Abstract: A programmable, medical imaging system which incorporates algorithms for enhancing the usability of the system for clinicians is described. With respect to programmability, and in one aspect, the present invention relates to a programmable system which includes a learn mode usable for script generation. In the learn mode, a user can rehearse a sequence of actions and save those actions to be replayed later. In another aspect, the present invention is directed to an algorithm which provides a non-blocking, synchronous interface to an underlying asynchronous architecture. Generally, the algorithm decouples the client-server portion of the application from the synchronous development environment. Using this algorithm, a programmer can develop a non-blocking, highly interactive, client-server application without having to resort to asynchronous programming techniques.

Abstract: The present invention, in one form, is a system which, in one embodiment, varies DAS gain to better accommodate different scanning parameters between different scans, even at the same slice thickness. Specifically, in one embodiment, the DAS gain is varied, or modulated, as a function of slice thickness, x-ray tube current and voltage levels, scan time, and average detector gain. The DAS gain is modulated using a gain factor Gain.sub.-- Fac which is determined in accordance with each of the above-mentioned scanning parameters. The gain factor Gain.sub.-- Fac is then used to determine an appropriate DAS gain for such parameters. Particularly, DAS gains are stored in a look-up table in the CT system computer, and the gain factor Gain.sub.-- Fac is used to select the appropriate DAS gain from the look-up table. The determined DAS gain is then utilized to correct data acquired during a scan.

Abstract: The present invention, in one form, is a system for reducing noise artifacts in three-dimensional image reconstruction using data acquired in a helical scan. More specifically, a standard deviation ratio of reconstructed images with and without helical weighting is identified. Such standard deviation ratio is then used to generate filter coefficients, which are then applied to the data in an adaptive smoothing algorithm.

Abstract: The present invention, in one form, is a method for detecting a partial volume artifact in scan data acquired during a tomographic scan. In accordance with one embodiment of the algorithm, an object of interest is scanned to generate scan data. Sampling pairs of the scan data are identified and used to generate an inconsistency map. The inconsistency map is weighted and filtered to generate a partial volume signature which identifies partial volume artifacts.

Abstract: The present invention, in one embodiment, is an interference detection assembly for detecting patient and patient table interference with a gantry of a computed tomography system. The assembly, in one form, includes a frusto-conical capacitive plate secured to a leading frusto-conical surface of the gantry bore. The capacitive plate is coupled to a control unit which detects changes in the capacitance of the capacitive plate. When the plate is discharged below a threshold charge, the control unit generates a signal which may be used to automatically interrupt a scan.

Abstract: The present invention, in one form, is a scatter collimator for a computed tomography system including an x-ray source. The scatter collimator is positioned between a detector array and an object to be imaged. The scatter collimator includes a housing, a plurality of attenuating blades and a plurality of attenuating wires. The blades and wires are mounted to the housing, and oriented substantially perpendicular to each other. Particularly, the blades and wires form a two-dimensional shielding grid. The blades also are oriented so that they are radially and focally aligned with the x-ray source. A detector element of the detector array is secured to the housing so that the blades and wires are between the detector element and the x-ray source. The detector element, in one form, includes a scintillation element which is coated with a light-retaining material.

Abstract: The present invention, in one form, is a brake assembly for a tilting gantry. The brake assembly is coupled to the gantry in substantially the same manner as a driving actuator is connected to the gantry, and includes a hydraulic cylinder, a piston, a reservoir and a valve. The cylinder includes a first end, a second end, and a sidewall extending between the first end and the second end to define a chamber. The piston includes a head and an arm which is configured to couple to the gantry. The piston is positioned within the hydraulic cylinder so that the head of the piston is in the cylinder chamber and the piston arm extends through a piston opening of the first end of the hydraulic cylinder. The reservoir is configured to retain hydraulic fluid, and the valve is connected in series circuit between the hydraulic cylinder and the reservoir.

Abstract: Methods and systems for performing a tomographic scan which allow an operator to define a non-circular orbit so that a detector can be positioned close to a patient at each view are described. Such methods and systems provide that the patient to detector distance is reduced, which improves spatial resolution for the scan. In one embodiment, and to achieve a non-circular orbit, the camera and table/patient are moved with respect to one another. Specifically, the table is pinned in position and set to lateral and vertical positions during set-up. The same lateral and vertical table positions are maintained during the scanning phase. To get the camera closer or farther from the patient/table, the camera is pitched in or out. The camera head is tilted to achieve a tilt angle of zero degrees for all changes in pitch. As the camera pitches in and out, the central axis of the camera moves along the longitudinal axis of the table.

Abstract: The present invention, in one embodiment, is a system for performing image reconstruction from raw projection data acquired in a tomographic scan. More specifically, the system implements an estimation algorithm for raw projection data which does not require fully pre-processing all raw projection data for image reconstruction. Particularly, raw projection for a base view is pre-processed to generate pre-processed projection data for the base view. A linear calibration algorithm generates a linearization vector using at least a portion of the fully pre-processed projection data for the base view. The linearization vector is then applied to raw projection data for subsequent views to generate estimated pre-processed projection data for such subsequent views.

