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Showing papers on "Image resolution published in 1986"


Journal ArticleDOI
TL;DR: A new method for rapid NMR imaging dubbed FLASH ( fast low-a ngle sh ot) imaging is described which allows measuring times of the order of 1 s (64 × 128 pixel resolution) or 6 s (256 × 256 pixels), resulting in about a 100-fold reduction in measuring time without sacrificing spatial resolution.

1,227 citations


Journal ArticleDOI
TL;DR: In this paper, a multiplicative model was used to relate the image variance for a given land-use category to the individual variances associated with image speckle and target texture.
Abstract: A multiplicative model was used to relate the image variance for a given land-use category to the individual variances associated with image speckle and target texture. Speckle was treated as a random process governed by signal fading and was considered to be statistically independent of the textural variations associated with the spatial variations of the scattering properties of visually "uniform" distributed targets. Seasat SAR imagery of Oklahoma was used to evaluate the textural autocorrelation function of five land-use categories: water, forest, pasture, urban, and cultivated. It was found that the maximum classification accuracy achievable using first-order statistics was 72 percent and that this level of accuracy was obtainable only by significantly degrading the spatial resolution in order to increase the number of independent samples per pixel. In contrast, second-order statistics-specifically, image contrast and inverse moment-provided a classification accuracy of 88 percent, with only a modest degradation in spatial resolution. A second study using SIR-A imagery of five forested regions has shown that the use of textural information can improve the classification accuracy among the five forest types from 75 to 93 percent.

526 citations


Journal ArticleDOI
TL;DR: A system that takes a gray level image as input, locates edges with subpixel accuracy, and links them into lines and notes that the zero-crossings obtained from the full resolution image using a space constant ¿ for the Gaussian, are very similar, but the processing times are very different.
Abstract: We present a system that takes a gray level image as input, locates edges with subpixel accuracy, and links them into lines. Edges are detected by finding zero-crossings in the convolution of the image with Laplacian-of-Gaussian (LoG) masks. The implementation differs markedly from M.I.T.'s as we decompose our masks exactly into a sum of two separable filters instead of the usual approximation by a difference of two Gaussians (DOG). Subpixel accuracy is obtained through the use of the facet model [1]. We also note that the zero-crossings obtained from the full resolution image using a space constant ? for the Gaussian, and those obtained from the 1/n resolution image with 1/n pixel accuracy and a space constant of ?/n for the Gaussian, are very similar, but the processing times are very different. Finally, these edges are grouped into lines using the technique described in [2].

502 citations


Journal ArticleDOI
TL;DR: FLASH (Fast Low‐Angle SHot) imaging is a new method for rapid NMR imaging which has been demonstrated to provide abdominal images without artifacts due to respiratory or peristaltic motions.
Abstract: FLASH (Fast Low-Angle SHot) imaging is a new method for rapid NMR imaging which has been demonstrated to provide abdominal images without artifacts due to respiratory or peristaltic motions The sequence typically employs 15° radiofrequency excitation pulses and acquires a free induction decay signal in the form of a gradient echo Here FLASH images are recorded in the presence of dynamic processes with time constants even smaller than the measuring time of about 2 s for an image with a 128 × 128-pixel resolution Experiments are carried out on flow phantoms and on rabbits yielding heart images without gating of the cardiac motion © 1986 Academic Press, Inc

400 citations


Journal ArticleDOI
TL;DR: This article deals with a three-dimensional (3D) variant of the FLASH method that allows the recording of a 3D-data set of 128X 128 X 128 pixels within an acquisition time of only 4 min.
Abstract: Fast low-angle shot (FLASH) imaging is a new technique for rapid magnetic resonance (MR) imaging that reduces acquisition times to seconds while retaining spatial resolution. This article deals with a three-dimensional (3D) variant of the FLASH method that allows the recording of a 3D-data set of 128 X 128 X 128 pixels within an acquisition time of only 4 min. The method is demonstrated using a 2.35 T 40 cm bore MR system. Experiments are carried out on rabbit head and human extremities. Depending on the field of view, the isotropic resolution is 1 mm or even less leading to cross-sectional images with a 1 mm slice thickness. In principle, FLASH imaging techniques are applicable to any MR system without the need of major hardware modifications. However, high-speed computers, large storage capacity, and rapid image display routines greatly facilitate an advantageous use of the 3D-FLASH variant.

