Abstract: A system for converting video camera images, obtained when the camera scans radiation generated images, to frames of electrical signals; the radiation generated images are obtained responsive to pulses applied to activate a radiation source during pulse periods; the system applies the pulses at a rate of at least 15 per second and means are provided for reading out the frames at a rate of at least 15 per second.

Abstract: Improved cryogenic magnet systems for use in NMR imaging devices comprising an electro-magnet immersed in a first tank containing a first liquid gas, the first tank located in a container evacuated to a high vacuum, a refrigerating system external to said container, and coupling means for coupling a cold head of the refrigerating system to radiation shielding means surrounding said first tank for lowering the temperature of the shielding means to thereby reduce boil-off of said liquid gas.

Abstract: A gamma camera comprises a scintillation crystal having an index of refraction of 1.80-190, a collimator for imaging the object on one face of the scintillation crystal, an array of photodetectors arranged around the opposite face of the scintillation crystal, and a light guide interposed between the opposite face of the scintillation crystal and the plurality of photodetectors. The light guide is selected to have an index of refraction of at least 1.60, higher than in the conventional gamma camera, whereupon it has been found that the detection efficiency and the positional accuracy of each scintillation event can be increased, to thereby increase the sensitivity and the spatial resolution of the gamma camera.

Abstract: Apparatus for examining a body, particularly useful in tomography, for producing transverse sectional images of the body, comprises scanning means supported by a carriage coupled to its mounting via a pair of links defining, with the carriage and its mounting, a four-link, parallel-motion mechanism which, upon oscillation of the links, effects a curvilinear movement of the carriage with respect to the body, and thereby a curvilinear traverse of the body by the scanning means. The carriage is also rotatably mounted on the machine frame enabling the carriage, and the scanning means supported thereon, also to be rotated about the body either incrementally or continuously.

Abstract: A digital radiographic method and apparatus are described for the visualization of a portion of the circulatory system of a subject by feeding a catheter through a blood vessel while its progress is observed by exposing the respective portion of the subject's body to penetrating radiation, e.g., X-rays. In the described method and apparatus, all the prior positions of the catheter are stored so that all such prior positions visited by the catheter are displayed with each display of its current position. In addition, during the feeding of the catheter through the blood vessel, a substance relatively opaque to the radiation is injected into the blood vessel, whereby the digitized images of the previous catheter visits which are stored and displayed also include the image of the blood vessel and its junctures as revealed by the injected substance.

Abstract: A plasma electron source has an apertured cathode, and a housing for defining a cavity behind the aperture. A trigger electrode, in communication with the cavity, is responsive to a short-duration trigger pulse for establishing plasma in the cavity. The plasma is sustained in the cavity subsequent to the termination of the trigger pulse by a bias circuit, which biases the cavity at a relatively low voltage with respect to the cathode for a period of time much longer than the duration of the trigger pulse.

Abstract: A gamma camera has a scintillation medium responsive to radiation stimuli for producing an exponentially decaying scintillation at a location where a radiation stimulus interacts with the medium; a photodetector system responsive to a scintillation for producing outputs; and computation circuitry responsive to such outputs for producing intrinsic signals which have the same temporal nature as a scintillation and which are processed to produce coordinate signals representative of the coordinates of the scintillation producing such outputs. The computation circuitry includes truncation circuitry for electronically shortening the duration of intrinsic signals so that the computation circuitry effectively operates with signals of shorter duration than the scintillations.

Abstract: An image-reconstructive technique for examining a body by means of penetrating radiation, such as X-rays, is described in which a pre-body collimator having a two-dimensional array of radiation-transmitting holes each bordered by radiation non-transmitting walls is disposed between the body and the source of radiation, and a plurality of exposures are made onto a radiation-sensitive surface, in which the radiation is projected through the collimator while the radiation source is at a plurality of different locations, such that during the successive exposures, the radiation from the source passes through different ray paths defined by the holes in the pre-body collimator. The radiation level received by each of the radiation-sensitive surface elements is detected, stored, and processed to reconstruct the two-dimensional radiation pattern but with enhanced resolution. Preferably a post-body collimator is also used to suppress scattering. Described are a four-exposure procedure and a nine-exposure procedure.

