Showing papers on "Optical tomography published in 2009"
TL;DR: The results show that 3D modeling can be combined with measured data from multiple wavelengths to reconstruct chromophore concentrations within the tissue, and it is possible to recover scattering spectra, resulting from the dominant Mie-type scatter present in tissue.
Abstract: Diffuse optical tomography, also known as near infrared tomography, has been under investigation, for non-invasive functional imaging of tissue, specifically for the detection and characterization of breast cancer or other soft tissue lesions. Much work has been carried out for accurate modeling and image reconstruction from clinical data. NIRFAST, a modeling and image reconstruction package has been developed, which is capable of single wavelength and multi-wavelength optical or functional imaging from measured data. The theory behind the modeling techniques as well as the image reconstruction algorithms is presented here, and 2D and 3D examples are presented to demonstrate its capabilities. The results show that 3D modeling can be combined with measured data from multiple wavelengths to reconstruct chromophore concentrations within the tissue. Additionally it is possible to recover scattering spectra, resulting from the dominant Mie-type scatter present in tissue. Overall, this paper gives a comprehensive over view of the modeling techniques used in diffuse optical tomographic imaging, in the context of NIRFAST software package.
684 citations
TL;DR: A graph-theoretic segmentation method for the simultaneous segmentation of multiple 3-D surfaces that is guaranteed to be optimal with respect to the cost function and that is directly applicable to the segmentations of 3- D spectral OCT image data is reported.
Abstract: With the introduction of spectral-domain optical coherence tomography (OCT), much larger image datasets are routinely acquired compared to what was possible using the previous generation of time-domain OCT. Thus, the need for 3-D segmentation methods for processing such data is becoming increasingly important. We report a graph-theoretic segmentation method for the simultaneous segmentation of multiple 3-D surfaces that is guaranteed to be optimal with respect to the cost function and that is directly applicable to the segmentation of 3-D spectral OCT image data. We present two extensions to the general layered graph segmentation method: the ability to incorporate varying feasibility constraints and the ability to incorporate true regional information. Appropriate feasibility constraints and cost functions were learned from a training set of 13 spectral-domain OCT images from 13 subjects. After training, our approach was tested on a test set of 28 images from 14 subjects. An overall mean unsigned border positioning error of 5.69 plusmn 2.41 mum was achieved when segmenting seven surfaces (six layers) and using the average of the manual tracings of two ophthalmologists as the reference standard. This result is very comparable to the measured interobserver variability of 5.71 plusmn 1.98 mum.
618 citations
TL;DR: A review of recent mathematical and computational advances in optical tomography can be found in this paper, where the physical foundations of forward models for light propagation on microscopic, mesoscopic and macroscopic scales are discussed.
Abstract: 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.
575 citations
TL;DR: During the preliminary clinical studies on 27 patients, the LOIS-64 was able to visualize 18 out of 20 malignant lesions suspected from mammography and ultrasound images and confirmed by the biopsy performed after the optoacoustic tomography (OAT) procedure.
Abstract: We designed, fabricated and tested the laser optoacoustic imaging system for breast cancer detection LOIS-64, which fuses optical and acoustic imaging techniques in one modality by utilizing pulsed optical illumination and ultrawide-band ultrasonic detection of resulting optoacoustic OA signals. The system was designed to im- age a single breast slice in craniocaudal or mediolateral projection with an arc-shaped array of 64 ultrawide-band acoustic transducers. The system resolution on breast phantoms was at least 0.5 mm. The single-channel sensitivity of 1.66 mV/Pa was estimated to be suffi- cient for single-pulse imaging of 6t o 11 mm tumors through the whole imaging slice of the breast. The implemented signal processing using the wavelet transform allowed significant reduction of the low- frequency LF acoustic noise, allowed localization of the optoacous- tic signals from tumors, and enhanced the contrast and sharpened the boundaries of the optoacoustic images of the tumors. During the pre- liminary clinical studies on 27 patients, the LOIS-64 was able to visu- alize 18 out of 20 malignant lesions suspected from mammography and ultrasound images and confirmed by the biopsy performed after the optoacoustic tomography OAT procedure. © 2009 Society of Photo-
514 citations
TL;DR: A system for three-dimensional whole-body optoacoustic tomography of small animals for applications in preclinical research and capable of generating images of individual organs and blood vessels through the entire body of a mouse with spatial resolution of approximately 0.5 mm.
