization of cells in concentrated suspensions using multispectral diffuse optical tomography.  

Science.gov (United States)

Based on a non-spherical model of particle scattering, we investigate the capabilities and limitations of a T-matrix based inverse algorithm to morphologically characterize cells in concentrated suspensions. Here the cells are modeled as randomly orientated spheroidal particles with homogenous dielectric properties and suspended in turbid media. The inverse algorithm retrieves the geometrical parameters and the concentration of cells simultaneously by inverting the reduced scattering coefficient spectra obtained from multispectral diffuse optical tomography (MS-DOT). Both round and spheroidal cells are tested and the role of multiple and higher order scattering of particles on the performance of the algorithm is evaluated using different concentrations of cells. PMID:23372258

Hajihashemi, Mohammad Reza; Li, Xiaoqi; Jiang, Huabei

2012-10-01

386

Tomografia de coerência óptica broncoscópica / Optical coherence tomography in conjunction with bronchoscopy  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese OBJETIVO: Avaliar a viabilidade e o potencial do uso da tomografia de coerência óptica em conjunto com um broncoscópio convencional na avaliação das vias aéreas. MÉTODOS: Estudo piloto baseado em um modelo experimental ex vivo com três animais: um coelho adulto da raça Nova Zelândia e dois suínos da [...] raça Landrace. Um cateter de imagem de tomografia de coerência óptica foi inserido no canal de trabalho de um broncoscópio flexível para alcançarmos a traqueia distal dos animais. As imagens foram obtidas sistematicamente em toda a traqueia ao longo das paredes, partindo da porção distal para a proximal. RESULTADOS: O cateter de imagem se adaptou com facilidade ao canal de trabalho do broncoscópio. Imagens em alta resolução de cortes transversais da traqueia foram obtidas em tempo real, sendo delineadas microestruturas, tais como epitélio, submucosa, cartilagem e camada adventícia nas paredes anteriores e laterais da traqueia. As camadas correspondentes do epitélio, mucosa e cartilagens foram claramente diferenciadas. Na parede posterior, foi possível identificar mucosa, submucosa e musculatura traqueal. CONCLUSÕES: O uso de tomógrafo de coerência óptica em conjunto com um broncoscópio flexível é viável. A tomografia de coerência óptica produz imagens de alta resolução que permitem visualizar a microanatomia da traqueia, inclusive estruturas que normalmente são visualizadas somente na histologia convencional. Abstract in english OBJECTIVE: To evaluate the feasibility of and the potential for using optical coherence tomography in conjunction with conventional bronchoscopy in the evaluation of the airways. METHODS: This was a pilot study based on an ex vivo experimental model involving three animals: one adult New Zealand rab [...] bit and two Landrace pigs. An optical coherence tomography imaging catheter was inserted through the working channel of a flexible bronchoscope in order to reach the distal trachea of the animals. Images of the walls of the trachea were systematically taken along its entire length, from the distal to the proximal portion. RESULTS: The imaging catheter was easily adapted to the working channel of the bronchoscope. High-resolution images of cross sections of the trachea were taken in real time, precisely delineating microstructures, such as the epithelium, submucosa, and cartilage, as well as the adventitia of the anterior and lateral tracheal walls. The corresponding layers of the epithelium, mucosa, and cartilage were clearly differentiated. The mucosa, submucosa, and trachealis muscle were clearly identified in the posterior wall. CONCLUSIONS: It is feasible to use an optical coherence tomography imaging catheter in combination with a flexible bronchoscope. Optical coherence tomography produces high-resolution images that reveal the microanatomy of the trachea, including structures that are typically seen only on images produced by conventional histology.

Ascedio José, Rodrigues; Celso Kiyochi, Takimura; Pedro Alves, Lemos Neto; Viviane Rossi, Figueiredo.

387

Tomografia de coerência óptica broncoscópica Optical coherence tomography in conjunction with bronchoscopy  

Directory of Open Access Journals (Sweden)

Full Text Available OBJETIVO: Avaliar a viabilidade e o potencial do uso da tomografia de coerência óptica em conjunto com um broncoscópio convencional na avaliação das vias aéreas. MÉTODOS: Estudo piloto baseado em um modelo experimental ex vivo com três animais: um coelho adulto da raça Nova Zelândia e dois suínos da raça Landrace. Um cateter de imagem de tomografia de coerência óptica foi inserido no canal de trabalho de um broncoscópio flexível para alcançarmos a traqueia distal dos animais. As imagens foram obtidas sistematicamente em toda a traqueia ao longo das paredes, partindo da porção distal para a proximal. RESULTADOS: O cateter de imagem se adaptou com facilidade ao canal de trabalho do broncoscópio. Imagens em alta resolução de cortes transversais da traqueia foram obtidas em tempo real, sendo delineadas microestruturas, tais como epitélio, submucosa, cartilagem e camada adventícia nas paredes anteriores e laterais da traqueia. As camadas correspondentes do epitélio, mucosa e cartilagens foram claramente diferenciadas. Na parede posterior, foi possível identificar mucosa, submucosa e musculatura traqueal. CONCLUSÕES: O uso de tomógrafo de coerência óptica em conjunto com um broncoscópio flexível é viável. A tomografia de coerência óptica produz imagens de alta resolução que permitem visualizar a microanatomia da traqueia, inclusive estruturas que normalmente são visualizadas somente na histologia convencional.OBJECTIVE: To evaluate the feasibility of and the potential for using optical coherence tomography in conjunction with conventional bronchoscopy in the evaluation of the airways. METHODS: This was a pilot study based on an ex vivo experimental model involving three animals: one adult New Zealand rabbit and two Landrace pigs. An optical coherence tomography imaging catheter was inserted through the working channel of a flexible bronchoscope in order to reach the distal trachea of the animals. Images of the walls of the trachea were systematically taken along its entire length, from the distal to the proximal portion. RESULTS: The imaging catheter was easily adapted to the working channel of the bronchoscope. High-resolution images of cross sections of the trachea were taken in real time, precisely delineating microstructures, such as the epithelium, submucosa, and cartilage, as well as the adventitia of the anterior and lateral tracheal walls. The corresponding layers of the epithelium, mucosa, and cartilage were clearly differentiated. The mucosa, submucosa, and trachealis muscle were clearly identified in the posterior wall. CONCLUSIONS: It is feasible to use an optical coherence tomography imaging catheter in combination with a flexible bronchoscope. Optical coherence tomography produces high-resolution images that reveal the microanatomy of the trachea, including structures that are typically seen only on images produced by conventional histology.

