US 5,910,728 A · Simultaneous acquisition of spatial harmonics (SMASH): ultra-fast imaging with radiofrequency coil arrays

Abstract

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.

Claims26

Dependent claims

A method of magnetic resonance imaging of a continuous region of a body by conditioning nuclear spins and measuring RF signals indicative of the conditioned spins, wherein the method includes performing multiple steps of spin conditioning and of collecting of RF measurement signal responses from the region, establishing an ordered data set of collected RF signals, and performing a spatial transformation of the ordered data set to produce a magnetic resonance image of said region, wherein the method includes the steps of

1) for a spin conditioning step
i) receiving an RF measurement signal response simultaneously in each of plural RF receiving coils which each have a different spatial sensitivity, thereby acquiring a plurality of response signals
ii) forming at least two distinct combinations of said plurality of response signals, including a first combination signal and one or more remaining combination signals
iii) applying said first combination signal to an entry of said ordered data set that corresponds to said spin conditioning step, and applying the remaining combination signals to fill further entries of said ordered data set which are offset from said entry that corresponds to the spin conditioning step,
2) performing additional spin conditioning steps and repeating steps i)-iii) for each additional spin conditioning step to thereby fill said ordered data set while reducing spin conditioning steps performed, and
3) performing a spatial transformation of the filled and ordered data set into a magnetic resonance image of said continuous region thereby imaging said continuous region with reduced data acquisition time.

3 more elements

A magnetic resonance imaging (MRI) apparatus of the type having a magnet for establishing a magnetic field, means for conditioning nuclear spins in a continuous region and means for collecting a signal response from the conditioned spins, said means for conditioning and said means for collecting being operated in repetitive cycles to collect signal responses in an ordered data set, and including a processor which applies a spatial transformation to the ordered data set to produce a magnetic resonance image having a characteristic resolution and field of view over said region, wherein the apparatus includes

a plurality of coils for receiving said signal responses, the coils forming an array and each having a different spatial sensitivity so as to each receive a different signal response, and
means for combining the signal responses received in one conditioning step in said plural individual coils of said array to form a plurality of distinct combination signals corresponding to independent spatial representations of spin data from said region, each of said plurality of distinct combination signals being applied to fill an entry of said ordered data set which is offset from other entries of said data set, and thereby filling said data set with multiple combination signals formed from the signal responses received in each conditioning step
said processor applying a spatial transform to the filled ordered data set to thereby produce said image having the characteristic resolution and field of view over the region while reducing required spin conditioning.

Dependencies are inferred from the claim text.

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

Life of this patent

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

Life of this patent

Abstract

Claims26