Abstract: A transmitter (24) and gradient amplifiers (20) transmit radio frequency excitation and other pulses to induce magnetic resonance in selected magnetic dipoles and cause the magnetic resonance to be focused into a series of echoes (66) at each of a plurality of preselected echo positions following each excitation. A receiver (38) converts each echo into a data line. Calibration data lines having a close to zero phase-encoding are collected and used to generate correction parameters (102) for each of the echo positions. These parameters include relative echo center positions (96) and unitary complex correction vectors (106). The calibration data lines for each of the preselected positions are one-dimensionally Fourier transformed (82) and multiplied (90) by the same complex conjugate reference echo (80). These data lines are then inverse Fourier transformed (92) to generate an auxiliary data array (94).

Abstract: A flexible catheter or other object for insertion into an object is designed for use in connection with magnetic resonance (MR) imaging techniques. The catheter carries a closed loop coil arrangement tuned to the RF excitation frequency used in operation of an MR imager. The coil arrangement includes turns which lie substantially in non-parallel planes when the axis of the catheter is in a straight line. The coil arrangement may include two coils which are constituted by different sections of an electrically conductive track carried on a flexible, insulating substrate. According to another embodiment, the coil arrangement may comprise two separate closed loop tuned coils each constituted by a narrow metallized track carried on a flexible, insulating substrate. In another embodiment, the coil comprises turns of a saddle form.

Abstract: Radiation from a subject (18) which is received by a scintillation crystal (12) interacts with the scintillation crystal to produce a burst of scintillation light photons. The depth distribution at which the interaction occurs varies in accordance with the energy of the received radiation. Low-energy radiation tends to interact at a shallow depth relative to a front face of the scintillation crystal and radiation with a high energy tends to interact relatively deeply into the crystal. A moment processor (20) processes electronic information from photomultiplier tubes (14) which view the scintillation crystal to generate zero-th moment or energy information, first moment or coordinate information and second moment or depth information. The event information is filtered (34, 62, 66, 82) in accordance with depth (26), e.g., sorted into acceptable/unacceptable information, information corresponding to each of two or more energies of radiation, and the like.

Abstract: A magnetic resonance imaging apparatus includes a main field magnet (12) for generating a temporally constant magnetic field through an examination region. A radio frequency transmitter (84) excites and manipulates magnetic resonance in selected dipoles in the examination region. A receiver (90) demodulates magnetic resonance signals received from the examination region, a processor (74) reconstructs the demodulated resonance signals into an image representation. A plurality of fingerprint gradient magnetic field coils (24, 26) induce gradient magnetic fields across the temporally constant magnetic field. Each of the fingerprint gradient coils (24, 26) includes a generally spiral winding (32A-32D) having a first crossectional dimension (H) perpendicular to the temporally constant magnetic field which is at least twice a second crossectional dimension (W) in a direction parallel to the temporally constant magnetic field.

Abstract: A camera for use in coincidence imaging includes detectors (10a, 10b) disposed about an examination region (12). Coincidence logic (14) determines whether gamma rays are detected by each of the detectors (10a, 10b) occur within a specified time interval. If so, the energy and positions of the detected events are determined. Energy discrimination circuitry (20a, 20b) associated with each detector (10a, 10b) determines if the detected events fall within a specified energy window. A list mode processor (22) generates a list of coincidence events. A rebinning processor (24) rebins the events, and a weight processor (26) weights each coincidence event based on the energy of the detected gamma rays.

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). Two cylindrical members (26, 46) define an annular gap (58). A shim set (60) for shimming the uniformity of the magnetic field is mounted in the gap (58). The shim set includes a plurality of shim trays (62), each of which defines a plurality of shim receiving pockets (64). A bottom wall (81) of each pocket is spaced from the cylindrical member (26) by side walls (76) and feet (78) to minimized heat flow. Shim tray covers (68) have flanges (90) and narrow contact surfaces (94) which are cammed against surfaces (61) of spacers (56) to press the cover on the tray and the tray feet against the cylinder (26) while minimizing heat flow through the spacers to the shims.

Abstract: A sequence controller (40) controls the pulses applied by the radio transmitter (24) and the gradient amplifiers (20) and gradient coils (22) such that each repetition includes a prepreparation sequence segment, such as a presaturation sequence segment and a magnetization transfer contrast correction (MTC) segment, and a plurality of image sequence segments. More specifically, each of the image sequence segments induce resonance, phase and frequency-encode the resonance, and generate one or more views of data, all within a corresponding one of a plurality of slabs or sub-regions (74.sub.1, 74.sub.2, . . .) of an image volume (72). More precisely to the preferred embodiment, the imaging sequence segments interleave the slabs such that resonance is not excited concurrently in adjacent slabs, without exciting resonance and collecting a view in a non-adjacent slab. The views are sorted (80) by slab and stored in corresponding slab data memories (82).

