Three-dimensional Optical Tomography Research Articles

Spectroscopic Three-Dimensional Imaging of Light Scattering Medium by Detection of Ultrasonic Velocity Change owing to Light Illumination

An experimental apparatus that automatically detects the ultrasonic velocity change of a phantom due to light absorption was fabricated. Optical three-dimensional images of the phantom were constructed by illumination at a light intensity under the skin exposure limit of a continuous-wave diode laser. It was confirmed that the image of optical absorption distribution at the specified depth of the phantom could be obtained.

Multispectral breast imaging using a ten‐wavelength, source/detector channels silicon photodiode‐based diffuse optical tomography system

We describe a compact diffuse optical tomography system specifically designed for breast imaging. The system consists of 64 silicon photodiode detectors, 64 excitation points, and 10 diode lasers in the near-infrared region, allowing multispectral, three-dimensional optical imaging of breast tissue. We also detail the system performance and optimization through a calibration procedure. The system is evaluated using tissue-like phantom experiments and an in vivo clinic experiment. Quantitative two-dimensional (2D) and three-dimensional (3D) images of absorption and reduced scattering coefficients are obtained from these experiments. The ten-wavelength spectra of the extracted reduced scattering coefficient enable quantitative morphological images to be reconstructed with this system. From the in vivo clinic experiment, functional images including deoxyhemoglobin, oxyhemoglobin, and water concentration are recovered and tumors are detected with correct size and position compared with the mammography.

Three-dimensional optical imaging in layered media

The present paper deals with the reconstruction of three-dimensional objects from the scattered far-field. The configuration under study is typically the one used in the Optical Diffraction Tomography (ODT), in which the sample is illuminated with various angles of incidence and the scattered field is measured for each illumination. The retrieval of the sample from the scattered field is accomplished numerically by solving the inverse scattering problem. We present herein a fast method for solving the inverse scattering problem based on the Coupled Dipole Method (CDM) and applied it for complex background configuration such as buried objects in a layered medium. Numerical experiments are reported and robustness against the presence of noise in the data is analyzed.

Real-time automated 3D sensing, detection, and recognition of dynamic biological micro-organic events

In this paper, we present an overview of three-dimensional (3D) optical imaging techniques for real-time automated sensing, visualization, and recognition of dynamic biological microorganisms. Real time sensing and 3D reconstruction of the dynamic biological microscopic objects can be performed by single-exposure on-line (SEOL) digital holographic microscopy. A coherent 3D microscope-based interferometer is constructed to record digital holograms of dynamic micro biological events. Complex amplitude 3D images of the biological microorganisms are computationally reconstructed at different depths by digital signal processing. Bayesian segmentation algorithms are applied to identify regions of interest for further processing. A number of pattern recognition approaches are addressed to identify and recognize the microorganisms. One uses 3D morphology of the microorganisms by analyzing 3D geometrical shapes which is composed of magnitude and phase. Segmentation, feature extraction, graph matching, feature selection, and training and decision rules are used to recognize the biological microorganisms. In a different approach, 3D technique is used that are tolerant to the varying shapes of the non-rigid biological microorganisms. After segmentation, a number of sampling patches are arbitrarily extracted from the complex amplitudes of the reconstructed 3D biological microorganism. These patches are processed using a number of cost functions and statistical inference theory for the equality of means and equality of variances between the sampling segments. Also, we discuss the possibility of employing computational integral imaging for 3D sensing, visualization, and recognition of biological microorganisms illuminated under incoherent light. Experimental results with several biological microorganisms are presented to illustrate detection, segmentation, and identification of micro biological events.

Three-dimensional optical tomographic imaging of scattering objects in tissue-simulating turbid media using independent component analysis

An information-theory-based approach for the detection and three-dimensional localization of scattering targets embedded in a turbid medium, such as a tumor in the breast, is introduced. The approach uses multisource illumination of the medium, multidetector transillumination signal acquisition, and independent component analysis of the information theory for target detection and localization. The efficacy of the approach is demonstrated by detecting and obtaining location information about scattering targets embedded in human breast tissue-simulating turbid media of thickness 50 times the transport mean-free path.

