Abstract: A rotatable gantry portion (16) is rotatably mounted on the stationary gantry portion (18) of a SPECT camera. A plurality of radiation detector heads (10a, 10b, 10c) are mounted to the rotating gantry. A transmission radiation source holder and collimator assembly (40, 42) is mounted to the rotatable gantry portion opposite one of the detector heads. A transmission radiation source (60) is mounted in a lead shield (62) with an opening (64) pointing toward an examination region (12). A shutter (66) is rotatable between a closed position in which a lead arc segment (70) blocks the opening (64), a calibration orientation in which tin (72) covers opening (64), and an open position in which an opening (74) is aligned with the opening (64). A safety interlock means (80) locks the shutter in the closed position and against rotation when the radiation source holder is removed from the rotatable gantry portion. A collimator (42) has lead side walls (200) and tin or tin alloy septa (202).

Abstract: A toroidal x-ray tube (I) is supported and selectively positioned by a gantry (II). The x-ray tube includes a toroidal housing (A) in which a rotor (30) is rotatably mounted. One or more cathodes (C) are mounted on the rotor for generating an electron beam which strikes an anode (B) to generate a beam of x-rays which passes through a window (20) and strikes an annular ring of detectors (160). A grid bias control circuit (100) selectively applies a continuously adjustable bias to a grid (36) for regulating the electron current, hence the intensity of the x-ray beam. A scintillating optical fiber (110) extends around the exterior of the window. The scintillation optical fiber includes fluorescent dopant (116) which convert a very small fraction of the x-rays into optical light which is transmitted along the fibers to an opto-electric transducer (118). The opto-electric transducer is connected with the grid bias control circuit.

Abstract: A primary gradient coil assembly (22) is mounted in the inner bore or cylinder (20) of a vacuum dewar (18) that surrounds a superconducting magnet assembly (10). A pair of end ring assemblies, such as electrically conductive lapped segment loops (38) are supported by the gradient coil assembly (22). The end ring segments are capacitively coupled. A plurality of removable radio frequency coil element assemblies (40) are selectively attached to and detached from the gradient coil assembly. Each of the removable RF coil element assembly includes a dielectric housing (50), a longitudinally extending conductor element (52), an electrical connector (44), and circuit components (54) which connects the longitudinal conductor element with the electrical connector. The connector is electrically connected, at radio frequencies, with the ring assembly (38). A mechanical interlock (60) mechanically locks and selectively releases the removable element assemblies (40) to the gradient coil assembly.

Abstract: A magnet assembly (10) generates a temporally constant magnetic field through a central bore (12). A whole body gradient coil assembly (30) and a whole body radio frequency coil (36) are mounted in the central bore. A insertable gradient coil assembly (40), such as a head gradient coil, is selectively insertable into and removable from the bore (12). The insertable gradient coil assembly generates linear magnetic field gradients (90) within its bore for encoding magnetic resonance excited and manipulated by radio frequency signals from the whole body radio frequency coil. In regions (96) outside of the insertable gradient coil, the insertable gradient coil produces magnetic field gradients of the same strength as magnetic field gradients generated within its bore. Resonating dipoles within regions (96) contribute encoded magnetic resonance signals which are indistinguishable from the encoded magnetic resonance signals generated from within the insertable gradient coil bore.

Abstract: During a cardiac cine examination, a multiplicity of imaging sequences, each about 20 msec long, are applied following the R-wave. Each imaging sequence includes a saturation portion in which a bi-modal pre-saturation pulse (38) and a spoiler gradient (56) are applied. The bi-modal RF pulse has a relatively low tip angle, about 50.degree., but is repeated sufficiently often that blood in regions (30a, 30b) parallel to a selected slice (32) are driven toward saturation. Each imaging sequence further includes a gradient echo or other conventional imaging sequence during an imaging portion to generate magnetic resonance data (60). Each imaging sequence is repeated twice for each temporal interval with the same phase encoding, but once with the relative phase of the signal in the slice and the relative phase of the signals from within the pair of regions (30a, 30b) reversed. These two signals are combined such that the signals from within the slice add and the signals from with the pair of regions subtract.

Abstract: An x-ray source (14) is rotated along a non-circular path (18) to irradiate a subject in an examination region (10) with a fan beam (16) of radiation. Radiation detectors convert rays of the fan beam which have traversed the examination region into electronic data which is stored as data fans in an initial data memory (22). Each data fan is zero-filled (24) and convolved by a convolver (30). Preferably, the convolver transforms each data fan into Fourier-space (32), filters each data fan in Fourier-space with a roll-off filter (36), and converts the filtered data fan back from Fourier-space (38). Each fan is weighted (42) by a 1/cos weighting function and stored in a weighted data memory (44). Rays which are redundant in a 180.degree.+ fan reconstruction are removed (46) from the convolved data fans. A pixel driven backprojector (50) backprojects each convolved and redundant ray removed data fan into an image memory (56).

