Showing papers on "Optical tomography published in 2012"
TL;DR: In vivo performance of a camera-based hybrid fluorescence molecular tomography system for 360° imaging combined with X-ray computed tomography (XCT) resulted in the most accurate FMT performance to date, indicating that addition of FMT optics into the XCT gantry may be a potent upgrade for small-animal XCT systems.
Abstract: The development of hybrid optical tomography methods to improve imaging performance has been suggested over a decade ago and has been experimentally demonstrated in animals and humans. Here we examined in vivo performance of a camera-based hybrid fluorescence molecular tomography (FMT) system for 360° imaging combined with X-ray computed tomography (XCT). Offering an accurately co-registered, information-rich hybrid data set, FMT-XCT has new imaging possibilities compared to stand-alone FMT and XCT. We applied FMT-XCT to a subcutaneous 4T1 tumor mouse model, an Aga2 osteogenesis imperfecta model and a Kras lung cancer mouse model, using XCT information during FMT inversion. We validated in vivo imaging results against post-mortem planar fluorescence images of cryoslices and histology data. Besides offering concurrent anatomical and functional information, FMT-XCT resulted in the most accurate FMT performance to date. These findings indicate that addition of FMT optics into the XCT gantry may be a potent upgrade for small-animal XCT systems.
236 citations
TL;DR: An accurate model-based inversion algorithm for 3-D optoacoustic image reconstruction is proposed and validated and superior performance versus commonly-used backprojection inversion algorithms is showcased by numerical simulations and phantom experiments.
Abstract: In many practical optoacoustic imaging implementations, dimensionality of the tomographic problem is commonly reduced into two dimensions or 1-D scanning geometries in order to simplify technical implementation, improve imaging speed or increase signal-to-noise ratio. However, this usually comes at a cost of significantly reduced quality of the tomographic data, out-of-plane image artifacts, and overall loss of image contrast and spatial resolution. Quantitative optoacoustic image reconstruction implies therefore collection of point 3-D (volumetric) data from as many locations around the object as possible. Here, we propose and validate an accurate model-based inversion algorithm for 3-D optoacoustic image reconstruction. Superior performance versus commonly-used backprojection inversion algorithms is showcased by numerical simulations and phantom experiments.
204 citations
02 Jul 2012
TL;DR: In this article, a supercontinuum-based optical coherence tomography (OCT) was used for biomedical tissue and materials imaging, where low noise, Gaussian-like supercontinua were generated at five wavelength regions.
Abstract: We have been investigating ultrahigh resolution optical coherence tomography using supercontinuum. Low noise, Gaussian like supercontinua were generated at five wavelength regions. Ultrahigh resolution cross-sectional and three dimensional imaging were demonstrated for biomedical tissues and materials.
116 citations
Patent•
31 May 2012
TL;DR: In this paper, a rotary coupler is used to interface with an optical tomography imaging probe, where the rotary coupler is in optical communication with the sample arm and the first optical fiber is disposed in a common protective sheath.
Abstract: In part, the invention relates to an image data collection system. The system can include an interferometer having a reference arm that includes a first optical fiber of length of LI and a sample arm that includes a second optical fiber of length of L2 and a first rotary coupler configured to interface with an optical tomography imaging probe, wherein the rotary coupler is in optical communication with the sample arm. In one embodiment, L2 is greater than about 5 meters. The first optical fiber and the second optical fiber can both be disposed in a common protective sheath. In one embodiment, the system further includes an optical element configured to adjust the optical path length of the reference arm, wherein the optical element is in optical communication with the reference arm and wherein the optical element is transmissive or reflective.
111 citations
TL;DR: Through accurate correlation with the histological gold standard, OCT is shown to enable a clear delineation of tumor boundary from surrounding adipose tissue, and identification of microarchitectural features.
Abstract: Optical coherence tomography (OCT) is a high-resolution imaging modality with the potential to provide in situ assessment to distinguish normal from cancerous tissue. However, limited image penetration depth has restricted its utility. This paper demonstrates the feasibility of an OCT needle probe to perform interstitial imaging deep below the tissue surface. The side-facing needle probe comprises miniaturized focusing optics consisting of no-core and GRIN fiber encased within either a 22- or 23-gauge needle. 3-D OCT volumetric data sets were acquired by rotating and retracting the probe during imaging. We present the first published image of a human breast cancer tumor margin, and of human axillary lymph nodes acquired with an OCT needle probe. Through accurate correlation with the histological gold standard, OCT is shown to enable a clear delineation of tumor boundary from surrounding adipose tissue, and identification of microarchitectural features.
