Abstract: A rotating X-ray tube comprises a cathode assembly including a cathode and a cathode current supply, and an anode assembly having an anode current controlled via the cathode current supply. A filament for emitting electrons is separated from the cathode. A cathode cup supports the filament and provides electron field shaping assistance. The X-ray tube further comprises a distributed capacitance for affecting the cathode cup electron field, and an insulator leakage resistance. The cathode cup is allowed to float on the insulator leakage resistance, whereby voltage associated with the distributed capacitance and the leakage resistance is allowed to remain relatively constant.

Abstract: An integral yoke/transducer connector has built-in probe switches for detecting when a transducer probe has been removed from its yoke. Based on the status of the probe switch and other feedback information, a system controller activates the out-of-holder probe if it has priority. In this manner, a probe can be automatically activated when it is lifted out of its yoke, thereby eliminating the need to trace a desired probe to its connector/port via the cable. Once a probe/port is auto-selected, it remains the only active probe/port until the probe is placed back in the yoke (or its transducer connector is disconnected from the port on the imaging unit). Placement of the probe in its corresponding yoke opens the probe switch which is built into the yoke/connector assembly.

Abstract: A helium cooled superconducting magnet assembly including helium gas recondensing apparatus to return liquid helium to the helium supply in the helium vessel includes a recondenser positioned in the helium vessel above the helium supply connected to a cryocooler in a dual-sleeve assembly enabling breaking of thermal joints with thermal isolation from the helium for servicing of the cryocooler during superconducting operation of the magnet assembly, and providing recondensing of helium gas to fall by gravity back to the helium supply.

Abstract: A transmit power supply optimization method optimizes power supply voltage to high voltage transmitters of an ultrasound imaging apparatus for each operating mode of the apparatus. The method comprises the steps of linking the operating mode of the apparatus, the output of the high voltage transmitters, and the power supply. It is then determined when a change in optimum power supply voltage will be desired. Operation of the high voltage transmitter power supply and the high voltage transmitters is coordinated to react to the determination that a change in optimum power supply voltage will be desired, before the change in optimum power supply voltage is actually desired. Finally, a distributed power supply filter is provided to allow the high voltage transmitters to operate while the change in optimum power supply voltage is occurring.

Abstract: Apparatus and methods for generating z-axis profiles for a CT system detector are described. In one form, the method includes the steps of directing x-ray beams having different z-axis centroids and slice thicknesses at the detector and collecting detector signals for each beam. The detector signal for a first beam is then subtracted from the detector signal for a second beam to obtain a differential, or composite, detector signal which corresponds to a third beam having yet another z-axis centroid and slice thickness. The full z-axis profile of the detector is generated from measured detector signals and composite detector signals.

Abstract: Methods and apparatus for performing a computed tomography scan are described. In one embodiment of the apparatus, a twin beam computed tomography scanner includes a beam splitter, an x-ray source for generating an x-ray to be projected generally towards, and at least partially through, an object, and a detector array comprising a plurality of detector cells arranged to form at least two cell rows. The beam splitter is positioned so that the x-ray projected from the x-ray source is substantially split to form at least two beams prior to being projected at least partially through the object.

Abstract: The present invention, in one form, is a method for performing image reconstruction from projection data acquired in a multislice helical scan. More specifically, a helical weighting factors is generated and then a modified weighting factor Wm(.beta.,.gamma.), which is a shifted and weighted average version of the helical weighting factor, is generated. The modified weighting factor is then applied to projection data.

Abstract: Row variable offsets in a large area solid state x-ray detector are compensated for. Initially, a calibration is performed to determine the row variable offsets. The calibration is achieved by measuring the average offset of each row. During normal operation, this offset is compensated for in a converting circuit. The required signal range of the converting circuit is consequently reduced.

Abstract: A method is provided for rapidly measuring change in T.sub.2 * in a region of an MR imaging subject, the method employing a double gradient echo sequence with spiral readout. In this technique, two gradient echoes are acquired after a single RF excitation. A first readout trajectory spirals out from the center of k-space, i.e., k.sub.r =0, to some maximum radius, and then a second readout trajectory spirals back towards the center of k-space. A gradient echo is formed each time a k-space trajectory passes through the center of k-space. The signal intensity of the two echoes allows the calculation of the T.sub.2 * values on a pixel by pixel basis. The ability to measure changes in T.sub.2 * allows measurement of change in perfusion to be quantified.

