B1-insensitive T2 preparation for improved coronary magnetic resonance angiography at 3 T
B1-insensitive T2 preparation for improved coronary magnetic resonance angiography at 3 T
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DOI：
10.1002/mrm.20835
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发表时间：
2006-04-01
影响因子：
3.3
通讯作者：
Pettigrew, RI
中科院分区：
文献类型：
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作者：
Nezafat, R;Stuber, M;Pettigrew, RI
在3 T时，RF场的有效波长与人体尺寸相当，导致B-1驻波效应和额外的相位变化。与1.5 T相比，该效应伴随着B-0场不均匀性的增加。这种组合导致用于冠状动脉磁共振血管造影（MRA）的复合MLEV加权T-2准备（T-2 Prep）序列的磁化准备不均匀。提出了一种新的绝热重聚焦T-2 Prep序列，在该序列中，利用硬RF脉冲将磁化倾斜到横向平面中，并利用一对绝热快通RF脉冲进行重聚焦。随后使用硬RF脉冲将等色线返回到纵轴。数值模拟预测了对源自B、不均匀性的伪影的良好抑制，同时实现了冠状动脉与周围组织之间的良好对比度增强。体内研究证实了这一点，在体内研究中，在没有T-2 Prep的情况下，使用MLEV加权T-2 Prep和建议的绝热T-2 Prep获得冠状动脉MR血管造影。使用绝热T-2 Prep在3 T下实现了定量和定性冠状动脉MRA图像测量的改善。
At 3 T, the effective wavelength of the RF field is comparable to the dimension of the human body, resulting in B-1 standing wave effects and extra variations in phase. This effect is accompanied by an increase in B-0 field inhomogeneity compared to 1.5 T. This combination results in nonuniform magnetization preparation by the composite MLEV weighted T-2 preparation (T-2 Prep) sequence used for coronary magnetic resonance angiography (MRA). A new adiabatic refocusing T-2 Prep sequence is presented in which the magnetization is tipped into the transverse plane with a hard RF pulse and refocused using a pair of adiabatic fast-passage RF pulses. The isochromats are subsequently returned to the longitudinal axis using a hard RF pulse. Numerical simulations predict an excellent suppression of artifacts originating from B, inhomogeneity while achieving good contrast enhancement between coronary arteries and surrounding tissue. This was confirmed by an in vivo study, in which coronary MR angiograms were obtained without a T-2 Prep, with an MLEV weighted T-2 Prep and the proposed adiabatic T-2 Prep. Improved quantitative and qualitative coronary MRA image measurement was achieved using the adiabatic T-2 Prep at 3 T.