Abstract: In a transmit apparatus, a multi-channel radio frequency transmitter (30, 46) includes a plurality of transmit elements (32) defining at least two independently operable transmit channels. A transmit configuration selector (54) determines a selected transmit configuration (60) specifying amplitude and phase applied to each transmit channel to generate a B1 field in a corresponding selected region (90) of a subject (38) coupled with the radio frequency transmitter. The transmit configuration selector determines the selected transmit configuration based on B1 mapping (58) of the subject and a B1 field quality assessment employing at least two different B1 field quality measures.

Abstract: A radio frequency coil for magnetic resonance imaging or spectroscopy includes a plurality of generally parallel conductive members (70) surrounding a region of interest (14). One or more end members (72, 74) are disposed generally transverse to the plurality of parallel conductive members. A generally cylindrical radio frequency shield (32) surrounds the plurality of generally parallel conductive members. Switchable circuitry (80, 80?) selectably has: (i) a first switched configuration (90, 90?) in which the conductive members are operatively connected with the one or more end members; and (ii) a second switched configuration (92, 92?) in which the conductive members are operatively connected with the radio frequency shield. The radio frequency coil operates in a birdcage resonance mode in the first switched configuration and operates in a TEM resonance mode in the second switched configuration.

Abstract: A radio frequency coil for magnetic resonance imaging includes an active coil member (70, 701, 170, 270) that defines an imaging volume. The active coil member has a first open end (74) with a first cross-sectional dimension (dactive). A shield coil member (72, 721, 722, 723, 724, 725, 172, 1722, 272) substantially surrounds the active coil member. The shield coil member has a constricted open end (88) arranged proximate to the first open end of the active coil member with a constricted cross-sectional dimension (dconst) that is less than the cross-sectional dimension (dShieid) of the shield coil member In some embodiments, the radio frequency coil further includes an outer shield coil member (100) that is substantially larger than the shield coil member (72, 721, 722, 723, 724, 725, 172, 1722, 272), and surrounds both the active coil member and the shield coil member.

Abstract: Multi-slice magnetic resonance imaging of a region of interest of an imaging subject (16) is performed using a radio frequency coil (40) arranged to generate a B1 magnetic field in the region of interest. One or more processors (44, 82, 88, 110) determine a B1 field value for each slice that is representative of the B1 field over a selected area of the slice, accounting for subject effects on the BI field, and determine an adjusted per-slice radio frequency excitation for each slice that adjusts the B1 field value for the slice to a selected value. A magnetic resonance imaging system (10, 44, 46, 50, 52) acquires magnetic resonance imaging data for each slice using the adjusted per-slice radio frequency excitation for that slice. A reconstruction processor (58) reconstructs the acquired magnetic resonance imaging data into a reconstructed image representation.

Abstract: In a magnetic resonance imaging system (10), a main magnet (20) generates a substantially uniform main magnetic field (B0) through an examination region (14). An imaging subject (16) generates inhomogeneities in the main magnetic field (B0). One or more shim coils are positioned adjacent a gradient coil (26). The gradient coil (26) is driven in halves by first and second power sources (28, 30) which have slightly dissimilar power characteristics which induce an inductive coupling between the shim coil (60) and the gradient coil (26). The shim coil (60) is designed to produce a desired magnetic field, such that the inductive coupling of the shim coils (60) to the gradient coil (26) is substantially minimized while the inhomogeneities in the main magnetic field (B0) caused by the imaging subject are corrected based on prespecified spatial characteristics.

Abstract: A radio frequency coil system (38) for magnetic resonance imaging includes a plurality of parallel spaced apart rungs (60) which each includes rung capacitors (68). An end cap (64) is disposed at a closed end (66) of the coil system (38). An RF shield (62) is connected to the end cap (64) and surrounds the rungs (60), extending in a direction substantially parallel to rungs (60). The RF coil system (38) may be used as birdcage, TEM, hybrid, combination birdcage and TEM, or other.