Abstract: A subject's respiratory cycle is monitored (70) and analyzed (74) to determine a probability table (76). The probability table is continuously updated to provide a dynamic indication of the center between most stationary and most moving halves or other characteristic points within the respiratory cycle. At the beginning of each repeat time (TR), as resonance is excited (40), the output of the respiratory monitor is checked (80) and a determination is made (82) whether the patient is currently in the most stationary half or the most moving half of the respiratory cycle. Data lines generated in one half of the respiratory cycle are phase-encoded (84, 88) to generate a data line in each of a plurality of segments of k-space on one side of the central, zero phase-encoding point. Echoes occurring during the other half of the respiratory cycle are phase-encoded to generate data lines in segments of k-space on an opposite side of the central phase-encode angle.

Abstract: A multimode radio frequency coil (50.sub.1) receives resonance signals from a region of interest while allowing arbitrary placement of the coil. A peripheral electrical conductor (62) is divided into four symmetric segments by capacitors (76), (78), (80), (82). A pair of crossing conductors (64, 66) are connected between 90.degree. offset diagonally opposite portions of the peripheral loop (62). The crossing conductors include capacitors (68, 70) when not connected and include capacitors (68, 70, 86, 88) when connected at their midpoints. With this configuration, the coil supports orthogonal modes (72, 74) within the plane of the coil and, additionally, a third orthogonal mode (84) perpendicular to the plane of the coil. To image an extended region, a plurality of coils are overlapped to minimize mutual inductance relative to a first mode. An adjustable capacitor (90) across one of the coils adjusts mutual inductance relative to the second mode.

Abstract: An x-ray tube of CT or other radiographic scanner has a focal spot (30) from which x-rays with an energy distribution (32) are generated. As the x-ray source rotates a peak (34), the radiation energy distribution seen by each detector (24) through a physical collimator shifts. Each line of data generated by the detectors has a shifting energy distribution across its data values which creates artifacts in reconstructed images. A filter (50) includes a convolver (52) which convolves the lines of data with deconvolution functions from a memory (54) in a recursive loop (56) in accordance with a relative angular position of the x-ray tube and the corresponding detector. Filtered data lines are subtracted (56) from unconvolved data values to generate values with reduced off-focal radiation components. Filtered data is conveyed to a convolver (82) and a backprojector (84) which backprojects the data across an image memory (86).

Abstract: A latent image is formed on a stimulable phosphor plate (10) by irradiating the phosphor plate with x-rays from an x-ray source (14). To develop the stimulable phosphor plate, the plate is irradiated with light of a different wavelength from developer light source (32). The light from the developer light source causes the stimulable phosphor plate to give off light of yet another characteristic wavelength. Light from the stimulable phosphor plate is filtered (38) to remove the wavelength of the developer light and focused (42) on a light sensing element (46) of a time delay and integration video camera (34). The stimulable phosphor plate and the video camera are moved relative to each other and the rate of movement is monitored (60).

Abstract: A novel scatter filter for use in positron emission tomography which filters out deflected rays of energy due to Compton scattering which generally have a lower energy. The filter allows most of the undeflected rays to pass through by providing a layer of material having a particular density and atomic number between the detector and the source. Multiple layers of filters may also be provided to filter out characteristic x-rays from the first layer of filter.

Abstract: This invention addresses the practical implementation of PET imaging capability on a conventional gamma camera. The primary subject of this invention is the addition of a real time processor to perform the rebinning calculations and other on-the-fly calculations and procedures to make PET imaging on a gamma camera more practical. The rebinning or transformation operation described above is performed on-the-fly as each event pair is detected with an event throughput rate sufficient for clinical applications. This transformation process is performed by a chain of digital signal processing subsystems (or similar real time processors), with the resultant transformed data stored in a memory subsystem until a sufficient number of events have been received to produce an image of acceptable quality.

Abstract: A sequence control (40) causes a transmitter (24) and gradient amplifiers (20) to transmit radio frequency excitation and other pulses to induce magnetic resonance in selected dipoles and cause the magnetic resonance to be focused into a series of echoes in each of a plurality of data collection intervals following each excitation. A receiver (38) converts each echo into a data line. Calibration data lines having a close to zero phase-encoding are collected during each of the data collection intervals. The calibration data lines in each data collection interval are zero-filled (86) to generate a complete data set and Fourier transformed (88) into a series of low resolution complex images (90.sub.1, 90.sub.2, . . . 90.sub.n), each corresponding to one of the data collection intervals. The low resolution images are normalized (92) and their complex conjugates taken (94). Imaging data lines are sorted by a data collection interval and zero-filled (104) to create full data sets.