Abstract: We develop a system for three-dimensional whole-body optoacoustic tomography of small animals for applications in preclini- cal research. The tomographic images are obtained while the objects of study phantoms or mice are rotated within a sphere outlined by a concave arc-shaped array of 64 piezocomposite transducers. Two pulsed lasers operating in the near-IR spectral range 755 and 1064 nm with an average pulsed energy of about 100 mJ, a repeti- tion rate of 10 Hz, and a pulse duration of 15 to 75 ns are used as optical illumination sources. During the scan, the mouse is illumi- nated orthogonally to the array with two wide beams of light from a bifurcated fiber bundle. The system is capable of generating images of individual organs and blood vessels through the entire body of a mouse with spatial resolution of 0.5 mm. © 2009 Society of Photo-Optical
306 citations
TL;DR: The data demonstrate that benign and malignant lesions can be distinguished by quantitative three-dimensional DOT based on large optical data sets and show good discriminatory power.
Abstract: We have developed a novel parallel-plate diffuse optical tomography (DOT) system for three-dimensional in vivo imaging of human breast tumor based on large optical data sets. Images of oxy-, deoxy-, and total hemoglobin concentration as well as blood oxygen saturation and tissue scattering were reconstructed. Tumor margins were derived using the optical data with guidance from radiology reports and magnetic resonance imaging. Tumor-to-normal ratios of these endogenous physiological parameters and an optical index were computed for 51 biopsy-proven lesions from 47 subjects. Malignant cancers (N=41) showed statistically significant higher total hemoglobin, oxy-hemoglobin concentration, and scattering compared to normal tissue. Furthermore, malignant lesions exhibited a twofold average increase in optical index. The influence of core biopsy on DOT results was also explored; the difference between the malignant group measured before core biopsy and the group measured more than 1 week after core biopsy was not significant. Benign tumors (N=10) did not exhibit statistical significance in the tumor-to-normal ratios of any parameter. Optical index and tumor-to-normal ratios of total hemoglobin, oxy-hemoglobin concentration, and scattering exhibited high area under the receiver operating characteristic curve values from 0.90 to 0.99, suggesting good discriminatory power. The data demonstrate that benign and malignant lesions can be distinguished by quantitative three-dimensional DOT.
231 citations
TL;DR: Inverse transport consists of reconstructing the optical properties of a domain from measurements performed at the domain's boundary as mentioned in this paper, which finds applications in medical imaging (optical tomography, optical molecular imaging) and in geophysical imaging (remote sensing in the Earth's atmosphere).
Abstract: Inverse transport consists of reconstructing the optical properties of a domain from measurements performed at the domain's boundary. This review concerns several types of measurements: time-dependent, time-independent, angularly resolved and angularly averaged measurements. We review recent results on the reconstruction of the optical parameters from such measurements and the stability of such reconstructions. Inverse transport finds applications e.g. in medical imaging (optical tomography, optical molecular imaging) and in geophysical imaging (remote sensing in the Earth's atmosphere).
202 citations
TL;DR: The application of model-based image reconstruction is reviewed, together with a numerical modelling approach to light propagation in tissue as well as generalized image reconstruction using boundary data, whereby the use of spectral and dual-modality systems can improve contrast and spatial resolution.
Abstract: 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.
192 citations
TL;DR: In this paper, the authors review the recent developments in the field of biomedical optical imaging, emphasizing technologies that have been moved from 'bench top to bedside' and enable unprecedented visualization of the tissue microstructure and enable quantitative mapping of disease-specific endogenous and exogenous substances.