274 citations


Journal ArticleDOI
TL;DR: The method, the iterative image space reconstruction algorithm (ISRA), is able to reconstruct data from a scanner with a spatially variant point spread function in less time than other proposed algorithms.
Abstract: The trend in the design of scanners for positron emission computed tomography has traditionally been to improve the transverse spatial resolution to several millimeters while maintaining relatively coarse axial resolution (1-2 cm). Several scanners are being built with fine sampling in the axial as well as transverse directions, leading to the possibility of the true volume imaging. The number of possible coincidence pairs in these scanners is quite large. The usual methods of image reconstruction cannot handle these data without making approximations. It is computationally most efficient to reduce the size of this large, sparsely populated array by back-projecting the coincidence data prior to reconstruction. While analytic reconstruction techniques exist for back-projected data, an iterative algorithm may be necessary for those cases where the point spread function is spatially variant. A modification of the maximum likelihood algorithm is proposed to reconstruct these back-projected data. The method, the iterative image space reconstruction algorithm (ISRA), is able to reconstruct data from a scanner with a spatially variant point spread function in less time than other proposed algorithms. Results are presented for single-slice data, simulated and actual, from the PENN-PET scanner.

241 citations


Journal ArticleDOI
17 Apr 1986-Nature
TL;DR: In this paper, the authors report successful measurements of fringe visibility and closure phase by this technique, together with evidence that the method is applicable to objects as faint as magnitude 15.5.
Abstract: The angular resolution of long-exposure optical images taken with large telescopes at the best sites is limited by atmospheric phase fluctuations to ∼0.5–1 arc s; that is, ∼10–50 times worse than the theoretical diffraction limit. In contrast, the measurement of visibilities and closure phases of fringe patterns in short-exposure images, taken through an aperture mask comprising a non-redundant array of three or more holes, offers the prospect of reliable diffraction-limited imaging using methods well established in very long baseline interferometry (VLBI) at radio wavelengths. Here we report successful first measurements of fringe visibility and closure phase by this technique, together with evidence that the method is applicable to objects as faint as magnitude 15.

186 citations


Journal ArticleDOI
TL;DR: A technique for determining the vector displacement that maximizes the spatially local cross-correlation between an image and a reference image as a continuous function of the image space is presented.
Abstract: A technique for determining the vector displacement that maximizes the spatially local cross-correlation between an image and a reference image as a continuous function of the image space is presented. This is applied to solar observations of granulation made during a condition of rapidly changing atmospheric distortion, a particular turbulence condition wherein features are remapped without loss of spatial resolution.

105 citations


Proceedings ArticleDOI
10 Dec 1986-Scopus
TL;DR: This paper evaluates three adaptive binarization techniques viz., a contrast measure approach, a weighted running average approach and a second derivative approach, and compares them to global Binarization methods.
Abstract: The extraction of a binary image from a gray level image is a common image processing operation particularly for document image analysis and optical character recognition. Various methods for this task are described in the literature including global and adaptive binarization. This paper evaluates three adaptive binarization techniques viz., a contrast measure approach, a weighted running average approach and a second derivative approach, and compares them to global binarization methods. Experiments with noisy document (postal letter mail) images lead to the following conclusions. Image contrast binarization often yields nearly the same results as the edge operator, with considerably less computation and is less sensitive to parameter settings. In addition, the edge operator is more sensitive to image resolution than the contrast operator. The weighted running-average approach is highly sensitive to the parameters involved in the calculation of the average but produces a quick binarization.