Computer-Assisted Instrumentation during Endoscopic Transaxillary First Rib Resection for Thoracic Outlet Syndrome: A Safe Alternate Approach

The purpose of this article is to discuss the feasibility of using computer-enhanced instrumentation to improve visualization and therefore patient safety during transaxillary first rib resection. From November 1998 to July 2005, 105 patients who had failed conservative treatment underwent 131 procedures for thoracic outlet decompression. Eighty-nine endoscopic transaxillary first rib resections were completed using Aesop/Hermes integrated voice control instrumentation (Computer Motion, Goleta, CA). Since February 2003, dissection in 42 procedures was performed using the daVinci Surgical System (Intuitive Surgical, Inc, Sunnyvale, CA). The surgical findings with cervical bands correlated with the preoperative symptoms. One hundred percent of patients with a combination of neurogenic and arterial thoracic outlet syndrome (TOS) requiring cervical rib resection had Roos type I and/or II bands. Additional surgical findings included the following: combination of neurogenic and arterial TOS without cervical ribs or neurogenic TOS alone had type III, IV, or V bands, and patients with venous compression (100%) had type VII bands. No mortalities or permanent neurovascular injuries occurred. There was a 6.1% postoperative complication rate. Persistent myofibrositis was found in 34% of patients with ongoing symptoms. The daVinci three-dimensional optical imaging system enhances visualization, thereby promoting telemanipulation of soft tissue structures in a relatively inaccessible working space. Endoscopic computerized instrumentation in transaxillary first rib resection decreases the risk of neurovascular injury, promotes complete decompression, and therefore provides a safe alternative to standard first rib resections.

Three-dimensional whole-head optical tomography of passive motor evoked responses in the neonate

Optical tomography has been used to reconstruct three-dimensional images of the entire neonatal head during motor evoked responses. Data were successfully acquired during passive movement of each arm on four out of six infants examined, from which eight sets of bilateral images of hemodynamic parameters were reconstructed. Six out of the eight images showed the largest change in total hemoglobin in the region of the contralateral motor cortex. The mean distance between the peak response in the image and the estimated position of the contralateral motor cortex was 10.8 mm. These results suggest that optical tomography may provide an appropriate technique for non-invasive cot-side imaging of brain function.

A 3D view on free-floating, space-fixed and surface-bound para-phenylene nanofibres

Nanofibres from para-hexaphenylene and functionalized quaterphenylene molecules aregrown on mica surfaces and are thereafter transferred into solution, where they either freelyrotate in water or are space-fixed in sucrose. From freely rotating aggregates highlyanisotropic angular intensity distributions of emitted light for individual aggregates aredetermined. Luminescence is enhanced at the nanofibre tip as compared to the broad sideby about an order of magnitude probably due to waveguiding along the long axis of theaggregates. For dense arrays of nanofibres on mica the increase of emitted intensity towardsthe substrate plane in the direction of the long axes of the nanofibres is smallerand it depends on the effective thickness of the nanofibre films. The differencebetween individual aggregates and aggregate arrays is interpreted in terms of lightscattering at surface roughness inside the nanofibre film and on the border of theunderlying mica substrate. Aggregates fixed in solution, with the help of femtosecondlaser scanning microscopy, allow us to obtain two-photon absorption spectra offunctionalized nanofibres between 720 and 900 nm as well as morphological featuresfrom three-dimensional optical images. The lateral resolution is about 400 nm.