107 citations
TL;DR: A novel technique for retrieving phase information from OCT volumes of the outer retina is presented, providing a quantitative analysis of such phase information and showing that it can improve the sensitivity to OS length change by more than an order of magnitude, down to 45 nm, slightly thicker than a single OS disc.
Abstract: The cone photoreceptor’s outer segment (OS) experiences changes in optical path length, both in response to visible stimuli and as a matter of its daily course of renewal and shedding. These changes are of interest, to quantify function in healthy cells and assess dysfunction in diseased ones. While optical coherence tomography (OCT), combined with adaptive optics (AO), has permitted unprecedented three-dimensional resolution in the living retina, it has not generally been able to measure these OS dynamics, whose scale is smaller than OCT’s axial resolution of a few microns. A possible solution is to take advantage of the phase information encoded in the OCT signal. Phase-sensitive implementations of spectral-domain optical coherence tomography (SD-OCT) have been demonstrated, capable of resolving sample axial displacements much smaller than the imaging wavelength, but these have been limited to ex vivo samples. In this paper we present a novel technique for retrieving phase information from OCT volumes of the outer retina. The key component of our technique is quantification of phase differences within the retina. We provide a quantitative analysis of such phase information and show that–when combined with appropriate methods for filtering and unwrapping–it can improve the sensitivity to OS length change by more than an order of magnitude, down to 45 nm, slightly thicker than a single OS disc. We further show that phase sensitivity drops off with retinal eccentricity, and that the best location for phase imaging is close to the fovea. We apply the technique to the measurement of sub-resolution changes in the OS over matters of hours. Using custom software for registration and tracking, these microscopic changes are monitored in hundreds of cones over time. In two subjects, the OS was found to have average elongation rates of 150 nm/hr, values which agree with our previous findings.
103 citations
TL;DR: A new tomographic algorithm that combines the logical filtered back-projection and the simultaneous algebraic reconstruction technique is proposed to reconstruct the flame sections from the images to improve the visualization and characterization of a burner flame.
Abstract: This paper presents the design, implementation, and evaluation of an optical fiber imaging based tomographic system for the 3-D visualization and characterization of a burner flame. Eight imaging fiber bundles coupled with two RGB charge-coupled device cameras are used to acquire flame images simultaneously from eight different directions around the burner. The fiber bundle has 30k picture elements and an objective lens with a 92° angle of view. The characteristic evaluation of the imaging fiber bundles and the calibration of the system were conducted to ensure the accuracy of the system. A new tomographic algorithm that combines the logical filtered back-projection and the simultaneous algebraic reconstruction technique is proposed to reconstruct the flame sections from the images. A direct comparison between the proposed algorithm and other tomographic approaches is conducted through computer simulation for different test templates and numbers of projections. The 3-D reconstruction of the cross- and longitudinal-sections of a burner flame from image projections obtained from the imaging system was also performed. The effectiveness of the imaging system and computer algorithm is assessed through experimental tests.
97 citations
TL;DR: In this article, the radiative transport equation and diffusion approximation are used as light transport models and solutions in different size domains are investigated for reconstruction of absorption and scattering distributions in quantitative photoacoustic tomography.
Abstract: Quantitative photoacoustic tomography is a novel hybrid imaging technique aiming at estimating optical parameters inside tissues. The method combines (functional) optical information and accurate anatomical information obtained using ultrasound techniques. The optical inverse problem of quantitative photoacoustic tomography is to estimate the optical parameters within tissue when absorbed optical energy density is given. In this paper we consider reconstruction of absorption and scattering distributions in quantitative photoacoustic tomography. The radiative transport equation and diffusion approximation are used as light transport models and solutions in different size domains are investigated. The simulations show that scaling of the data, for example by using logarithmic data, can be expected to significantly improve the convergence of the minimization algorithm. Furthermore, both the radiative transport equation and diffusion approximation can give good estimates for absorption. However, depending on the optical properties and the size of the domain, the diffusion approximation may not produce as good estimates for scattering as the radiative transport equation.
95 citations
TL;DR: The feasibility of three-dimensional and high-resolution whole-body optoacoustic imaging of small animal using a conventional linear array was demonstrated and the scanning geometry may be used for other linear arrays and is therefore expected to be of great interest for opto-acoustic tomography at macroscopic and mesoscopic scale.
