Parker D L, Buswell H R, Goodrich K C, Alexander A L, Keck N, Tsuruda J S
Department of Radiology, University of Utah, Salt Lake City 84132, USA.
Magn Reson Med. 1995 Aug;34(2):283-6. doi: 10.1002/mrm.1910340221.
Magnetization transfer (MT) techniques have been shown to significantly reduce background soft-tissue signal in time-of-flight magnetic resonance angiography. To achieve sufficient suppression, radio frequency (RF) pulses with tip angles on the order of 1000 degrees are typically used, resulting in significant RF power deposition in the patient. Although these power deposition levels do not exceed the FDA guidelines, they are significantly higher than those used in typical imaging techniques. The use of these same magnetization transfer pulses in applications at field strengths higher than 1.5 T will require MT power levels which exceed FDA safety standards. This report demonstrates that the total power deposition required to achieve background tissue suppression can be significantly reduced by the application of the saturation pulses only during the phase-encoding steps corresponding to the central portion of "k space." This technique allows equivalent soft tissue suppression with approximately 10% of the energy deposition of conventional magnetization transfer techniques.
磁化传递（MT）技术已被证明能在飞行时间磁共振血管造影中显著降低背景软组织信号。为实现充分抑制，通常使用翻转角约为1000度的射频（RF）脉冲，这会导致患者体内有大量RF功率沉积。尽管这些功率沉积水平未超过FDA指南，但明显高于典型成像技术中使用的水平。在高于1.5 T的场强应用中使用相同的磁化传递脉冲将需要超过FDA安全标准的MT功率水平。本报告表明，仅在与“k空间”中心部分对应的相位编码步骤期间应用饱和脉冲，可显著降低实现背景组织抑制所需的总功率沉积。该技术能实现与传统磁化传递技术约10%的能量沉积相当的软组织抑制效果。
