Abstract:
:The adiabatic Shinnar-Le Roux (SLR) algorithm for radiofrequency (RF) pulse design enables systematic control of pulse parameters such as bandwidth, RF energy distribution and duration. Some applications, such as diffusion-weighted imaging (DWI) at high magnetic fields, would benefit from RF pulses that can provide greater B1 insensitivity while adhering to echo time and specific absorption rate (SAR) limits. In this study, the adiabatic SLR algorithm was employed to generate 6-ms and 4-ms 180° semi-adiabatic RF pulses which were used to replace the refocusing pulses in a twice-refocused spin echo (TRSE) diffusion-weighted echo planar imaging (DW-EPI) sequence to create two versions of a twice-refocused adiabatic spin echo (TRASE) sequence. The two versions were designed for different trade-offs between adiabaticity and echo time. Since a pair of identical refocusing pulses is applied, the quadratic phase imposed by the first is unwound by the second, preserving the linear phase created by the excitation pulse. In vivo images of the human brain obtained at 7Testa (7T) demonstrate that both versions of the TRASE sequence developed in this study achieve more homogeneous signal in the diffusion-weighted images than the conventional TRSE sequence. Semi-adiabatic SLR pulses offer a more B1-insensitive solution for diffusion preparation at 7T, while operating within SAR constraints. This method may be coupled with any EPI readout trajectory and parallel imaging scheme to provide more uniform coverage for diffusion tensor imaging at 7T and 3T.
journal_name
Magn Reson Imagingjournal_title
Magnetic resonance imagingauthors
Balchandani P,Qiu Ddoi
10.1016/j.mri.2014.04.003subject
Has Abstractpub_date
2014-09-01 00:00:00pages
804-12issue
7eissn
0730-725Xissn
1873-5894pii
S0730-725X(14)00127-1journal_volume
32pub_type
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journal_title:Magnetic resonance imaging
pub_type: 杂志文章,评审
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更新日期:2006-09-01 00:00:00
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更新日期:2003-04-01 00:00:00
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更新日期:2000-04-01 00:00:00
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更新日期:2007-01-01 00:00:00
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更新日期:1994-01-01 00:00:00
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