Abstract: By reason of the nature of the scanning regimen followed by a scanning gamma camera head, and the shape of the active region of the head, not all of the elemental areas of a scanned radiation field are observed by the active region of the head for the same period of time. This non-uniformity sensitivity of the system is corrected by correction factors that are either analytically calculated or experimentally determined for each given elemental area of the map. The map of an unknown radiation source obtained by following the scanning regimen is corrected by applying the sensitivity correction factors to the contents of corresponding elemental areas of the map.

Abstract: The intensity distribution of a radiation field imaged on a scintillation crystal of a gamma camera can be quantified by assigning to each elemental area of the crystal, a number representing the number of light events calculated to have occurred in the given elemental area within a predetermined period of time. The resolution of the camera is improved by weighting the contents of the elements in the memory in accordance with the probability that an event, calculated to have occurred in a given elemental area, actually occurred therein, such that the weighted contents of the memory more closely approaches the actual density distribution of light events as compared to the unweighted contents of the memory.

Abstract: A map of a radiation field produced by a gamma camera is corrected for three types of spatially dependent errors in a manner that corrects for each error independently of the others. The errors corrected for are dislocations which result from the non-linearity of the optics, photomultipliers and electronics of the camera, energy window variations resulting from inhomogeneity of the optical system which includes the crystal, light guide, and photomultipliers, and the non-uniform sensitivity of the head resulting from the non-uniform stopping power of the crystal and collimator of the camera head. The map is corrected by obtaining a set of correction factors associated with each type of error using a calibration technique that insures independence between the various correction factors, and applying the correction factors to the map obtained in a nuclear imaging process in a way that independently corrects the map for each type of error.

Abstract: The dead time of a nuclear imaging system is compensated for when recording a representation of a dynamically changing radiation field into an image memory by injecting into the system synthetic pulses which resemble, in terms of amplitude and shape, the pulses produced by the system in response to interaction with stimuli from the radiation field, and by determining the percentage of synthetic pulses which are processed by the system. A correction factor based on such percentage is applied to the representation of the field. The synthetic pulses are injected into the system at a predetermined rate with respect to the rate of pulses processed by the system in response to interactions with stimuli from the radiation field. This predetermined rate is functionally related to the rate at which input signals are processed by the system.

Abstract: A fan beam of the type described herein is oriented so as to be coplanar with the cross-section of a body to be reconstructed. Pure rotational movement is imparted to the fan beam by rotating the same about a fixed center of rotation such that the fan beam sweeps out an area in the plane of the cross-section; and the absorption coefficients over such area can be computed in a known manner from measurements of the intensities of the beams emerging from the area swept out thereby.When one extremity of the fan beam passes through the fixed center of rotation, the area swept-out by the fan beam during one revolution thereof is circular, the center of which is coincident with the fixed center and the periphery of which is tangent to the other extremity of the fan beam. When the fixed center lies outside the fan beam, the area swept-out is annular and is defined by concentric circles whose centers are coincident with the fixed center and whose peripheries are respectively tangent to the extremities of the fan beam.

Abstract: Light coupling means interposed between the photosensitive surfaces of an array of photodetectors and a scintillation crystal has a recess associated with at least one of the photodetectors, the recess being located in the light coupling means within the volumetric projection of the photosensitive surface of said at least one of the photodetectors. The recess is filled with material having an index of refraction different from the index of refraction of the light coupling means such that the index, throughout the recess, is uniform. The provision of the material with a different index in the recess serves to alter the direction of light from a light event in the crystal as the light passes through the light coupling means thereby modifying the relative amount of light received by each of the photodetectors of the array, and thereby improving spatial linearity, uniformity and resolution.

