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OPTIMIZATION TECHNIQUE FOR REDUCED FIELD OF VIEW THREE DIMENSIONAL FAST SPIN ECHO IMAGING

IP.com Disclosure Number: IPCOM000241069D
Publication Date: 2015-Mar-24
Document File: 2 page(s) / 31K

Publishing Venue

The IP.com Prior Art Database

Abstract

The disclosed invention provides a technique to optimize parameters of a saturation module when combined with three dimensional fast spin echo (3D FSE) to achieve robust image quality. The technique includes searching for certain parameters to optimize a saturation module. The parameters include RF flip angle of each very selective saturation (VSS) pulses which are typically 3 or 4 VSS pulses and gap between end of a crusher for previous VSS pulse and beginning of next VSS pulse. The technique sets a minimum value of the gap at a value larger than zero. The value of the gap is such that eddy current reduces. In order to find an optimum value of the parameters, residual longitudinal magnetization after the saturation module is calculated for a range of T1 and magnetic flux density B1 inhomogeneity value based on Bloch simulation. The Bloch simulation requires initial value of magnetization prior to onset of saturation module.

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OPTIMIZATION TECHNIQUE FOR REDUCED FIELD OF VIEW THREE DIMENSIONAL FAST SPIN ECHO IMAGING

BACKGROUND

The present invention relates generally to three dimensional fast spin echo (3D FSE) imaging and more particularly to an optimization technique for reduced field of view (FOV) 3D FSE imaging.

Generally, very selective saturation (VSS) radiofrequency (RF) pulses are used ahead of three dimensional fast spin echo (3D FSE) (Cube) to reduce scan time by limiting excitation within a small FOV. Multiple VSS pulses are used to achieve insensitivity to magnetic flux density (B1) RF and magnetic (B0) field inhomogeneity.

In a conventional technique zero gaps is maintained between end of a crusher for previous VSS pulse and beginning of next VSS pulse. Due to no gap, eddy current is acquired which results in phase error artifacts for 3D FSE imaging. Also the conventional technique uses a constant initial value of magnetization for tissue with different T1 value which provides Cube with reduced FOV sensitive to B1 inhomogeniety.

It would be desirable to have an efficient technique to optimize outer volume suppression radiofrequency (RF) pulses for reduced field of view (FOV) three dimensional fast spin echo (3D FSE) imaging.

DETAILED DESCRIPTION

The disclosed invention provides a technique to optimize parameters of a saturation module when combined with three dimensional fast spin echo (3D FSE) to achieve robust image quality.

The technique includes searching for certain parameters to optimize a saturation module. The parameters include RF flip angle of each very selective saturation (VSS) pulses which are typically 3 or 4 VSS pulses and gap between end of a crusher for previous VSS pulse and beginning of next VSS pulse. The same duration of gap is also applied between the end of the crusher of the last VSS pulse and the beginning of Cube excitation. The technique sets a minimum value of the gap at a value larger than zero. The value of the gap is such that eddy current effect from the crusher does not disrupt Cube acquisition which otherwise results in phase error artifacts.

In order to find an optimum value of the parameters, residual longitudinal magnetization after the saturation module is calculated for a range of T1 and magnetic flux density B1 inhomogeneity value based on Bloch simulation. The average of the magnetization is used as a metric to find optimum set of the parameters. The Bloch simulation requires initial value of magnetization prior to onset of saturation module. The technique uses initial magnetization which is adaptive to the T1 value, namely, large initial magnetization for small T1 and small for large T1 instead of using a constant initial value for tissue with different T1 value. The technique uses more accurate initial magnetization by plugging in a typical dead time used in Cube. Further, the technique uses Bloch simulation to calculate longitudinal magnetization at the beginning of saturation module for a given T1...