Abstract: This paper reviews the recent developments in the field of biomedical optical imaging, emphasizing technologies that have been moved from 'bench top to bedside'. Important new developments in this field allow for unprecedented visualization of the tissue microstructure and enable quantitative mapping of disease-specific endogenous and exogenous substances. With these advances, optical imaging technologies are becoming powerful clinical tools for non-invasive and objective diagnosis, guided treatment and monitoring therapies. Recent developments in visible and infrared diffuse spectroscopy and imaging, spectral imaging, optical coherence tomography, confocal imaging, molecular imaging and dynamic spectral imaging are presented together with their derivative medical devices. Their perspectives and challenges are discussed.
171 citations
TL;DR: A novel method based on optical coherence tomography (OCT) for the accurate measurement of the refractive index of in vitro human teeth that has great potential for the clinical diagnosis of early dental caries.
Abstract: We describe a novel method based on optical coherence tomography (OCT) for the accurate measurement of the refractive index of in vitro human teeth. We obtain the refractive indices of enamel, dentin, and cementum to be 1.631+/-0.007, 1.540+/-0.013, and 1.582+/-0.010, respectively. The profile of the refractive index is readily obtained via an OCT B scan across a tooth. This method can be used to study the refractive index changes caused by dental decay and therefore has great potential for the clinical diagnosis of early dental caries.
153 citations
TL;DR: A wide-field method for obtaining three-dimensional images of turbid media that provides more accurate quantification of optical absorption and higher resolution than standard diffuse reflectance measurements is presented.
Abstract: We present a wide-field method for obtaining three-dimensional images of turbid media. By projecting patterns of light of varying spatial frequencies on a sample, we reconstruct quantitative, depth resolved images of absorption contrast. Images are reconstructed using a fast analytic inversion formula and a novel correction to the diffusion approximation for increased accuracy near boundaries. The method provides more accurate quantification of optical absorption and higher resolution than standard diffuse reflectance measurements.
TL;DR: It is found that the speckle-free feature of PAT results directly from the optical absorption contrast, which engenders strong correlations among the photoacoustic waves from the absorbers.
Abstract: Purpose: A long-standing conundrum is why photoacoustic tomography (PAT) possesses the unique ability to produce images devoid of speckle artifacts while all other coherent imaging technologies do not.
Methods: In this paper, we explain the inherent mechanism that suppresses speckle in PAT, and the analysis was validated by simulations based on an experimental PAT system.
Results: We found that the speckle-free feature of PAT results directly from the optical absorption contrast.
Conclusions: All optical absorbers expand on laser excitation, and therefore all initial photoacoustic pressure rises are positive, which engenders strong correlations among the photoacoustic waves from the absorbers. As a result, prominent boundaries always build up in photoacousticimages and suppress the interior speckle.
TL;DR: The ability to image protoporphyrin IX in mouse phantoms was assessed and the system is ready for in vivo use to study biological production of this endogenous marker of tumors.
Abstract: A prototype small animal imaging system was created for coupling fluorescence tomography (FT) with x-ray microcomputed tomography (microCT). The FT system has the potential to provide synergistic information content resultant from using microCT images as prior spatial information and then allows overlay of the FT image onto the original microCT image. The FT system was designed to use single photon counting to provide maximal sensitivity measurements in a noncontact geometry. Five parallel detector locations are used, each allowing simultaneous sampling of the fluorescence and transmitted excitation signals through the tissue. The calibration and linearity range performance of the system are outlined in a series of basic performance tests and phantom studies. The ability to image protoporphyrin IX in mouse phantoms was assessed and the system is ready for in vivo use to study biological production of this endogenous marker of tumors. This multimodality imaging system will have a wide range of applications in preclinical cancer research ranging from studies of the tumor microenvironment and treatment efficacy for emerging cancer therapeutics.
TL;DR: In this paper, the authors show that it suffices to restrict ourselves to piecewise constant diffusion and piecewise analytic absorption coefficients to regain uniqueness, and show that both parameters can simultaneously be determined from complete measurement data on an arbitrarily small part of the boundary.
Abstract: A prominent result of Arridge and Lionheart (1998 Opt. Lett. 23 882–4) demonstrates that it is in general not possible to simultaneously recover both the diffusion (aka scattering) and the absorption coefficient in steady-state (dc) diffusion-based optical tomography. In this work we show that it suffices to restrict ourselves to piecewise constant diffusion and piecewise analytic absorption coefficients to regain uniqueness. Under this condition both parameters can simultaneously be determined from complete measurement data on an arbitrarily small part of the boundary.