93 citations


Journal ArticleDOI
TL;DR: It is demonstrated that using the filter coefficients to reconstruct the image removes the truncation artifacts and improves the resolution, but determining the autoregressive (AR) portion of the ARMA filter by algorithms that minimize the forward and backward prediction errors leads to significant image degradation.
Abstract: The modeling of data is an alternative to conventional use of the fast Fourier transform (FFT) algorithm in the reconstruction of magnetic resonance (MR) images. The application of the FFT leads to artifacts and resolution loss in the image associated with the effective window on the experimentally-truncated phase encoded MR data. The transient error modeling method treats the MR data as a subset of the transient response of an infinite impulse filter (H(z) = B(z)IA(z)). Thus, the data are approximated by a deterministic autoregressive moving average (ARMA) model. The algorithm for calculating the filter coefficients is described. It is demonstrated that using the filter coefficients to reconstruct the image removes the truncation artifacts and improves the resolution. However, determining the autoregressive (AR) portion of the ARMA filter by algorithms that minimize the forward and backward prediction errors (e.g., Burg) leads to significant image degradation. The moving average (MA) portion is determined by a computationally efficient method of solving a finite difference equation with initial values. Special features of the MR data are incorporated into the transient error model. The sensitivity to noise and the choice of the best model order are discussed. MR images formed using versions of the transient error reconstruction (TERE) method and the conventional FFT algorithm are compared using data from a phantom and a human subject. Finally, the computational requirements of the algorithm are addressed.

86 citations


Patent
28 Oct 1986
TL;DR: An image change detection system for observing an environment to be monitored, such as a region proximate a vehicle, by sensing energy from the region and generating a plurality of pixels which form an image of the region is presented in this article.
Abstract: An image change detection system for observing an environment to be monitored, such as a region proximate a vehicle, by sensing energy from the region and generating a plurality of pixels which form an image of the region. The system stores a first image of the region and matches pixels of a subsequent image of the region with pixels of the first image to detect deviations between corresponding pixels. The system indicates when the pixel deviations exceed a preselected threshold to detect an abnormal condition in the region. Also a method of monitoring the environment about a vehicle by sensing a first image, sensing a subsequent image, matching the pixels of the subsequent image with the pixels of the first image to detect deviations between corresponding pixels, and indicating when pixel deviations exceed a preselected threshold.

Journal Article
TL;DR: Comparative clinical studies on temporomandibular joints (TMJ) between the LEGP and fan beam collimators also confirm the superior image quality obtained with the fanbeam collimator.
Abstract: A long bore fan beam collimator for imaging the head was designed and constructed for a SPECT system with a rotating scintillation camera. In order to avoid the patient9s shoulder during rotation of the camera with a thick camera housing, the long bore design is necessary to allow the collimator to get close to the patient9s head for improved spatial resolution. Operating at the minimum radius of rotation, the prototype fan beam collimator provides about the same spatial resolution as the high resolution collimator, while the geometric efficiency is equal to ∼85% of that of the general purpose and ∼55% higher than the high resolution collimator. Images from a phantom study demonstrate good image quality and are void of artifacts. Comparative clinical studies on temporomandibular joints (TMJ) between the LEGP and fan beam collimators also confirm the superior image quality obtained with the fan beam collimator.

Journal ArticleDOI
TL;DR: In this article, a two-dimensional position-sensitive PET detector was used in a multi-slice PET scanner, where the pulses are shortened and integrated for 240 nsec, which results in a countrate capability of up to 1 Mcps without significant loss of spatial resolution.
Abstract: We have designed, constructed and begun to evaluate a two-dimensional position-sensitive detector which will be used in a multi-slice PET scanner. We have measured 5.2 mm transverse and 6.0 mm axial spatial resolution, with an array of thirty 5-cm PMTs (10-columns by 3 rows). The pulses are shortened and integrated for 240 nsec, which results in a countrate capability of up to 1 Mcps without significant loss of spatial resolution. Although the one-dimensional detector upon which this one is based used analog processing to determine the position of an event, we now use digital processing because of the potential advantages it offers. We can implement variable integration which allows one to choose the optimal setting for high countrate capability and best spatial resolution. Resolution did not improve with longer integration times to the degree expected; however, at 240-nsec integration time resolution was only 0.6 mm worse than the best resolution achieved with longer integration time. This shorter integration time considerably extends our countrate capability and may obviate the need for variable integration for all but the highest countrates. The ability to perform position arithmetics more complicated than a simple centroid calculation might also help localizing the event in two dimensions. Digital processing allows us to use different biases for the transverse and axial centroid calculations, and to vary the bias as a function of position, which helps to extend the useful area.