Abstract: A toroidal x-ray tube housing (A) is composed of multiple sections which are clamped together and sealed by elastomeric gaskets (128). An annular anode (B) is mounted to the housing with coolant passages (12, 14) extending thereadjacent. A rotor (30) is rotated within the toroidal housing by a motor (60). At least one cathode assembly (C) is mounted to the rotor adjacent the anode. The rotor is supported by magnetic bearings (40) whose active coils are separated from the vacuum region by a magnetic window (48). Alternately, a series of vanes (136, 138) are provided to divide the vacuum chamber into a high vacuum region (132) adjacent the cathode and anode and a low vacuum region (134) adjacent the motor (60) and bearings (40, 150, 152) for rotatably supporting the rotor within the housing. An active vacuum pump, preferably a ion pump (112) and a getter (114) are hermetically sealed into the vacuum region for maintaining the vacuum.

Abstract: A time-delay and integration camera assembly (A) is mounted to view a rotating or other cyclically moving object (B). A lens (30) focuses light from a field of view (10) onto an array (32) of light sensitive elements having N lines of elements. A tachometer (50) monitors rotation of the rotating object and a timing control (54) causes a light sensitive array control (34) to start stepping lines of data along the lines of light sensitive elements toward a shift register (36) as a leading edge (20) of a region of interest (12) enters the field of view. Each time the region of interest moves 1/Nth of the way across the field of view, the lines of data are stepped another time along the lines of light sensitive elements. Digital video signals are sorted (74) among a plurality of image memories (76.sub.1, 76.sub.2, . . . , 76.sub.M) each image memory corresponding to a corresponding region of interest (12.sub.1, 12.sub.2, . . . , 12.sub.M).

Abstract: A magnetic resonance gantry (A) includes a magnet (12) which generates a uniform magnetic field in a thin (under 15 cm thick) imaging volume (10). Gradient coils (30) and radio frequency coils (20) transmit radio frequency and gradient magnetic field pulses of conventional imaging sequences into the imaging volume. A patient support surface (42) moves a patient continuously through the imaging volume as the pulses of the magnetic resonance sequence are applied. A tachometer (52) monitors movement of the patient. A frequency scaler (54) scales the frequency of the RF excitation pulses applied by the transmitter (22) and the demodulation frequency of the receiver (26) in accordance with the patient movement such that the selected slice moves in synchrony with the patient through the imaging volume. The slice select gradient is indexed after magnetic resonance signals to generate a full set of views for reconstruction into a two-dimensional image representation of the slice are generated.

Abstract: A magnetic resonance imaging machine includes a toroidal vacuum dewer (24) which contains a superconducting magnet (10). A radio frequency coil (32) is mounted within a cylindrical bore (26) of the vacuum dewer. A cylindrical, dielectric former (46) supports an RF shield (34), a z-gradient coil (50), an x-gradient coil (52), and a y-gradient coil (54). The x and y-gradient coils are each composed of four like spiral coil constructions. A metallic layer is cut with cut lines (64) to define a generally spiral coil winding pattern. In a high current density region (68) in which the coil windings are narrower than a preselected width, the cut lines (76) are thinner. In lower current density regions (70), the cut lines (78) are thicker. In lower current density regions, two cut lines are defined between adjacent coil windings such that the coil windings are limited to a maximum width.

Abstract: A probe (3) for use in in vivo imaging of a microscopic internal region (1) of a patient's body using magnetic resonance techniques incorporates a member (7) having a surface having a pattern of projections (9) formed thereon. In use the surface contacts the surface of the region to trap between the projections molecules in the region, thereby to restrict diffusion of the molecules and so improve resolution of the image obtained.

Abstract: The magnetic field assembly of a magnetic resonance imaging device includes an annular superconducting magnet (10) which is mounted within a toroidal vacuum vessel (24). A cylindrical member (26) defines a central bore through which the superconducting magnets generate a temporally constant primary magnetic field. A cylindrical, dielectric former (46) is mounted in the bore displaced a small distance from the cylindrical member. A radio frequency coil (32) is mounted within the cylindrical member defining a patient receiving examination region. An RF shield (34) is mounted around the exterior peripheral surface of the former. Primary gradient coils (40) are mounted around and potted to the exterior of the dielectric former around the RF shield. Gradient shield or secondary coils (44) are potted around an exterior of the cylindrical member within the vacuum chamber. As illustrated in FIG.

Abstract: A subject in an examination region (14) moves axially as an x-ray source (12) rotates therearound. Views corresponding to a spiral path around a volume of interest in the patient are sampled, interpolated (46), and reconstructed (54) into a three-dimensional image representation (56). This process is repeated a plurality of times to generate a plurality of three-dimensional image representations of the same volume at time displaced intervals. The plurality of image representations are temporally interpolated (110) to generate a series of image representations, each one of which represents the same time or time interval, i.e., a four-dimensional image representation that is linear in all four dimensions. Preferably, a contrast agent is injected into the patient such that the data represents the movement of contrast agent through the volume of interest.