TL;DR: A compressed sensing method is introduced to develop a new tomographic algorithm for spectrally-resolved bioluminescence tomography that uses the nature of the source sparsity to improve the reconstruction quality with a regularization implementation.
Abstract: Through restoration of the light source information in small animals in vivo, optical molecular imaging, such as fluorescence molecular tomography (FMT) and bioluminescence tomography (BLT), can depict biological and physiological changes observed using molecular probes. A priori information plays an indispensable role in tomographic reconstruction. As a type of a priori information, the sparsity characteristic of the light source has not been sufficiently considered to date. In this paper, we introduce a compressed sensing method to develop a new tomographic algorithm for spectrally-resolved bioluminescence tomography. This method uses the nature of the source sparsity to improve the reconstruction quality with a regularization implementation. Based on verification of the inverse crime, the proposed algorithm is validated with Monte Carlo-based synthetic data and the popular Tikhonov regularization method. Testing with different noise levels and single/multiple source settings at different depths demonstrates the improved performance of this algorithm. Experimental reconstruction with a mouse-shaped phantom further shows the potential of the proposed algorithm. (C) 2009 Optical Society of America
TL;DR: The method was successfully examined with numerically and experimentally generated data and was found to be ideally suited for practical implementations in tomographic schemes of varying complexity, including multiprojection illumination systems and multispectral optoacoustic tomography studies of tissue biomarkers.
Abstract: We report on a new quantification methodology of optoacoustic tomographic reconstructions under heterogeneous illumination conditions representative of realistic whole-body imaging scenarios. Our method relies on the differences in the spatial characteristics of the absorption coefficient and the optical energy density within the medium. By using sparse-representation based decomposition, we exploit these different characteristics to extract both the absorption coefficient and the photon density within the imaged object from the optoacoustic image. In contrast to previous methods, this algorithm is not based on the solution of theoretical light transport equations and it does not require explicit knowledge of the illumination geometry or the optical properties of the object and other unknown or loosely defined experimental parameters, leading to highly robust performance. The method was successfully examined with numerically and experimentally generated data and was found to be ideally suited for practical implementations in tomographic schemes of varying complexity, including multiprojection illumination systems and multispectral optoacoustic tomography (MSOT) studies of tissue biomarkers.
TL;DR: The authors investigate the detection capacity and physical limits of tomographic optoacoustic imaging by simulating signals originating from absorbing spheres in tissue-mimicking media and employ a modified optOacoustic equation to incorporate wavelength-dependent propagation and attenuation of diffuse light and ultrasound.
Abstract: Optoacoustic imaging is emerging as a noninvasive imaging modality that can resolve optical contrast through several millimeters to centimeters of tissue with the resolution achieved by ultrasound imaging. More recently, applied at multiple illumination wavelengths, multispectral optoacoustic tomography (MSOT) offered the ability to effectively visualize tissue biomarkers by resolving their distinct spectral signatures. While the imaging potential of the method has been demonstrated, little is known on the sensitivity performance in resolving chromophoric and fluorescent substances, such as optical functional and molecular reporters. Herein the authors investigate the detection capacity and physical limits of tomographic optoacoustic imaging by simulating signals originating from absorbing spheres in tissue-mimicking media. To achieve this, a modified optoacoustic equation is employed to incorporate wavelength-dependent propagation and attenuation of diffuse light and ultrasound. The theoretical predictions are further validated in phantom experiments involving Cy5.5, a common near-infrared fluorescent molecular agent.
TL;DR: This work has developed a fluorescence lifetime diffuse optical tomography (DOT) system for in vivo preclinical imaging and demonstrates feasibility of FLT-DOT through a progressive series of experiments.
