Showing papers on "Image resolution published in 1975"

Application of Annihilation Coincidence Detection to Transaxial Reconstruction Tomography

Abstract: A study was carried out to investigate the use of annihilation coincidence detection (ACD) in emmision transaxial reconstruction tomography. The ACD was evaluated in terms of spatial resolution and sensitivity with depth, detection efficiency, effect of pulse-height analysis on resolution and efficiency, correction for attenuation, and cold spot contrast. A prototype positron emission transaxial tomograph (PETT) consisting of a hexagonal array of 24 Nal (Tl) detectors employing ACD was constructed. A fast Fourier transform algorithm was employed to generate the reconstructed image. Computer simulations and phantom and animal studies were carried out to demonstrate that this approach yields tomographic radionuclide images that have high resolution and contrast (hot and cold spot) and that are independent of activity above and below the plane examined. The ACD yields a quantitative nuclear medicine imaging device with high detection efficiency. Comparisons are presented between the ACD and the scintillation camera and scanner. Discussion of the possible applications of the PETT in nuclear medicine is included.

Self-scanned digicon: a digital image tube for astronomical spectroscopy.

Abstract: We have successfully fabricated, tested, and operated a digital image tube consisting of a magnetically focused image intensifier tube in which a self-scanned linear array of 1024 silicon photodiodes operating in the EBS mode serves as the photoelectron image detector, amplifier, and intermediate image storage device. Integral on-chip MOS shift registers driven by an external clock sequentially interrogate the photodiodes through MOS FET multiplex switch arrays. Each output frame is a sequence of 256 analog pulses on each of four video lines. Laboratory and observing tests show that the output signal is photoelectron shot noise limited over at least a range of 1-100,000 detected photoelectrons per picture element, indicating that single photon detection is achieved. High-resolution astronomical spectroscopy has been carried out in the coude spectrograph of the 2.7-m telescope at McDonald Observatory. Examples are shown.

n-Beam lattice images. VI. Degradation of image resolution by a combination of incident-beam divergence and spherical aberration

Abstract: Lattice images were computed with increasing incident-beam divergence with spherical aberration taken into account. The effect is as if the outer diffracted beams transmitted by the objective aperture do not contribute to the image, so that the resolution is effectively less than that expected from the aperture size. Images of Nb12O29, calculated with the inclusion of this effect, show improved agreement with experimental images.

Automated Video-Angiocardiographic Image Analysis

Abstract: This paper describes a hardware-software system for handling the two main groups of cardiological data: a) physiological variables such as voltages, pressures, etc., and b) morphological data, derived from x-ray images or angiocardiograms, such as dimensions, areas, or volumes. We will concentrate in particular on some aspects of automated image processing–i. e., the analysis of the size, shape, and contraction pattern of the ventricles from video-angiocardiograms.

Image enhancement method and apparatus

Abstract: Combined optical and electronic apparatus provide for various types of image enhancement by producing two images of the same scene which differ by a predetermined property, and by electronically subtracting the images to yield a video difference signal which emphasizes or deemphasizes a predetermined characteristic of the scene at which the apparatus is pointed. Various types of image enhancement are obtained by simultaneous scanning of the images produced by two imaging systems in which a relative difference in properties between the images such as deliberate misalignment, optical density difference, image resolution, image magnification or image receptor displacement is introduced to create a particular type of enhancement. The intensities from pairs of scanned spots are subtracted on a point-by-point basis to yield a video difference signal which when displayed provides an image enhanced in a particular manner. Property differences are in general introduced in the aperture plane, at the optics or in the image plane. The subject system can be arranged for edge enhancement, size discrimination, emphasis of lines in a predetermined direction, peripheral image enhancement, and central image or boresite enhancement. This system is particularly useful in clutter rejection for TV-based target tracking systems.

Digital Processing of Annular Coded-Aperture Imagery

Abstract: In the past, annular coded aperture images have been recon-structed by correlating an appropriately scaled annulus with the coded image. The basic improvement suggested in this paper is the addition of a linear radial frequency weighting in the Fourier plane. Reconstructions of point and disk objects were simulated with a computer program. The results show the advantage of this modification in the processing scheme. When the assumption is made that the detector is an Anger camera, the resolution obtained with the improved processing of the coded image is equal to that obtained with conventional apertures. An actual object consisting of the letter E was imaged with an annular aperture and a scintillation camera. The reconstruction with and without the improved processing is presented. In addition, the annulus is intermediate between the pinhole and the Fresnel zone plate with regard to both collection efficiency and the number of counts required for a given signal-to-noise ratio (SNR). It therefore offers an improvement over pinhole apertures without demanding the increased count rate and resolution required of detectors when Fresnel zone plate coded apertures are used.

