Abstract: A localized coil (30) is disposed in the temporally constant magnetic field of a magnetic resonance imaging system. The localized coil is designed in five steps: a static problem formulation step, a static current solution step, a discretization step, a current loop connection step, and a high frequency solution step. One radio frequency coil designed by this process to be carried on a circularly cylindrical former includes two coil sections (60, 62) disposed on opposite sides of the dielectric former. Each of the two coil sections includes a pair of inner loops (64.sub.1, 64.sub.2) disposed symmetrically relative to a z=0 plane of symmetry and a second pair of loops (68.sub.1, 68.sub.2) also disposed symmetrically about the plane of symmetry. To raise self-resonance frequency, the inner and outer loops are connected in parallel. The resonance frequency is fine-tuned with reactive elements (66.sub.1, 66.sub.2).

Abstract: A volume image memory (24) stores an electronic image representation of a volumetric region, such as the volumetric region examinedby a medical diagnostic scanner (10). A sub-region of interest of the volume is selected (30) and the surface of the selected region or object of interest is divided into triangular surface regions with a triangular surface processor (38). A vertex merging processor (40) examines the triangles to locate vertices spaced by less than a preselected minimum. Vertices closer than the preselected minimum are replaced with a vertex at a median position merging the triangle into adjacent triangles. A vertex removal processor (50) identifies groups of triangles having a common vertex (V.sub.c) that form a pyramid. The surface normals (N) of the triangles which define the pyramid are examined to determine whether they are within a preselected deviation of parallel. The altitude of the pyramid, i.e., a distance between the common vertex and an average plane (P.sub.

Abstract: An exoskeleton material (12), such as a thermoplastic mesh, is heat softened. The heat softened material is stretched over and conformed to a soft tissue region of the patient, such as a patient's breast. The material is allowed or caused to set or harden and is affixed (14) to a patient support (10) such that the soft tissue is firmly constrained. Magnetic resonance visible markers (18) are affixed to the exoskeleton material adjacent the soft tissue. The patient is examined with a magnetic resonance imaging device (20) to generate a three-dimensional image representation (28) for display on a monitor (32). Using the markers, a wand (40) with emitters (42) receivers (44), and a coordinate system relationship processor (48) determines, a relation or transform between a coordinate system of the patient and a coordinate system of the image is determined and displayed on the monitor. A trajectory for a biopsy, resection, or the like, is planned using a guide (50).

Abstract: A patient is positioned on a patient support (12) and a gantry (16) carrying an x-ray source (10) and a radiation detector assembly (14) are rotated around the subject. The detector assembly includes a video camera (28) which is run in a synchronous mode to generate a first plurality of images at regular temporal intervals T.sub.blanking. Because each image requires a finite time for generation, it is acquired over an interval of arc between a starting angular orientation (A.sub.S .degree., B.sub.S .degree.) and a terminal angular orientation (A.sub.T .degree., B.sub.T .degree.). A position encoder (40) monitors the terminal positions of each of the first series of images. The patient is then injected with a radiographic dye and the gantry is rotated in a reverse direction. A comparator compares the stored terminal angular positions of each forward direction image and the current angular position of the gantry.

Abstract: A magnetic resonance system is used to excite high .gamma. dipoles, such as hydrogen, and lower .gamma. dipoles, such as phosphorous, to resonate concurrently. A multiply-tuned radio frequency coil (40) is disposed around the region of interest. The multiply-tuned radio frequency coil is tuned to the resonance frequency of the high .gamma. dipoles and the resonance frequency of the low .gamma. dipoles. The coil has an inner coil section, defined by a first leg or ring (92) and a second leg or ring (94), which is tuned by added capacitance substantially to the resonance frequency of the low .gamma. dipole. A first outer coil section which is defined by a third leg or ring (90) and the first leg or ring. A second outer coil section defined by the second leg or ring (94) and a fourth leg or ring (96). The first and second outer sections, together with the inner coil section define a coil which has a co-rotating mode and a counter-rotating mode.

Abstract: A magnetic resonance imaging system includes a magnet system which includes pole pieces and an energizing coil. The end portions of the pole pieces are made from a material which, does not support eddy currents, such as insulated iron powder. An object to be imaged is placed in the gap between the pole pieces. A gradient coil system imposes desired gradient fields in the gap between the pole pieces. The gradient magnetic field sequences are controlled such that, for each gradient pulse or a particular polarity there is applied a compensating pulse of the same magnitude, but the opposite polarity. Each compensating gradient has an integral which is relatively small. Remanent magnetism in the end portions of the pole pieces is thereby substantially avoided.

Abstract: A ferromagnetic flux path (20) extends between pole pieces (30,32). A superconducting coil (62) in series with a persistence switch (64) encircles the flux path. A pair of resistive coils (50,52) are disposed one at each pole piece. The resistive coils are overdriven near to the point of thermal failure to produce a 0.5 T or other preselected field strength in a gap between the pole pieces. The persistence switch is closed to stabilize and hold the flux through the superconducting coil. The resistive magnets are ramped down or shut off. During imaging, a smaller amount of current is directed to the resistive coils to supplement and focus the magnetic field from the superconducting coil through the gap between the poles. In this manner, high strength magnetic fields are generated in the gap using a relatively inexpensive combination of resistive and superconducting coils.

