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Image Reconstruction (image + reconstruction)

Distribution by Scientific Domains

Medical Sciences	75%
Engineering	10%
Life Sciences	5%
3 Other Domains	10%

Selected Abstracts

Image reconstruction for a partially immersed imperfectly conducting cylinder by genetic algorithm

INTERNATIONAL JOURNAL OF IMAGING SYSTEMS AND TECHNOLOGY, Issue 4 2009
Wei Chien
Abstract This article presents a computational approach to the imaging of a partially immersed imperfectly conducting cylinder. An imperfectly conducting cylinder of unknown shape and conductivity scatters the incident transverse magnetic (TM) wave in free space while the scattered field is recorded outside. Based on the boundary condition and the measured scattered field, a set of nonlinear integral equations, and the inverse scattering problem are reformulated into an optimization problem. We use genetic algorithm (GA) to reconstruct the shape and the conductivity of a partially immersed imperfectly conducting cylinder. The genetic algorithm is then used to find out the global extreme solution of the cost function. Numerical results demonstrated that, even when the initial guess is far away from the exact one, good reconstruction can be obtained. In such a case, the gradient-based methods often get trapped in a local extreme. In addition, the effect of random noise on the reconstruction is investigated. © 2009 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 19, 299,305, 2009 [source]

Image reconstruction of a buried perfectly conducting cylinder illuminated by transverse electric waves

INTERNATIONAL JOURNAL OF IMAGING SYSTEMS AND TECHNOLOGY, Issue 6 2005
Yueh-Cheng Chen
Abstract This article presents a computational approach to the image reconstruction of a perfectly conducting cylinder illuminated by transverse electric waves. A perfectly conducting cylinder of unknown shape buried in one half-space and scatters the incident wave from another half-space where the scattered field is recorded. Based on the boundary condition and the measured scattered field, a set of nonlinear integral equations is derived, and the imaging problem is reformulated into an optimization problem. The steady state genetic algorithm is then employed to find out the global extreme solution of the cost function. Numerical results demonstrated that, even when the initial guess is far away from the exact one, good reconstruction can be obtained. In such a case, the gradient-based methods often get trapped in a local extreme. In addition, the effect of different noise on the reconstruction is investigated. © 2006 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 15, 261,265, 2005 [source]

Image reconstruction of buried inhomogeneous dielectric cylinders coated on a conductor

INTERNATIONAL JOURNAL OF IMAGING SYSTEMS AND TECHNOLOGY, Issue 3 2005
Chun Jen Lin
Abstract The image reconstruction of buried inhomogeneous dielectric cylinders coated on a conductor with known cross-section is investigated. Inhomogeneous dielectric cylinders coated on a conductor is buried in one half space and scatter a group of unrelated waves incident from another half space, where the scattered field is recorded. By proper arrangement of the various unrelated incident fields, the difficulties of ill-posedness and nonlinearity are circumvented, and the permittivity distribution can be reconstructed through simple matrix operations. The algorithm is based on the moment method and the unrelated illumination method. Numerical results show that good reconstruction has been obtained both with and without Gaussian noise in measured data. © 2005 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 15, 172,177, 2005 [source]

Image reconstruction with a shift-variant filtration in circular cone-beam CT,

INTERNATIONAL JOURNAL OF IMAGING SYSTEMS AND TECHNOLOGY, Issue 5 2004
Lifeng Yu
Abstract It is well known that cone-beam data acquired with a circular orbit are insufficient for exact image reconstruction. Despite this, because a cone-beam scanning configuration with a circular orbit is easy to implement in practice, it has been widely employed for data acquisition in, e.g., micro-CT and CT imaging in radiation therapy. The algorithm developed by Feldkamp, Davis, and Kress (FDK) and its modifications, such as the Tent,FDK (T-FDK) algorithm, have been used for image reconstruction from circular cone-beam data. In this work, we present an algorithm with spatially shift-variant filtration for image reconstruction in circular cone-beam CT. We performed computer-simulation studies to compare the proposed and existing algorithms. Numerical results in these studies demonstrated that the proposed algorithm has resolution properties comparable to, and noise properties better than, the FDK algorithm. As compared to the T-FDK algorithm, our proposed algorithm reconstructs images with an improved in-plane spatial resolution. © 2005 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 14, 213,221, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ima.20026 [source]