Three-dimensional localization and optical imaging of objects in turbid media with independent component analysis

A new approach for optical imaging and localization of objects in turbid media that makes use of the independent component analysis (ICA) from information theory is demonstrated. Experimental arrangement realizes a multisource illumination of a turbid medium with embedded objects and a multidetector acquisition of transmitted light on the medium boundary. The resulting spatial diversity and multiple angular observations provide robust data for three-dimensional localization and characterization of absorbing and scattering inhomogeneities embedded in a turbid medium. ICA of the perturbations in the spatial intensity distribution on the medium boundary sorts out the embedded objects, and their locations are obtained from Green's function analysis based on any appropriate light propagation model. Imaging experiments were carried out on two highly scattering samples of thickness approximately 50 times the transport mean-free path of the respective medium. One turbid medium had two embedded absorptive objects, and the other had four scattering objects. An independent component separation of the signal, in conjunction with diffusive photon migration theory, was used to locate the embedded inhomogeneities. In both cases, improved lateral and axial localizations of the objects over the result obtained by use of common photon migration reconstruction algorithms were achieved. The approach is applicable to different medium geometries, can be used with any suitable photon propagation model, and is amenable to near-real-time imaging applications.

Three-dimensional diffuse optical imaging of hand joints: System description and phantom studies

Abstract In this paper we describe a three-dimensional (3D) continuous wave (CW) diffuse optical tomography (DOT) system and present 3D volumetric reconstruction studies using this DOT system with simple phantom models that simulate hand joints. The CCD-based DOT system consists of 64×64 source/detector fiber optic channels, which are arranged in four layers, forming a cylindrical fiber optic/tissue interface. Phantom experiments are used to evaluate system performance with respective to axial spatial resolution, optical contrast and target position for detection of osteoarthritis where cartilage is the primary target region of interest. These phantom studies suggest that we are able to quantitatively resolve a 2 mm thick “cartilage” and qualitatively resolve a 1 mm thick “cartilage” using our 3D reconstruction approach. Our results also show that optical contrast of 3:1–7:1 between the “disease cartilage” and normal cartilage can be quantitatively recovered. Finally, the target position along axial direction on image reconstruction is studied. All the images are obtained using our 3D finite-element-based reconstruction algorithm.

Spatial deconvolution technique to improve the accuracy of reconstructed three-dimensional diffuse optical tomographic images

A straightforward spatial deconvolution operation is presented that seeks to invert the information-blurring property of first-order perturbation algorithms for diffuse optical tomography (DOT) image reconstruction. The method that was developed to generate these deconvolving operators, or filters, was conceptually based on the frequency-encoding process used in magnetic resonance imaging. The computation of an image-correcting filter involves the solution of a large system of linear equations, in which known true distributions and the corresponding recovered distributions are compared. Conversely, application of a filter involves only a simple matrix multiplication. Simulation results show that application of this deconvolution operation to three-dimensional DOT images reconstructed by the solution of a first-order perturbation equation (Born approximation) can yield marked enhancement of image quality. In the examples considered, use of image-correcting filters produces obvious improvements in image quality, in terms of both location and mirco(a) of the inclusions. The displacements between the true and recovered locations of an inclusion's centroid location are as small as 1 mm, in an 8-cm-diameter medium with 1.5-cm-diameter inclusions, and the peak value of the recovered micro(a) for the inclusions deviates from the true value by as little as 5%.

Time-resolved optical mammography using a liquid coupled interface

A method has been devised for generating three-dimensional optical images of the breast using a 32-channel time-resolved system and a liquid-coupled interface. The breast is placed in a hemispherical cup surrounded by sources and detectors, and the remaining space is filled with a fluid with tissue-like optical properties. This approach has three significant benefits. First, cups can accommodate a large range of breast sizes, enabling the entire volume of the breast to be sampled. Second, the coupling of the source and detector optics at the surface is constant and independent of the subject, enabling intensity measurements to be employed in the image reconstruction. Third, the external geometry of the reconstructed volume is known exactly. Images of isolated targets with contrasting absorbing and scattering properties have been acquired, and the performance of the system has been evaluated in terms of the contrast, spatial resolution, and localization accuracy. These parameters were strongly dependent on the location of the targets within the imaged volume. Preliminary images of a healthy human subject are also presented, which reveal subtle heterogeneity, particularly in the distribution of scatter. The ability to detect an absorbing target adjacent to the breast is also demonstrated.

