Abstract: A method and apparatus for controlling multiplexing of a transducer having more elements than the imaging system has receive channels. The active aperture is shifted in increments of a predetermined number of transducer elements, e.g., eight. While the active aperture is maintained constant for a predetermined number of vectors, the phase center of the vectors in the group is shifted so that offset is minimized. In the case wherein the active aperture is successively shifted by eight elements, the offset is varied between +4 and -4 during the interval between shifts of the active aperture.

Abstract: A polycrystalline ceramic scintillator exhibiting reduced afterglow includes between about 5 and 50 mole percent Gd.sub.2 O.sub.3, between about 0.02 and 12 mole percent of either Eu.sub.2 O.sub.3 or Nd.sub.2 O.sub.3 as a rare earth activator oxide, and between about 0.003 and 0.5 mole percent of either Pr.sub.2 O.sub.3 and Tb.sub.2 O.sub.3 as an afterglow reducer. The remainder of the scintillator composition is Y.sub.2 O.sub.3. The resulting scintillator is especially useful for a radiation detector of the type having a plurality of radiation receiving channels. A scintillator body is disposed in each channel so that radiation being received therein is incident on the scintillator body and causes the body to convert the incident radiation to light energy of a predetermined wavelength. The radiation detector also includes means for converting the light energy from the scintillator into electrical signals which are proportional to the amount of radiation incident on the scintillator body.

Abstract: A programmable probe multiplexer which can be reconfigured for use with multiple imaging systems having different channel counts. The probe uses a system code that informs the multiplexer of the number of channels on the system to which it is connected. The multiplexer hardware in turn adjusts the program or channel map to reconfigure the probe to accommodate the system. In particular, the probe can sense the presence of a system type and then reconfigure and optimize performance automatically, or the probe can be reprogrammed by the system, allowing great flexibility in the design and optimization of imaging parameters. The probe supports this concept through the use of a series of programmable switches and the appropriate logic to assign input channels to output channels.

Abstract: The present invention, in one form, is an apparatus for performing image reconstruction using data obtained by a helical scan. In reconstructing an image in accordance with the present invention, projection data arrays corresponding to data planes associated with the slice to be imaged are generated. Weighting factors are then applied to the data arrays to assign a weight to each particular data element thereby creating a weighted projection data array. The weighted projection data array is then filtered and back projected to create an image data array from which an image slice is generated. In accordance with the present invention, the weighting function used in creating the weighted projection data array is based upon a plane of reconstruction which is not necessarily perpendicular to the z-axis.

Abstract: The present invention, in one form, is an apparatus for performing image reconstruction using data obtained by a dual beam helical scan. In reconstructing an image in accordance with the present invention, projection data from each fan beam measurement is weighted by weighting factors to obtain a reconstructed slice. The data arrays selected and weighting factors applied vary depending on the table speed and the detector spacing measured at the axis of gantry rotation, i.e., the detector z spacing.

Abstract: In a method for maximizing frame rate of an ultrasound imaging apparatus, ultrasound B and color mode vector density are reduced. Initially, an actual displayed image size is determined. A minimum vector density requirement is then determined for B which will provide a useful image based on the actual displayed image size. The number of vectors in the image is then adjusted to meet the minimum vector density requirement.

Abstract: A system is provided for MR imaging wherein a volume within an imaging subject positioned with respect to the system contains both water molecules and fat tissue proximate to one another. The water molecules and fat tissue are selectively saturated by first determining whether application of a first RF excitation pulse of a first RF frequency to the volume, in association with a gradient magnetic field having a selected polarity with respect to an axis, would saturate fat tissue in a band lying closer to or farther from a selected location than a band of saturated water molecules. The first frequency comprises the sum of a center frequency and a first offset frequency having a magnitude and polarity determined by the gradient magnetic field.

Abstract: A method and an apparatus for activating one of a plurality of connected transducers in response to the operator picking up that transducer. This enables the selection of a transducer without the need for pressing a button or key. Automatic selection is accomplished by placing a proximity sensor located within the holder of the transducer or on the transducer itself to indicate whether the transducer is being held by its holder. Switches are also incorporated to detect when a transducer connector has been plugged into each port on the ultrasound imaging machine. Depending on the order in which unactivated normal transducers attain a state whereby the respective normal transducer is both connected and out of its holder, a stack of probe identifiers is created. Identifiers for connected special transducers are added to the stack below any probe identifiers for normal transducers. The identifier at the top of the stack indicates the transducer which will be activated next, i.e.

Abstract: A dynamic firing sequence for ultrasound imaging apparatus can be achieved in accordance with the present invention. Initially, operator selected parameters are provided and predetermined system constants are stored. The operator selected parameters in B mode include imaging depth. The operator selected parameters in Doppler mode include velocity scale, doppler range gate position and Doppler range gate size. The operator selected parameters in color mode include velocity scale and region of interest depth. PRI and minimum vector time are calculated using the operator selected parameters and the predetermined system constants. These calculations are used to maximize interleaving, thereby maximizing frame rate.

