Abstract: A gradient coil assembly (22) generates substantially linear gradient magnetic fields through an examination region (14). The gradient coil assembly (22) includes a pair of primary gradient coil sets (22a, 22b) and a pair of shield coil sets (23a, 23b) which are disposed in an overlapping relationship. One gradient coil set is displaced relative to the other gradient coil set such that the mutual inductance between the two is minimized. Preferably, the coil sets (22a, 22b, 23a, 23b) are asymmetric, such that the sweet spot of each coil is displaced from the geometric center of each coil. One primary gradient coil set (22a) is a high efficiency, high switching speed coil to enhance performance of ultrafast magnetic resonance sequences, while the second primary gradient coil set (22b) is a low efficiency coil which generates a high quality gradient magnetic field, but with slower switching speeds.

Abstract: Interventional MRI imaging leads to the development of open magnets such as for example C-magnet 1, in which it is correspondingly more difficult to generate a large field in order to obtain a good signal-to-noise ratio. To overcome this, a pre-polarizing unit 7 is provided which utilizes a HTSC magnet, for example of YBCO, which is brought adjacent to the patient to assist in generating the main field, and then rapidly withdrawn to position 8, in order to enable the r.f. signals to be detected in the presence of the field of the C-magnet 1.

Abstract: A uniplanar gradient coil assembly (40) generates substantially linear gradient magnetic fields through an examination region (14). The gradient coil assembly (40) includes at least a pair of primary uniplanar gradient coil sets (40a, 40b) and a pair of shield coil sets (41a, 41b) which are disposed in an overlapping relationship. One gradient coil set is displaced relative to the other gradient coil set such that the mutual inductance between the two is minimized. Preferably, the coil sets (40a, 40b, 41a, 41b) are symmetric, such that the sweet spot of each coil is coincident with the geometric center of each coil. One primary uniplanar gradient coil set (40a) is a high efficiency, high switching speed coil to enhance performance of ultrafast magnetic resonance sequences, while the second primary uniplanar gradient coil set (40b) is a low efficiency coil which generates a high quality gradient magnetic field, but with slower switching speeds.

Abstract: The present invention is directed to an MRI apparatus. It includes a main magnet 12 that generates a substantially uniform temporally constant main magnetic field, B0, through an examination region 14 wherein an object being imaged is positioned. A magnetic gradient generator produces magnetic gradients in the main magnetic field across the examination region 14. A transmission system includes an RF transmitter 24 that drives an RF coil 26 which is proximate to the examination region 14. A sequence control 40 manipulates the magnetic gradient generator and the transmission system to produce an MRI pulse sequence, such as an FSE pulse sequence. The MRI pulse sequence induces magnetic resonance echos 66 from the object. A reception system includes a receiver 30 that receives and demodulates the echos 66 at varying sample rates and varying bandwidths.

Abstract: The present invention is directed to an MRI apparatus including a main magnet (12) that generates a substantially uniform temporally constant main magnetic field, B0, through an examination region (14) wherein an object being imaged is positioned. A magnetic gradient generator produces magnetic gradients in the main magnetic field across the examination region (14). A transmission system includes an RF transmitter (24) that drives an RF coil (26) which is proximate to the examination region (14). A sequence control (40) manipulates the magnetic gradient generator and the transmission system to produce an MRI pulse sequence. The MRI pulse sequence induces an initial set of contiguous spin echos and a subsequent set of gradient echos which stem from the object. A reception system includes a receiver (30) that receives and demodulates the spin and gradient echos.

Abstract: A penetrating radiation source (14) is disposed on one side of a object (10) which is on a object support (12). A flat panel radiation detector (18) is stationarily disposed on the opposite side of the object (10) than the source (14). A moving system (16, 50, 52) moves the source (14) with respect to the object (10). In each position (Xi, Yi, Zi) of the source (14) a center ray of the x-ray beam strikes the detector (18) at a corresponding location (xi, yi, 0). For each position (Xi, Yi, Zi) of the source (14), the image (xi, yi, 0) of an object located on a focal plane offsets by a vector displacement (Di) relative to a reference position (xo, yo, zo) of the image when the source is at (X0, Y0, Z0). A processor (28) shifts and interpolates each view by the different vector displacements corresponding to each of the focal planes (L1, L2, . . . ) and integrates the images to generate a series of slice image representations which are stored in a volume image memory (30).

Abstract: Methods of designing an active shield for substantially zeroing an electro-magnetic field on one side of a predetermined boundary in open magnetic resonance imaging systems and in open electric systems are provided. The methods include defining a finite length geometry for a primary structure which, in the case of zeroing a magnetic field, carries a first current distribution on its surface. A finite length geometry is also defined for a secondary structure which, in the case of zeroing a magnetic field, carries a second current distribution on its surface. In the case of zeroing an electric field, the current distributions are replaced with charge distributions. A total magnetic or electric field resulting from a combination of the first and second current or charge distributions respectively is constrained such that normal components (in the magnetic field case) or tangential components (in the electric field case) thereof substantially vanish at the surface of one of the primary and secondary structures.