Superresolution of three-dimensional optical imaging by use of evanescent waves

We simulate a three-dimensional optical diffraction tomography experiment in which superresolution is achieved by illuminating the object with evanescent waves generated by a prism. We show that accounting for multiple scattering between the object and the prism interface is mandatory to obtain superresolved images. Because the Born approximation leads to poor results, we propose a nonlinear inversion method for retrieving the map of permittivity of the object from the scattered far field. We analyze the sensitivity to noise of our algorithm and point out the importance of using incident propagative waves together with evanescent waves to improve the robustness of the reconstruction without losing the superresolution.

Three-dimensional optical tomographic imaging of supersonic jets through inversion of phase data obtained through the transport-of-intensity equation.

We report experimental results of quantitative imaging in supersonic circular jets by using a monochromatic light probe. An expanding cone of light interrogates a three-dimensional volume of a supersonic steady-state flow from a circular jet. The distortion caused to the spherical wave by the presence of the jet is determined through our measuring normal intensity transport. A cone-beam tomographic algorithm is used to invert wave-front distortion to changes in refractive index introduced by the flow. The refractive index is converted into density whose cross sections reveal shock and other characteristics of the flow.

Three-dimensional subwavelength optical imaging using the coupled dipole method

We simulate a three-dimensional optical diffraction tomography experiment in which the scattered field from an unknown object is measured for various observation and incident angles. We propose a fast inversion scheme based on the coupled dipole method that enables us to reconstruct the three-dimensional map of permittivity of the object from the far-field data. We show that a power of resolution of $\ensuremath{\lambda}∕4$ can be expected and that the method is robust to noise.

Imaging changes in blood volume and oxygenation in the newborn infant brain using three-dimensional optical tomography

Induced haemodynamic and blood oxygenation changes occurring within the brain of a ventilated newborn infant have been imaged in three dimensions using optical tomography. Noninvasive measurements of the flight times of transmitted light were acquired during illumination of the brain by laser pulses at wavelengths of 780 nm and 815 nm. The oxygen and carbon dioxide partial pressures were adjusted through alterations to the ventilator settings, resulting in changes to the cerebral blood volume and oxygenation. Three-dimensional images were generated using the physiologically associated differences in the measured data, obviating the need for data calibration using a separate reference measurement. The results exhibit large changes in absorption coefficient at both wavelengths. Images corresponding to differences in concentrations of oxy- and deoxyhaemoglobin are in qualitative agreement with known physiological data.

Ultrasound-modulated optical computed tomography of biological tissues

An optical imaging technique called ultrasound-modulated optical computed tomography is demonstrated for tomographic imaging of biological tissues. Ultrasound-modulated optical signals are extracted from scattered light to provide projection data for the image reconstruction. A filtered back-projection algorithm is implemented to reconstruct an image reflecting optical tissue properties from angular and linear scans of an ultrasonic beam across a sample. This reconstruction-based imaging technique provides a way to obtain images of cross sections containing the scanned ultrasonic axis in biological tissues, which enables three-dimensional ultrasound-modulated optical imaging. The technique combines the contrast advantage of optical waves and the resolution advantage of ultrasonic waves.