Abstract: A gamma camera and a counterweight are mounted to a support structure. A motor causes the support structure to move about a pivot axis. A controller measures the rate of motion of the support structure and compares that rate to a predetermined rate. The controller causes a second motor to move the counterweight a distance based on the difference between the measured and predetermined rates. The process is repeated until the difference is less than a threshold value. In a second embodiment, the current drawn by the motor is measured. The controller causes the counterweight to move a distance based on the measured current. The support structure is rotated about an axis of rotation to a 90 degree position prior to moving the support structure and to a 0 degree position prior to moving the counterweight.

Abstract: A coil assembly (40) includes a first, birdcage type head coil assembly (42) dimensioned to receive a patient's head and a second, neck coil assembly (44) including an anterior coil portion (44a) and a posterior coil portion (44b) dimensioned to receive the patient's neck region. The head and neck coils are partially overlapped. A first cable extends (98a) from the anterior coil portion past the birdcage head coil assembly and a second coaxial cable (98b) extends from the posterior portion past the birdcage head coil assembly. A first decoupling circuit (104a) is disposed in the first coaxial cable beyond a guard ring (106) and a second decoupling circuit (104b) is disposed in the second coaxial cable adjacent the region of overlap between the head and neck coil assemblies. The decoupling circuits are positioned and tuned to prevent radio frequency communication along the coaxial cable sheath between the head and neck coil assemblies.

Abstract: Radiation indicative of an object being imaged is detected and a data set indicative of the detected radiation is generated. Negative cells within the data set are located and ordered for processing. A negative cell is selected for processing. A mask region is defined in relation to the selected cell, and positive cells within the mask region are identified. A correction factor is determined, the value of the positive cells is adjusted accordingly. The value of the selected cell is also adjusted so that the count value of the data set remains constant. If the value of the selected cell is still negative, new correction factors are determined and the values of the positive cells and the selected cell are again adjusted. The process is repeated until all of the negative cells within the data set have been processed. An image indicative of the object is then generated.

Abstract: A magnetic resonance imaging apparatus includes main field coils (10) for generating a temporally uniform magnetic field longitudinally through a central bore (12). A whole body gradient magnetic field coil (30) and radio frequency coil (36) are disposed around the bore. An insertable coil assembly (40) includes an insertable gradient coil, a radio frequency coil (74) and a radio frequency shield (76). The insertable gradient coil includes a pair (62, 64) of x-gradient windings (FIGS. 3 and 4), a pair (66, 68) of y-gradient windings (FIGS. 5 and 6), and a pair (70, 72) of z-gradient windings (FIGS. 7 and 8), which are wrapped around inner and outer surfaces of a dielectric former (60). The x, y, and z insertable gradient coil pairs are configured such that they generate uniform magnetic field gradients within the insertable coil assembly when its central axis is positioned transverse to the direction of the temporally uniform magnetic field generated by the main field coils.

Abstract: When a magnetic resonance imaging sequence is retrieved from memory (58), one of the slice select, phase-encode to read gradient profiles are retrieved for one of the slice select, phase-encode, read gradients. The two gradient profiles have a common field of view if a read gradient or slice thickness if a slice select gradient, but have different motion sensitizations. The reference gradient profile G.sub.1 stored in a memory (52) and the motion sensitized gradient profile G.sub.2 stored in a memory (56) are weighted (60, 62) by weighting functions .alpha..sub.1, .alpha..sub.2 which are selected in accordance with the selected motion sensitivity and a selected one of the field of view or slice thickness. The weighted profiles are combined (64) to generate a motion sensitized gradient with the selected motion sensitivity, field of view or slice thickness.

Abstract: One or more time delay and integration camera assemblies (A) are mounted in a housing (100) which is rotated by a motor (40, 106) relative to a vertical axis. A tachometer or encoder (44) produces signals whose frequency or voltage varies in accordance with an angular velocity of the camera assemblies about the vertical axis. A clock generator (46) converts the angular velocity signals into clocking signals for controlling movement of vertical lines of data values (20) along an array (14) of light sensitive elements to a shift register (22). In one embodiment, the clock generator includes a divider (82) which converts the angular velocity signal into a voltage, a comparator (84) which compares the first voltage with a second voltage, and a voltage controlled oscillator (88) which oscillates to generate the clocking signal. A second divider (88) defines a feedback loop between the output of the voltage controlled oscillator and the comparator for generating the second voltage.