Journal ArticleDOI
TL;DR: Energy-filtered transmission electron microscopy was used to image the distributions of uranium and carbon in uranyl acetate stained catalase crystals, and the effects of plural inelastic and elastic-inelastic scattering were sufficiently large to show crystalline structure in unprocessed pre-edge inel elastic images.

Journal Article
TL;DR: A single-slice positron camera has been developed with good spatial resolution and high count rate capability and an iterative reconstruction algorithm was modified which ignores the missing data in the gaps between the six detectors and gives artifact-free images.
Abstract: A single-slice positron camera has been developed with good spatial resolution and high count rate capability. The camera uses a hexagonal arrangement of six position-sensitive NaI(Tl) detectors. The count rate capability of NaI(Tl) was extended to 800k cps through the use of pulse shortening. In order to keep the detectors stationary, an iterative reconstruction algorithm was modified which ignores the missing data in the gaps between the six detectors and gives artifact-free images. The spatial resolution, as determined from the image of point sources in air, is 6.5 mm full width at half maximum. We have also imaged a brain phantom and dog hearts.

Journal Article
TL;DR: Two-dimensional, prereconstruction filtering with optimized Metz filters was determined to improve image contrast, while decreasing the noise level for SPECT studies, and a dramatic improvement in image quality was observed with the clinical application of this filter.
Abstract: A number of radiopharmaceuticals of great current clinical interest for imaging are labeled with radionuclides that emit medium- to high-energy photons either as their primary radiation, or in low abundance in addition to their primary radiation. The imaging characteristics of these radionuclides result in gamma camera image quality that is inferior to that of 99mTc images. Thus, in this investigation 111In and 123I contaminated with ∼4% 124I were chosen to test the hypothesis that a dramatic improvement in planar and SPECT images may be obtainable with digital image restoration. The count-dependent Metz filter is shown to be able to deconvolve the rapid drop at low spatial frequencies in the imaging system modulation transfer function (MTF) resulting from the acceptance of septal penetration and scatter in the camera window. Use of the Metz filter was found to result in improved spatial resolution as measured by both the full width at half maximum and full width at tenth maximum for both planar and SPECT studies. Two-dimensional, prereconstruction filtering with optimized Metz filters was also determined to improve image contrast, while decreasing the noise level for SPECT studies. A dramatic improvement in image quality was observed with the clinical application of this filter to SPECT imaging.

Proceedings ArticleDOI
Neeraj Khurana1, C-L Chiang1
01 Apr 1986
TL;DR: In this article, a dual microchannel intensifier is coupled to a solid state camera to detect and amplify the extremely faint light emitted by the transistors in saturation, and computer image processing techniques are then employed to boost the sensitivity.
Abstract: A new tool to analyze the hot electron problems at the product level is introduced. The method combines the latest night vision technology and computer image processing techniques to precisely locate the transistors most vulnerable to hot electron degradation. A dual microchannel intensifier is coupled to a solid state camera to detect and amplify the extremely faint light emitted by the transistors in saturation. Computer image processing techniques are then employed to boost the sensitivity. Time resolution of hot electron events is achieved by `gating' the intensifier. To date, we have achieved a time resolution of l5ns, spatial resolution of l?m with a sensitivity of 10nA per ?m of substrate current. At the sensitivity level of our instrument we can even detect hot electron events which cause no degradation.

