Inhomogeneity correction using an estimated linear field map

Irarrázabal, Pablo; Meyer, Craig H.; Nishimura, Dwight G.; Macovski, Albert

doi:10.1002/mrm.1910350221

Cited by 163 publications

(164 citation statements)

References 17 publications

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“…The sums of the images corresponding to the lipid resonance and water resonance are shown in Figure 8. A full resolution, self-derived, B 0 map was used to correct for main field inhomogeneities using the linear algorithm described in Irarrazabal et al (24). The B 0 map was generated by time segmentation of the data into images corresponding to different echo times (10).…”

Section: Resultsmentioning

confidence: 99%

“…[24] is 2N ␦ , which means that the magnitude of this function, normalized to the on-resonance limit, can be written as:…”

Section: Spectral Response Functionmentioning

confidence: 99%

“…[23] was neglected, Eq. [24] and Eq. [25] are only approximations to the spectral response function and trying to algebraically/linearly correct for it can produce inaccurate results.…”

Section: Spectral Response Functionmentioning

confidence: 99%

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Rosette spectroscopic imaging: Optimal parameters for alias‐free, high sensitivity spectroscopic imaging

Schirda

Tanase

Boada

2009

Magnetic Resonance Imaging

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Purpose: To optimize the Rosette trajectories for fast, high sensitivity spectroscopic imaging experiments and to compare this acquisition technique with other chemical shift imaging (CSI) methods. Materials and Methods:A framework for comparing the sensitivity of the Rosette Spectroscopic Imaging (RSI) acquisition to other spectroscopic imaging experiments is outlined. Accounting for hardware constraints, trajectory parameters that provide for optimal sampling and minimal artifact production are found. Along with an analytical expression for the number of excitations to be used in an RSI experiment that is provided, the theoretical precompensation weights used for optimal image reconstruction are derived. Results:The spectral response function for RSI is shown to be approximately the same as the point spread function of standard Fourier reconstructions. While the signal-tonoise ratio (SNR) for an RSI experiment is reduced by the inherent nonuniform sampling of these trajectories, their circular k-space support and speed of spatial encoding leads to greater SNR efficiency and improvements in the total data acquisition time relative to the gold standard CSI approach with square k-space support and to similar efficiency to spiral CSI acquisitions. Numerical simulations and in vivo experimental data are presented to demonstrate the properties of this data acquisition technique. Conclusion:This work demonstrates the use of Rosette trajectories and how to achieve improved efficiency for these trajectories in a two-dimensional spectroscopic imaging experiment. CHEMICAL SHIFT IMAGING (CSI; 1) has been the mainstay of MR spectroscopic imaging because of its simple implementation, reliability, and ease of image reconstruction. This technique has been widely used for observing the changes in the metabolic signature of tissues during evolving pathological and/or physiological conditions. CSI owes its ease of implementation and analysis to the Fourier encoding approach upon which is based. In this approach, the spectral-spatial information is encoded in a rectilinear manner that favors the acquisition of very high-resolution information along the spectral axis and relatively low resolution along the spatial directions. Several fast CSI sequences, mostly using Cartesian trajectories, have been introduced to reduce the long experimental duration associated with this method. However, an extensive theoretical study (2) found their SNR efficiency to be lower than the one for standard CSI. For applications where higher spatial resolution is desired over a narrower spectral bandwidth, trajectory designs that cover a disk in kspace, periodically sampling its center and circular edge, using time-dependent gradients with readouts as long as the CSI readout, offer a convenient means to achieve significant speedups in data acquisition while maintaining adequate SNR efficiency. This stems from the fact that the readout period could be used to acquire multiple spatial frequency values which, in turn, leads to a reduction in the total num...

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Section: Resultsmentioning

confidence: 99%

“…[24] is 2N ␦ , which means that the magnitude of this function, normalized to the on-resonance limit, can be written as:…”

Section: Spectral Response Functionmentioning

confidence: 99%

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Rosette spectroscopic imaging: Optimal parameters for alias‐free, high sensitivity spectroscopic imaging

Schirda

Tanase

Boada

2009

Magnetic Resonance Imaging

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“…The key to our method is to begin the iteration at each pixel with an initial guess that is closer to the true value by exploiting correlations within neighboring pixels. We assume that the field map is spatially smooth (17,18) and use a region growing algorithm guided by a low-resolution reconstruction. We will refer to the field map estimation method proposed by Reeder (7) as the "pixel independent method" and to our new scheme as the "region growing method," described below with reference to Figs.…”

Section: Methodsmentioning

confidence: 99%

Field map estimation with a region growing scheme for iterative 3‐point water‐fat decomposition

Reeder

Shimakawa

et al. 2005

Magnetic Resonance in Med

203

327

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Robust fat suppression techniques are required for many clinical applications. Multi-echo water-fat separation methods are relatively insensitive to B 0 field inhomogeneity compared to the fat saturation method. Estimation of this field inhomogeneity, or field map, is an essential and important step, which is well known to have ambiguity. For an iterative water-fat decomposition method recently proposed, ambiguities still exist, but are more complex in nature. They were studied by analytical expressions and simulations. To avoid convergence to incorrect field map solutions, an initial guess closer to the true field map is necessary. This can be achieved using a region growing process, which correlates the estimation among neighboring pixels. Further improvement in stability is achieved using a low-resolution reconstruction to guide the selection of the starting pixels for the region growing. The proposed method was implemented and shown to significantly improve the algorithm's immunity to field inhomogeneity. Magn Reson Med 54: 1032-1039, 2005.

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“…If each acquisition or shot is moving away from the k-space origin at the same speed in such a way that samples at the same distance from origin are acquired at the same time for every acquisition, off-resonance effects are manifested as blurring. This is the case of spiral-like readouts (1,17).…”

Section: K-space Propertiesmentioning

confidence: 99%

Fast three‐dimensional k‐space trajectory design using missile guidance ideas

Mir¹,

Guesalaga²,

Spiniak³

et al. 2004

Magnetic Resonance in Med

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Three-dimensional (3D) k-space trajectories are needed to acquire volumetric images in MRI. While scan time is determined by the trajectory efficiency, image quality and distortions depend on the shape of the trajectories. There are several 3D trajectory strategies for sampling the k-space using rectilinear or curve schemes. Since there is no evidence about their optimality in terms of image quality and acquisition time, a new design method based on missile guidance ideas is explored. Since air-to-air missile guidance shares similar goals and constraints with the problem of k-space trajectory design, a control approach for missiles is used to design a 3D trajectory. The k-space is divided into small cubes, and each one is treated as a target to be sampled. The main goal is to cover the entire space as quickly and efficiently as possible, with good performance under different conditions. This novel design method is compared to other trajectories using simulated and real data.

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Inhomogeneity correction using an estimated linear field map

Cited by 163 publications

References 17 publications

Rosette spectroscopic imaging: Optimal parameters for alias‐free, high sensitivity spectroscopic imaging

Rosette spectroscopic imaging: Optimal parameters for alias‐free, high sensitivity spectroscopic imaging

Field map estimation with a region growing scheme for iterative 3‐point water‐fat decomposition

Fast three‐dimensional k‐space trajectory design using missile guidance ideas

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