Abstract
The simultaneous acquisition of spatial harmonics (SMASH) method of imaging with detector arrays can reduce the number of phase-encoding steps, and MRI scan time several-fold. The original approach utilized numerical gradient-descent fitting with the coil sensitivity profiles to create a set of composite spatial harmonics to replace the phase-encoding steps. Here, an analytical approach for generating the harmonics is presented. A transform is derived to project the harmonics onto a set of sensitivity profiles. A sequence of Fourier, Hilbert, and inverse Fourier transform is then applied to analytically eliminate spatially dependent phase errors from the different coils while fully preserving the spatial-encoding. By combining the transform and phase correction, the original numerical image reconstruction method can be replaced by an analytical SMASH procedure (ASP). The approach also allows simulation of SMASH imaging, revealing a criterion for the ratio of the detector sensitivity profile width to the detector spacing that produces optimal harmonic generation. When detector geometry is suboptimal, a group of quasi-harmonics arises, which can be corrected and restored to pure harmonics. The simulation also reveals high-order harmonic modulation effects, and a demodulation procedure is presented that enables application of ASP to a large numbers of detectors. The method is demonstrated on a phantom and humans using a standard 4-channel phased-array MRI system. (C) 2000 Wiley-Liss, Inc.
Original language | English (US) |
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Pages (from-to) | 716-725 |
Number of pages | 10 |
Journal | Magnetic Resonance in Medicine |
Volume | 43 |
Issue number | 5 |
DOIs | |
State | Published - 2000 |
Externally published | Yes |
Keywords
- ASP
- Harmonics
- Image reconstruction
- Phase correction
- Phase- encoding
- Phased-arrays MRI
- SMASH
ASJC Scopus subject areas
- Radiology Nuclear Medicine and imaging