Abstract: A quadrature multiple coil array (30) includes a plurality of quadrature coil pairs (50.sub.1, 50.sub.2, . . . , 50.sub.n). Each coil pair includes a loop coil (50) or other coil which is sensitive to radio frequency signal components that are perpendicular to the coil and a flat Helmholtz coil (54) or other coil which is sensitive to radio frequency components parallel to the plane of the coil. The coils of each of the quadrature coil pairs are overlapped (56) by an amount which minimizes coupling between the coils. This enables resonance signals to be picked-up concurrently in quadrature by each of the quadrature pairs and be demodulated by a corresponding series of receivers (32.sub.1, 32.sub.2, . . . , 32.sub.n). The data from the overlapping regions to which each quadrature pair is sensitive are reconstructed (36) into image representations (38). The image representations are aligned either automatically (40) or by the operator and displayed on a video monitor (44).

Abstract: A toroidal vacuum dewer (22) holds a superconducting magnet assembly (10) which generates a substantially temporally constant magnetic field through a central bore (12). A whole body gradient coil (30) and a whole body RF coil assembly (32) are mounted to a cylindrical member (24) of the dewar. An insertable gradient coil assembly (40) is selectively insertable into and removable from the bore. The insertable gradient coil assembly includes gradient coils for selectively generating magnetic field gradients along three mutually orthogonal axes, e.g. x, y, and z-axes. A flexible cable (42) connects the insertable gradient coil with a series of current amplifiers (44). The current amplifiers selectively generate current pulses which are fed along feed conductors (84) of the coil assembly and which return along return conductors (86) of the cable. The feed and return conductors are configured such that the net feed and the net return current traverse the same effective path in opposite directions.

Abstract: A housing (A) which has a radiation transmissive window (52) defines a coolant oil reservoir (50). An x-ray tube (B) is mounted within the cooling oil reservoir. The x-ray tube includes a vacuum envelope having a cylindrical wall portion (10). A cylindrical sleeve (70) is mounted around the cylindrical wall (10) defining a narrow coolant oil gap (100). In one embodiment, a motor (16) rotates the vacuum envelope and an anode (14). The cylindrical sleeve (70) and the cylindrical rotating vacuum envelope wall portion (10) with the cooling oil film in the gap define a journal bearing which minimizes the horsepower requirements of the motor (16). A diaphragm (102) is expanded to reduce the thickness of the coolant oil film in the journal bearing gap. The cylindrical sleeve (70) is preferably constructed of a radiation blocking material such that the body of coolant oil (50) is shielded from x-rays (42).

Abstract: A source (A) of images, such as a CT scanner (10), a magnetic resonance imaging apparatus (12), and the like produces a plurality of basis images (I.sub.0, I.sub.1, I.sub.2, I.sub.3 . . . ). Two of the basis images are subtracted and divided (70, 72) by a number of interpolation increments (L.sub.1) to form a first differential image (I.sub..DELTA.1). The first and the third basis images are subtracted and divided (76, 78) by a number of available interpolation increments (L.sub.2) to form a second differential image (I.sub..DELTA.2). Four differential images are selectively combined and divided by a product of the first and second available increments (82, 84) to form a second order differential image (I.sup.2.sub..DELTA.12). An array of adders (D) selectively adds the first differential image to a currently displayed image stored in an image memory E each time a track ball (104) moves a cursor one increment in a horizontal position.

Abstract: A radio frequency signal detector coil arrangement (17) for a magnetic resonance apparatus comprising a planar coil (25) and an annular magnetic flux rejecting arrangement (25) disposed coaxially with the planar coil, on one side thereof, which reduces the sensitivity of the planar coil to signals from sources remote from the axis of the planar coil. One embodiment of the flux reducing arrangement comprises an annular superconducting member (35) disposed between the planar coil and the body (31). In other embodiments it comprises an arrangement of coils which conform to a tubular surface coaxial with the planar coil, and electrically connected therewith.

Abstract: An image intensifier 18 is comprised of an evacuated chamber, an input surface 16 having a florescent material thereon for converting incident radiation into a visible light representative of the incident radiation, a photocathode layer 20 disposed closely adjacent the input surface for emitting a cloud of free electrons 22 into the evacuated chamber in proportion to the intensity of visible light at each point thereon, and an output surface 26 having a scintillating material thereon for converting electrons impinging thereon into a relatively bright light image proportional to the electron energy at each point on the output surface said light image having a first aspect ratio. An electrical potential 24 accelerates the free electrons from the photo-cathode to the output surface. A fiber optic bundle 28 comprised of an input face, positioned outside the chamber to view the bright light image at the output surface, and an output face 34 is provided.

Abstract: A radiographic imaging system is comprised of a radiation source 12, a radiation adsorbing grid assembly 18, an image producing element 22 a controller 34, an exposure sequence start means 28 and a grid assembly oscillation means 20. The radiation source and grid define a subject receiving gap, wherein an object under examination is disposed, and through which the source propagates a beam of radiation onto the face of the image producing element. The controller recognizes when the exposure sequence start means is activated and starts the exposure sequence. The exposure sequence is comprised of an exposure preparation interval and an exposure interval. The exposure preparation interval is comprised of a radiation source preparation time and a point-in-time when the grid assembly oscillation commences oscillating the grid assembly.