Abstract: Apparatus for examining a body by means of penetrating radiation such as X- or .gamma.- rays has a radiation beam assembly comprising a member with a radiation source for producing a collimated beam of penetrating radiation, and a member with detector means for receiving radiation from the source. Guide means slidably mount the members on a support structure containing a circle of reconstruction within which the body is located. The members are located on opposite sides of the center of the circle of reconstruction and are translatable as a unit in parallel paths to cause the beam to sweep through and define the plane of the circle of reconstruction. A flexible connection links the members together for maintaining a fixed spatial relationship therebetween during translation at least while the beam sweeps through the circle of reconstruction.

Abstract: The normality of a cell labelled with a lipid soluble fluorescent dye and excited with a beam of polarized light can be evaluated by measuring the time dependence of the state of polarization of fluorescence emitted by the cell which is determined by simultaneously measuring the intensities of fluorescence polarized in directions parallel and perpendicular to the direction of polarization of the excitation beam.The state of polarization of a cell changes markedly as a function of excitation time when the cell is abnormal (i.e., malignant), while the state of polarization of a cell remains substantially constant when the cell is normal. Classification of cells in a population by way of the stability of the state of polarization provides guidance in determining the presence of malignancy in the population.

Abstract: Cells in a population labelled with a lipid soluble fluorescent dye and excited with a beam of polarized light can be classified according to the distribution of the state of polarization of fluorescence emitted by a cell. The intensities of fluorescence, polarized in directions parallel and perpendicular to the direction of polarization of the excitation beam, are measured simultaneously to obtain the state of polarization.The state of polarization, so determined, bears a functional relationship to the fluidity of the plasma membrane of the cell and is thus a measure of the cell's function. Consequently, classification of cells in a population by the distribution of the state of polarization of the fluorescence emitted in response to their excitation enables different types of cells to be distinguished according to biological function. For example, white blood cells can be differentially analyzed using the method of the present invention.

Abstract: Radiation imaging apparatus includes a scintillation crystal responsive to radiation stimuli for producing light events, and a plurality of photodetectors arranged in a predetermined array relative to the crystal, each of the photodetectors having a light-sensitive surface facing the crystal and being responsive to a light event for producing an output signal. Coupling means associated with each photodetector applies its output signal to coordinate computing circuitry which computes the coordinates of a light event from signals applied thereto.In one embodiment of the invention, at least one of the coupling means includes a threshold linear gate for applying the output of the photodetector with which the coupling means is associated, to the coordinate computation circuitry only if the input to this particular photodetector exceeds a predetermined threshold.

Abstract: Coordinates of a light event, computed by signal processing equipment from output signals developed by an array of photodetectors of radiation imaging apparatus in response to the interaction of a radiation stimulus with a scintillation crystal, are validated only if a representation of the total energy of the light event lies within an energy window functionally related to the coordinates of the light event. In this manner, only desirable radiation stimuli interacting with the crystal are detected, and undesirable, indirect or scattered radiation stimuli interacting with the crystal are discriminated against.

Abstract: Perinatal lung maturity is evaluated by determining the fluorescence polarization of a sample of pulmonary effluent containing pulmonary surfactant labeled with a fluorescent dye. The sample is excited with polarized radiation for causing the dye to fluoresce. I.sub.81 and I.sub.195, the intensities of fluorescence polarized in directions parallel to, and perpendicular to, the direction of polarization of the excitation radiation, are measured. From these measurements, the fluorescence polarization P, where P = (I.sub..parallel. - I.sub..perp.)/(I.sub..parallel. + I.sub.195), is determined. The value of P, which is functionally related to the microviscosity of the constituents of the surfactant, has been found to decrease with perinatal lung maturity. When the sample is amniotic fluid containing fetal pulmonary effluent, the evaluation of lung maturity can be carried out antepartum. Postpartum evaluation can be carried out by sampling neonatal tracheal or pharyngeal aspirates.