5304930 Remotely positioned MRI system

Crowley, Christopher J.; Rose, Freeman H

doi:10.1016/0730-725x(95)90085-j

Cited by 2 publications

(7 citation statements)

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“…In this case the transverse magnetization can be repeatedly refocused and remeasured, regaining the SNR, lost to the factor of ffiffiffiffi ffi g x p in the denominator of (27). This approach to regaining SNR in inhomogeneous field imaging appears in the work of Crowley and Rose, though in a somewhat different context, see [6,7].…”

Section: B2 Dependence Of Snr On Gradient Strength and Magnet Qualitymentioning

confidence: 98%

“…Very interesting recent work, using matched inhomogeneous B 0 and B 1 fields, shows that it is possible to obtain well resolved spectra in the presence of fairly large B 0 field inhomogeneities, see [8,13]. The previous approaches to imaging all rely on single point acquisition techniques, which use a refocusing pulse for each point or small group of points measured in k-space, see [13,1,2,7,6]. Such sequences are generally not well suited for human imaging.…”

Section: Introductionmentioning

confidence: 98%

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A novel technique for imaging with inhomogeneous fields

Epstein¹,

Magland²

2006

Journal of Magnetic Resonance

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We introduce a simple, efficient, low-SAR method for magnetic resonance imaging in the presence of a static field with a permanent, and possibly large gradient. The technique, which is called slant-slice imaging is essentially a spin-echo imaging sequence except that the imaging slice is oriented such that the static field gradient can be used in conjunction with applied gradients during readout. Data are collected for 2D slices. Unlike single point imaging techniques, entire lines of k-space are acquired with each readout. The slant-slice pulse sequence is used to obtain high quality images, using a clinical scanner to simulate a static field with a large permanent gradient. The effects of the inhomogeneity are quantified by two parameters nu and q, which are useful for assessing the utility of a magnet design for 3D-MR imaging.

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Section: B2 Dependence Of Snr On Gradient Strength and Magnet Qualitymentioning

confidence: 98%

Section: Introductionmentioning

confidence: 98%

A novel technique for imaging with inhomogeneous fields

Epstein¹,

Magland²

2006

Journal of Magnetic Resonance

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“…(4) Using gradient fields, the excited magnetization is 'spatially encoded'. (5) The signal is acquired, possibly with additional spatial encoding.…”

Section: Inhomogeneous Fields Without Critical Points:mentioning

confidence: 99%

“…While the Bloch equation analysis of selective excitation applies, essentially verbatim, a few remarks are in order. If B 0 always points in the same direction, as in (5), then the usual analysis from the homogeneous case applies without change. In general, the direction of B 0 may vary slowly over the field of view.…”

Section: Inhomogeneous Fields Without Critical Points:mentioning

confidence: 99%

“…In general, the direction of B 0 may vary slowly over the field of view. In this case, we can still use a selective RF-pulse designed for use with a B 0 -field having a permanent gradient, but uniform direction, as in equation (5). In appendix A we show that the main consequence of nonorthogonality between B 0 and B 1 is a decrease in the effective amplitude of B 1 .…”

Section: Inhomogeneous Fields Without Critical Points:mentioning

confidence: 99%

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Magnetic resonance imaging in inhomogeneous fields

Epstein¹

2004

Inverse Problems

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In this paper, we explain the principles underlying imaging with an inhomogeneous B 0 -field and show how SNR and SAR considerations place limits on the size of the relative field inhomogeneity. We explore problems of imaging with a background field that varies in both magnitude and direction, both with and without critical points. We give a simple geometric explanation for the difficulties that arise when attempting to use fields such that B 0 has a saddle point, and construct examples of fields where B 0 has isolated, nonzero minima.

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5304930 Remotely positioned MRI system

Cited by 2 publications

References 0 publications

A novel technique for imaging with inhomogeneous fields

A novel technique for imaging with inhomogeneous fields

Magnetic resonance imaging in inhomogeneous fields

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