Comparison of image reconstruction by using near-field and far-field data for an imperfect conductor

INTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 2 2001
Chien-Ching Chiu
Abstract Image reconstruction by using near-field and far-field data for an imperfectly conducting cylinder is investigated. A conducting cylinder of unknown shape and conductivity scatters the incident wave in free space and the scattered near and far fields are measured. By using measured fields, the imaging problem is reformulated into an optimization problem and solved by the genetic algorithm. Numerical results show that the convergence speed and final reconstructed results by using near-field data are better than those obtained by using far-field data. This work provides both comparative and quantitative information. © 2001 John Wiley & Sons, Inc. Int J RF and Microwave CAE 11: 69,73, 2001. [source]

Magnitude image CSPAMM reconstruction (MICSR)

MAGNETIC RESONANCE IN MEDICINE, Issue 2 2003
Moriel NessAiver
Abstract Image reconstruction of tagged cardiac MR images using complementary spatial modulation of magnetization (CSPAMM) requires the subtraction of two complex datasets to remove the untagged signal. Although the resultant images typically have sharper and more persistent tags than images formed without complementary tagging pulses, handling the complex data is problematic and tag contrast still degrades significantly during diastole. This article presents a magnitude image CSPAMM reconstruction (MICSR) method that is simple to implement and produces images with improved contrast and tag persistence. The MICSR method uses only magnitude images , i.e., no complex data , but yields tags with zero mean, sinusoidal profiles. A trinary display of MICSR images emphasizes their long tag persistence and demonstrates a novel way to visualize myocardial deformation. MICSR contrast and contrast-to-noise ratios (CNR) were evaluated using simulations, a phantom, and two normal volunteers. Tag contrast 1000 msec after the R wave trigger was 3.0 times better with MICSR than with traditional CSPAMM reconstruction techniques, while CNRs were 2.0 times better. Magn Reson Med 50:331,342, 2003. © 2003 Wiley-Liss, Inc. [source]

Evaluation of the visibility and the course of the mandibular incisive canal and the lingual foramen using cone-beam computed tomography

CLINICAL ORAL IMPLANTS RESEARCH, Issue 7 2010
Nikos Makris
Abstract Objectives: To assess the visibility and the course of the incisive canal and the visibility and the location of the lingual foramen using cone-beam computed tomography (CBCT). Methods: In total, 100 CBCT examinations of patients for preoperative planning were used for this study. The examinations were taken using the NewTom 3G CBCT unit, applying a standardized exposure protocol. Image reconstruction from the raw data was performed using the NewTom software. Three experts were asked to assess the visibility of the incisive canal using a four-point rating scale. The position of the incisive canal was recorded in relation to the lower, buccal and lingual border of the mandible using the application provided by the CBCT software. Results: The incisive canal was definitely visible in 83.5% of the scans and the mean endpoint was approximately 15 mm anterior to the mental foramen. The mean distance from the lower border of the mandible was 11.5 mm and its course was closer to the buccal border of the mandible in 87% of the scans. The lingual foramen was definitely visible in 81% of the scans. Conclusions: The high detection rate of the incisive canal and the lingual foramen in the anterior region of the mandible using CBCT indicates the potentional high preoperative value of CBCT scan for surgical procedures in the anterior mandible. To cite this article: Makris N, Stamatakis H, Syriopoulos K, Tsiklakis K, van der Stelt PF. Evaluation of the visibility and the course of the mandibular incisive canal and the lingual foramen using cone-beam computed tomography. Clin. Oral Impl. Res. 21, 2010; 766,771. doi: 10.1111/j.1600-0501.2009.01903.x [source]

Image reconstructions from two orthogonal projections

INTERNATIONAL JOURNAL OF IMAGING SYSTEMS AND TECHNOLOGY, Issue 2 2003
Yuanmei Wang
Abstract A vector entropy optimization-based neural network approach is presented to handle image reconstructions from two orthogonal projections. An accurate and parallel reconstruction is attained with this method allowing parallel implementation. This is an attempt to extract the image information from two projections. It is especially meaningful for clinical applications and three-dimensional modeling of the coronary arteries. © 2003 Wiley Periodicals, Inc. Int J Imaging Syst Technol 13, 141,145, 2003; Published online in Wiley Inter-Science (www.interscience.wiley.com). DOI 10.1002/ima.10036 [source]

