Department of Radiology, Washington University, St. Louis, Missouri, USA.
Magn Reson Med. 2018 Jul;80(1):101-111. doi: 10.1002/mrm.27009. Epub 2017 Nov 20.
To develop a phase-based B mapping technique accounting for the effects of imperfect RF spoiling and magnetization relaxation.
The technique is based on a multi-gradient-echo sequence with 2 successive orthogonal radiofrequency (RF) excitation pulses followed by the train of gradient echoes measurements. We have derived a theoretical expression relating the MR signal phase produced by the 2 successive RF pulses to the B field and B -related frequency shift. The expression takes into account effects of imperfections of RF spoiling and T and T2* relaxations.
Our computer simulations and experiments revealed that imperfections of RF spoiling cause significant errors in B mapping if not accounted for. By accounting for these effects along with effects of magnetization relaxation and frequency shift, we demonstrated the high accuracy of our approach. The technique has been tested on spherical phantoms and a healthy volunteer.
In this paper, we have proposed, implemented, and demonstrated the accuracy of a new phase-based technique for fast and robust B mapping based on the measured MR signal phase, frequency, and relaxation. Because imperfect RF spoiling effects are accounted for, this technique can be applied with short TRs and therefore substantially reduces the scan time. Magn Reson Med 80:101-111, 2018. © 2017 International Society for Magnetic Resonance in Medicine.
开发一种基于相位的 B 映射技术，该技术考虑了射频（RF）激发不完全和磁化弛豫的影响。
该技术基于具有 2 个连续正交 RF 激发脉冲的多梯度回波序列，随后是梯度回波测量序列。我们已经推导出了一个理论表达式，该表达式将由 2 个连续 RF 脉冲产生的 MR 信号相位与 B 场和与 B 相关的频移相关联。该表达式考虑了 RF 激发不完全和 T 和 T2*弛豫的影响。
我们的计算机模拟和实验表明，如果不考虑 RF 激发不完全的影响，B 映射会产生显著的误差。通过考虑这些效应以及磁化弛豫和频移的影响，我们证明了我们方法的高精度。该技术已在球形 phantom 和健康志愿者上进行了测试。
在本文中，我们提出、实现并证明了一种新的基于相位的快速、稳健的 B 映射技术的准确性，该技术基于测量的 MR 信号相位、频率和弛豫。由于考虑了 RF 激发不完全的影响，因此该技术可以在较短的 TR 下应用，从而大大减少了扫描时间。磁共振医学 80：101-111，2018. © 2017 国际磁共振学会。