Abstract: Purpose: Optoacoustic imaging relies on the detection of ultrasonic waves induced by laser pulse excitations to map optical absorption in biological tissue. A tomographic geometry employing a conventional ultrasound linear detector array for volumetric optoacoustic imaging is reported. The geometry is based on a translate-rotate scanning motion of the detector array, and capitalizes on the geometrical characteristics of the transducer assembly to provide a large solid angular detection aperture. A system for three-dimensional whole-body optoacoustic tomography of small animals is implemented. Methods: The detection geometry was tested using a 128-element linear array (5.0/7.0 MHz, Acuson L7, Siemens), moved by steps with a rotation/translation stage assembly. Translation and rotation range of 13.5 mm and 180°, respectively, were implemented. Optoacoustic emissions were induced in tissue-mimicking phantoms andex vivo mice using a pulsed laser operating in the near-IR spectral range at 760 nm. Volumetric images were formed using a filtered backprojection algorithm. Results: The resolution of the optoacoustic tomography system was measured to be better than 130μm in-plane and 330 μm in elevation (full width half maximum), and to be homogenous along a 15 mm diameter cross section due to the translate-rotate scanning geometry. Whole-body volumetric optoacoustic images of mice were performed ex vivo, and imaged organs and blood vessels through the intact abdominal and head regions were correlated to the mouse anatomy. Conclusions: Overall, the feasibility of three-dimensional and high-resolution whole-body optoacoustic imaging of small animal using a conventional linear array was demonstrated. Furthermore, the scanning geometry may be used for other linear arrays and is therefore expected to be of great interest for optoacoustic tomography at macroscopic and mesoscopic scale. Specifically, conventional detector arrays with higher central frequencies may be investigated.
93 citations
TL;DR: In this article, the authors overview the basic principles, recent results, advantages, limitations, and future of the optical clearing method in application to many fields of biology and medicine and discuss the possibility of noninvasive assessment of molecular diffusion in tissues using the optical coherence tomography technique.
Abstract: In this paper, we overview the basic principles, recent results, advantages, limitations, and future of the optical clearing method in application to many fields of biology and medicine. We also discuss the possibility of noninvasive assessment of molecular diffusion in tissues using the optical coherence tomography technique. Issues of safety and toxicity of application of different endogenous and exogenous molecules to tissues are outlined.
92 citations
TL;DR: The combined PAT/DOT system takes full advantages of two different modalities to provide complementary information and most accurate recovery of tissue optical properties and will allow the hybrid system to test in humans with breast cancer in the near future.
Abstract: Purpose : The authors present the design and evaluation of a second-generation (G2) hybrid photoacoustictomography(PAT) and diffuse optical tomography (DOT) imaging system for detection of breast cancer. The combined PAT/DOT system takes full advantages of two different modalities to provide complementary information and most accurate recovery of tissue optical properties. Methods : This system was designed to produce cross-section images of breast tissue with a ring-shaped home-made array of 64 wideband acoustic transducers combined with an array of 16/16 source/detector optical fiber bundles. A scanning light delivery system was built to illuminate a large area of breast tissue for optimized tissue penetration. Finite element reconstruction methods for quantitative PAT and DOT were utilized to recover absorption and scattering coefficients of tissue-mimicking phantoms andex vivotumortissue. Results : Performances of the acoustic transducer array and the PAT/DOT system were investigated in detail. Frequency response of the transducers is from 380 kHz to 1.48 MHz and maximum frequency response is up to 2 MHz. Directivity of a single element in the array is ±30°. The PAT/DOT system offers a spatial resolution of ∼0.5 mm for PAT and of ∼4.0 mm for DOT. Quantitatively accurate absorption and scattering coefficients were obtained from both the phantom andex vivo experiments. Conclusions : The PAT/DOT system provided better PATimages when the targets were smaller in size and located near the center of the background phantom, while better DOT images were obtained when the targets were larger in size and located away from the center of the background. The successful results obtained from both the phantom andex vivo experiments will allow us to test the hybrid system in humans with breast cancer in the near future.
TL;DR: In this paper, a spectral-domain optical coherence tomography system based on an integrated optical spectrometer is presented, with a maximum imaging depth of 1 mm and axial resolution of 25 and 20 μm in air, respectively, for the 800-and 1300-nm ranges.