Ascedio José Rodrigues

2012-04-01

388

Enhancement of Optical Coherence Tomography Images of the Retina by Normalization and Fusion  

Directory of Open Access Journals (Sweden)

Full Text Available This paper describes an image processing method applied to Optical Coherence Tomography (OCT images of the retina. The aim is to achieve improved OCT images from the fusion of sequential OCT scans obtained at identical retinal locations. The method is based on the normalization of the acquired images and their fusion. As a result, a noise reduction and an image enhancement are reached. Thanks to the resulting improvement in retinal imaging, clinical specialists are able to evaluate more efficiently eyes pathologies and anomalies. This paper presents the proposed method and gives some evaluation results.

M. Paques

2008-12-01

389

Statistical Analysis of Reliability in edge detection techniques using Optical Coherent Tomography image  

Directory of Open Access Journals (Sweden)

Full Text Available Optical Coherence Tomography (OCT has many uses in medicine and engineering biology. It is a non-invasive technique where Edge detection in image processing playing a significant role in characterization of boundaries and identifying the structural properties in image. In this paper, Choroidal neovascularization – OCT image is comparatively analysis by various Edge Detection techniques. Statistical analysis of Mean Square Error (MSE is compared with multidimensional scaling methods. On the reliability of scaling, inter-correlation matrix in calculated from correction, dissimilarly and Euclidean distance model is evolved. Resultant graph described the characteristics of edge detection techniques.

G MOHANDASS

2013-04-01

390

Signal and resolution enhancements in partial coherence interferometry and optical coherence tomography  

International Nuclear Information System (INIS)

rsion causing severe artifacts in the signals of optical coherence tomography. In order to achieve optimum resolution by applying a light source with a broad emission spectrum, the dispersion of the object to be measured has to be compensated. To demonstrate the resolution enhancement due to dispersion compensation, measurements have been performed with a variety of light sources of different spectral bandwidths with and without dispersion compensation in different materials, in a model eye, and in vivo. In this way an axial resolution of circa 5 ?m in the human retina has been achieved representing a two-fold improvement compared to presently used technology. (author)

391

Evaluation of coronary arterial lesions due to Kawasaki disease using optical coherence tomography.  

Science.gov (United States)

Optical coherence tomography (OCT) is a high-resolution intracoronary arterial imaging modality. We describe 2 patients who were admitted to undergo coronary angiography and OCT for follow-up of Kawasaki disease with coronary artery aneurysms. OCT clearly demonstrated thrombus, stenosis, fibrotic intimal thickening with lamellar calcification, and partial disappearance of the tunica media at the aneurysm site. In addition, focal calcification, intimal thickening, and medial irregularity were observed even in regions of coronary arterial walls that appeared to be normal using coronary angiography. OCT is useful for evaluating coronary arterial sequelae of Kawasaki disease. PMID:24999171

Kakimoto, Nobuyuki; Suzuki, Hiroyuki; Kubo, Takashi; Suenaga, Tomohiro; Takeuchi, Takashi; Shibuta, Shoichi; Ino, Yasushi; Akasaka, Takashi; Yoshikawa, Norishige

2014-08-01

392

Three-dimensional cellular-level imaging using full-field optical coherence tomography  

International Nuclear Information System (INIS)

An ultrahigh-resolution full-field optical coherence tomography (OCT) system has been developed for cellular-level imaging of biological media. The system is based on a Linnik interference microscope illuminated with a tungsten halogen lamp, associated with a high-resolution CCD camera. En face tomographic images are produced in real time, with the best spatial resolution ever achieved in OCT (0.7 ?m x 0.9 ?m, axial x transverse). A shot-noise limited detection sensitivity of 80 dB can be reached with an acquisition time per image of 1 s. Images of animal ophthalmic biopsies and vegetal tissues are shown

393

Comparison of diffusion approximation and higher order diffusion equations for optical tomography of osteoarthritis  

Science.gov (United States)

In this study, a simplified spherical harmonics approximated higher order diffusion model is employed for 3-D diffuse optical tomography of osteoarthritis in the finger joints. We find that the use of a higher-order diffusion model in a stand-alone framework provides significant improvement in reconstruction accuracy over the diffusion approximation model. However, we also find that this is not the case in the image-guided setting when spatial prior knowledge from x-rays is incorporated. The results show that the reconstruction error between these two models is about 15 and 4%, respectively, for stand-alone and image-guided frameworks.

Yuan, Zhen; Zhang, Qizhi; Sobel, Eric; Jiang, Huabei

2009-09-01

394

Gold nanorods tailored as tracers for sentinel lymph node biopsy imaged by photothermal optical coherence tomography  

Science.gov (United States)

Gold nanorods (GNRs) have been demonstrated as a scattering imaging agent or therapeutic agent. Because of their narrow window, biocompatibility, and uniform small size for blood circulation, GNRs are well suited to serve as imaging contrast agents. Especially, strong phothothermal (PT) e