Abstract: In an x-ray imaging system, an x-ray detector assembly includes an x-ray detector and a support assembly secured to the x-ray detector for supporting an antiscatter grid assembly. The x-ray detector preferably includes a matrix of crystal detectors. The support assembly includes a foam bezel having one or more magnets disposed therein. The antiscatter grid assembly includes an antiscatter grid secured to a metal frame. The one or more magnets disposed in the bezel are situated so as to align with the metal frame of the antiscatter grid assembly when the antiscatter grid assembly is coupled to the x-ray detector assembly. The strengths of the one or more magnets are such as to allow the antiscatter grid assembly to be removably secured to the x-ray detector assembly. Alternatively, the one or more magnets may be secured to the metal frame of the antiscatter grid assembly and corresponding metal plates may be placed in the support assembly.

Abstract: A frameless stereotactic CT scanner includes a virtual needle display for planning image-guided interventional procedures. The virtual needle is useful for planning the introduction of an object such as a biopsy probe into a patient at an entry point along a trajectory to a target point within the patient. Using an imaging device, the patient is scanned to generate an image volume data set of an area of the patient. Using a stereotactic mechanical arm assembly mounted on one end to the imaging device, a surgical planning device is positioned adjacent the patient on the imaging device. A display includes a first transverse axial view of the patient taking through an image slice corresponding to the virtual needle entry point on the patient and, a second transverse axial view of the patient taken on an image slice of the image volume data set corresponding to a target point within the patient.

Abstract: A gamma camera system includes two or more radiation detector heads and which are mounted opposite each other to a gantry for rotation about a subject. A transmission radiation source assembly is mounted to the front face of at least one of the detectors and can be moved across the face of the detector. The source assembly includes a radiation attenuating housing, a leaded bronze source holder, and a radionuclide source. The radionuclide source is retained in a longitudinal groove disposed in the source holder. The source holder may be rotated into open, closed, and access positions. The transmission radiation emitted by the source assembly is directed across the examination region, attenuated by the subject, and detected by the opposed detector. The gamma camera system also includes a filter which selectively attenuates the transmission radiation to obtain a desired attenuation profile which prevents saturation of the opposed detector.

Abstract: A frameless stereotactic tomographic scanner includes an imaging device defining a coordinate system in scanner space (.PI.). A localizer device includes a base portion mounted in a fixed relationship to the imaging device and a free end adapted for selective movement into varied positions near a patient body disposed on the imaging device. A position transducer associated with the localizer device generates, in a localizer space (), localizer device tip location information as the localizer device is moved near the patient body. A localizer space to scanner space transform processor converts the localizer tip location information to converted localizer tip location information in an image space (). The imaging device is adapted to generate patient body image information in the image space () regarding the patient body disposed on the device. A display unit is included for displaying the patient body image information together with the localizer tip position information on a human readable display monitor.

Abstract: An endocavity RF coil assembly for an MRI apparatus includes a reusable probe (30). The reusable probe has a hollow outer cover (60) having a closed distal end and (62) an open proximate end (64). The distal end (62) is formed to fit into a cavity of a subject being examined. An active RF coil element (72) is rigidly formed about an internal sleeve (70) which is located within the distal end (62) of the outer cover (60). A tuning and matching circuit is disposed within the outer cover (60) on the proximate end (64) side of the active RF coil element (72). The tuning and matching circuit is arranged on a printed circuit board (74) and attached to the active RF coil element (72). An over-molded form (90) is connected to the proximate end (64) of the outer cover (60). The over-molded form (90) is arranged such that it seals the proximate end (64) of the outer cover (60) closed.

Abstract: A method of designing a shielded gradient coil assembly (22) for magnetic resonance imaging systems is provided. The gradient coil structure comprises two sets of primary gradient coils (60, 62) and a single set of a shielded (screening) coils (64). This configuration is suitable for MR applications utilizing a double duty gradient configuration including a high-efficiency primary coil set that enhances the performance of ultra fast MR sequencing while minimizing the dB/dt and eddy current effects, and including a low-efficiency primary coil set having a high-quality gradient field that is suitable for conventional imaging applications with inherently low dB/dt and eddy current levels. In addition, a minimum inductance/energy algorithm assists in the design of the two primary and the one secondary gradient sets.