Journal ArticleDOI
TL;DR: In this article, a staggered exponential multistrata (SEMS) detection system was proposed to improve the spatial resolution of high resolution PETs and PETs designed for small objects such as the brain, animals, limbs and infants.
Abstract: The design of a staggered-exponential-multistrata (SEMS) detection system is presented. This design replaces the conventional detector ring with multiple staggered layers of detector rings. The thickness of the layers is increasing exponentially. The SEMS design can improve the spatial resolution, allowing the detector ring to be smaller and obviate the need for detector wobbling. The improvement is particularly significant in high resolution PETs and PETs designed for small objects such as the brain, animals, limbs and infants. Image resolution approaching the theoretical limit of positron-range can be achieved for the entire field of view (FOV), rather than just at the center of the FOV in the conventional design. The reduction in detector ring size increases the sensitivity and lower the cost of both the gantry and detection system. The elimimation of detector motion simplifies the gantry mechanics and cost. In addition, the image artifact resulting from the frequency beating of the heart cycle and detector wobbling cycle are also eliminated. The high resolution, high sensitivity, compactness and low cost make this design suitable for researches.

Proceedings ArticleDOI
25 Nov 1986
TL;DR: In this article, the authors developed new methods for mosaicking SPOT images and increasing the ground resolution of multispectral data using the capability of acquiring data with HRV instruments in twin mode of operation to obtain an image size of approximately 117 by 110 kilometers.
Abstract: In order to take advantage of all the capabilities of SPOT system, we developed new methods for mosaicking SPOT images and increasing the ground resolution of multispectral data. The mosaicking method uses the capability of acquiring data with HRV instruments in twin mode of operation (overlap of three kilometers between the two data strips) to obtain an image size of approximately 117 by 110 kilometers. To reduce the processing time, we do not use a general mosaicking method, but a simplified one which takes into account the radiometric and geometric performances of the SPOT satellite. One of the major SPOT advantages is to provide data with a 10 meters resolution. In order to take fully advantage of this capability, we designed a process which can produce multispectral SPOT images with a 10 meters resolution. To achieve this goal, we had to design special geometric corrections which can insure a perfect superimposability of the Panchromatic and multispectral data. An other exposed problem is linked with the mixing method to be used, in order to insure a good radiometric result. These products have been developped on an operational way, in order to be sold in a near future by SPOT IMAGE.

Journal ArticleDOI
TL;DR: In this paper, the SPOT satellite system was used to provide MSS data at 20m resolution and panchromatic data at 10m resolution for soil and landsystem analysis in north-west Europe.
Abstract: A problem in using multispectral scanner(MSS) data for soil and landsystem analysis in north-west Europe is the poor spatial resolution which is insufficient to provide adequate within-field data. The SPOT satellite system will provide MSS data at 20m resolution and panchromatic data at 10m resolution. For any given ground feature the SPOT MSS mode will provide considerably more sample areas than LANDSAT 80m data. The object of this study is to determine how far variation in surface soil parameters can be detected and quantified on the basis of SPOT data.

Patent
27 Feb 1986
TL;DR: In this article, the light image is scanned in such a pattern between element exposures so that each digital image pixel has a nearest neighbor digital image pixels that was produced by a different sensor element.
Abstract: Apparatus having three interline area image sensors (24, 26, 28) each with a sparse array of elements. Each sensor is responsive to a different spectral region of a light image of a photographic negative. Each sensor element senses a plurality of light image pixels to produce analog signals. The light image is scanned in such a pattern between element exposures so that each digital image pixel has a nearest neighbor digital image pixel that was produced by a different sensor element. These analog signals are digitized (A/D) and arranged in a memory plane (60) to form a high resolution digital image.

Journal ArticleDOI
TL;DR: Computer simulations show that the proposed camera design incorporates several new features to obtain good spatial resolution from thicker crystals of sodium iodide allows parallax error correction and (possibly) Compton scattering correction at gamma energies up to 511 keV.
Abstract: The shortcomings of conventional scintillation cameras are analysed theoretically with a view towards improving performance at gamma ray energies above 140 keV. A camera design is proposed which incorporates several new features to obtain good spatial resolution from thicker crystals of sodium iodide. Computer simulations show that in addition to having good efficiency and spatial resolution, the new design allows parallax error correction and (possibly) Compton scattering correction at gamma energies up to 511 keV.