Abstract: A CT scanner includes a stationary gantry (A) defining an examination region (12) and a rotating gantry (C) which rotates about the examination region. Multiple fan beam generators (B), each capable of producing a beam of radiation directed through the examination region, are mounted to the rotating gantry. The radiation beams are collimated (42) into a plurality of parallel thin fan shaped beams (301, 302, . . . 30n) that are projected through the examination region. X-rays are detected by at least an arc of x-ray detectors (14) or a plurality of parallel rings of detectors (141, 142, . . . 14n). The detectors generate signals indicative of the radiation received which are processed by a reconstruction processor (18) into a volumetric image representation for display on a monitor (20). In one embodiment, the signals are reconstructed into a series of spaced parallel slices. The object is indexed and additional slices are collected and reconstructed between previously reconstructed slices.

Abstract: An object (14) is positioned on an object support (16). A radiation source (10) projects a beam of radiation through a region of interest (12) of the object. A plurality of focal planes (F1, F2, . . . , Fn) mark the center of selected slice images through the region of interest. A gantry (20) rotates the radiation source (10) around a circular trajectory (22) as an encoder (26) monitors a radius (r) of the trajectory and an angular position (&phgr;) of the radiation source (10) around the trajectory (22). A look-up table (40) is addressed with the selected focal plane(s) (F1, F2, . . . , Fn) and (r, &phgr;) to generate a correction or shift value (S1, . . . , Sn.) for each selected focal plane (F1, F2, . . . , Fn). A flat panel detector (18) is read out a plurality of times to generate a plurality of electronic data views as the radiation source rotates.

Abstract: When imaging a region of a patient using a contrast agent, for example in magnetic resonance imaging apparatus including a superconducting magnet 2, it is usual to take an image before and after injection of a contrast agent from an injector 5 into the patient. The invention provides a second injector 8 which contains a sample of the patient's blood or saline or other injectable medium which leads directly to the region of interest being imaged in the patient via a catheter 9, which has an expandible tip which can be expanded to block off the vessel in question. The injector can then be used to inject a bolus of injectable medium into the region of interest, whereupon a further image can be taken, and the catheter can be collapsed to unblock the vein whereupon an image in the presence of the contrast agent can be taken.

Abstract: A pair of annular magnets (10) generate a vertical magnetic flux field through an imaging volume (12). The flux is focused by a pair of Rose rings (26) of high cobalt steel. A high order shim set includes a plurality of permanently magnetized or magnetized iron rings (32a, 32b, 32c, 32d) which cooperatively interact with the magnet assembly to optimize the homogeneity of the magnetic flux through the imaging volume. One of the permanent magnetic rings (32d), is mounted with an opposite polarity relative to the others. The magnetized rings are mounted in a non-ferrous, electrically insulating support structure (34) such that gradient coils (50) can be positioned behind the permanent magnet rings. A flux return path (14, 16, 18, 20, 22, 24) provides a low flux resistant path from adjacent the Rose ring at one side of the imaging volume remotely around the imaging volume to a position adjacent the Rose ring at the other side of the imaging volume.

Abstract: In a magnetic resonance imaging apparatus, a whole-body RF coil (42) disposed circumferentially around an examination region (14) is tuned to a first Larmor frequency, e.g., that of hydrogen. A first transmitter (44) transmits RF signals at the first Larmor frequency. A first T/R switch (40) electronically switches the whole-body RF coil (42) between a transmit mode in which it is electronically connected to the first transmitter (44) for exciting resonance in hydrogen nuclei, and a receive mode in which it is electronically connected to a first receiver channel for demodulating magnetic resonance signals received from resonating hydrogen nuclei. An insertable lung coil (70) is positioned inside the whole-body RF coil (42) around the examination region.

Abstract: A nuclear medicine gamma camera for diagnostic imaging includes a rotating gantry (16) which defines a subject receiving aperture (18). A support (10) supports a subject (12) being examined within the subject receiving aperture (18). A plurality of detector heads (20a-c) is movably attached to the rotating gantry (16). The detector heads (20a-c) are rotated about the subject (12) with the rotation of the rotating gantry (16). A plurality of radiation sources (30a-c) are mounted to the detector heads (20a-c) such that transmission radiation (32a-c) from the radiation sources (30a-c) is directed toward and received by corresponding detector heads (20a-c) positioned across the subject receiving aperture (18) from the radiation sources (30a-c). Translation means (22a-c) independently translates the detector heads (20a-c) laterally in directions tangential to the subject receiving aperture (18).