Abstract: An alegebraic reconstruction matrix generator (90) generates an algebraic reconstruction matrix P. A gradient trajectory memory (94) contains elements k.sub.n which describe the k-space trajectory of a time-varying read gradient wave form. An A-matrix generator (96) generates a coefficient matrix A from the elements k.sub.n. A D-matrix generator (100) generates a diagonal matrix D having elements d.sub.n. Using the elements of matrices A and D, an H-matrix generator creates a matrix H. An inverter (110) inverts the matrix to obtain H.sup.-1. A transposer (112) transposes matrix A to obtain A.sup.T. A multiplication processor (114) combines H.sup.-1, A.sup.T, and D to obtain the algebraic reconstruction matrix P. A multiplication processor (122) then combines the matrix P and an array of image data lines b to generate an image matrix array X which is stored in an image memory (124). A one-dimensional column Fourier transform processor and associated memory (125) transforms and stores the image matrix array.

Abstract: Resonance is excited in a first slab (12) and manipulated to generate a plurality of data lines (16, 18) which span a fraction of k-space, e.g. a quarter of the phase encoding steps along a y-direction. Resonance is then excited in a second slab (22) displaced from the first slab and another series of data lines are generated. A resonance is excited and data lines generated in a plurality of additional slabs (32, 42). A resonance is excited in a slab (52) which partially overlaps the slab (12), e.g., has three of four slices in common. A series of data lines in the slab (52) are phase encoded with a different fraction of k-space. Two sets of differently phase encoded data sets have been generated in the example of FIGS. 2a and 2b.

Abstract: An x-ray tube includes an anode, a cathode, and an electrode disposed in an evacuated envelope. The electrode is positioned such that the electrode is remote from an area in immediate proximity to the envelope. An electric field defined by electrode is of sufficient strength such that arcing preferentially occurs between the electrode and the anode as opposed to occurring between the cathode and anode. The electrode is further situated such that metal sputtered from the electrode substantially falls in a define region on the anode and serves as an active getter for pumping gas from the envelope. The electrode is composed of an active metal which, upon being passively heated by the anode, also acts as a getter material to aid in pumping gas from the envelope.

Abstract: An x-ray tube is disposed within an x-ray tube housing defining a chamber filled with oil or other cooling medium for cooling the x-ray tube. The x-ray tube includes an envelope enclosing an evacuated chamber in which an anode assembly is rotatably mounted to a bearing assembly and interacts with a cathode assembly for production of x-rays. The bearing assembly includes a bearing housing and a plurality of bearings disposed on a surface of the bearing housing. A heat sink is coupled to the bearing assembly and provides a thermally conductive path between the bearing assembly and the cooling medium in the x-ray tube housing for providing direct cooling of the bearing assembly during operation.

Abstract: A gantry (10) includes a large diameter bearing having an outer race (12) and an inner race (16) which surrounds an examination region. An x-ray tube (18) and collimator (52) are mounted to the inner race, as is a flat panel detector (20) and a mechanical mechanism (50) for moving the flat panel detector closer to and further from the examination region. A timing and control circuit (30) controls a motor (22) which indexes the inner race around the examination region, an x-ray power supply (32) which pulses the x-ray tube in a fluoroscopic mode at discrete positions around the examination region, and a read out circuit (34) which reads out a frame of data after each pulse of the x-ray tube. The read out frames of data are stored in a frame memory (36) and reconstructed by a reconstruction processor (38) into a volumetric image representation for storage in a volume image memory (40).

Abstract: An imaging apparatus (18) includes a frameless stereotactic arm apparatus (30) including a first base portion (42) mounted in a fixed relationship to the imaging device. A second free end (40) of the arm assembly is adapted to move into varied positions near a specimen disposed on the imaging apparatus. At least one pivot joint (44, 48, 52, 56, 60) is provided between the first base portion and the free end of the arm for permitting selective relevant movement between the arm members. Electro-mechanical and electro-magnetic brake devices are provided at respective joints to selectively lock the free end of the arm assembly to the base portion. The brakes are responsive to a brake command signal (210) generated by the imaging device. A low pass filter (240) conditions the brake command signal to substantially eliminate high frequency electromagnetic switching noise in the stereotactic arm.

Abstract: A medical diagnostic imaging device (A) compensates for non-uniform line correlated noise generated in an image receptor (26). The image receptor receives x-rays transmitted from an x-ray source (12) and generates a raster line of image data. The image receptor includes an active area (30), a first reference zone (32) bounded on a first side of the active area, and a second reference zone (34) bounded on a second side of the active area opposite to the first side. The reference zones prevent image information from being received by corresponding pixels of the raster line. The outputs of a first plurality of raster line pixels corresponding to the first reference zone (32) are averaged, and the outputs of a second plurality of raster line pixels corresponding to the second reference zone (34) are averaged.

