Advancements in Angular Domain Optical Imaging in Biological Tissues PDF Download
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Author: Fartash Vasefi
Publisher:
ISBN:
Category : Light
Languages : en
Pages : 550
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Book Description
Angular Domain Imaging (ADI) is a technique for performing optical imaging through highly scattering media. The basis for the technique is the micro-machined Angular Filter Array (AFA), which provides a parallel collection of micro-tunnels that accept ballistic/quasi-ballistic image-bearing photons and reject multiply scattered photons that result in image-destroying background noise. At high scattering levels, ADI image contrast declines due to the non-uniform scattered background light within the acceptance angle of the AFA. In this thesis, I developed multiple methodologies to correct for this problem and enhance ADI image contrast at higher scattering levels. These methodologies included combining ADI with time gating, polarization gating and employing image processing to estimate the background scattered light and use this information to enhance ADI image contrast and resolution. Furthermore, I conducted a comprehensive experimental investigation on a new AFA geometry designed to reduce the reflections within the micro-tunnels to reduce the unwanted background noise caused by multiply scattered photons. Building on previous studies with ADI in a trans-illumination configuration, I demonstrated that ADI could also be used to capture information-carrying photons from diffuse light back-reflected from tissue, where illumination was from the same side as the AFA. This mode of operation will enable applications of ADI where trans-illumination of samples is not possible. I also developed a tomographic ADI modality that rotated the sample and compiled ADI shadowgrams at each angle into a sinogram, followed by reconstruction of a transverse image with depth information. I also exploited the collimation detection capabilities of the AFA to extract photons emitted by a fluorophore embedded at depth within a turbid medium. The fluorescent imaging system using AFA offered higher resolution and contrast compared to a conventional lens and lens-pinhole fluorescent detection system in both in vitro and animal tests. Optical imaging with an AFA does not depend on coherence of the light source or the wavelength of light. Therefore, it is a promising candidate for multispectral/hyperspectral imaging to localize absorption and/or fluorescence in tissue and may have particular importance in cancer optical imaging.
Author: Fartash Vasefi
Publisher:
ISBN:
Category : Light
Languages : en
Pages : 550
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Book Description
Angular Domain Imaging (ADI) is a technique for performing optical imaging through highly scattering media. The basis for the technique is the micro-machined Angular Filter Array (AFA), which provides a parallel collection of micro-tunnels that accept ballistic/quasi-ballistic image-bearing photons and reject multiply scattered photons that result in image-destroying background noise. At high scattering levels, ADI image contrast declines due to the non-uniform scattered background light within the acceptance angle of the AFA. In this thesis, I developed multiple methodologies to correct for this problem and enhance ADI image contrast at higher scattering levels. These methodologies included combining ADI with time gating, polarization gating and employing image processing to estimate the background scattered light and use this information to enhance ADI image contrast and resolution. Furthermore, I conducted a comprehensive experimental investigation on a new AFA geometry designed to reduce the reflections within the micro-tunnels to reduce the unwanted background noise caused by multiply scattered photons. Building on previous studies with ADI in a trans-illumination configuration, I demonstrated that ADI could also be used to capture information-carrying photons from diffuse light back-reflected from tissue, where illumination was from the same side as the AFA. This mode of operation will enable applications of ADI where trans-illumination of samples is not possible. I also developed a tomographic ADI modality that rotated the sample and compiled ADI shadowgrams at each angle into a sinogram, followed by reconstruction of a transverse image with depth information. I also exploited the collimation detection capabilities of the AFA to extract photons emitted by a fluorophore embedded at depth within a turbid medium. The fluorescent imaging system using AFA offered higher resolution and contrast compared to a conventional lens and lens-pinhole fluorescent detection system in both in vitro and animal tests. Optical imaging with an AFA does not depend on coherence of the light source or the wavelength of light. Therefore, it is a promising candidate for multispectral/hyperspectral imaging to localize absorption and/or fluorescence in tissue and may have particular importance in cancer optical imaging.