Abstract: A method to provide large sheets of Nb.sub.3 Sn superconducting material suitable for use as a superconducting gradient shield in a magnetic resonance imaging system magnet by heating an anodized Nb-1 Zr sheet, tin dipping and reacting the sheet, and subsequently quenching the sheet in a purged atmosphere to provide an improved time constant and lowered Jc heating when used in a superconducting magnetic field.

Abstract: An ultrasonic transducer having reduced total electrical impedance is constructed by stacking a plurality of piezoelectric transducer element arrays on top of each other. For a given thickness, the electrical impedance of a multilayer stack of piezoelectric transducer element arrays is a function of the number of layers. If the number of layers equals two, then the electrical impedance of the total stack-up of layers is reduced by a factor of one-quarter relative to the electrical impedance of a single layer of equal thickness. This facilitates matching the overall transducer impedance to that of the connecting cable.

Abstract: The present invention, in one form, is a method for enhancing image sharpness in images generated from CT scan data by using enhancement masks. The enhancement masks are generated, in one embodiment, by generating difference image data from the original age data and low pass filtered image data. The original image data CT numbers are assigned to image regions, e.g., bone, air, and soft tissue, and based on such CT number classifications, certain data in the difference image is fully or partially suppressed. Subsequent to suppressing some difference image data, the difference image data set, which is sometimes referred to as an enhancement mask, is then combined With the original image data to increase image sharpness.

Abstract: A method for making a rotating X-ray tube provides a rotating anode having an integral stem. Initially, a cathode which emits electrons is provided. Next, a preheated anode target which radiates x-ray in response to bombardment by the electrons is provided. The method further comprises the steps of providing an anode stem and inertia welding the preheated anode target to the anode stem to form a rotating anode with an integral stem.

Abstract: An electrophysiology table includes a dual section table top comprising a pair of elongated planar sections in superimposed planar to planar relationship. One of the table top sections is adapted to be manually moveable axially horizontally over the other section, the other section is electric motor powered for axial horizontal motion to advance the dual section table top to a new position where the manual moveable section is optimized. The table is also adapted to be vertically adjusted as well as to be tilted or angulated. With the two sections locked, the motorized section may move the table along the tilt slope.

Abstract: Apparatus 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: The present invention, in one form, is a method for determining and applying a ZCAL correction vector to the channel outputs from the detector array in a multi-slice CT system. More specifically, and in accordance with one embodiment of the present invention, the signal gain for each detector cell, or channel, at multiple z-axis locations is measured. For each channel, a correction polynomial Q.sub.n is fitted to the signal variation curve as a function of z-axis position so that the correction polynomial value multiplied by its channel signal produces a constant value over the operational range of z-axis positions. Beam positions (Z.sub.r) are measured as a function of each position reference signal (D.sub.r) and the Z position of the beam at the sensor channel and the location of the focal spot are determined. The z-axis location for each channel and the ZCAL correction vector are then determined. The ZCAL correction vector is then multiplied by the channel signal to calibrate the channel signal.

Abstract: A compound lens for focusing ultrasound emitted from an ultrasound probe having an array of piezoelectric transducer elements. The compound lens has an inner lens part with a convex cylindrical front face and a rear face which is acoustically coupled to the front face of the transducer array, and an outer lens part with a concave cylindrical rear face which is acoustically coupled to the convex cylindrical front face of the inner lens part. The inner lens part may be in the form of a conventional silicone rubber focusing lens. The outer lens part is made of an acoustic medium having a higher acoustic velocity and greater durability than silicone rubber, e.g., polymethylpentene, nylon and high-density polyethylene. Also the outer lens part has greater chemical resistance than silicone rubber.

Abstract: A brightness detector is used to control the x-ray exposure and the displayed image level in a diagnostic x-ray imaging system. Initially, a region of interest of an image is specified. The average pixel value within the specified region of interest of the image is then found, ignoring regions below a preselected low signal level threshold. Finally, the average pixel value is fed back to the x-ray generator to control the x-ray exposure. The average pixel value is also used to determine a scaling factor to be applied to the image in order to maintain an optimum brightness level when the desired x-ray exposure cannot be attained.

Abstract: A superconducting magnet shield includes a plurality of overlapping NbTi sheets welded together with a plurality of welds extending along elongated parallel slots in the overlap region with the slots extending in the direction of superconducting current flow.

Abstract: A container of ultrasound coupling medium, used in conjunction with an ultrasound imaging system, is stored for operator convenience and patient comfort. Initially, at least one location on the ultrasound imaging system is identified, which has a predetermined thermal profile. The container of coupling medium is then stored at any of the identified locations to maintain the coupling medium at a desired temperature.