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PHASE CYCLED MULTIPLE ECHO STEADY STATE FREE PRECESSION IMAGING

IP.com Disclosure Number: IPCOM000033821D
Publication Date: 2004-Dec-29
Document File: 7 page(s) / 1M

Publishing Venue

The IP.com Prior Art Database

Abstract

In an embodiment, a phase cycled multiple echo steady state free precession imaging includes combining the use of phase cycling [6] with a multiecho SSFP sequence for fat-water separation and chemical shift imaging. While TR is extended by the acquisition of additional echoes, phase cycling can reduce the associated artifacts, and greater proportion of time is spent acquiring signal between RF excitations relative to the multi-acquisition method.

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PHASE CYCLED MULTIPLE ECHO STEADY STATE FREE PRECESSION IMAGING

FIELD OF THE INVENTION

[0001]   This invention relates to steady state free precession imaging, and more particularly, to phase cycled steady state free precession imaging especially, in a magnetic resonance imaging (MRI) apparatus.

BACKGROUND OF THE INVENTION

[0002]    In general, steady state free precession (SSFP) imaging is known to offer high fluid and fat signal independent of repetition time, which often necessitates use of chemical shift imaging for distinguishing spin types.

[0003]   Conventional techniques rely on spectral response of imaged spins to a particular pattern of excitation phase and flip angles [1-3].   However, these techniques rely on an extremely short repetition time e.g. in the order of 2.2-2.4 ms, which places limitation on resolution and also demands high radiofrequency (RF) pulse characteristics. 

[0004]   More recent methods are capable of distinguishing lipid and water with the phase of the acquired signal, either with several acquisitions with incrementing echo times (TE) [4], or with a single echo at a specific TE and repetition time (TR) [5].  While potentially more robust and less demanding on gradient hardware, all of these conventional methods are susceptible to field inhomogeneity, producing imperfect fat-water separation or banding artifacts at longer repetition times.

[0005]    Thus, there exists a need in the art for an imaging, wherein the method allows producing an image without field inhomogeneity, imperfect fat-water separation or banding artifacts at longer repetition times.

SUMMARY OF THE INVENTION

[0006]    In an embodiment, a phase cycled multiple echo steady state free precession imaging includes combining the use of phase cycling [6] with a multiecho SSFP sequence for fat-water separation and chemical shift imaging.  While TR is extended by the acquisition of additional echoes, phase cycling can reduce the associated artifacts, and greater proportion of time is spent acquiring signal between RF excitations relative to the multi-acquisition method. 

BRIEF DESCRIPTION OF THE DRAWINGS

[0007]    FIG. 1 shows an example of 3-echo SSFP sequence design according to this invention.

[0008]    FIG. 2 shows an example of a 2-echo SSFP sequence design according to this invention.

DETAILED DESCRIPTION OF THE INVENTION

[0009]    Various embodiments of the present invention provide a phase cycled multiple echo steady state free precession imaging especially for use in an MRI.

[0010]    In general, a phase cycled multiple echo steady state free precession imaging according to one embodiment of this invention includes combining the use of phase cycling [6] with a multiecho SSFP sequence for fat-water separation and chemical shift imaging.  While TR is extended by the acquisition of additional echoes, phase cycling can reduce the associated artifacts, and greater proportion of time is spent acquiring signal between RF excitations relative to the multi-...