摘要:
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 that are projected through the examination region. X-rays are detected by at least an arc of x-ray detectors or a plurality of parallel rings of detectors (14 1 , 14 2 ,...14 n ). 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. In another embodiment, the region of interest moves such that each beam traverses a spiral path spanning one of a plurality of contiguous slabs. The multiple fan beam generators may be contained within a single elongated x-ray tube. Alternatively, the multiple fan beams can be generated by a plurality of angularly displaced x-ray tubes.
摘要:
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 centre 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. By displacing one gradient coil set relative to the other, mutual inductance is minimized, which maximizes peak gradient, rise time, and slew rate, while dB/dt levels are minimized. Arranging asymmetric gradient coil sets in an overlapping, phased array reduces coil resistance, which increases duty cycle and reduces heat dissipation to eliminate extra costs for a cooling system.
摘要:
A magnetic resonance apparatus includes a main magnetic field source (12) for providing a magnetic field (B 0 ) along a main field axis. A transmitter (34) and transmit coils (30, 32) excite a nuclei of an object to resonate. The resonating nuclei generate magnetic resonance signals detected by a volume coil (50) including a pair of end rings (70, 72) separated along a coil axis (Y). The end rings (70, 72) are electrically interconnected by a plurality of rungs (74) disposed about the rings. A conductive loop (80) is concentrically disposed between and inductively coupled to the end rings. The loop includes an electrical conductor (82) preferably surrounding the rungs (74), and positioned parallel to the end rings (70, 72). A capacitive element (84), in electrical communication with the conductor (82), is selected or adjusted to tune the loop (80) to signals at a selected frequency. Moreover, the loop (80) is slidably positionable along the coil axis (Y) and has an adjustable capacitor (84) to match or tune the loop to signals at the selected frequency.
摘要:
A radiation detector includes slit collimator. A radiation detector receives radiation which has been received in each of the slits. The aspect ratio of the detector is approximately three, and each semiconductor radiation detector (106) has a transverse dimension (C y ) which is less than that of its respective slit (W y ). A reconstruction processor generates an image indicative of the radiation received by the detectors. The detector may be rotated about a fixed axis (109). Alternately, the detector may be translated in coordination with its rotation to provide a substantially square field of view.
摘要:
An asymmetric sampling scheme for use with a nuclear medicine gamma camera facilitates collection of a full set of higher resolution emission data and lower resolution transmission data with one complete 360° rotation of the gantry. The gantry contains a plurality of radiation detectors and at least one adjustably mounted radiation source. During a scan, the gantry is incrementally rotated about a subject receiving aperture by a predetermined step size throughout a first 180° of a rotation (P 1 , ..., P 6 ). The gantry is then rotated about the subject receiving aperture by one-half the predetermined step size (P 7 or P 8 ). The gantry is then incrementally rotated about the subject receiving aperture by the predetermined step size throughout the remaining 180° of the scan (P 8 , ..., P 12 ). Emission data collected during the second half of the scan (P 8 , ..., P 12 ) is interleaved into the data from the first half of the scan. Such sampling reduces overall scan time by cutting the number of steps approximately in half, therefore, eliminating 50% of the dead time while the gantry rotates and comes to rest.
摘要:
An MRI apparatus includes a local endovaginal probe ( 30 ) for receiving magnetic resonance in a study of the endopelvic fascia surrounding the female urethra. The probe ( 30 ) includes a shaft portion ( 62 ) an insert portion ( 60 ), the insert portion to be inserted into the vaginal cavity of a female subject. The insert portion (60) , in order to have maximum efficiency in imaging the endopelvic fascia, is designed to specific dimensions to achieve the optimum balance between image quality and patient comfort. In an imaging sequence, a main magnet assembly produces a main magnetic field through an imaging region. A whole-body RF coil excites and manipulates magnetic resonance in the vicinity of the vaginal cavity. The probe (30) detects the magnetic resonance, which is received and demodulated. The received magnetic resonance is then reconstructed into an image representation of the tissue surrounding the vaginal cavity of the subject.
摘要:
A connection device (70) provides electrical connection between a stator motor (50) of an x-ray tube and a stator cord (56). The connection device is connected with the x-ray tube housing (30) by threading a threaded portion into a corresponding threaded aperture in the housing to create a leak-tight seal. The threaded portion is rigidly connected with a connecting portion, such as a bayonet socket, which receives a corresponding fitting (102) of the stator cord. An electrical conduction path, hermetically sealed in the connecting device, provides electrical connection between the socket and the interior of the housing. The connection device allows the stator cord to be quickly connected or disconnected from the housing yet provides a seal which resists leakage of cooling oil from the housing.
摘要:
The origin of a cone or fan beam of B, γ, or x radiation is moved in a continuous path such as a circle or is stepped among a two-dimensional grid of preselected points. The cone beam of radiation passes through an imaging plane (44) in a patient (14) and is detected by a detector array (16) . A data collection circuit samples the detector array to generate radiation intensity sub-images. A circuit monitors the shifting of the focal spot and controls an image shifting circuit to shift physical coordinates of the sampled sub-image analogously. A sub-imaging combining circuit interleaves or otherwise combines spatially shifted sub-images. In one embodiment, the combined sub-images forms a higher resolution composite image representation. In another embodiment, a plurality of combined, spatially shifted sub-images are collected at angularly offset orientations around the subject and are reconstructed into a higher resolution composite image representation.