Abstract: Local molecular and physiological processes can be imaged in vivo through perturbations in the fluorescence lifetime (FLT) of optical imaging agents. In addition to providing functional information, FLT methods can quantify specific molecular events and multiplex diagnostic and prognostic information. We have developed a fluorescence lifetime diffuse optical tomography (DOT) system for in vivo preclinical imaging. Data is captured using a time-resolved intensified charge coupled device (ICCD) system to measure fluorescence excitation and emission in the time domain. Data is then converted to the frequency domain, and we simultaneously reconstruct images of yield and lifetime using an extension to the normalized Born approach. By using differential phase measurements, we demonstrate DOT imaging of short lifetimes (from 350 ps) with high precision (+/-5 ps). Furthermore, this system retains the efficiency, speed, and flexibility of transmission geometry DOT. We demonstrate feasibility of FLT-DOT through a progressive series of experiments. Lifetime range and repeatability are first measured in phantoms. Imaging of subcutaneous implants then verifies the FLT-DOT approach in vivo in the presence of inhomogeneous optical properties. Use in a common research scenario is ultimately demonstrated by imaging accumulation of a targeted near-infrared (NIR) fluorescent-labeled peptide probe (cypate-RGD) in a mouse with a subcutaneous tumor.
TL;DR: First results on a method enabling mechanical scanning-free tomography with submicrometer axial resolution by multiple-wavelength digital holographic microscopy are presented, applied to erythrocytes investigation to retrieve the cellular membrane profile in three dimensions.
Abstract: We present first results on a method enabling mechanical scanning-free tomography with submicrometer axial resolution by multiple-wavelength digital holographic microscopy. By sequentially acquiring reflection holograms and summing 20 wavefronts equally spaced in spatial frequency in the 485–670 nm range, we are able to achieve a slice-by-slice tomographic reconstruction with a 0.6–1 μm axial resolution in a biological medium. The method is applied to erythrocytes investigation to retrieve the cellular membrane profile in three dimensions.
Patent•
30 Jan 2009TL;DR: In this paper, a cylindrical sheath to be inserted into a subject, an optical fiber disposed in the internal space of the sheath, a rotatably-supporting portion fixed to the optical fiber in the vicinity of a distal end of the optical fibre, and a holding portion to hold the distal optical system.
Abstract: An OCT optical probe to be inserted into a subject includes: a cylindrical sheath to be inserted into a subject; an optical fiber disposed in the internal space of the sheath; a rotatably-supporting portion fixed to the optical fiber in the vicinity of a distal end of the optical fiber; a distal optical system to deflect light emitted from the distal end of the optical fiber toward the subject; a holding portion to hold the distal optical system such that the optical system is rotatably supported by the rotatably-supporting portion; and a flexible shaft covering the optical fiber in the internal space, wherein the holding portion is fixed to a distal end of the flexible shaft. Using the OCT optical probe of the invention, the problem of degradation of measurement accuracy due to optical insertion loss and optical reflection loss at a rotary joint can be eliminated inexpensively and safely.
TL;DR: Three dimensional multispectral fluorescence optical tomography small animal imaging system with an innovative geometry using a truncated conical mirror shows good correlation of the reconstructed image with the location of the fluorescence probe as determined by subsequent optical imaging of cryosections of the mouse.
Abstract: We have developed a three dimensional (3D) multispectral fluorescence optical tomography small animal imaging system with an innovative geometry using a truncated conical mirror, allowing simultaneous viewing of the entire surface of the animal by an EMCCD camera. A conical mirror collects photons approximately three times more efficiently than a flat mirror. An x-y mirror scanning system makes it possible to scan a collimated excitation laser beam to any location on the mouse surface. A pattern of structured light incident on the small animal surface is used to extract the surface geometry for reconstruction. A finite element based algorithm is applied to model photon propagation in the turbid media and a preconditioned conjugate gradient (PCG) method is used to solve the large linear system matrix. The reconstruction algorithm and the system feasibility are evaluated by phantom experiments. These experiments show that multispectral measurements improve the spatial resolution of reconstructed images. Finally, an in vivo imaging study of a xenograft tumor in a mouse shows good correlation of the reconstructed image with the location of the fluorescence probe as determined by subsequent optical imaging of cryosections of the mouse.
TL;DR: The different hand-held based NIR devices developed to date are reviewed, in terms of the measurement techniques implemented (continuous wave, time or frequency-domain), the imaging methods used, and the specific applications towards which they were applied.