Spectral weighting for distributed backward propagation image reconstruction in diffraction tomography

INTERNATIONAL JOURNAL OF IMAGING SYSTEMS AND TECHNOLOGY, Issue 5-6 2008
Hua Lee
Abstract The objective of this work is to provide the formulation of the spatial-frequency weighting of distributed filtered backward propagation in multiple-projection diffraction tomography. This formulation provides the precise frequency-weighting characteristics for the generalized tomographic data-acquisition configurations. © 2008 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 18, 307,309, 2008 [source]

Image reconstruction of a buried perfectly conducting cylinder illuminated by transverse electric waves

Image reconstruction with a shift-variant filtration in circular cone-beam CT,

Position-dependent defocus processing for acoustic holography images

INTERNATIONAL JOURNAL OF IMAGING SYSTEMS AND TECHNOLOGY, Issue 3 2002
Ruming Yin
Acoustic holography is a transmission-based ultrasound imaging method that uses optical image reconstruction and provides a larger field of view than pulse-echo ultrasound imaging. A focus parameter controls the position of the focal plane along the optical axis, and the images obtained contain defocused content from objects not near the focal plane. Moreover, it is not always possible to bring all objects of interest into simultaneous focus. In this article, digital image processing techniques are presented to (1) identify a "best focused" image from a sequence of images taken with different focus settings and (2) simultaneously focus every pixel in the image through fusion of pixels from different frames in the sequence. Experiments show that the three-dimensional image information provided by acoustic holography requires position-dependent filtering for the enhancement step. It is found that filtering in the spatial domain is more computationally efficient than in the frequency domain. In addition, spatial domain processing gives the best performance. © 2002 Wiley Periodicals, Inc. Int J Imaging Syst Technol 12, 101,111, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ima.10017 [source]

Constrained total least-squares computations for high-resolution image reconstruction with multisensors

INTERNATIONAL JOURNAL OF IMAGING SYSTEMS AND TECHNOLOGY, Issue 1 2002
Michael K. Ng
Multiple undersampled images of a scene are often obtained by using a charge-coupled device (CCD) detector array of sensors that are shifted relative to each other by subpixel displacements. This geometry of sensors, where each sensor has a subarray of sensing elements of suitable size, has been popular in the task of attaining spatial resolution enhancement from the acquired low-resolution degraded images that comprise the set of observations. With the objective of improving the performance of the signal processing algorithms in the presence of the ubiquitous perturbation errors of displacements around the ideal subpixel locations (because of imperfections in fabrication), in addition to noisy observation, the errors-in-variables or the total least-squares method is used in this paper. A regularized constrained total least-squares (RCTLS) solution to the problem is given, which requires the minimization of a nonconvex and nonlinear cost functional. Simulations indicate that the choice of the regularization parameter influences significantly the quality of the solution. The L-curve method is used to select the theoretically optimum value of the regularization parameter instead of the unsound but expedient trial-and-error approach. The expected superiority of this RCTLS approach over the conventional least-squares theory-based algorithm is substantiated by example. © 2002 John Wiley & Sons, Inc. Int J Imaging Syst Technol 12, 35,42, 2002 [source]

Multicriteria maximum likelihood neural network approach to positron emission tomography

INTERNATIONAL JOURNAL OF IMAGING SYSTEMS AND TECHNOLOGY, Issue 6 2000
Yuanmei Wang
Abstract The emerging technology of positron emission image reconstruction is introduced in this paper as a multicriteria optimization problem. We show how selected families of objective functions may be used to reconstruct positron emission images. We develop a novel neural network approach to positron emission imaging problems. We also studied the most frequently used image reconstruction methods, namely, maximum likelihood under the framework of single performance criterion optimization. Finally, we introduced some of the results obtained by various reconstruction algorithms using computer-generated noisy projection data from a chest phantom and real positron emission tomography (PET) scanner data. Comparison of the reconstructed images indicated that the multicriteria optimization method gave the best in error, smoothness (suppression of noise), gray value resolution, and ghost-free images. © 2001 John Wiley & Sons, Inc. Int J Imaging Syst Technol 11, 361,364, 2000 [source]

Comparison of image reconstruction by using near-field and far-field data for an imperfect conductor