Author: Eldon Ng
Publisher:
ISBN:
Category :
Languages : en
Pages : 254
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Book Description
Optical imaging is a modality that can detect optical contrast within a biological sample that is not detectable with other conventional imaging techniques. Optical transillumination images of tissue samples are degraded by optical scatter. Angular Domain Imaging (ADI) is an optical imaging technique that filters scattered photons based on the trajectory of the photons. Previous angular filters were limited to one-dimensional arrays greatly limiting the imaging capability of the system We have developed a 2D Angular Filter Array (AFA) that is capable of acquiring two-dimensional projection images of a sample. The AFA was constructed using rapid prototyping techniques. The contrast and the resolution of the AFA were evaluated. The results suggest that a 2D AFA can be used to acquire two-dimensional projection images of a sample with a reduced acquisition time compared to a scanning 1D AFA.
Author: Yoko Hoshi
Publisher: MDPI
ISBN: 3039361007
Category : Science
Languages : en
Pages : 246
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Book Description
Jöbsis was the first to describe the in vivo application of near-infrared spectroscopy (NIRS), also called diffuse optical spectroscopy (DOS). NIRS was originally designed for the clinical monitoring of tissue oxygenation, and today it has also become a useful tool for neuroimaging studies (functional near-infrared spectroscopy, fNIRS). However, difficulties in the selective and quantitative measurements of tissue hemoglobin (Hb), which have been central in the NIRS field for over 40 years, remain to be solved. To overcome these problems, time-domain (TD) and frequency-domain (FD) measurements have been tried. Presently, a wide range of NIRS instruments are available, including commonly available commercial instruments for continuous wave (CW) measurements, based on the modified Beer–Lambert law (steady-state domain measurements). Among these measurements, the TD measurement is the most promising approach, although compared with CW and FD measurements, TD measurements are less common, due to the need for large and expensive instruments with poor temporal resolution and limited dynamic range. However, thanks to technological developments, TD measurements are increasingly being used in research, and also in various clinical settings. This Special Issue highlights issues at the cutting edge of TD DOS and diffuse optical tomography (DOT). It covers all aspects related to TD measurements, including advances in hardware, methodology, the theory of light propagation, and clinical applications.
Author: Xunbin Wei
Publisher: Springer Nature
ISBN: 9811576270
Category : Medical
Languages : en
Pages : 309
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Book Description
The book introduces readers to the basic principle of optical imaging technologies. Focusing on human disease diagnostics using optical imaging methods, it provides essential information for researchers in various fields and discusses the latest trends in optical imaging. In recent decades, there has been a huge increase in imaging technologies and their applications in human diseases diagnostics, including magnetic resonance imaging, x-ray computed tomography, and nuclear tomographic imaging. This book promotes further developments to extend optical imaging to a wider range of disease diagnostics. It is a valuable resource for researchers and students in the field of biomedical optics, as well as for clinicians.
Author: Rongguang Liang
Publisher: Springer Science & Business Media
ISBN: 3642283918
Category : Science
Languages : en
Pages : 391
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Book Description
This book provides an introduction to design of biomedical optical imaging technologies and their applications. The main topics include: fluorescence imaging, confocal imaging, micro-endoscope, polarization imaging, hyperspectral imaging, OCT imaging, multimodal imaging and spectroscopic systems. Each chapter is written by the world leaders of the respective fields, and will cover: principles and limitations of optical imaging technology, system design and practical implementation for one or two specific applications, including design guidelines, system configuration, optical design, component requirements and selection, system optimization and design examples, recent advances and applications in biomedical researches and clinical imaging. This book serves as a reference for students and researchers in optics and biomedical engineering.
