Automated shimming of B0 for spectroscopic imaging

Tropp, James; Derby, Kevin; Hawryszko, Christine; Sugiura, Satoshi; Yamagata, Hitoshi

doi:10.1016/0022-2364(89)90140-6

Cited by 18 publications

(22 citation statements)

References 12 publications

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“…On the other hand, only 1 2 projections are needed with FASTMAP. Spectroscopic imaging of the water signal results in long measuring times that are prohibitive for in vivo application (8,9). Imaging of phase differences has therefore become the more standard method to encode the magnetic field information, enabling adjustment times as low as 10 min (10)(11)(12).…”

Section: Discussionmentioning

confidence: 99%

“…(8)(9)(10)(11)(12)(13). Some of these techniques rely on the acquisition of chemical shift images (8,9) whereas others use phase difference images (10)(11)(12). However, based on arguments of shim coil design, Gruetter and Boesch (13) have shown that it is not necessary to acquire the data in images, but the magnetic field measurement acquired along a few linear projections is sufficient to characterize the magnetic field in terms of spherical harmonic functions.…”

Section: Introductionmentioning

confidence: 97%

“…The exclusive use of these three coils had a deeper cause in the fact that away from the magnet center, adjustment of higher-order shim coils will interfere with that of lower-order coils, which may result in impractical procedures (7). (8)(9)(10)(11)(12)(13). Some of these techniques rely on the acquisition of chemical shift images (8,9) whereas others use phase difference images (10)(11)(12).…”

Section: Introductionmentioning

confidence: 98%

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Automatic, localized in Vivo adjustment of all first‐and second‐order shim coils

Gruetter

1993

Magnetic Resonance in Med

840

733

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The implementation of a "fast, automatic shimming technique by mapping along projections" (FASTMAP) on a 2.1-Tesla whole-body system is described. The method provides a localized adjustment of all first- (X, Y, Z) and second-order (Z2, ZX, ZY, X2-Y2, 2XY) coils in 2 min. The time savings are achieved by mapping the magnetic field along six projections rather than from whole-imaging data sets. An analysis of noise error propagation suggests that in 64-ml volumes the residual linewidths obtained with the method are negligible when the signal-to-rms-noise ratio is above 30. The initial application of the method to localized 13C, 31P, and 1H spectroscopy of the human brain resulted in linewidths of approximately 2 Hz for 13C (144-ml volume), approximately 2.5 Hz for 31P (36-ml volume) and approximately 4 Hz for 1H (36-ml volume) with symmetric and reproducible lineshapes.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 98%

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Automatic, localized in Vivo adjustment of all first‐and second‐order shim coils

Gruetter

1993

Magnetic Resonance in Med

840

733

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“…The significant signal gain makes it unnecessary to perform signal averaging. The total acquisition of 1 usually only one iteration of FASTERMAP is needed starting from a default in vivo brain shim file. Shim adjustments using FASTERMAP are also more reliable because the noise in the field maps is essentially manifested as increased linewidth (1 3).…”

Section: Discussionmentioning

confidence: 99%

Improvements on an in Vivo automatic shimming method (FASTERMAP)

Shen

Rycyna

Rothman

1997

Magnetic Resonance in Med

124

114

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Improvements on a localized, automatic shimming method described by Gruetter and Boesch (J. Magn. Reson. 96, 323-334 (1992)) and Gruetter (Magn. Reson. Med. 29, 804-811 (1993)) are presented. A spin-echo sequence employing a double sech refocusing scheme is used to acquire a field map along linear projections that improves the signal-to-noise ratio by at least a factor of two over the stimulated echo sequence previously used. To further improve the reliability of shim adjustments, a variance-weighted polynomial regression analysis is performed. This also extends the scope of application of this technique to global shimming. Localized 1H spectra of human brain shimmed by this method are presented.

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“…Many ingenious methods based on phase mapping or spectroscopic imaging have been devised to perform automatic slice shimming. [1][2][3][4][5][6] Due to the heterogeneity of organs and the limited number of shim coils accessible to whole-body spectrometers it is often necessary to constrain tissue volume to be shimmed to the intended region of interest (ROI), which is usually a slice for single-slice imaging or a slab for multislice imaging. Within the selected ROI, B 0 inhomogeneity is approximated by a combination of several spherical harmonics that correspond to specific shim coils.…”

Section: Introductionmentioning

confidence: 99%

Effect of degenerate spherical harmonics and a method for automatic shimming of oblique slices

Shen

2001

NMR in Biomedicine

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Several spherical harmonics degenerate on an oblique plane. Two-dimensional field mapping of an oblique slice causes ambiguity in determination of the degenerate spherical harmonics terms. Therefore, automatic shimming of oblique slices may lead to erroneous adjustment of shims corresponding to the degenerate spherical harmonics. In this paper an automatic slice shimming technique derived from the FASTMAP method (Gruetter R. Magn. Reson. Med. 1993; 29, 804-811) is proposed. This new method unequivocally determines and corrects all of the first- and the second-order shims for slices of arbitrary orientation.

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Automated shimming of B0 for spectroscopic imaging

Cited by 18 publications

References 12 publications

Automatic, localized in Vivo adjustment of all first‐and second‐order shim coils

Automatic, localized in Vivo adjustment of all first‐and second‐order shim coils

Improvements on an in Vivo automatic shimming method (FASTERMAP)

Effect of degenerate spherical harmonics and a method for automatic shimming of oblique slices

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