Incomplete oblique projections method for solving regularized least-squares problems in image reconstruction

INTERNATIONAL TRANSACTIONS IN OPERATIONAL RESEARCH, Issue 4 2008
H. D. Scolnik
Abstract In this paper we improve on the incomplete oblique projections (IOP) method introduced previously by the authors for solving inconsistent linear systems, when applied to image reconstruction problems. That method uses IOP onto the set of solutions of the augmented system Ax,r=b, and converges to a weighted least-squares solution of the system Ax=b. In image reconstruction problems, systems are usually inconsistent and very often rank-deficient because of the underlying discretized model. Here we have considered a regularized least-squares objective function that can be used in many ways such as incorporating blobs or nearest-neighbor interactions among adjacent pixels, aiming at smoothing the image. Thus, the oblique incomplete projections algorithm has been modified for solving this regularized model. The theoretical properties of the new algorithm are analyzed and numerical experiments are presented showing that the new approach improves the quality of the reconstructed images. [source]

Molecular imaging in small animals,roles for micro-CT

JOURNAL OF CELLULAR BIOCHEMISTRY, Issue S39 2002
Erik L. Ritman
Abstract X-ray micro-CT is currently used primarily to generate 3D images of micro-architecture (and the function that can be deduced from it) and the regional distribution of administered radiopaque indicators, within intact rodent organs or biopsies from large animals and humans. Current use of X-ray micro-CT can be extended in three ways to increase the quantitative imaging of molecular transport and accumulation within such specimens. (1) By use of heavy elements, other than the usual iodine, attached to molecules of interest or to surrogates for those molecules. The accumulation of the indicator in the physiological compartments, and the transport to and from such compartments, can be quantitated from the imaged spatial distribution of these contrast agents. (2) The high spatial resolution of conventional X-ray attenuation-based CT images can be used to improve the quantitative nature of radionuclide-based tomographic images (SPECT & PET) by providing correction for attenuation of the emitted gamma rays and the accurate delineation of physiological spaces known to selectively accumulate those indicators. Similarly, other imaging modalities which also localize functions in 2D images (such as histological sections subsequently obtained from the same specimen), can provide a synergistic combination with CT-based 3D microstructure. (3) By increasing the sensitivity and specificity of X-ray CT image contrast by use of methods such as: K-edge subtraction imaging, X-ray fluorescence imaging, imaging of the various types of scattered X-ray and the consequences of the change in the speed of X-rays through different tissues, such as refraction and phase shift. These other methods of X-ray imaging can increase contrast by more than an order of magnitude over that due to conventionally-used attenuation of X-ray. To fully exploit their potentials, much development of radiopaque indicators, scanner hardware and image reconstruction and analysis software will be needed. J. Cell. Biochem. Suppl. 39: 116,124, 2002. © 2002 Wiley-Liss, Inc. [source]

Accelerating non-contrast-enhanced MR angiography with inflow inversion recovery imaging by skipped phase encoding and edge deghosting (SPEED)

JOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 3 2010
Zheng Chang PhD
Abstract Purpose: To accelerate non-contrast-enhanced MR angiography (MRA) with inflow inversion recovery (IFIR) with a fast imaging method, Skipped Phase Encoding and Edge Deghosting (SPEED). Materials and Methods: IFIR imaging uses a preparatory inversion pulse to reduce signals from static tissue, while leaving inflow arterial blood unaffected, resulting in sparse arterial vasculature on modest tissue background. By taking advantage of vascular sparsity, SPEED can be simplified with a single-layer model to achieve higher efficiency in both scan time reduction and image reconstruction. SPEED can also make use of information available in multiple coils for further acceleration. The techniques are demonstrated with a three-dimensional renal non-contrast-enhanced IFIR MRA study. Results: Images are reconstructed by SPEED based on a single-layer model to achieve an undersampling factor of up to 2.5 using one skipped phase encoding direction. By making use of information available in multiple coils, SPEED can achieve an undersampling factor of up to 8.3 with four receiver coils. The reconstructed images generally have comparable quality as that of the reference images reconstructed from full k -space data. Conclusion: As demonstrated with a three-dimensional renal IFIR scan, SPEED based on a single-layer model is able to reduce scan time further and achieve higher computational efficiency than the original SPEED. J. Magn. Reson. Imaging 2010;31:757,765. © 2010 Wiley-Liss, Inc. [source]