Journal ArticleDOI
TL;DR: Etablissement d'equations permettant la determination de la resolution a partir de mesures des profils de pulverisation; discussion des possibilites d'application and des erreurs introduites en fonction du rapport entre la resolution and l'epaisseur des couches elementaires.
Abstract: Etablissement d'equations permettant la determination de la resolution a partir de mesures des profils de pulverisation; discussion des possibilites d'application et des erreurs introduites en fonction du rapport entre la resolution et l'epaisseur des couches elementaires

Journal Article
TL;DR: It would be a pity if digital image readers of the future have to decide which terminal or station is best on the basis of image aesthetics rather than diagnostic performance.


Journal ArticleDOI
TL;DR: In this article, the authors demonstrate high resolution ESR imaging in solids with a spatial resolution of 10 μ m by applying a stepped gradient technique, which is a step gradient technique.
Abstract: We demonstrate high resolution ESR imaging in solids with a spatial resolution of 10 μ m by applying a stepped gradient technique.

Journal ArticleDOI
TL;DR: In this paper, the Wedge and Strip readout system was used in microchannel plate detectors for the Extreme Ultraviolet Explorer and FAUST space astronomy programs, and it was shown that the resolution and imaging are highly stable and that the flat field performance is essentially limited by photon statistics.
Abstract: We discuss application of the Wedge and Strip readout system in microchannel plate detectors for the Extreme Ultraviolet Explorer and FAUST space astronomy programs. Anode designs with high resolution (>600 × 600 pixels) in imaging and spectroscopy applications have been developed. Extension of these designs to larger formats (100mm) with higher resolution (3000 × 3000 pixels) are considered. We show that the resolution and imaging are highly stable and that the flat field performance is essentially limited by photon statistics. Very high speed event response has also been achieved with output pulses having durations of less than 10 nanoseconds.

Journal ArticleDOI
TL;DR: In this paper, the imaging requirements for several fields of application are discussed, with particular reference to the fields of semiconductors, biology and medicine, and the imaging techniques include light optical, secondary electron, PIXE, backward and forward scattering, channeling contrast and transmission imaging with energy loss and scattering contrast.
Abstract: The accurate location, identification and irradiation of a specimen in a scanning proton microprobe or similar instrument and the correct interpretation of the collected data often depends critically on the spatial resolution and information content of any images that can be formed. The accommodation of all imaging requirements in turn places severe demands on the instrumentation. The imaging techniques discussed include light optical, secondary electron, PIXE, backward and forward scattering, channeling contrast and transmission imaging with energy loss and scattering contrast. The images may be bright field or dark field and live or processed and they make available a wide range of information concerning the specimen. Some images, such as the PIXE maps, provide information at 1 μm resolution. Others, such as scanning transmission maps, are an order of magnitude better. The imaging requirements for several fields of application are discussed, with particular reference to the fields of semiconductors, biology and medicine.

Patent
Andrew A. Modla1
21 Feb 1986
TL;DR: In this paper, a camera field-of-view is mapped with full depth of focus into electronic memory, along with data concerning the distances between the camera and these points in image space.
Abstract: A camera field-of-view is mapped with full depth-of-focus into electronic memory. Data concerning image intensities at selected points in image space are stored, along with data concerning the distances between the camera and these points in image space. Images with any focus and depth-of-focus can be generated by scanning the electronic memory during a reading thereof and convolving the data concerning image intensity with an adjustable-bandwidth low-pass spatial filter. The bandwidth of that filter is adjusted dependent on the data concerning distances between camera and points in image space. This image storage and image retrieval procedure conserves the size of electronic memory required to store and retrieve images with any focus and depth-of-focus.

Journal ArticleDOI
TL;DR: Experiments demonstrate that the near-edge structure in the x-ray absorption coefficient of an element is affected by chemistry and local environment and can be exploited in x-rays both to identify and enhance the detectability of different chemical states of the same element.
Abstract: The near-edge structure in the x-ray absorption coefficient of an element is affected by chemistry and local environment. Experiments demonstrate that this property can be exploited in x-ray imaging both to identify and enhance the detectability of different chemical states of the same element. Chemical contrast images are obtained by digital subtraction of absorption images taken at carefully selected energy values.