Abstract: A frame (A) of a diagnostic imaging device such as a CT scanner or an MRI device has a bore defining a patient examination region (12). A first x-ray source (B) is mounted to a frame (C) for rotation around the examination region (12). An arc of first radiation detectors (14) detects x-rays which have traversed the examination region. A first image reconstruction processor (18) reconstructs a tomographic image representation from signals generated by the first radiation detectors. A fluoroscopy device (D) is mechanically coupled to the diagnostic scanner for generating and displaying at least substantially real-time fluoroscopic projection image representations on a display monitor (60). A second x-ray source (32) transmits x-rays to an amorphous silicon flat panel radiation detector (36). A second image reconstruction processor (58) reconstructs the fluoroscopic projection image representations from signals generated by the flat panel radiation detector (36).

Abstract: A magnetic resonance imaging apparatus (10) includes a couch (54) for supporting a region of interest of a subject (44) being examined in an examination region. A main magnet for generating a substantially uniform temporally constant main magnetic field through the examination region includes a stationary pole piece (24), a movable pole piece (22), a ferrous flux return path (26), and a magnetic flux generator that selectively generates magnetic flux that flows between the pole pieces (22, 24) through the examination region and through the ferrous flux return path (26) which connects the pole pieces (22, 24). The stationary pole piece (24) is arranged adjacent a first side of the examination region.

Abstract: A less-claustrophobic, quadrature, radio-frequency head coil (42) includes first and second broken end rings (90, 92) connected to each other in parallel by a plurality of leg conductors (94). At least two of the leg conductors are interconnected by a third arcuate conductor segment (98) axially displaced from planes of the first and second end rings to provide an opening (44) over a subject's face. The opening reduces patient claustrophobia and permits access to the patient for life-support devices or the practice of interventional medicine. The end rings have a fixed capacitance (C.sub.1, C.sub.2) between each pair of leg conductors. The fixed capacitance C.sub.1 between at least one pair of leg conductors and the fixed capacitance C.sub.2 between at least the pair of leg conductors adjacent the opening, where C.sub.2 >C.sub.1. A two-port feed (66, 68) circumferentially attached to the coil generally opposite the opening matches the individual linear modes.

Abstract: A three dimensional magnetic resonance imaging technique is utilized to generate 1/Nth of a complete data set from a first selected slab (38a). The data set is complete in a read direction and a first phase encode direction and 1/Nth complete in a second phase encode direction. The selected slab is shifted by 1/Nth its dimension in the second phase encode direction and another 1/Nth complete data set is generated. This process is repeated until N data sets are generated. The N data sets are reconstructed into a slice image which slice images are stacked in a three dimensional final image memory (94) and which are projected (96) along a selected projection direction into a projection image (40). The process is repeated with each new data set replacing the oldest data set in memories (84.sub.1, 84.sub.2 . . .) to generate a stack of slice images which are projected into the projection image. At any time during the process, projection direction can be changed and the sliced data reprojected.

Abstract: A localized shim coil (34) for use in a magnetic resonance imaging system includes a plurality of conductive elements (22a-d). The plurality of conductive elements (62a-d) are connected to a current source (64). The plurality of conductive elements (62a-d) are arranged adjacent to a localized region of a subject being imaged such that current flowing through the conductive elements generates a localized magnetic field. A plurality of series connected choke and resister pairs (66a-d) and (68a-d), respectively, are connected to the plurality of conductive elements (62a-d). The chokes (66a-d) present high impedance to currents having frequencies substantially the same as a resonant frequency of the magnetic resonance imaging system. The resisters (68a-d) balance the current flowing through each conductive element (62a-d).

Abstract: An explosive forming process provides an anode (10) suitable for use in a high energy x-ray tube. The process includes applying a shaped charge (54, 80, 90, 92) to a refractory material which has been formed in the general shape of the anode. The configuration of the charge is calculated to provide a target area (16) on the anode of uniform, high density which does not tend to outgas in the high vacuum conditions of the x-ray tube. The explosive process is capable of forming anodes with much larger diameters than is possible with conventional forging techniques.

Abstract: A movable patient supporting portion (10) of a patient couch (A) includes a socket (26) for receiving a mating plug (24) on a localized coil (B). The patient couch selectively inserts the localized coil and a supported patient into a bore (14) of a cryogenic magnet system (C). The localized coil includes a resistor (86) whose magnitude identifies the coil. A coil identification interrogator (84) interrogates the coil identification resistor and derives a corresponding binary coil identification. The coil identification addresses a look-up table (90) to retrieve diagnostic test information, an identification of a coil for a human-readable display, and, preferably, an identification of an isocenter of the coil. A diagnostic test unit (92) electrically tests the coil through the plug and socket connection with the diagnostic tests prescribed by the look-up table.