Improved slice selection for R2* mapping during cryoablation with eddy current compensation,

JOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 1 2008
Aiming Lu PhD
Abstract Purpose To improve the slice profile and image quality of R2* mapping in the iceball during cryoablation with ultrashort echo time (UTE) imaging by compensating for eddy currents induced by the selective gradient when half-pulse radiofrequency (RF) excitation is employed to achieve UTEs. Materials and Methods A method to measure both B0 and linear eddy currents simultaneously is first presented. This is done with a least-square fitting process on calibration data collected on a phantom. Eddy currents during excitation are compensated by redesigning the RF pulse and the selective gradient accordingly, while that resultant from the readout gradient are compensated for during image reconstruction. In vivo data were obtained continuously during the cryoablation experiments to calculate the R2* values in the iceball and to correlate them with the freezing process. Results Image quality degradation due to eddy currents is significantly reduced with the proposed approaches. R2* maps of iceball throughout the cryoablation experiments were achieved with improved quality. Conclusion The proposed approaches are effective for compensating eddy currents during half-pulse RF excitation as well as readout. TEs as short as 100 ,sec were obtained, allowing R2* maps to be obtained from frozen tissues with improved quality. J. Magn. Reson. Imaging 2008;28:190,198. © 2008 Wiley-Liss, Inc. [source]

Effect of bone chip orientation on quantitative estimates of changes in bone mass using digital subtraction radiography

JOURNAL OF PERIODONTAL RESEARCH, Issue 3 2003
André Mol
Objectives:, To assess the effect of the orientation of arbitrarily shaped bone chips on the correlation between radiographic estimates of bone loss and true mineral loss using digital subtraction radiography. Methods:, Twenty arbitrarily shaped bone chips (dry weight 1,10 mg) were placed individually on the superior lingual aspect of the interdental alveolar bone of a dry dentate hemi-mandible. After acquiring the first baseline image, each chip was rotated 90 degrees and a second radiograph was captured. Follow-up images were created without the bone chips and after rotating the mandible 0, 1, 2, 4, and 6 degrees around a vertical axis. Aluminum step tablet intensities were used to normalize image intensities for each image pair. Follow-up images were registered and geometrically standardized using projective standardization. Bone chips were dry ashed and analyzed for calcium content using atomic absorption. Results:, No significant difference was found between the radiographic estimates of bone loss from the different bone chip orientations (Wilcoxon: P > 0.05). The correlation between the two series of estimates for all rotations was 0.93 (Spearman: P < 0.05). Linear regression analysis indicated that both correlates did not differ appreciably ( and ). Conclusion:, It is concluded that the spatial orientation of arbitrarily shaped bone chips does not have a significant impact on quantitative estimates of changes in bone mass in digital subtraction radiography. These results were obtained in the presence of irreversible projection errors of up to six degrees and after application of projective standardization for image reconstruction and image registration. [source]

Alias-free image reconstruction using Fresnel transform in the phase-scrambling Fourier imaging technique

MAGNETIC RESONANCE IN MEDICINE, Issue 2 2008
Satoshi Ito
Abstract An image reconstruction technique that reduces aliasing artifacts by scalable image reconstruction in magnetic resonance imaging (MRI) is proposed. The signal obtained by the phase-scrambling Fourier transform (PSFT) imaging technique can be transformed to the signal described in the Fresnel transform equation of the objects. Therefore, image reconstruction can be performed not only by inverse FT but also by inverse Fresnel transform. When a phase-scrambling coefficient is given in a certain range, image reconstruction by inverse Fresnel transform allows shrinking of images over rather wide scales. Thus, reduced aliasing images can be reconstructed even from signals that produce serious aliasing artifacts by standard inverse FT reconstruction. Simulation and experimental studies reveal that the proposed method can be used to produce reduced aliasing images. Magn Reson Med 60:422,430, 2008. © 2008 Wiley-Liss, Inc. [source]