Abstract: We present experimental results of a spectral-domain optical coherence tomography system based on an integrated optical spectrometer. A 195-channel arrayed-waveguide-grating (AWG) spectrometer with 0.4-nm channel spacing centered at 1300 nm and a 125-channel AWG with 0.16-nm channel spacing centered at 800 nm have been fabricated in silicon oxynitride waveguide technology. Interferometric distance measurements have been performed by launching light from a broadband source into a free-space Michelson interferometer, with its output coupled into the AWG. A maximum imaging depth of 1 mm and axial resolution of 25 and 20 μm in air are demonstrated for the 800- and 1300-nm ranges, respectively.
TL;DR: The results establish that the optimized mesh-based Monte Carlo (mMC) method is a computationally efficient solution for optical tomography studies in terms of both calculation time and memory utilization.
Abstract: We evaluated the potential of mesh-based Monte Carlo (MC) method for widefield time-gated fluorescence molecular tomography, aiming to improve accuracy in both shape discretization and photon transport modeling in preclinical settings. An optimized software platform was developed utilizing multithreading and distributed parallel computing to achieve efficient calculation. We validated the proposed algorithm and software by both simulations and in vivo studies. The results establish that the optimized mesh-based Monte Carlo (mMC) method is a computationally efficient solution for optical tomography studies in terms of both calculation time and memory utilization. The open source code, as part of a new release of mMC, is publicly available at http://mcx.sourceforge.net/mmc/.
25 Mar 2012
TL;DR: A variant of the Fienup algorithm is developed to incorporate the condition of sparsity and to successively estimate and refine the phase starting from the magnitude measurements and it is shown that the proposed iterative algorithm possesses Cauchy convergence properties.
Abstract: We address the problem of phase retrieval, which is frequently encountered in optical imaging. The measured quantity is the magnitude of the Fourier spectrum of a function (in optics, the function is also referred to as an object). The goal is to recover the object based on the magnitude measurements. In doing so, the standard assumptions are that the object is compactly supported and positive. In this paper, we consider objects that admit a sparse representation in some orthonormal basis. We develop a variant of the Fienup algorithm to incorporate the condition of sparsity and to successively estimate and refine the phase starting from the magnitude measurements. We show that the proposed iterative algorithm possesses Cauchy convergence properties. As far as the modality is concerned, we work with measurements obtained using a frequency-domain optical-coherence tomography experimental setup. The experimental results on real measured data show that the proposed technique exhibits good reconstruction performance even with fewer coefficients taken into account for reconstruction. It also suppresses the autocorrelation artifacts to a significant extent since it estimates the phase accurately.
TL;DR: Computational tools to further improve OPT image acquisition and tomographic reconstruction provide semi-automatic and precise positioning of a sample at the axis of rotation and a fast and robust algorithm for determination of postalignment values throughout the specimen as compared to existing methods.
Abstract: Since it was first presented in 2002, optical projection tomography (OPT) has emerged as a powerful tool for the study of biomedical specimen on the mm to cm scale. In this paper, we present computational tools to further improve OPT image acquisition and tomographic reconstruction. More specifically, these methods provide: semi-automatic and precise positioning of a sample at the axis of rotation and a fast and robust algorithm for determination of postalignment values throughout the specimen as compared to existing methods. These tools are easily integrated for use with current commercial OPT scanners and should also be possible to implement in “home made” or experimental setups for OPT imaging. They generally contribute to increase acquisition speed and quality of OPT data and thereby significantly simplify and improve a number of three-dimensional and quantitative OPT based assessments.
TL;DR: Optical imaging could play a major role in the move from imaging of structure and morphology to the visualization of the individual biologic processes underlying disease and could, therefore, contribute to more accurate diagnostics and improved treatment efficacy.
Abstract: OBJECTIVE. Optical imaging is experiencing significant technologic advances. Simultaneously, an array of specific optical imaging agents has brought new capabilities to biomedical research and is edging toward clinical use. We review progress in the translation of macroscopic optical imaging—including fluorescence-guided surgery and endoscopy, intravascular fluorescence imaging, diffuse fluorescence and optical tomography, and multispectral optoacoustics (photoacoustics)—for applications ranging from tumor resection and assessment of atherosclerotic plaques to dermatologic and breast examinations. CONCLUSION. Optical imaging could play a major role in the move from imaging of structure and morphology to the visualization of the individual biologic processes underlying disease and could, therefore, contribute to more accurate diagnostics and improved treatment efficacy.
