Feldman Rebecca E, Islam Haisam M, Xu Junqian, Balchandani Priti
Translational and Molecular Imaging Institution, Icahn School of Medicine at Mount Sinai, New York, New York, USA.
Bioengineering Department, Stanford University, Stanford, California, USA.
Magn Reson Med. 2016 Feb;75(2):709-17. doi: 10.1002/mrm.25654. Epub 2015 Mar 10.
Simultaneous multislice (SMS) imaging is a powerful technique that can reduce image acquisition time for anatomical, functional, and diffusion weighted magnetic resonance imaging. At higher magnetic fields, such as 7 Tesla, increased radiofrequency (RF) field inhomogeneity, power deposition, and changes in relaxation parameters make SMS spin echo imaging challenging. We designed an adiabatic 180° Power Independent of Number of Slices (PINS) pulse and a matched-phase 90° PINS pulse to generate a SEmi-Adiabatic Matched-phase Spin echo (SEAMS) PINS sequence to address these issues.
We used the adiabatic Shinnar Le-Roux (SLR) algorithm to generate a 180° pulse. The SLR polynomials for the 180° pulse were then used to create a matched-phase 90° pulse. The pulses were sub-sampled to produce a SEAMS PINS pulse-pair and the performance of this pulse-pair was validated in phantoms and in vivo.
Simulations as well as phantom and in vivo results, demonstrate multislice capability and improved B1 -insensitivity of the SEAMS PINS pulse-pair when operating at RF amplitudes of up to 40% above adiabatic threshold.
The SEAMS PINS approach presented here achieves multislice spin echo profiles with improved B1 -insensitivity when compared with a conventional spin echo.
同时多切片（SMS）成像是一种强大的技术，可减少解剖、功能和扩散加权磁共振成像的图像采集时间。在更高的磁场（如7特斯拉）下，射频（RF）场不均匀性增加、功率沉积以及弛豫参数变化使得SMS自旋回波成像具有挑战性。我们设计了一种绝热180°切片数无关功率（PINS）脉冲和一个匹配相位90°PINS脉冲，以生成半绝热匹配相位自旋回波（SEAMS）PINS序列来解决这些问题。
我们使用绝热Shinnar Le-Roux（SLR）算法生成一个180°脉冲。然后使用该180°脉冲的SLR多项式创建一个匹配相位90°脉冲。对这些脉冲进行子采样以产生一个SEAMS PINS脉冲对，并在体模和体内验证了该脉冲对的性能。
模拟以及体模和体内结果表明，当在高于绝热阈值40%的射频幅度下操作时，SEAMS PINS脉冲对具有多切片能力且对B1不敏感。
与传统自旋回波相比，本文提出的SEAMS PINS方法可实现具有更高B1不敏感性的多切片自旋回波轮廓。