Author: Jorge Bouza Dominguez
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
In this thesis, a new time-dependent model for describing light propagation in biological media is proposed. The model is based on the simplified spherical harmonics approximation and is represented by a set of coupled parabolic partial differential equations (TD-pSPN equations). In addition, the model is extended for modeling the time-dependent response of fluorescent agents in biological tissues and the ensuing time-domain propagation of light therein. In a comparison with Monte Carlo simulations, it is shown that the TD-pSPN equations present unique features in its derivation that makes it a more accurate alternative to the diffusion equation (DE). The TD-pSPN model (for orders N > 1) outperforms the DE in the description of the propagation of light in near-nondiffusive media and in all the physical situations where DE fails. Often, only small orders of the SP N approximation are needed to obtain accurate results. A diffuse optical tomography (DOT) algorithm is also implemented based on the TD-pSPN equations as the forward model using constrained optimization methods. The algorithm uses time-dependent (TD) data directly. Such an approach is benefited from both the accuracy of the SPN models and the richness of TD data. In the calculation of the gradient of the objective function, a time-dependent adjoint differentiation method is introduced that reduces computation time. Several numerical experiments are performed for small geometry media with embedded inclusions that mimic small animal imaging. In these experiments, the values of the optical coefficients are varied within realistic bounds that are representative of those found in the range of the near-infrared spectrum, including high absorption values. Single and multi-parameter reconstructions (absorption and diffusion coefficients) are performed. The reconstructed images based on the TD-pSPN equations (N > 1) give better estimates of the optical properties of the media than the DE. On the other hand, crosstalk effects and small artifacts appeared in all the cases (more intense in the DE images). Comparatively, the reconstructed images show a lesser influence of these undesirable 'effects than other approaches found in the literature. The results suggest that the DOT algorithm based on the TD-pSPN model is an accurate alternative to the DE for imaging optical properties of biological media. These results directly benefict the fields of therapeutics and time-domain optical imaging of biological tissues. Particularly, the presented work is a decisive step in the elaboration of an optical scanner for small animal imaging at our lab. Thus, a positive impact in the areas of clinical diagnosis and biomedical research are expected.
Author: Nicusor Iftimia
Publisher: Wiley
ISBN: 9780470619094
Category : Science
Languages : en
Pages : 537
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Book Description
This book provides students, teachers, researchers and clinicians with a strong and established source of information on advanced optical technologies that show real promise of being translated to clinical use.
Author: Lin An
Publisher:
ISBN:
Category :
Languages : en
Pages : 127
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Book Description
Optical coherence tomography is a rapidly developing optical imaging modality capable of noninvasively providing depth resolved information of biological tissue at micrometer scale. Since its first report in 1991, it has made tremendous progress leading to successful applications in a number of fields, such as ophthalmology, gastroenterology, dermatology, dentistry, dermatology, cardiology, etc. According to [1], there are more than 15,000 OCT units that had been put into service in ophthalmic clinic by 2009, which represented approximately $1 billion market. The total amount paid by Medicare for OCT scans has increased from $1 billion per year in 2001 to $7 billion per year by 2008. The market size has kept growing in recent years. Reported in [2] by IBISWorld (an American research company), the OCT has achieved an annual growth rate of 27.4% since 2007. In 2012, the revenue is expected to be $478.4 million, which is 24.7% larger than last year. Despite the massive success, there are still several technical issues that need to be addressed, which could help the OCT technology to deliver even better imaging quality. In this thesis, we described several OCT technologies that can be used to double the imaging depth, realize functional vasculature imaging of biological tissue and increase the imaging speed of OCT system. Aim 1: Use of a scanner to introduce spatial frequency modulation to OCT spectral interferograms for in vivo full-range Fourier-domain optical coherence tomography. A novel method was developed that could easily introduce a modulation frequency onto the X-direction (i.e., B-scan) of the FDOCT scanning system, enabling full-range Fourier-domain Optical Coherence Tomography (frFDOCT). Compared to the conventional FDOCT system, the newly developed frFDOCT system can provide increased system sensitivity and deeper imaging depth. The previous technology that can achieve frFDOCT either needed