TL;DR: The advancement of OCT technology to image heart development is reviewed and some of the recent findings utilizing OCT imaging under environmental control for longitudinal imaging are reported.
Abstract: Optical coherence tomography (OCT) has great potential for deciphering the role of mechanics in normal and abnormal heart development. OCT images tissue microstructure and blood flow deep into the tissue (1-2 mm) at high spatiotemporal resolutions allowing unprecedented images of the developing heart. Here, we review the advancement of OCT technology to image heart development and report some of our recent findings utilizing OCT imaging under environmental control for longitudinal imaging. Precise control of the environment is absolutely required in longitudinal studies that follow the growth of the embryo or studies comparing normal versus perturbed heart development to obtain meaningful in vivo results. These types of studies are essential to tease out the influence of cardiac dynamics on molecular expression and their role in the progression of congenital heart defects.
TL;DR: In this paper, the authors identify the challenges in flame tomography and review existing techniques for the quantitative characterization of flames, including passive optical tomography, laser-based and electrical tomography.
TL;DR: In this paper, a general formalism of the symbols of the operators in the form of singular and regular generalized functions is presented, and suggestions for their use in experimental data processing in quantum tomography are given.
Abstract: Explicit expressions for most interesting quantum observable operators in optical tomography representation are found. A general formalism of the symbols of the operators is presented in the optical tomography representation. The symbols of the operators in the form of singular and regular generalized functions are found, and suggestions for their use in experimental data processing in quantum tomography are given.
TL;DR: A new framework for model-based tomographic reconstructions is presented, which is based on a wavelet-packet representation of the imaged object and the acquired projection data, which leads to an approximately separable model matrix, for which reconstruction at each spatial frequency band is independent and requires only a fraction of the projection data.
Abstract: The use of model-based algorithms in tomographic imaging offers many advantages over analytical inversion methods. However, the relatively high computational complexity of model-based approaches often restricts their efficient implementation. In practice, many modern imaging modalities, such as computed-tomography, positron-emission tomography, or optoacoustic tomography, normally use a very large number of pixels/voxels for image reconstruction. Consequently, the size of the forward-model matrix hinders the use of many inversion algorithms. In this paper, we present a new framework for model-based tomographic reconstructions, which is based on a wavelet-packet representation of the imaged object and the acquired projection data. The frequency localization property of the wavelet-packet base leads to an approximately separable model matrix, for which reconstruction at each spatial frequency band is independent and requires only a fraction of the projection data. Thus, the large model matrix is effectively separated into a set of smaller matrices, facilitating the use of inversion schemes whose complexity is highly nonlinear with respect to matrix size. The performance of the new methodology is demonstrated for the case of 2-D optoacoustic tomography for both numerically generated and experimental data.
01 Jan 2012
TL;DR: A new method for three-dimensional reconstruction of coronary arteries using Frequency Domain Optical Coherence Tomography images to fuse the information about the curvature of the artery, derived from biplane angiographies, with the information regarding the lumen wall, which is produced from the FD-OCT examination.
Abstract: The aim of this study is to describe a new method for three-dimensional (3D) reconstruction of coronary arteries using Frequency Domain Optical Coherence Tomography (FD-OCT) images. The rationale is to fuse the information about the curvature of the artery, derived from biplane angiographies, with the information regarding the lumen wall, which is produced from the FD-OCT examination. The method is based on a three step approach. In the first step the lumen borders in FD-OCT images are detected. In the second step a 3D curve is produced using the center line of the vessel from the two biplane projections. Finally in the third step the detected lumen borders are placed perpendicularly onto the path based on the centroid of each lumen border. The result is a 3D reconstructed artery produced by all the lumen borders of the FD-OCT pullback representing the 3D arterial geometry of the vessel.
TL;DR: In this paper, a method for the numerical correction of optical aberrations based on indirect sensing of the scattered wavefront from point-like scatterers (guide stars) within a three-dimensional broadband interferometric tomogram is presented.
Abstract: We present a method for the numerical correction of optical aberrations based on indirect sensing of the scattered wavefront from point-like scatterers (“guide stars”) within a three-dimensional broadband interferometric tomogram. This method enables the correction of high-order monochromatic and chromatic aberrations utilizing guide stars that are revealed after numerical compensation of defocus and low-order aberrations of the optical system. Guide-star-based aberration correction in a silicone phantom with sparse sub-resolution-sized scatterers demonstrates improvement of resolution and signal-to-noise ratio over a large isotome. Results in highly scattering muscle tissue showed improved resolution of fine structure over an extended volume. Guide-star-based computational adaptive optics expands upon the use of image metrics for numerically optimizing the aberration correction in broadband interferometric tomography, and is analogous to phase-conjugation and time-reversal methods for focusing in turbid media.