Abstract: An MRI apparatus is provided. The apparatus includes a main magnet for generating a main magnetic field in an examination region, a plurality of gradient coils for generating gradient fields within the main field, an RF transmit coil for transmitting RF signals into the examination region and exciting magnetic resonance in a subject disposed therein in accordance with a plurality of imaging parameters, the transmitted RF signals having a SAR associated therewith, and a SAR processor for maintaining the transmitted RF signals below a prescribed SAR level.

Abstract: A gradient coil for a magnetic resonance imaging apparatus (10) includes a primary coil (16) defining an inner cylindrical surface (60), and shield coil (18) or coils defining a coaxial outer cylindrical surface (62). Coil jumps (74)connect the primary and shield coils (16, 18). The coil jumps (74) define a non-planar current-sharing surface (64) extending between inner and outer contours (66, 68) that coincide with the inner and outer cylindrical surfaces (60, 62), respectively. The coil (16, 18, 74) defines a current path that passes across the current sharing surface (64) between the inner and outer contours (66, 68) a plurality of times. Optionally, some primary coil turns (70) are electrically interconnected to define an isolated primary sub coil (P2) that together with a second shield (S2, S2?, S2?) enables a discretely or continuously selectable field of view.

Abstract: A transverse electromagnetic (TEM) coil is provided. The TEM coil includes an electrically conductive shell and an end plate disposed at a first end of the shell. The TEM coil also includes a plurality of TEM elements disposed within the shell, the plurality of TEM elements being shorter than the shell.

Abstract: Multi-slice magnetic resonance imaging of a region of interest of an imaging subject (16) is performed using a radio frequency coil (40) arranged to generate a B1 magnetic field in the region of interest. One or more processors (44, 82, 88, 110) determine a B1 field value for each slice that is representative of the B1 field over a selected area of the slice, accounting for subject effects on the BI field, and determine an adjusted per-slice radio frequency excitation for each slice that adjusts the B1 field value for the slice to a selected value. A magnetic resonance imaging system (10, 44, 46, 50, 52) acquires magnetic resonance imaging data for each slice using the adjusted per-slice radio frequency excitation for that slice. A reconstruction processor (58) reconstructs the acquired magnetic resonance imaging data into a reconstructed image representation.

Abstract: An MRI apparatus is provided. The apparatus includes a main magnet for generating a main magnetic field in an examination region, a plurality of gradient coils for generating gradient fields within the main field, an RF transmit coil for transmitting RF signals into the examination region and exciting magnetic resonance in a subject disposed therein in accordance with a plurality of imaging parameters, the transmitted RF signals having a SAR associated therewith, and a SAR processor for maintaining the transmitted RF signals below a prescribed SAR level.

Abstract: A gradient coil for a magnetic resonance imaging apparatus (10) includes a primary coil (16) defining an inner cylindrical surface (60), and shield coil (18) or coils defining a coaxial outer cylindrical surface (62). Coil jumps (74) connect the primary and shield coils (16, 18). The coil jumps (74) define a non-planar current-sharing surface (64) extending between inner and outer contours (66, 68) that coincide with the inner and outer cylindrical surfaces (60, 62), respectively. The coil (16, 18, 74) defines a current path that passes across the current sharing surface (64) between the inner and outer contours (66, 68) a plurality of times. Optionally, some primary coil turns (70) are electrically interconnected to define an isolated primary sub coil (P2) that together with a second shield (S2, S2?, S2?) enables a discretely or continuously selectable field of view.

Abstract: In a method for aligning a magnetic field-modifying structure (74) in a magnet bore (12) of a magnetic resonance imaging scanner (8), a reference magnetic field map of the magnet bore (12) is measured without the magnetic field-modifying structure (74) inserted. The magnetic field-modifying structure (74) is inserted into the magnet bore (12). A second magnetic field map of the magnetic bore (12) is measured with the magnetic field-modifying structure (74) inserted. At least one odd harmonic component of the first and second magnetic field maps is extracted. The magnetic field-modifying structure (74) is aligned in the magnet bore (12) based on a comparison of the odd harmonic component of the first and second magnetic field maps.

