A magnetic resonance (MR) imaging apparatus and technique exploits spatial information inherent in a surface coil array to increase MR image acquisition speed, resolution and/or field of view. Partial signals are acquired simultaneously in the component coils of the array and formed into two or more signals corresponding to orthogonal spatial representations. In a Fourier embodiment, lines of the k-space matrix required for image production are formed using a set of separate, preferably linear combinations of the component coil signals to substitute for spatial modulations normally produced by phase encoding gradients. The signal combining may proceed in a parallel or flow-through fashion, or as post-processing, which in either case reduces the need for time-consuming gradient switching and expensive fast magnet arrangements. In the post-processing approach, stored signals are combined after the fact to yield the full data matrix. In the flow-through approach, a plug-in unit consisting of a coil array with an on board processor outputs two or more sets of combined spatial signals for each spin conditioning cycle, each directly corresponding to a distinct line in k-space. This partially parallel imaging strategy, dubbed SiMultaneous Acquisition of Spatial Harmonics (SMASH), is readily integrated with many existing fast imaging sequences, yielding multiplicative time savings without a significant sacrifice in spatial resolution or signal-to-noise ratio. An experimental system achieved two-fold improvement in image acquisition time with a prototype three-coil array, and larger factors are achievable with ther coil arrangements.

Simultaneous acquisition of spatial harmonics (SMASH): ultra-fast imaging with radiofrequency coil arrays

A magnetic resonance (MR) imaging apparatus and technique exploits spatial information inherent in a surface coil array to increase MR image acquisition speed, resolution and/or field of view. Magnetic resonance response signals are acquired simultaneously in the component coils of the array and, using an autocalibration procedure, are formed into two or more signals to fill a corresponding number of lines in the signal measurement data matrix. In a Fourier embodiment, lines of the k-space matrix required for image production are formed using a set of separate, preferably linear combinations of the component coil signals to substitute for spatial modulations normally produced by phase encoding gradients. One or a few additional gradients are applied to acquire autocalibration (ACS) signals extending elsewhere in the data space, and the measured signals are fitted to the ACS signals to develop weights or coefficients for filling additional lines of the matrix from each measurement set. The ACS lines may be taken offset from or in a different orientation than the measured signals, for example, between or across the measured lines. Furthermore, they may be acquired at different positions in k-space, may be performed at times before, during or after the principal imaging sequence, and may be selectively acquired to optimized the fitting for a particular tissue region or feature size. The in vivo fitting procedure is readily automated or implemented in hardware, and produces an enhancement of image speed and/or quality even in highly heterogeneous tissue. A dedicated coil assembly automatically performs the calibration procedure and applies it to measured lines to produce multiple correctly spaced output signals. One application of the internal calibration technique to a subencoding imaging process applies the ACS in the central region of a sparse set of measured signals to quickly form a full FOV low resolution image. The full FOV image is then used to determine coil sensitivity related information and dealias folded images produced from the sparse set.

Coil array autocalibration MR imaging

A pair of 8-shaped coils vertically sandwiches an object to be examined for providing a magnetic field in the horizontal direction perpendicular to the body axis in the object. A pair of rectangular coils also vertically sandwiches the object for providing a magnetic field in the vertical direction in the object. The pair of 8-shaped coils is connected for detecting a first magnetic resonance signal from the object and the pair of rectangular coils is connected for detecting a second magnetic resonance signal from the object. A phase of one of an output of the pair of 8-shaped coils and an output of the pair of rectangular coils is shifted by 90° and summing a shifted output and the other output. An upper coil assembly of the 8-shaped coil pair and the rectangular coil pair is connected to a lower coil assembly at one end thereof in the lateral direction of the object and is pivotal to be freely opened and closed. To mount the coil assembly to the object, the upper coil assembly is opened, the object is placed on the lower coil assembly, and the upper coil assembly is closed.

Magnetic resonance imaging apparatus

A magnetic resonance image is formed by measuring RF signals in an array of RF coils, forming a set of spatial harmonics and tailoring the set of spatial harmonics to form a set of tailored spatial harmonics that are adjusted variations in at least one of angulation of an image plane, field of view, and coils sensitivity calibration. The magnetic resonance image may also be formed by generating a set of encoding functions representative a spatial distribution of receiver coil sensitivities and spatial modulations corresponding to the gradient encoding steps, transforming the set of encoding functions to generate a new set of functions representative of distinct spatial positions in the image, and applying the new set of functions to a set of MR signals to form the magnetic resonance image. Matrices inverted during the process of forming the magnetic resonance image may be conditioned by thresholding the eigenvalues of the matrix prior to inversion.

Parallel magnetic resonance imaging techniques using radiofrequency coil arrays

An interface that couples a surface coil array having N receiving elements to an NMR scanner having M preamplifier inputs. The interface includes an RF switch array and a transmit/receive bias circuit. The RF switch array and the transmit/receive bias circuit are controlled by a control logic circuit. In response to a predetermined input, the control logic circuit causes a predetermined subset of the N receiving elements to be couple to the preamplifier inputs of the NMR scanner. Preferably, N may be larger than M.

Peripheral vascular array

Superconducting magnets (10) of a magnetic resonance imager create static magnetic fields through an examination region (12). Gradient magnetic field coils (30) under control of a gradient magnetic field control (42) generate gradient magnetic fields across the examination region (12), as a whole. A plurality of surface coils (36, 38) receive radio frequency signals from each of two distinct subregions within the examination region (12). The two receiver coils are connected with separate receivers (601, 602) which demodulate the received magnetic resonance signals. The magnetic resonance signals are reconstructed (76) into an image representation (80, 82) of the first and second subregions. In the embodiment of FIGS. 1 and 2, a radio frequency transmitter (40) and a whole body coil (32) generate and manipulate the magnetic resonance signals within the first and second subregions. In the embodiment of FIGS. 3 and 4, a plurality of transmitters (401, 402, . . . ) convey RF signals to the surface coils such that the surface coils operate in both a transmit and receive mode. Regardless whether a single transmitter or a series of transmitters is utilized, a sequence control (44) controls the transmitter(s) and the gradient control (42) to conduct conventional magnetic resonance imaging sequences in coordination in both subregions.

Simultaneous magnetic resonance imaging of multiple human organs

A superconducting magnet (10) generates a uniform, static magnetic field through a central bore (12) along its longitudinal or z-axis. A biplanar gradient coil assembly (44) is inserted into the bore to create gradients across the static magnetic field along orthogonal x, y, and z-axes. A biplanar radio frequency coil assembly (50, 80) is inserted into the bore for transmitting radio frequency signals into a subject and receiving magnetic resonance signals from the subject. The radio frequency coil includes a first biplanar coil assembly (50) for generating RF signals in an x-direction and a second biplanar coil assembly (80) for generating RF signals in a y-direction. The two biplanar coil assemblies each include a plurality of conductors (52, 82) along a first plane and a second plurality of conductors (54, 84) along a parallel second plane. The conductors extend parallel to the z-direction. Capacitors (56, 58, 94) are connected in series with each of the conductors in order to control the current flow such that the current flow in each plane is uniform across the plane. The ends of the electrical conductors are connected together (66, 88) such that the current flows are equal and opposite in the two planes. A radio frequency transmitter (136) transmits RF signals to the quadrature biplanar coil assembly. A digital receiver (140) receives and demodulates radio frequency signals from the quadrature coil assembly. The demodulated signals are reconstructed (144) into an image representation for display on a video monitor (146).

Biplanar RF coil for magnetic resonance imaging systems

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Simultaneous magnetic resonance imaging of multiple human organs

Biplanar RF coil for magnetic resonance imaging systems