Improving k - t SENSE by adaptive regularization

MAGNETIC RESONANCE IN MEDICINE, Issue 5 2007
Dan Xu
Abstract The recently proposed method known as k - t sensitivity encoding (SENSE) has emerged as an effective means of improving imaging speed for several dynamic imaging applications. However, k - t SENSE uses temporally averaged data as a regularization term for image reconstruction. This may not only compromise temporal resolution, it may also make some of the temporal frequency components irrecoverable. To address that issue, we present a new method called spatiotemporal domain-based unaliasing employing sensitivity encoding and adaptive regularization (SPEAR). Specifically, SPEAR provides an improvement over k - t SENSE by generating adaptive regularization images. It also uses a variable-density (VD), sequentially interleaved k - t space sampling pattern with reference frames for data acquisition. Simulations based on experimental data were performed to compare SPEAR, k - t SENSE, and several other related methods, and the results showed that SPEAR can provide higher temporal resolution with significantly reduced image artifacts. Ungated 3D cardiac imaging experiments were also carried out to test the effectiveness of SPEAR, and real-time 3D short-axis images of the human heart were produced at 5.5 frames/s temporal resolution and 2.4 × 1.2 × 8 mm3 spatial resolution with eight slices. Magn Reson Med 57:918,930, 2007. © 2007 Wiley-Liss, Inc. [source]

Real-time accelerated interactive MRI with adaptive TSENSE and UNFOLD,

MAGNETIC RESONANCE IN MEDICINE, Issue 2 2003
Michael A. Guttman
Abstract Reduced field-of-view (FOV) acceleration using time-adaptive sensitivity encoding (TSENSE) or unaliasing by Fourier encoding the overlaps using the temporal dimension (UNFOLD) can improve the depiction of motion in real-time MRI. However, increased computational resources are required to maintain a high frame rate and low latency in image reconstruction and display. A high-performance software system has been implemented to perform TSENSE and UNFOLD reconstructions for real-time MRI with interactive, on-line display. Images were displayed in the scanner room to investigate image-guided procedures. Examples are shown for normal volunteers and cardiac interventional experiments in animals using a steady-state free precession (SSFP) sequence. In order to maintain adequate image quality for interventional procedures, the imaging rate was limited to seven frames per second after an acceleration factor of 2 with a voxel size of 1.8 × 3.5 × 8 mm. Initial experiences suggest that TSENSE and UNFOLD can each improve the compromise between spatial and temporal resolution in real-time imaging, and can function well in interactive imaging. UNFOLD places no additional constraints on receiver coils, and is therefore more flexible than SENSE methods; however, the temporal image filtering can blur motion and reduce the effective acceleration. Methods are proposed to overcome the challenges presented by the use of TSENSE in interactive imaging. TSENSE may be temporarily disabled after changing the imaging plane to avoid transient artifacts as the sensitivity coefficients adapt. For imaging with a combination of surface and interventional coils, a hybrid reconstruction approach is proposed whereby UNFOLD is used for the interventional coils, and TSENSE with or without UNFOLD is used for the surface coils. Magn Reson Med 50:315,321, 2003. Published 2003 Wiley-Liss, Inc. [source]

3D reconstruction of high-resolution STED microscope images

MICROSCOPY RESEARCH AND TECHNIQUE, Issue 9 2008
Annedore Punge
Abstract Tackling biological problems often involves the imaging and localization of cellular structures on the nanometer scale. Although optical super-resolution below 100 nm can be readily attained with stimulated emission depletion (STED) and photoswitching microscopy methods, attaining an axial resolution <100 nm with focused light generally required the use of two lenses in a 4Pi configuration or exceptionally bright photochromic fluorophores. Here, we describe a simple technical solution for 3D nanoscopy of fixed samples: biological specimens are fluorescently labeled, embedded in a polymer resin, cut into thin sections, and then imaged via STED microscopy with nanoscale resolution. This approach allows a 3D image reconstruction with a resolution <80 nm in all directions using available state-of-the art STED microscopes. Microsc. Res. Tech., 2008. © 2008 Wiley-Liss, Inc. [source]

2D EIT for biomedical imaging: Design, measurement, simulation, and image reconstruction

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 12 2007
Kim Hwa Lim
Abstract A 2D electrical impedance tomography (EIT) system has been developed at Duke University as an experimental system to test the forward and inverse algorithms for EIT application. The forward model is based on the 2nd-order finite element method (FEM), while the image reconstruction is based on the distorted Born iterative method (DBIM). The major contributions of this work are the application of the higher-order FEM as a forward solver, and the DBIM as an inverse solver to the integrated EIT system. The forward model has been validated with the measured data to within 0.5% accuracy. Excellent images have been reconstructed with these collected EIT data sets. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2989,2998, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22938 [source]