TL;DR: These results demonstrate that the scanner provides all that is necessary for reconstructing images of small animals using full tomographic reconstruction algorithms, which will be the next step, through its free-space optics design and the short pulse laser used, shows unprecedented timing resolution compared to other multi-view time-domain scanners.
Abstract: We present a non-contact diffuse optical tomography (DOT) scanner with multi-view detection (over 360°) for localizing fluorescent markers in scattering and absorbing media, in particular small animals. It relies on time-domain detection after short pulse laser excitation. Ultrafast time-correlated single photon counting and photomultiplier tubes are used for time-domain measurements. For light collection, seven free-space optics non-contact dual wavelength detection channels comprising 14 detectors overall are placed around the subject, allowing the measurement of time point-spread functions at both excitation and fluorescence wavelengths. The scanner is endowed with a stereo camera pair for measuring the outer shape of the subject in 3D. Surface and DOT measurements are acquired simultaneously with the same laser beam. The hardware and software architecture of the scanner are discussed. Phantoms are used to validate the instrument. Results on the localization of fluorescent point-like inclusions immersed in a scattering and absorbing object are presented. The localization algorithm relies on distance ranging based on the measurement of early photons arrival times at different positions around the subject. This requires exquisite timing accuracy from the scanner. Further exploiting this capability, we show results on the effect of a scattering hetereogenity on the arrival time of early photons. These results demonstrate that our scanner provides all that is necessary for reconstructing images of small animals using full tomographic reconstruction algorithms, which will be the next step. Through its free-space optics design and the short pulse laser used, our scanner shows unprecedented timing resolution compared to other multi-view time-domain scanners.
TL;DR: It is concluded that reconstructions based on the Mellin-Laplace transform are more robust to noise than the methods using first moments.
Abstract: We investigate the use of the Mellin–Laplace transform for reconstructing optical parameters from time-resolved optical tomography in diffusive media. We present here its definition, its mathematical properties, and its sensitivity to variations of optical properties. The method was validated on two-dimensional reconstructions from simulation in the reflection geometry. We conclude that reconstructions based on the Mellin–Laplace transform are more robust to noise than the methods using first moments.
TL;DR: A miniature optical coherence tomography (OCT) probe and high-resolution 3D OCT imaging results obtained with this probe, enabled by a unique high-fill-factor electrothermal MEMS mirror with hidden actuators and a novel wire-bonding-free (WBF) packaging technique are reported.
Abstract: This paper reports a miniature optical coherence tomography (OCT) probe and high-resolution 3-D OCT imaging results obtained with this side-view probe. The probe is only 2.8 mm in diameter, enabled by a unique high-fill-factor electrothermal MEMS mirror with hidden actuators and a novel wire-bonding-free packaging technique. The MEMS mirror has a large mirror aperture of 1 mm with a chip size of only 1.55 mm × 1.7 mm × 0.5 mm. The fabricated device achieves large 2-D scan optical angles up to 46° at only 4.8 V. The specific time-domain OCT system utilized is detailed, and the assembled side-view probe demonstrates multiple high-resolution 3-D OCT imaging results that demonstrate detailed images of a mouse ear and images detecting the presence of tumor cells, and the contrast with a normal tissue is qualitatively analyzed.
TL;DR: The proposed algorithm is an efficient way to align 3-D OCT volume data and correct the eye movement without using references and was applied on both simulated data for objective evaluation and experimental data for subjective evaluation.
Abstract: Eye movement artifacts occurring during 3-D optical coherence tomography (OCT) scanning is a well-recognized problem that may adversely affect image analysis and interpretation. A particle filtering algorithm is presented in this paper to correct motion in a 3-D dataset by considering eye movement as a target tracking problem in a dynamic system. The proposed particle filtering algorithm is an independent 3-D alignment approach, which does not rely on any reference image. 3-D OCT data is considered as a dynamic system, while the location of each A-scan is represented by the state space. A particle set is used to approximate the probability density of the state in the dynamic system. The state of the system is updated frame by frame to detect A-scan movement. The proposed method was applied on both simulated data for objective evaluation and experimental data for subjective evaluation. The sensitivity and specificity of the x-movement detection were 98.85% and 99.43%, respectively, in the simulated data. For the experimental data (74 3-D OCT images), all the images were improved after z-alignment, while 81.1% images were improved after x-alignment. The proposed algorithm is an efficient way to align 3-D OCT volume data and correct the eye movement without using references.