Abstract: A marker and probe for use in magnetic resonance imaging includes a vial for insertion within the body. The vial contains a material having a spin-lattice relaxation time less than that of the material of the body in a region being imaged. A coil arrangement having at least one coil tuned to the frequency of the magnetic resonance excited in the material during an excitation sequence is wound around the vial. The body is subjected to an T1 weighted examination sequence. The coil arrangement preferably has at least one turn which lies in a plane orthogonal to at least one other turn. Materials suitable for use in the vial include copper sulphate, iron chloride, or gadoliuium cholate. The vial consists of a material which does not exhibit a nuclear magnetic resonance spectrum.

Abstract: A CT scanner non-invasively examines a volumetric region and generates voxel values. A user adjustable 3D axis system defines mutually orthogonal sections and volume reprojections thus defining a cross reference relation between them. An affine transform translates and rotates the axis system from object space to image space whereby each axis defines the orientation of origin intersecting sections in one view port and the viewing direction of volume reprojections in another view port. An operator console selects an angular orientation of the coordinate axis. A cursor position designates coordinates in image space causing the cursor, typically crossed axes, to be displayed on a monitor at a corresponding location in each displayed image. The view port rotation and translation of the projected crossed cursors are reverse affine transformed to rotate and translate the axis system.

Abstract: A surface coil (26) is positioned against a subject in the image region to detect emanating radio frequency resonance signals. The detected signals are processed (52) into a magnetic resonance images representing the image region which include an image value for each of an array of pixel coordinates. There is a large change in magnitude between image values of pixels corresponding to the coil and adjacent pixels. Magnitudes and directions of pixel value change gradients are calculated (60) from the image values corresponding to pixels in each of a first set of magnetic resonance image slices representing axial and transaxial slices through the surface coil. A coordinate calculator (62) calculates image region coordinates corresponding to segments of the surface coil. From the image region coordinates of the surface coil segments, a surface coil sensitivity calculator (92) calculates coil sensitivity which is in turn used to enhance (94) the reconstructed images.

Abstract: A rotating gantry (20) is rotatably mounted to a stationary gantry for rotation around an axis of rotation. Gamma camera detector heads (22a, 22b, 22c) are mounted to the rotating gantry for rotation about a patient receiving region (14). A patient is supported on a first, cantilevered patient support portion (10) which is adjustable in height, and which selectively extends toward and away from a slab defined by the detector heads. In one mode of use, the first patient support portion (10) is supported on a second support surface (16) when fully cantilevered to minimize vibration and movement. In a second mode, the first patient support portion (10) is separated by a gap from the second support portion (16) and the region of interest of the patient is positioned over the gap. In this manner, radiation passing from the region of interest of the patient to the detector heads is not attenuated by a patient support structure. Further, the detector heads are mounted on tracks (30, 32) by rollers (44, 46).

Abstract: A gantry (18) that carries an x-ray source (14) and an x-ray detector (16) rotates around a test phantom (10) in a forward direction. A plurality of forward projection images are generated and stored in a forward image memory (42). The angle at which each forward direction projection image is generated is stored in a position memory (56). The gantry is then rotated in a reverse direction and a reverse direction image is generated at generally the same angular positions as in the forward rotation direction. The forward and reverse direction projection images of the phantom are analyzed to determine an offset or error between each corresponding forward and reverse angular image position. The offsets are stored in an angular position look-up table (80) and a pixel reregistration look-up table (82). In subsequent reverse scans, the angular position at which the reverse direction projection images are taken are altered in accordance with the angular offset for the corresponding angular position.

Abstract: An anode (16), (16') and a cathode (14), (14') are mounted in an evacuated envelope (12), (12') of an x-ray tube (10). One of the anode and cathode is rotatably mounted on bearings (20), (20') relative to the evacuated envelope. In the embodiment in which the anode is rotatably mounted relative to the evacuated housing, a rolling ring assembly (40) provides a current path from the anode through the evacuated housing to ground without the current path passing through the bearing (20). In this manner, pitting and other damage to the bearing due to arcing is eliminated. In the embodiment in which the cathode is rotatably mounted relative to the evacuated envelope, the anode and envelope rotate as the cathode is held stationary (58, 60). A plurality of rolling ring assemblies (40'.sub.1, 40'.sub.2, . . . ) provide electrical communication between electrical control circuitry disposed outside the rotating housing and the cathode assembly (14').