Abstract: The present invention, in one embodiment, is a system for performing image reconstruction from unfiltered scan data acquired in a tomographic scan. More specifically, the system implements an algorithm for unfiltered scan data which eliminates the requirement that the scan data for a particular view be fully filtered for image reconstruction. Particularly, unfiltered scan data for a base view is fully filtered to generate filtered scan data for the base view. At least a portion of the filtered scan data for the base view is then used for subsequent views. Particularly, for a subsequent view, only the high frequency components of unfiltered scan data for that view are filtered with a short filter. The filtered high frequency components then are added to the low frequency components of the filtered base view scan data to estimate fully filtered scan data for the subsequent view.

Abstract: The present invention, in one form, is a method for detecting reference channel blockage in a computed tomography system. The system includes an x-ray source, a detector and a reference channel. When scanning an object of interest, the x-ray source is supplied with an x-ray source current and projects an x-ray beam toward the detector and the reference channel. The detector, when impinged by the x-ray beam, generates projection data for reconstructing an image of the object of interest. The reference channel is configured to generate an actual reference channel signal when impinged by the x-ray beam. An expected reference signal is determined in accordance with the x-ray source current. The expected reference signal is then utilized to normalize the projection data.

Abstract: The present invention, in one form, is a method for improving grey-white matter differentiation between regions of an image to be reconstructed from data obtained by a CT scan. More particularly, in accordance with one form of the present invention, a re-mapping function is utilized to generate CT numbers. In accordance with such function, CT numbers that are outside the grey-white matter region are not "stretched". The CT numbers within such region are "stretched" with the larger "stretch" centered on the grey-white matter region and tapering off at the boundary. Using such a function, grey-white matter differentiation is improved without adversely affecting quality and accuracy.

Abstract: The present invention, in one form, corrects any error due to varying detector cell gains in the z-direction represented in data obtained by a scan in a CT system. The CT system includes an x-ray source which emits an x-ray beam from a focal spot, through a collimator aperture, and towards a detector having a plurality of detector cells. The geometry of the x-ray beam, the width of the collimator aperture and the focal spot size are used to determine the z-profile of the x-ray beam across the detector cells. Such z-profile is used to identify effective detector cell gains. The identified effective detector cell gains, rather than actual detector cell gains, are used to correct errors due to varying detector cell gains. Particularly, the identified effective detector cell gains are employed in a known correction algorithm to correct errors. A local average in an x-direction of actual detector cell gain z-profiles is used to determine a non-rectangular norm detector gain z-profile.

Abstract: The present invention, in one form, is a system for obtaining data measurement signals for producing a tomographic image of an object in a multislice scan. More specifically, detector cells in at least one channel of a detector array are electrically coupled, or ganged, so that the ganged channel provides one data measurement signal to be transmitted through the gantry slip ring. The signal distribution in the z-direction for the ganged channel is then determined using signals obtained by adjacent non-ganged detector cells.

Abstract: The present invention, in one form, is a method for improving image quality in Computed Tomography systems by using a partial volume artifact estimation algorithm. In accordance with one embodiment of the algorithm, an object of interest is scanned to generate image data. The image data is segmented into low attenuation data and high attenuation data. A gradient image is generated for two adjacent slices of the image data. The gradient image is then forward projected and squared. The squared gradient image is an estimation of partial volume artifacts in the image data, and therefore is removed from the image data.

Abstract: The present invention, in one form, is a system for performing image reconstruction from projection data acquired in a helical scan. More specifically, the system implements an incremental reconstruction algorithm for helical scan projection data which does not require filtering, weighting and backprojecting such projection data for generating each image. Particularly, an overscan weighting algorithm generates weighting factors to be applied to projection data to generate base image projection data. An update weighting algorithm generates update weighting factors to be applied to the base image projection data to generate subsequent image projection data.

Abstract: The present invention, in one form, is a method of determining focal spot position in a computed tomography system using conventional scan data. The computed tomography system includes, in one embodiment, a bowtie filter attenuating an x-ray beam along two symmetrically disposed raypaths. The symmetrical raypaths impinge upon respective detector channels at identifiable path lengths. The raypath lengths are compared to determine whether the focal spot has shifted.

Abstract: The present invention, in one form, is a system for modulating x-ray tube current as a function of gantry angle and slice location in a computed tomography system. In one embodiment, a desired noise level for a final image is selected, and a desired minimum x-ray photon reading and a desired average x-ray photon reading are identified to produce an image in accordance with the desired noise level. During scanning, actual x-ray photon readings are used with the desired average x-ray photon reading and the desired minimum x-ray photon reading to generate an x-ray modulating factor. This modulating factor is then used to modulate the x-ray tube current.

Abstract: Methods and systems for calibrating a digital gamma camera using a hole phantom are described. In one embodiment, the method includes the steps of performing offset adjustments and gain adjustments, and then using a source to flood the hole phantom, image data of the phantom is collected by the camera to be calibrated. The image data collected from such flood is used to generate a light distribution function for the camera. In addition, residual distortions are measured, and a spatial corrections map and an energy deficit map are created. A quality control image also can be generated to verify that the camera is calibrated.

Abstract: A pitcher's practice cage consists of a compactly-foldable fabric-covered tubular structure which provides a large ball-gathering area, within which hangs a target marked with areas whose striking "calls" the pitch, and a ball-collecting sloping back wall and floor which accumulates pitched balls. Bows which support the canvas cover, one bow rigidly-mounted on short left-and-right support members hinge-mounted closely adjacent to the bow so rigidly supported, permit the entire structure to be folded into a flat "package" for moving and storing.