Rapid B1+ mapping using a preconditioning RF pulse with TurboFLASH readout.
Rapid B1+ mapping using a preconditioning RF pulse with TurboFLASH readout.
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DOI：
10.1002/mrm.22423
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发表时间：
2010-08
影响因子：
3.3
通讯作者：
Axel, Leon
中科院分区：
文献类型：
--
作者：
Chung, Sohae;Kim, Daniel;Breton, Elodie;Axel, Leon
关键词：
在磁共振成像（MRI）中，射频（RF）场（B1 +）的不均匀性可导致信号强度变化和定量测量误差。通过独立绘制局部B1 +变化图，可以校正与射频相关的信号变化。在本研究中，我们提出了一种使用层面选择预调节（SS - Pre）射频脉冲的新型快速B1 +映射方法。在施加SS - Pre脉冲之后，立即执行具有中心k空间重排的快速小角度激发（TurboFLASH）成像序列，以捕捉由于B1 +变化而由SS - Pre脉冲产生的剩余纵向磁化。与参考的双角度法（DAM）相比，该方法速度明显更快。具体而言，DAM的总扫描时间等于2（图像数量）、相位编码线数量以及大约5倍T1的乘积，而SS - Pre方法大约需要5倍T1。该方法在3T全身MRI系统上进行了体外和体内验证。脑部和骨盆联合的B1 +测量结果与DAM的测量结果显示出极好的一致性和强相关性（平均差异 = 0.025；一致性的95%上下限分别为 - 0.07和0.12；R = 0.93，p < 0.001）。这种快速B1 +映射方法可用于多种应用，包括需要快速成像的身体成像。
In magnetic resonance imaging (MRI), radiofrequency (RF) field (B1 +) inhomogeneity can lead to signal intensity variations and quantitative measurement errors. By independently mapping the local B1 + variation, the RF-related signal variations can be corrected for. In this study, we present a new fast B1 + mapping method using a slice-selective pre-conditioning (SS-Pre) RF pulse. Immediately after applying a SS-Pre pulse, a turbo fast low angle shot (TurboFLASH) imaging sequence with centric k-space reordering is performed to capture the residual longitudinal magnetization by the SS-Pre pulse due to B1 + variation. Compared to the reference double-angle method (DAM), this method is considerably faster. Specifically, the total scan time for the DAM is equal to the product of 2 (number of images), the number of phase-encoding lines and approximately 5T1, whereas the SS-Pre method takes approximately 5T1. This method was validated in vitro and in vivo at a 3T whole-body MRI system. The combined brain and pelvis B1 + measurements showed excellent agreement and strong correlation with those by the DAM (mean difference=0.025;upper and lower 95% limits of agreement were -0.07 and 0.12;R=0.93,p<0.001). This fast B1 + mapping method can be used for a variety of applications, including body imaging where fast imaging is desirable.
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