Bashir Adil, Conradi Mark S, Woods Jason C, Quirk James D, Yablonskiy Ddmitriy A
Mallinckrodt Institute of Radiology, St. Louis, Missouri 63110, USA.
Magn Reson Med. 2009 Jan;61(1):239-43. doi: 10.1002/mrm.21821.
MRI with hyperpolarized gases, (3)He, (129)Xe, (13)C, and others, has the potential to become an important diagnostic technique for clinical imaging. Due to the nonreversible loss of magnetization in hyperpolarized gas imaging, the choice of the flip angle is a major factor that influences the signal intensity, and hence, the signal-to-noise ratio. Conventional automated radiofrequency (RF) calibration procedures for (1)H imaging are not suitable for hyperpolarized gas imaging. Herein, we have demonstrated a simple procedure for RF calibration for magnetic resonance imaging (MRI) with hyperpolarized gases that is easily adaptable to clinical settings. We have demonstrated that there exists a linear relationship between the RF transmitter voltages required to obtain the same nutation angle for protons (V(1H)) and hyperpolarized gas nuclei (V(3He)). For our (1)H and (3)He coils we found that V(3He) = 1.937 . V(1H) with correlation coefficient r(2) = 0.97. This calibration can be done as a one-time procedure during the routine quality assurance (QA) protocol. The proposed procedure was found to be extremely robust in routine scanning and provided an efficient method to achieve a desired flip angle, thus allowing optimum image quality.
使用超极化气体（如³He、¹²⁹Xe、¹³C等）的磁共振成像（MRI）有潜力成为临床成像的一项重要诊断技术。由于超极化气体成像中磁化强度的不可逆损失，翻转角的选择是影响信号强度进而影响信噪比的主要因素。传统的¹H成像自动射频（RF）校准程序不适用于超极化气体成像。在此，我们展示了一种用于超极化气体磁共振成像（MRI）的简单RF校准程序，该程序易于应用于临床环境。我们证明，对于质子（V(¹H)）和超极化气体原子核（V(³He)），获得相同章动角所需的RF发射机电压之间存在线性关系。对于我们的¹H和³He线圈，我们发现V(³He) = 1.937·V(¹H)，相关系数r² = 0.97。这种校准可以在常规质量保证（QA）协议期间作为一次性程序完成。所提出的程序在常规扫描中被发现极其稳健，并提供了一种实现所需翻转角的有效方法，从而实现最佳图像质量。