multiple steps for data capturing, which is time consuming, or required additional components which increased the system's complexity. The newly developed method generates a modulation spatial frequency in the spectral interferogram by simply offsetting the probe beam at the X-scanner. In this way, the frFDOCT could be easily realized through applying a Hilbert transformation. Aim 2: Using optical micro-angiography to achieve in vivo volumetric imaging of vascular perfusion within human retina and choroids. Optical Micro-Angiography (OMAG) is a functional extension of FDOCT technology. It can achieve visualization of vasculature network of biological tissue. In order to apply the OMAG method to image vasculature map of human retina and choroid, a phase compensation algorithm was developed, which could minimize the motion artifacts generated by the movements of human eye and head. The original scanning protocol of OMAG method could only achieve ~2 mm x 2 mm scanning area on the retina, which is relatively small for clinical applications. To achieve large field of view of vasculature visualization of retina and choroid, multiple small areas of retina were sequentially scanned. After being processed, all the vasculature maps coming from small areas were stitched together to produce a vasculature map of the whole retina and choroid, which is comparable to Fluorescein Angiography. Aim 3: Developing ultrahigh sensitive optical micro-angiography to achieve micro vasculature imaging of biological tissue. Though the OMAG has been successfully applied for visualizing vasculature networks of different biological tissue, there are several problems that need to be solved, such as lower flow sensitivity, longer imaging time and so on. To improve the vasculature image quality, we developed ultrahigh sensitive OMAG (UHS-OMAG). Unlike conventional OMAG, UHS-OMAG applied the OMAG algorithm onto the slow direction of FDOCT scan (Y-direction). Because the time interval between adjacent B-frames is much longer than that between adjacent A-lines, UHS-OMAG can achieve much higher flow sensitivity compared to the conventional OMAG. In addition, the UHS-OMAG usually employed high frame rate (typically 300 frames per second) to achieve 3D scan, it cost much less time to finish one 3D scan compared to the traditional OMAG. However, when it was applied to visualize vasculature map of human tissue, the motion artifacts caused by the inevitable movements is still the biggest challenge. Based on the phase difference calculated from two adjacent B-frames, a new phase compensation algorithm was developed. The UHS-OMAG system was then applied onto human retina and skin to produce detailed micro vasculature networks. Aim 4: Developing ultrahigh speed Spectral Domain OCT system through sequentially controlling two high speed line scan CMOS cameras. Since the report of OCT technology, the imaging speed is always the hot topic along its development path. Though one branch of FDOCT technology, swept source OCT, can run at several megahertz, SSOCT is still not approved by FDA for human eye imaging. The development of spectral domain OCT is more attractive from a commercialization perspective. Two identical high speed line cameras were employed to build two home build high speed spectrometers. Through sequentially controlling the reading time period of two cameras, the imaging speed of the whole system could reach twice higher than the single camera system. The newly built 800 nm SDOCT system which can work at 500,000 Hz A-lines capturing speed was then used to achieve in vivo 3D imaging in both high speed and large field of view mode. In addition, through combining with the OMAG algorithm, the newly developed system is capable of providing detailed micro-vasculature imaging of human retina and optic nerve head.
Author:
Publisher:
ISBN:
Category : Diagnostic imaging
Languages : en
Pages : 306
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Book Description
Author: Polly Bo Lai Tsui
Publisher:
ISBN:
Category : Fluorescence
Languages : en
Pages : 304
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Book Description
Optical imaging within scattering media is difficult because the highly scattered light obscures the structure. Angular Domain Imaging is an optical tomography technique using angular filters (Spatiofrequency filters and collimating arrays) to reject scattered light and accept non-scattered light. Two techniques are explored: direct-illumination through large scattering medium (5̃ cm), and indirect-illumination through shallow media (1̃-2mm) with fluorescence sources. Using enhancement techniques, such as background scattered light estimation, improve images quality and contrast ratio, and the system's scattering limit. Multi-spectrum ADI can provide new optical and chemical information of the sample, but filtration and wavelength selection are difficult. Monte Carlo simulations were used to study the effectiveness of incorporating ADI into FI applications and to analyze the two angular filters' performance in fluorescence shallow scattering. R6G and fluorescence slides emulate collagen layers in tissue in experiments validating the simulation results and demonstrating the effectiveness of ADI in FI.