Thermal imaging systems

Abstract: A single three-electrode linear detector replaces the conventional series or parallel linear detector array in a scanned image thermal detection system. The detector comprises an elongated semiconductor/photoconductor strip, typically 0.25 cm long and 50 μm wide, e.g., of cadmium mercury telluride. A bias current in the strip is arranged to give a photocarrier drift velocity in the strip which matches the image scanning velocity thereby giving enhanced image resolution. Modulation in photocarrier current which constitutes the detected image is measured as a bulk resistivity change between two readout electrodes positioned near one end of the strip.

Cross-Sectional Anatomic Images by Gamma Ray Transmission Scanning

Abstract: 60Co gamma-ray transmission data were measured along linear scan paths at a number of angular orientations with respect to the patient and submitted to a computer software program. Reconstructed images are displayed as digital density printouts and as isodensity contours on an x-y plotter or oscilloscope screen. Image resolution is limited primarily by factors such as collimation and the amount of transmission data collected; with the rather rudimentary apparatus at disposal, a spatial resolution better than 5 mm has been achieved.

Scan and Display Considerations in Processing Images by Digital Computer

Abstract: An analysis of the effects of finite aperture sizes in the scan and display of images is presented. The scanning aperture results in degrading the sample spectrum; the display results in a failure of the Shannon–Whittaker reconstruction theorem. Both effects can be partially corrected for, so as to give an image that is less degraded by scan and display. An example of correction of an actual image is presented as a demonstration.

Image of a sinusoidal complex object in a partially coherent optical system

Abstract: Combined effects of amplitude and phase variations on the irradiance in the image of a sinusoidal complex object are investigated for a partially coherent optical system. For this purpose, the general expression for the irradiance in the image of a sinusoidal complex object that has amplitude transmittance (C + A cos2πx0u) and phase distribution of the form exp(B cos2πx0u) is formulated for a partially coherent optical system. The image irradiance obtained in such an optical system consists of the fundamental frequency and a number of harmonics produced by the nonlinear modulation of the object. The characteristics of the image are assessed in terms of the image contrast, which is defined as the ratio of the coefficient of a harmonic component to the background. By use of the general formula, the image contrast of the fundamental and harmonic components up to sixth order can be calculated for the partially coherent optical system illuminated with bounded and annular illuminations. The typical nonlinear effect occurs in the low-spatial-frequency region. Especially, maxima of the contrast curves occur in the low-frequency region; they may be caused by nonlinearity of the system and effects of phase variations. Analysis and computation showed that, in image formation in a partially coherent optical system, phase variation in the object is extremely influential for the appearance of the image and its contrast.

Imaging with a Small Ultra Pure Germanium Gamma-Camera

Abstract: Semiconductor detector gamma-cameras promise marked improvement in spatial resolution, compared to NaI based system. In addition, solid state systems offer the potential of simultaneous imaging of multiple isotopes, or polychromatic nuclides. Beciuse semiconductor systems offer improved resolution, and expand the spectrum of radionuclides applicable to diagnostic imaging, their impact on nuclear medicine will be significant.

Multifrequent Microwave Holography at Close Range

Abstract: By recording and reconstructing several microwave holograms of the same object at different frequencies, and superposition of the complex amplitude of the reconstruced images in an appropriate manner, the resolving power can considerably be improved. Experiments in the 8-12 GHz region are presented with simple objects. The reconstruction is done numerically on a digital computer.

Longitudinal magnification in radiologic images of thick objects: a new concept in magnification radiography.

Abstract: New concepts which are useful for evaluating image resolution and distortion in magnification radiography are introduced. It is shown theoretically and experimentally that “longitudinal magnification” defined as the ratio of the magnified image size to the conventional image size for objects located in a plane perpendicular to the film, is given approximately by the square of the conventional magnification. Resolution in the radiographically magnified image of such objects is much higher than that obtained by optical magnification. This is confirmed experimentally by radiographs of square-wave test objects. The related image distortion is also discussed.

Semiconductor camera for detection of small tumors.

Abstract: Early detection of small tumors (approximately 3 mm) with only a moderate uptake ratio is often difficult because of poor statistics and a small signal-to-background ratio. The detection capability of a germanium semiconductor camera is analyzed to show that a very large number of counts is required even when the spatial resolution is matched to the size of the tumor. A potential enhancement of statistics using the tissue-scattered gamma rays is discussed based on the superior energy resolution of the semiconductor.

High spatial resolution position sensitive counter for use in muscle diffraction.

Abstract: A position sensitive counter with high spatial resolution is described for use in low angle X-ray scattering studies from live muscles. The main sources of spatial noise are evaluated to enable the design of the counter which has a spatial resolution of 100 mu m (FWHM), an efficiency of 85% for the detection of 1.54 AA X-rays and requires a gas flow of only approximately 10 ml/day to maintain suitable operation.