Adaptive finite element based tomography for fluorescence optical imaging in tissue

A three-dimensional fluorescence-enhanced optical tomography scheme based upon an adaptive finite element formulation is developed and employed to reconstruct fluorescent targets in turbid media from frequency-domain measurements made in reflectance geometry using area excitation illumination. The algorithm is derived within a Lagrangian framework by treating the photon diffusion model as a constraint to the optimization problem. Adaptively refined meshes are used to separately discretize maps of the forward/adjoint variables and the unknown parameter of fluorescent yield. A truncated Gauss-Newton method with simple bounds is used as the optimization method. Fluorescence yield reconstructions from simulated measurement data with added Gaussian noise are demonstrated for one and two fluorescent targets embedded within a 512ml cubical tissue phantom. We determine the achievable resolution for the area-illumination/area-detection reflectance measurement geometry by reconstructing two 0.4cm diameter spherical targets placed at at a series of decreasing lateral spacings. The results show that adaptive techniques enable the computationally efficient and stable solution of the inverse imaging problem while providing the resolution necessary for imaging the signals from molecularly targeting agents.

Three-dimensional optical tomography with the equation of radiative transfer

We report on the derivation and implementation of the first three-dimensional optical tomographic image reconstruction scheme that is based on the time-independent equation of radiative transfer (ERT) and allows for arbitrarily shaped medium boundaries and arbitrary spatial material distributions. The scheme builds on the concept of model-based iterative image reconstruction, in which a forward model provides prediction of detector readings, and a gradient-based updating scheme minimizes an appropriately de- fined objective function. The forward model is solved by using an even-parity formulation of the ERT, which lends itself to a finite- element discretization method. The finite-element technique pro- vides the suitable framework for predicting light propagation in arbi- trarily shaped three-dimensional media. For an efficient way of calculating the gradient of the objective function we have imple- mented an adjoint differentiation scheme. Initial reconstruction re- sults using synthetic data from simple media and a three- dimensional mesh of the human forehead illustrate the performance of the code. © 2003 SPIE and IS&T. (DOI: 10.1117/1.1587730)

Validation of In Vivo Assessment of Facial Soft-Tissue Volume Changes and Clinical Application in Midfacial Distraction: A Technical Report

The purpose of this study was to validate the assessment of visible volume changes of the facial soft tissue with an optical three-dimensional sensor and to introduce new parameters for the evaluation of the soft-tissue shape achieved from three-dimensional data of selected cases of midfacial distraction. Images of a truncated cone of known volume were assessed repeatedly with an optical three-dimensional sensor based on phase-measuring triangulation to calculate the volume. Two cubic centimeters of anesthetic solution was injected into the right malar region of 10 volunteers who gave their informed consent. Three-dimensional images were assessed before and immediately after the injections for the assessment of the visible volume change. In five patients who underwent midfacial distraction after a high quadrangular Le Fort I osteotomy, three-dimensional scans were acquired before and 6 and 24 months after the operation. The visible soft-tissue volume change in the malar-midfacial area and the mean distance of the accommodation vector that transformed the preoperative into the postoperative surface were calculated. The volume of the truncated cone was 235.26 +/- 1.01 cc, revealing a measurement uncertainty of 0.4 percent. The injections of anesthetic solution into the malar area resulted in an average visible volume change of 2.06 +/- 0.06 cc. The measurement uncertainty was 3 percent. In the five patients, the average distance of maxillary advancement was 6.7 +/- 2.3 mm after 6 months and 5.4 +/- 3.0 mm after 2 years. It was accompanied by a mean visible volume increase of 8.92 +/- 5.95 cc on the right side and 9.54 +/- 4.39 cc on the left side after 6 months and 3.54 +/- 3.70 cc and 4.80 +/- 3.47 cc, respectively, after 2 years. The mean distance of the accommodation vector was 4.41 +/- 1.94 mm on the right side and 4.74 +/- 1.32 mm on the left side after 6 months and 1.62 +/- 1.96 mm and 2.16 +/- 1.52 mm, respectively, after 2 years. The assessment of visible volume changes by optical three-dimensional images can be carried out with considerable accuracy. The determination of volume changes and accompanying accommodation vectors completes the cephalometric analysis during the follow-up of patients undergoing midfacial distraction. The new parameters will help to assess normative soft-tissue data on the basis of three-dimensional imaging with a view to an improved three-dimensional prediction of the operative outcome of orthognathic surgery.