Abstract: A SPECT system includes two or more radiation detector heads (32) and (34) which are mounted opposite each other to a gantry (30) for rotation about a subject. Each detector head has a collimator (38) mounted in front of the detector head. The collimator (38) is separated into a top portion (40) and a bottom portion (42). The top portion (40) and bottom portion (42) are spaced from each other to provide a gap (44) within the collimator (38). The gap (44) receives one or more devices to provide additional functionality during a scan. The insertable devices include a transmission radiation source (52), a calibration source, a radiation filter, and others.

Abstract: A subject receiving bore (12) of a magnetic resonance apparatus has an axial length to diameter ratio of less than 1.75:1 and preferably about 1:1. The temporally constant magnetic field generated by superconducting magnets (10) surrounding the bore has various magnetic field harmonic distortions including a Z12 harmonic distortion which is described generally by the equation Z.sup.12. In long bore magnets with a length to diameter ratio of 2:1 or more, harmonic distortions above Z6 are not present, or if present, not measured. A magnetic field probe (80 ) measures the magnetic field in the bore at a sufficient number of axial locations to measure at least the Z12 harmonic, e.g., 24 axially displaced locations. The probes are sampled at a sufficient number of angular increments, e.g., 32-36, that any present transverse spherical harmonics are sampled. Ferrous shims (62) are mounted in the bore in the pockets (58) of shim trays (44) to compensate for the Z12 and other sampled harmonics above Z6.

Abstract: A method of scatter correction for use with gamma cameras includes the steps of detecting and producing a first count value indicative of gamma radiation falling within a first energy range generally associated with a radionuclide photopeak. Gamma radiation falling within second and third energy ranges is also detected and a corresponding count produced. The second and third ranges are above and below the photopeak, respectively. The location of the second and third energy ranges is determined based on the energy resolution of the gamma camera such that a predetermined percentage of the radiation falling within the second and third ranges results from primary radiation. The second and third energy ranges may be located such that they are non-contiguous with the first energy range. Based on the count of radiation falling within the second and third ranges, the scatter radiation falling within the first energy range can be estimated, and the first count value corrected.

Abstract: A two-dimensional radiation detector (30) receives divergent ray penetrating radiation along conical or pyramidal ray paths which converge at an apex. The radiation may emanate from one or both of an x-ray tube (16) or radionuclei injected into a human subject. As the radiation detector rotates around the subject, it is repeatedly sampled to generate two-dimensional data sets h.sub.t (u,v) at each of a plurality of samplings t. Each two-dimensional data array is weighted (44) and divided into two components. A first component processor (48) convolves a first component of each two-dimensional array with respect to u for each v. A second component processor (50) processes a second component of each two-dimensional array (FIG. 6) including weighting each component with a geometrically dependent weighting function W from a weighting function computer (46). The processed first and second components are combined (52) and backprojected (54).

Abstract: A sequence control (40) causes a transmitter (24) and gradient amplifiers (20) to transmit appropriate radio frequency excitation and other pulses to induce magnetic resonance in selected dipoles and cause the magnetic resonance to be refocused into a series of echoes following each excitation. A receiver (38) converts each echo into a digital data line. Each data line is regridded (70) for uniformity in k-space (FIG. 4). The data lines are one-dimensionally Fourier transformed (72) in a frequency encode direction. The one-dimensionally Fourier transformed data lines are multiplied (80) with a phase correction vector. A phase correction vector determining system (82) determines a corresponding phase correction vector for each echo number or position following excitation from a series of calibration echoes. To compensate for a decrease in magnitude with echo position following excitation, the intensity of each data line is scaled (90) to a common magnitude.

Abstract: A scintillator crystal (22) for a diagnostic device (10) has a reflective surface which is dynamically adjustable. Radiation (42) from a diagnostic scan enters a detector (14a, 14b, 14c) and strikes the scintillator crystal (22). The scintillator crystal (22) converts the radiation into a plurality of scintillations or light photons (26) which travel in all directions. A plurality of photomultiplier tubes (30) are optically coupled to an optically transmissive plate (28) which is optically coupled to an exit surface of the scintillator crystal. The entrance surface of the scintillator crystal is polished and laminated with a liquid crystal layer (54). The liquid crystal layer has light dispersion and reflectivity properties which are dynamically adjustable in response to electrical (62) or chemical stimuli.

Abstract: A superconducting magnet (10) generates a uniform, static magnetic field through a central bore (12) along its longitudinal or z-axis. An insertable coil assembly (40) is inserted into the bore with a radio frequency shield (76, 84) for providing a radio frequency shield between the insertable coil assembly and a surrounding, whole body radio frequency coil assembly (32) and a whole body gradient magnetic field coil assembly (30). The insertable coil includes a gradient coil (44a) including conductors (52) mounted on a dielectric former (50) with a dielectric constant below 4.0. The conductors are relatively narrow and spaced relatively far apart to minimize capacitive coupling with a closely adjacent insertable radio frequency coil (70a). Filters (60, 64) are connected with the conductors of the gradient coil to prevent the gradient coil conductors from supporting radio frequency signals while permitting ready support of kHz frequency currents.