TL;DR: A real-time display of processed OCT images is demonstrated using a linear-in-wave-number (linear-k) spectrometer and a graphics processing unit (GPU) to avoid calculating the resampling process.
Abstract: Fourier domain optical coherence tomography (FD-OCT) requires resampling of spectrally resolved depth information from wavelength to wave number, and the subsequent application of the inverse Fourier transform. The display rates of OCT images are much slower than the image acquisition rates due to processing speed limitations on most computers. We demonstrate a real-time display of processed OCT images using a linear-in-wave-number (linear-k) spectrometer and a graphics processing unit (GPU). We use the linear-k spectrometer with the combination of a diffractive grating with 1200 lines/mm and a F2 equilateral prism in the 840-nm spectral region to avoid calculating the resampling process. The calculations of the fast Fourier transform (FFT) are accelerated by the GPU with many stream processors, which realizes highly parallel processing. A display rate of 27.9 frames/sec for processed images (2048 FFT size×1000 lateral A-scans) is achieved in our OCT system using a line scan CCD camera operated at 27.9 kHz.
TL;DR: In this article, a partial differential-equation (PDE) constrained approach to optical tomography that makes use of an all-at-once reduced Hessian sequential quadratic programming (rSQP) scheme is proposed.
Abstract: It is well acknowledged that transport-theory-based reconstruction algorithm can provide the most accurate reconstruction results especially when small tissue volumes or high absorbing media are considered. However, these codes have a high computational burden and are often only slowly converging. Therefore, methods that accelerate the computation are highly desirable. To this end, we introduce in this work a partial-differential-equation (PDE) constrained approach to optical tomography that makes use of an all-at-once 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 10–25, as compared to the commonly employed limited memory BFGS method. At the same time accuracy and robustness even in the presence of noise are not compromised.
TL;DR: The authors demonstrated on in vivo examples that the combination of anatomical coregistration, accurate optical tissue properties, multispectral acquisition, and a blocking-off FD-SP3 solution of the radiative transfer model significantly improves the accuracy of the BLT reconstructions.
Abstract: Purpose: Bioluminescenceimaging is a research tool for studying gene expression levels in small animal models of human disease. Bioluminescence light, however, is strongly scattered in biological tissue and no direct image of the light-emitting reporter probe’s location can be obtained. Therefore, the authors have developed a linear image reconstruction method for bioluminescencetomography (BLT) that recovers the three-dimensional spatial bioluminescent source distribution in small animals. Methods: The proposed reconstruction method uses third-order simplified spherical harmonics ( SP 3 ) solutions to the equation of radiative transfer for modeling the bioluminescence light propagation in optically nonuniform tissue. The SP 3 equations and boundary conditions are solved with a finite-difference (FD) technique on a regular grid. The curved geometry of the animal surface was taken into account with a blocking-off region method for regular grids. Coregistered computed tomography(CT) and magnetic resonance (MR)images provide information regarding the geometry of the skin surface and internal organs. The inverse source problem is defined as an algebraic system of linear equations for the unknown source distribution and is iteratively solved given multiview and multispectral boundary measurements. The average tissue absorption parameters, which are used for the image reconstruction process, were calculated with an evolution strategy (ES) from in vivo measurements using an implanted pointlike source of known location and spectrum. Moreover, anatomical information regarding the location of the internal organs and other tissue structures within the animal’s body are provided by coregistered MRimages. Results: First, the authors recovered the wavelength-dependent absorption coefficients (average error of 14%) with the ES under ideal conditions by using a numerical mouse model. Next, they reconstructed the average absorption coefficient of a small animal by using an artificial implanted light source and the validated ES. Last, they conducted twoin vivo animal experiments and recovered the spatial location of the implanted light source and the spatial distribution of a bioluminescent reporter system located in the kidneys. The source reconstruction results were coregistered to CT and MRimages. They further found that accurate bioluminescenceimage reconstructions could be obtained when segmenting a voidlike cyst with low-scattering and absorption parameters, whereas inaccurate image reconstructions were obtained when assuming a uniform optical parameter distribution instead. The image reconstructions were completed within 23 min on a 3 GHz Intel processor. Conclusions: The authors demonstrated onin vivo examples that the combination of anatomical coregistration, accurate optical tissueproperties, multispectral acquisition, and a blocking-off FD- SP 3 solution of the radiative transfer model significantly improves the accuracy of the BLT reconstructions.
