Department of Biomedical Engineering, University of Virginia, Charlottesville, Virginia, USA.
Cardiovascular Branch, Division of Intramural Research, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland, USA.
Magn Reson Med. 2023 Aug;90(2):552-568. doi: 10.1002/mrm.29663. Epub 2023 Apr 10.
To develop 2D turbo spin-echo (TSE) imaging using annular spiral rings (abbreviated "SPRING-RIO TSE") with compensation of concomitant gradient fields and B inhomogeneity at both 0.55T and 1.5T for fast T -weighted imaging.
Strategies of gradient waveform modifications were implemented in SPRING-RIO TSE for compensation of self-squared concomitant gradient terms at the TE and across echo spacings, along with reconstruction-based corrections to simultaneously compensate for the residual concomitant gradient and B field induced phase accruals along the readout. The signal pathway disturbance caused by time-varying and spatially dependent concomitant fields was simulated, and echo-to-echo phase variations before and after sequence-based compensation were compared. Images from SPRING-RIO TSE with no compensation, with compensation, and Cartesian TSE were also compared via phantom and in vivo acquisitions.
Simulation showed how concomitant fields affected the signal evolution with no compensation, and both simulation and phantom studies demonstrated the performance of the proposed sequence modifications, as well as the readout off-resonance corrections. Volunteer data showed that after full correction, the SPRING-RIO TSE sequence achieved high image quality with improved SNR efficiency (15%-20% increase), and reduced RF SAR (˜50% reduction), compared to the standard Cartesian TSE, presenting potential benefits, especially in regaining SNR at low-field (0.55T).
Implementation of SPRING-RIO TSE with concomitant field compensation was tested at 0.55T and 1.5T. The compensation principles can be extended to correct for other trajectory types that are time-varying along the echo train and temporally asymmetric in TSE-based imaging.
在 0.55T 和 1.5T 下，开发使用环形螺旋环（简称“SPRING-RIO TSE”）的 2D 涡轮自旋回波（TSE）成像，以补偿伴随的梯度场和 B 不均匀性，实现快速 T1 加权成像。
在 SPRING-RIO TSE 中实施梯度波形修改策略，以补偿在 TE 和回波间隔处的自平方伴随梯度项，以及基于重建的校正，以同时补偿残余伴随梯度和沿读出方向的 B 场感应相位积累。模拟了由时变和空间相关伴随场引起的信号通路干扰，并比较了序列补偿前后的回波间相位变化。通过体模和体内采集，还比较了无补偿、有补偿和笛卡尔 TSE 的 SPRING-RIO TSE 图像。
模拟显示了伴随场如何在无补偿的情况下影响信号演化，模拟和体模研究都演示了所提出的序列修改的性能，以及读出失谐校正。志愿者数据表明，在完全校正后，与标准笛卡尔 TSE 相比，SPRING-RIO TSE 序列实现了更高的图像质量，具有更高的 SNR 效率（提高 15%-20%）和更低的 RF SAR（降低约 50%），在低场（0.55T）下尤其具有潜在的优势，因为可以恢复 SNR。
在 0.55T 和 1.5T 下测试了具有伴随场补偿的 SPRING-RIO TSE 的实现。补偿原理可以扩展到其他沿回波链随时间变化且在 TSE 成像中时间不对称的轨迹类型，以进行校正。