Converging Collimation and a Large-Field-of-View Scintillation Camera

Abstract: Three low-energy multihole converging collimators were evaluated in reference to accepted imaging parameters using a prototype large-field-of-view scintillation camera. A substantial improvement in resolution and/or sensitivity with depth was observed. Because of the large detector, the inherent reduction in field size due to convergence was not detrimental to satisfactory imaging of most target volumes. Such collimation should prove to be of significant clinical value.

Nonredundant Point Distribution for Coded Aperture Imaging with Application to Three-Dimensional On-Line X-Ray Information Retrieving

Abstract: Conventional methods of displaying three-dimensional information in X-ray diagnostics like tomography or tomosynthesis are not capable of imaging fast moving objects because of the time-sequential recording process. To overcome this difficulty the method of coded aperture imaging using nonredundant point distributions is applied to X-ray imaging. The object coded by an array of X-ray sources is deconvoluted by means of an optical processing system using monochromatic, but spatially incoherent light. Experimental results obtained with simple objects show good resolution in detail as well as in depth. Moreover, an on-line system has been simulated using coded images on X-ray films with a TV-camera pick up in conjunction with an electrooptic relay tube.

Clinical efficacy of a large-field-of-view scintillation camera.

Abstract: In evaluating the clinical application of a prototype large-field-of- view scintillation camera, a significant increase in the quality of static and dynamic images was observed. With parallel-hole collimation, imaging time for large areas was reduced by more than 50 percent and a marked enhancement in resolution and sensitivity of lung images occurred in relation to those obtained with diverging collimation on a conventional camera. Using converging collimation, the prototype camera produced images of brain and other organs with considerably better depth response than comparative studies performed with standard size cameras. These results demonstrate that further clinically relevant improvement in scintillation camera performance is possible. (auth)

Temporal- and spatial-intensity-interferometer imaging through a random medium.

Abstract: We present experimental and theoretical results which show that temporal-intensity interferometry can be used to image coherently illuminated objects through a moving random medium. This system is compared with a spatial-intensity-interferometer imaging system (SIS) described by Beard and Barnoski. We show that the angular resolution of the temporal-intensity-interferometer imaging system (TIS) and the SIS is the average angular size of a scatterer, as seen from the detector.

Low level infrared camera (LLIR Camera)

Abstract: Photon images, typically but not necessarily, in the long or infrared wavngths are focussed upon the input face of a semiconductor plate. For an electronically controllable time input photon energy is converted to electrons free to move through a semiconductor substrate and integrated in thousands of PN diodes in the plane of the Plate. A deformographic film on the output face of the Plate is deformed according to the stored electron image. An optically reflective film is deposited over the deformographic film so that incident light from a first Schlieren Optic System scatters in accordance with the stored image and is focussed onto a further stage. The further stage includes an image intensifier which converts the scattered images to electron images, accelerates the electron images through electron optics and impacts them in an Image Storage Plate which amplifies the images and deforms a deformographic film-having an optically reflective surface. A second Schlieren Optics System converts the deformed image to an optical image and projects it onto moving film. Electronic synchronization allows the images to be recorded on moving film without distortion.

Component resolution indices for scintillation camera systems.

Abstract: From published overall resolution indices for three Anger camera systems, measured with three straight-bore collimators and 99mTc in air and with a water absorber present, the components due to inherent camera resolution, collimator geometry, and scatter are derived at various depths. Replacement of S-11 multiplier phototubes by bialkali phototubes improves calculated inherent Pho/Gamma III camera resolution by about 30% and by a further 33% upgrading to a high-performance model. At distances 2, 5, 8, and 10 cm from each collimator face with an intervening water absorber, mean scatter components of overall resolution indices are 6, 8, 9, and 10 mm, respectively. In typical clinical 99mm Tc imaging situations with a scattering medium present, the relative contributions of camera, collimator, and scatter to the total overall system resolution are presented.

An X‐ray television system for rapid recording and processing of diffraction patterns

Abstract: An X-ray television camera using a phosphor screen coupled to an image orthicon tube was prepared to detect and record diffraction patterns rapidly. It is about 750 times more sensitive than photographic film, producing a video signal of S/N = 10 for incident 4 × 104 Cu Kα quanta sec−1 mm−2, and has a dynamic range of 1:30 and a spatial resolution of 6.4 Lp mm−1. The detector system was tested by recording rotation patterns from a single-crystal of diformylhydrazine, where it was demonstrated that one can measure reflection intensities with an accuracy better than 10%. To process the TV picture by computer, an image readout device using a storage tube was built. The high sensitivity and the large detection window (42 mm in diameter) of the camera and the fast speed (40 μs for each 80 × 80 μm resolution element) of the readout device make the incorporated system most appropriate for rapid measurement of simultaneous reflexions from macromolecular crystals. The camera can also record small-angle diffraction patterns from muscle in an exposure time of a few seconds.