TL;DR: In this article, the authors demonstrate the sensitivity and overall performance of iterative correction for light attenuation in optoacoustic tomography as a function of number of iterations and accuracy of the tissue optical properties estimations.
Abstract: In this letter we experimentally demonstrate the sensitivity and overall performance of iterative correction for light attenuation in optoacoustic tomography as a function of number of iterations and accuracy of the tissue optical properties estimations. Experimental optoacoustic data were obtained by circularly illuminating a tissue-mimicking phantom with a high intensity pulsed near infrared laser and measuring the subsequent acoustic waves using a broadband acoustic hydrophone. We showcase an improvement in image fidelity and quantification due to the iterative inversion but find the method sensitive to the background optical properties and of a diverging behavior when increasing the number of iterations.
TL;DR: The effect of silica/gold nanoshells and titanium dioxide nanoparticles on the optical properties of skin is studied and in vivo measurements and Monte Carlo simulations are implemented to analyze the efficiency of using these nanoparticles as contrasting agents for optical coherence tomography (OCT) imaging of skin.
Abstract: The effect of silica/gold nanoshells and titanium dioxide nanoparticles on the optical properties of skin is studied. By implementing in vivo measurements and Monte Carlo simulations, we analyze the efficiency of using these nanoparticles as contrasting agents for optical coherence tomography (OCT) imaging of skin. In vivo measurements are performed on pig skin, where nanoparticle suspension drops have been applied. The identification of skin layers is performed by comparison with corresponding histology images. Experimental results exhibit an increase in contrast of the obtained OCT images after a single nanoparticles application. Multiple applications do not lead to increase in the obtained contrast. To interpret the obtained experimental OCT images of skin and understand the mechanisms of contrasting, a set of Monte Carlo calculations is performed. The results of the simulations exhibit good qualitative agreement with the experimental images, and prove that the contrasting originates from the nanoparticles added, while the contrast of inclusion originates from the absence of nanoparticles within it and their presence in the surrounding area.
TL;DR: In this paper, a surface topology and motion compensation system for microsurgery guidance and intervention based on common-path optical coherence tomography is developed for real-time depth tracking.
Abstract: A surface topology and motion compensation system for microsurgery guidance and intervention is developed based on common-path optical coherence tomography. A 1-D erosion-based edge-searching method and autoregressive predictor are applied to A-scan data for real-time depth tracking. Images using the topology and motion compensation technique are obtained. In addition, the motion compensation properties are studied. The system can be easily integrated with microsurgery tools and can be used for various clinical applications.
Posted Content•
TL;DR: A review of recent mathematical and computational advances in optical tomography can be found in this article, where the physical foundations of forward models for light propagation on microscopic, mesoscopic and macroscopic scales are discussed.
Abstract: This paper 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.
TL;DR: This work addresses the problem of three-dimensional optical imaging of mesoscopic systems where light exhibits sufficiently strong scattering so that the image reconstruction methods of computed tomography are not applicable, yet the detected light is not diffuse and the diffuse tomography can not be employed either.
Abstract: We consider the problem of optical tomographic imaging in the mesoscopic regime where the photon mean-free path is on the order of the system size. It is shown that a tomographic imaging technique can be devised which is based on the assumption of single scattering and utilizes a generalization of the Radon transform which we refer to as the broken-ray transform. The technique can be used to recover the extinction coefficient of an inhomogeneous medium from angularly resolved measurements and is illustrated with numerical simulations. The forward data for these simulations were obtained by numerically solving the radiative transport equation without any approximations. Tomographic imaging in slabs of different widths was considered and it was shown that the technique can tolerate a maximum width that corresponds to approximately six scattering events. It is also shown that the use of broken rays does not result in additional ill posedness of the inverse problem in comparison to the classical problem of inverting the Radon transform. Applications to biomedical imaging are described.