Abstract: In a method for aligning a magnetic field-modifying structure (74) in a magnet bore (12) of a magnetic resonance imaging scanner (8), a reference magnetic field map of the magnet bore (12) is measured without the magnetic field-modifying structure (74) inserted. The magnetic field-modifying structure (74) is inserted into the magnet bore (12). A second magnetic field map of the magnetic bore (12) is measured with the magnetic field-modifying structure (74) inserted. At least one odd harmonic component of the first and second magnetic field maps is extracted. The magnetic field-modifying structure (74) is aligned in the magnet bore (12) based on a comparison of the odd harmonic component of the first and second magnetic field maps.

Abstract: A pair of quadrature radio frequency coils (32, 34) disposed adjacent an imaging region (10) are typically loaded differently due to factors such as subject geometry, subject mass, and a relative distance from the subject. A tip angle adjustment circuit (50) monitors a combined tip angle adjacent a mid-plane of the examination region, such as by analyzing delivered and reflected power to each of the coils. An adjustment circuit (54) adjusts relative RF power or amplitude to produce a selected, combined tip angle in the examination region.

Abstract: A gradient coil assembly (22) generates magnetic field gradients across the main magnetic field of a magnetic resonance imaging apparatus and includes a base gradient coil set which generates magnetic field gradients which are substantially linear over a first useful imaging volume, and a correction gradient coil set which generates magnetic field gradients having substantially no first order moment. The correction gradient coil set produces third and higher order moments which combine with higher order terms of the base gradient coil set to produce magnetic field gradients which are substantially linear over a second useful imaging volume different from the first useful imaging volume. In a preferred embodiment, the second volume is continuously variable by adjusting the amounts of current applied to the base and correction coils.

Abstract: A gradient coil assembly (22) generates magnetic field gradients across the main magnetic field of a magnetic resonance imaging apparatus and includes a base gradient coil set which generates magnetic field gradients which are substantially linear over a first useful imaging volume, and a correction gradient coil set which generates magnetic field gradients having substantially no first order moment. The correction gradient coil set produces third and higher order moments which combine with higher order terms of the base gradient coil set to produce magnetic field gradients which are substantially linear over a second useful imaging volume different from the first useful imaging volume. In a preferred embodiment, the second volume is continuously variable by adjusting the amounts of current applied to the base and correction coils.

Abstract: A gradient coil assembly generates magnetic field gradients across the main magnetic field of a magnetic resonance imaging apparatus and includes a primary gradient coil (22p) switchable between a first configuration which generates magnetic field gradients which are substantially linear over a first useful imaging volume, and a second configuration which generates magnetic field gradients which are substantially linear over a second useful imaging volume. A first shield coil set (22s1) is complimentary to the primary gradient coil in one of the first and second configurations, and a second shield coil set (22s2), when either used alone or in combination with the first shield coil, is complimentary to the other of the first and second configurations.

Abstract: A pair of quadrature radio frequency coils (32, 34) disposed adjacent an imaging region (10) are typically loaded differently due to factors such as subject geometry, subject mass, and a relative distance from the subject. A tip angle adjustment circuit (50) monitors a combined tip angle adjacent a mid-plane of the examination region, such as by analyzing delivered and reflected power to each of the coils. An adjustment circuit (54) adjusts relative RF power or amplitude to produce a selected, combined tip angle in the examination region.

Abstract: A crossed-ladder RF coil assembly (48) is employed for quadrature excitation and/or reception in an open or vertical field magnetic resonance apparatus. The RF coil assembly (48, 70, 90) includes a pair of coil assemblies (50, 52; 70, 72; 100, 102) which are disposed in a parallel relationship. Coil arrays (50, 52; 100, 102) include at least two ladder RF coils (501, 502, 503; 521, 522, 523; 1001 . . . , 1008; 1021, . . . , 1028) which are disposed in an overlapping relationship and are rotated by 90° relative to one another. Each ladder RF coil of one coil array is rotated by 90° relative to adjoining ladder coils and each corresponding ladder RF coil of the other coil array. The crossed-ladder RF coil assembly provides better B1 field uniformity and elongated anatomical coverage for spine and neck imaging. In addition, the RF coil assembly reduces noise from the body at higher fields in vertical field magnetic resonance systems.