Abstract: A diagnostic imaging apparatus such as a magnetic resonance imaging (MRI) device includes a vacuum vessel (24) having a central helium reservoir (16) in which superconducting magnetic coil windings (10) are maintained at a superconducting temperature. The vacuum vessel defines a bore (12) within which a gradient tube assembly (30) and an RF coil (32) are received. The gradient tube assembly includes an integral tongue (66) extending from a patient end (48) thereof. A first constraint (70) retrains the gradient tube assembly in a “push-pull” arrangement in both directions along the z-axis. The constraint (70) is mounted to a patient-end of the vessel (24) at a lowermost (i.e., six o'clock) position. The constraint includes vibration isolators (94) interposed between the tongue and a saddle mount (72) to reduce vibration transmission from the gradient tube assembly to the vessel.

Abstract: A patient bed (1) of an MR imaging apparatus is provided with a tube (17) through which pre-polarised fluid can be injected into a patient in order to improve contrast when imaging veins, arteries or other vessels in the body. Fluid is delivered from pump (2) into a high field polarising magnet (3) and along a tube (4) to the patient. Valve (5) is provided so that fluid in the tube (4) downstream of the pre-polarised fluid can be discarded rather than being injected in the patient, and is associated with a reservoir into which the fluid to be discarded and the pre-polarised fluid can be rapidly injected. Then, when the pre-polarised fluid is injected into the patient, its magnetisation has not deteriorated by as much as it would have done if the tube (4) had been directly connected into the patient.

Abstract: A region of interest of a subject (20) on a subject support (18) is positioned above a ferrous pedestal (16, 116) that is supported on a ferrous floor yoke portion (76, 176). A lower imaging coil assembly (50) including a lower gradient coil (52), a radio frequency coil (54), and a lower pole piece (58) are disposed between the pedestal and a region of interest of the subject. An upper imaging coil assembly (40) including an annular gradient coil (42, 142) and an upper annular pole piece (44, 144) is supported from a ceiling ferrous yoke member (74, 174). The upper imaging coil assembly is supported by supports (70, 170) which are moved by drives (72, 78, 172) to raise and lower the upper imaging coil assembly. A laser gauging system (80, 180) gauges the position of the upper imaging coil assembly such that, with a control circuit (82), the upper imaging coil assembly is accurately repositioned at preselected imaging positions.

Abstract: A CT scanner includes a stationary gantry (10) defining an examination region (12) and a rotating gantry (16) which rotates about the examination region. At least two x-ray tubes (18a, 18b), each capable of producing a beam of radiation directed through the examination region, are mounted to the rotating gantry. The x-ray tubes are switchably connected to an electrical power supply (24). X-rays are detected by an arc of x-ray detectors (14) which generate signals indicative of the radiation received. These signals are processed by a reconstruction processor (32) into an image representation. A thermal calculator (60) estimates when an anode in one of the x-ray tubes (18) reaches a selected temperature. The thermal calculator (60) controls a switch (28) which is electrically connected between the x-ray tubes and the power supply. The switch selectively switches power from the power supply alternately to the x-ray tubes.

Abstract: A multi-modality diagnostic imaging system includes a first imaging subsystem (A), such as a computed tomographic (CT) system, for performing a first imaging procedure on a subject. A second imaging subsystem (B), such as a nuclear medicine system (NUC), performs a second imaging procedure on a subject. The second imaging subsystem (B) is remote from the first imaging system (A). A patient couch (28) supports a subject. A patient transfer subsystem (C) transfers a patient couch (28) between the first imaging subsystem (A) and the second imaging subsystem (B). The first and second imaging subsystems (A, B) can be operated concurrently to perform different imaging procedures on different subjects supported by separate patient couches. Data generated by the first imaging subsystem (A) can be used to correct emission data generated by the second imaging subsystem (B).

Abstract: A virtual C-arm support system 40 is used in a radiographic imaging apparatus of the type including an x-ray source 44 and an x-ray detector 48. The support system includes a first positioning system 42 operatively connected to the x-ray source for selectively positioning the x-ray source in a range of first orientations 120, 140, 170 relative to the examination region E. A second positioning system 46 is operatively connected to the x-ray detector 48 for selectively positioning the x-ray detector in a range of second orientations 122, 142, 172 relative to the examination region E. A control unit 60 is in operative command of at least one of the first and second positioning systems to maintain a predetermined spatial relationship between the x-ray source and the detector for each of the ranges of the first and second orientations relative to the examination region.

Abstract: A transmission radiation source assembly suitable for use in both SPECT and PET imaging includes a line source assembly having a medium energy transmission source. The line source assembly includes a primary collimator rotatably disposed about the medium energy transmission source. The primary collimator includes one or more beam limiting slots for shaping the width of a transmission beam emitted from the line source. An on/off collimator is rotatably disposed about the primary collimator and serves to control the on/off state of the line source. The on/off collimator includes a beam exit slot which, when aligned with one of the beam limiting slots allows the transmission beam to exit the line source. In order to sweep the transmission beam across an opposing detector head, the primary collimator and on/off collimator are synchronously rotated about an axis of rotation of the line source with the on/off collimator in the “on” position.