Abstract: A time gain compensation technique is applicable for use with ultrasound imaging systems, including systems having digital architecture. The time gain compensation apparatus of the present invention comprises a time gain compensation curve generator and the ability to drive the time gain compensation curve generator to provide digital generation of the time gain compensation curve. Digital generation of the time gain compensation curve is achieved by an initial gain and data represented by a series of slopes and associated time-dependent break-points.

Abstract: A dynamic apodization gain correction technique for use with ultrasound imaging systems comprises an apodization curve generator and the ability to drive the curve generator to provide digital generation of the apodization gain correction curve. The ability to drive the curve generator comprises an initial plurality of active elements and data represented by a series of slopes and associated time-dependent break-points.

Abstract: A system and process for electrically connecting all elements in a transducer array from one side. A flat block of piezoelectric ceramic material is patterned and drilled with a high-powered laser. The drilling is precisely controlled to define a series of vias which penetrate the ceramic block in the thickness direction. These vias facilitate electrical connection from one side of the ceramic block to the other side when the vias are sputtered or plated with electrically conductive material. In this way the electrodes on the front face of the transducer elements can be electrically connected from the rear to common ground or a signal source.

Abstract: The present invention, in one form, utilizes a region of reconstruction ROR in reconstructing an image from projection data. Particularly, once the region of reconstruction is established, a weighting function which is either a linear interpolation or a non-interpolation can be used. If 3.pi. of projection data is used, the weighting function can be divided into three parts. Each part corresponds to .pi. projection views. For a 50% overlapped reconstruction, the entire weighting functions advance .pi. degrees at a time, which synchronizes very well with the boundaries of the weighting functions. Section 1(S.sub.1) will contain projection views from 0 to .pi., section 2 (S.sub.2) contains views from .pi. to 2.pi., and section 3 (S.sub.3) contains views from 2.pi. to 3.pi.. In section S.sub.1, the weighting function is a ramp-up function, in section S.sub.2 the weighting function is a constant, and in section S.sub.3 the weighting function is ramped down.

Abstract: An adhesion system specifically designed to achieve a good-quality adhesive bond between a silicone rubber lens and a plastic matching layer of an ultrasonic transducer. The adhesion system includes a layer of conventional silicone adhesive applied on the silicone rubber lens and a layer of dichloro-di-p-xylylene residing between the silicone adhesive and the plastic matching layer. The layer of dichloro-di-p-xylylene is adhered to the silicone adhesive via a silicone primer and is adhered to the plastic matching layer via a silane primer. The layer of dichloro-di-p-xylylene provides adhesion promotion, a chemical barrier to protect the transducer array from the external environment and an electrical barrier to help protect the patient from the electrically alive transducer elements, without any adverse effect on the acoustic transmission characteristics of the transducer stack.

Abstract: A lightweight passive magnetic shielding system for a mobile magnetic resonance imaging (MRI) superconducting magnet is provided to enable transportation of the MRI while at superconducting operation within the regulations limiting the strength of the stray magnetic field of the MRI magnet and the weight of the vehicle including the MRI system.

Abstract: An acoustic power control technique computes relevant system transmit parameters in real-time by optimally combining a current system imaging configuration with an empirically derived measurement database. The database contains measurement information that is used by the acoustic power control technique to determine optimal transmit parameters for a given imaging situation. The optimal parameters are determined by adjusting the measured database parameters through the use of the current scanning parameters to maximize system performance. Utilizing system constraints, the acoustic power control technique computes the optimal transmit parameters to maximize system performance.

Abstract: Method for forming welded joints on superconducting foils to form long lengths of foil for use in superconducting magnet tapes including fixturing for controlling the accurate positioning of sheared foils and control of the overlap to be welded.

Abstract: A color adaptive frame averaging method for an ultrasound imaging system adds persistence to images. The color adaptive frame averaging is achieved by computing filter weighting coefficients and using the filter weighting coefficients to compensate for aliased color data. Frame rate compensation is achieved by adjusting the filter weighting coefficients. In accordance with the present invention, the color adaptive frame averaging method comprises a filter, such as an infinite impulse response filter.

Abstract: An automated qualitative image quality method is used for an ultrasound imaging system. Initially, an impulse response of the system is determined. The impulse response is used with a cystic filling determination to achieve automated qualitative image quality for the ultrasound imaging system. The impulse response of the system is determined using a wire-in-water test. That is, a wire target is put in a water tank. Next, a transducer is set to be perpendicular to the axis of the wire, to get a cross-section of the wire. Sound waves are transmitted and reflected echoes are received at different gain settings. Curve fitting techniques are then used to form a system beam profile. Finally, acoustic peak to noise and detail resolution qualitative image quality measurements are made using the system beam profile. The cystic filling of the system is determined by defining a first region of interest in a darkened region of an image and a second region of interest in a surrounding region of the image.

Abstract: A doppler dead zone avoidance method is used in an ultrasound imaging apparatus to avoid the situation where time of flight equals PRI, or the time between doppler firings. Initially, range gate size and transmit parameters are optimized. This optimization of range gate size and transmit parameters is used to minimally adjust an operator selected velocity scale, as needed. Higher velocity scales can be achieved, based on optimization and minimization.