TL;DR: It is shown that SLOT is a valuable technique to study the internal structure of the mouse lung using rapid scanning of samples of a size of several millimeters allowing volumetric visualization by using intrinsic contrast mechanisms of previously fixed lung lobes.
Abstract: The current study focuses on the use of scanning laser optical tomography (SLOT) in imaging of the mouse lung ex vivo. SLOT is a highly efficient fluorescence microscopy technique allowing rapid scanning of samples of a size of several millimeters, thus enabling volumetric visualization by using intrinsic contrast mechanisms of previously fixed lung lobes. Here, we demonstrate the imaging of airways, blood vessels, and parenchyma from whole, optically cleared mouse lung lobes with a resolution down to the level of single alveoli using absorption and autofluorescence scan modes. The internal structure of the lung can then be analyzed nondestructively and quantitatively in three-dimensional datasets in any preferred planar orientation. Moreover, the procedure preserves the microscopic structure of the lung and allows for subsequent correlative histologic studies. In summary, the current study has shown that SLOT is a valuable technique to study the internal structure of the mouse lung.
TL;DR: This work describes an approach termed "temperature-modulated fluorescence tomography" that can acquire fluorescence images at focused ultrasound resolution that is well suited to resolve small fluorescence targets located several centimeters deep in tissue.
Abstract: High scattering in biological tissues makes fluorescence tomography inverse problem very challenging in thick medium. We describe an approach termed “temperature-modulated fluorescence tomography” that can acquire fluorescence images at focused ultrasound resolution. By utilizing recently emerged temperature sensitive fluorescence contrast agents, this technique provides fluorescence images with high resolution prior to any reconstruction process. We demonstrate that this technique is well suited to resolve small fluorescence targets located several centimeters deep in tissue.
TL;DR: This work developed and optimized a UOT system employing a photorefractive crystal-based interferometer and attained the ability to image through a tissue-mimicking phantom of 9.4 cm in thickness, which has never been reached previously by UOT.
Abstract: Ultrasound-modulated optical tomography (UOT) has the potential to reveal optical contrast deep inside soft biological tissues at an ultrasonically determined spatial resolution. The optical imaging depth reported so far has, however, been limited, which prevents this technique from broader applications. Our latest experimental exploration has pushed UOT to an unprecedented imaging depth. We developed and optimized a UOT system employing a photorefractive crystal-based interferometer. A large aperture optical fiber bundle was used to enhance the efficiencies for diffuse light collection and photorefractive two-wave-mixing. Within the safety limits for both laser illumination and ultrasound modulation, the system has attained the ability to image through a tissue-mimicking phantom of 9.4 cm in thickness, which has never been reached previously by UOT.
TL;DR: Characterization and three-dimensional (3-D) localization of human cancerous prostate tissue embedded in normal prostate tissue were demonstrated using backscattering scanning polarization imaging and an inverse imaging reconstruction algorithm, optical tomography using independent component analysis (OPTICA).
Abstract: Characterization and three-dimensional (3-D) localization of human cancerous prostate tissue embedded in normal prostate tissue were demonstrated using backscattering scanning polarization imaging and an inverse imaging reconstruction algorithm, optical tomography using independent component analysis (OPTICA). Two-dimensional (2-D) backscattering images of a prostate tissue sample illuminated with a scanning laser beam were measured with a CCD camera to obtain multiple angular views of the target embedded inside the tissue. The recorded sets of 2-D images were used to determine the existence and 3-D location of the cancerous prostate tissue using the algorithm. The difficulty arises in the backscattering geometry because the profile of the incident beam and the surface property of the tissue sample appreciably affect the spatial distribution of the backscattered light. This challenge was addressed by: (1) synthesizing a "clean" background image of the host medium; and (2) numerically marching the propagation of the scattered light from the hidden target to the surface of the tissue sample until matching the retrieved independent component. The OPTICA algorithm was improved specifically for the backscattering model, and used to obtain 3-D locations of the cancerous tissue embedded in normal host tissue. The retrieved results were found in good agreement with the known 3-D positions of the cancerous tissue.