Offline, multidetector intensity interferometers , I. Theory

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2006
Aviv Ofir
ABSTRACT Stellar amplitude interferometry is limited by the need to have optical distances fixed and known to a fraction of the wavelength. We suggest reviving intensity interferometry, which requires hardware which is many orders of magnitude less accurate, at the cost of more limited sensitivity. We present an algorithm to use the very high redundancy of a uniform linear array to increase the sensitivity of the instrument by more than a 100-fold. When using an array of 100 elements, each almost 100 m in diameter, and conservative technological improvements, we can achieve a limiting magnitude of about mb= 14.4. Digitization, storage, and offline processing of all the data will also enable interferometric image reconstruction from a single observation run, and application of various algorithms at any later time. Coronagraphy, selectively suppressing only the large-scale structure of the source, can be achieved by specific aperture shapes. We conclude that after three decades of abandonment optical intensity interferometry deserves another review. [source]

Retrospective cine 3He ventilation imaging under spontaneous breathing conditions: a non-invasive protocol for small-animal lung function imaging

NMR IN BIOMEDICINE, Issue 2 2007
Vasile Stupar
Abstract A non-invasive and free-breathing hyperpolarized (HP) 3He imaging protocol for small animals was implemented and validated on rats for lung function imaging. Animals were allowed to breathe a mixture of air and 3He from a mask and a gas reservoir fitted to their heads. Radial imaging sequences were used, and MRI signal intensity changes were monitored for retrospective cine image reconstruction. The ventilation cycle of the animals was imaged with a 100,ms temporal resolution. The sliding window imaging technique was applied to reconstruct 5,ms time-shifted image series covering the complete breathing cycle. Image series were processed to extract quantitative ventilation parameters such as the gas arrival time. The reproducibility and the non-invasiveness of this ventilation imaging protocol were evaluated by multiple acquisitions on the same animals. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Encoding and reconstruction in parallel MRI

NMR IN BIOMEDICINE, Issue 3 2006
Klaas P. Pruessmann
Abstract The advent of parallel MRI over recent years has prompted a variety of concepts and techniques for performing parallel imaging. A main distinguishing feature among these is the specific way of posing and solving the problem of image reconstruction from undersampled multiple-coil data. The clearest distinction in this respect is that between k -space and image-domain methods. The present paper reviews the basic reconstruction approaches, aiming to emphasize common principles along with actual differences. To this end the treatment starts with an elaboration of the encoding mechanisms and sampling strategies that define the reconstruction task. Based on these considerations a formal framework is developed that permits the various methods to be viewed as different solutions of one common problem. Besides the distinction between k -space and image-domain approaches, special attention is given to the implications of general vs lattice sampling patterns. The paper closes with remarks concerning noise propagation and control in parallel imaging and an outlook upon key issues to be addressed in the future. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Image reconstructions from two orthogonal projections

Efficient estimation of three-dimensional curves and their derivatives by free-knot regression splines, applied to the analysis of inner carotid artery centrelines

JOURNAL OF THE ROYAL STATISTICAL SOCIETY: SERIES C (APPLIED STATISTICS), Issue 3 2009
Laura M. Sangalli
Summary., We deal with the problem of efficiently estimating a three-dimensional curve and its derivatives, starting from a discrete and noisy observation of the curve. This problem is now arising in many applicative contexts, thanks to the advent of devices that provide three-dimensional images and measures, such as three-dimensional scanners in medical diagnostics. Our research, in particular, stems from the need for accurate estimation of the curvature of an artery, from image reconstructions of three-dimensional angiographies. This need has emerged within the AneuRisk project, a scientific endeavour which aims to investigate the role of vessel morphology, blood fluid dynamics and biomechanical properties of the vascular wall, on the pathogenesis of cerebral aneurysms. We develop a regression technique that exploits free-knot splines in a novel setting, to estimate three-dimensional curves and their derivatives. We thoroughly compare this technique with a classical regression method, local polynomial smoothing, showing that three-dimensional free-knot regression splines yield more accurate and efficient estimates. [source]