Department of Radiology, University of Texas Southwestern Medical Center, Dallas, Texas, USA.
Bioengineering, University of Texas at Dallas, Richardson, Texas, USA.
J Magn Reson Imaging. 2018 Oct;48(4):1104-1111. doi: 10.1002/jmri.26021. Epub 2018 Sep 15.
The 3D short tau inversion recovery (STIR) sequence is routinely used in clinical MRI to achieve robust fat suppression. However, the performance of the commonly used adiabatic inversion pulse, hyperbolic secant (HS), is compromised in challenging areas with increased B and B inhomogeneities, such as brachial plexus at 3T.
To demonstrate the frequency offset corrected inversion (FOCI) pulse as an efficient fat suppression STIR pulse with increased robustness to B and B inhomogeneities at 3T, compared to the HS pulse.
Prospective.
SUBJECTS/PHANTOM: Initial evaluation was performed in phantoms and one healthy volunteer by varying the B field, while subsequent comparison was performed in three healthy volunteers and five patients without varying the B .
FIELD STRENGTH/SEQUENCE: 3T; 3D TSE-STIR with HS and FOCI pulses.
Brachial plexus images were qualitatively evaluated by two musculoskeletal radiologists independently using a four-point grading scale for fat suppression, shading artifacts, and nerve visualization.
The Wilcoxon signed-rank test with P < 0.05 was considered statistically significant.
Simulations and phantom experiments demonstrated broader bandwidth (2.5 kHz vs. 0.83 kHz, increased B robustness) at the same adiabatic threshold and lower adiabatic threshold (5 μT vs. 7 μT at 3.5 ppm, increased B robustness) at the same bandwidth with the FOCI pulse compared to the HS pulse With increased bandwidth, the FOCI pulse achieved robust fat suppression even at 50% of maximum B strength, while the HS pulse required >75% of maximum B strength. Compared to the standard 3D TSE-STIR with HS pulse, the FOCI pulse achieved uniform fat suppression (P < 0.05), better nerve visualization (P < 0.05), and minimal shading artifacts (P < 0.01) in brachial plexus at 3T.
The FOCI pulse has increased robustness to B and B inhomogeneities, compared to the HS pulse, and enables uniform fat suppression in brachial plexus at 3T.
1 Techinical Efficacy: Stage 1 J. Magn. Reson. Imaging 2018;48:1104-1111.
在临床 MRI 中，3D 短 tau 反转恢复（STIR）序列通常用于实现强大的脂肪抑制。然而，在 3T 时，常见的绝热反转脉冲——双曲正割（HS），在 B 和 B 不均匀性增加的挑战性区域中的性能受到影响，例如臂丛神经。
与 HS 脉冲相比，证明频率偏移校正反转（FOCI）脉冲作为一种有效的脂肪抑制 STIR 脉冲，在 3T 时对 B 和 B 不均匀性具有更高的鲁棒性。
前瞻性。
受试者/体模：通过改变磁场，在体模和一名健康志愿者中进行了初始评估，而随后在三名健康志愿者和五名无磁场变化的患者中进行了比较。
磁场强度/序列：3T；3D TSE-STIR 采用 HS 和 FOCI 脉冲。
两名肌肉骨骼放射科医生独立使用四点分级量表对脂肪抑制、阴影伪影和神经可视化进行定性评估。
采用 Wilcoxon 符号秩检验，P<0.05 认为具有统计学意义。
与 HS 脉冲相比，模拟和体模实验表明 FOCI 脉冲具有更宽的带宽（2.5 kHz 与 0.83 kHz，增加了 B 的鲁棒性）和更低的绝热阈值（3.5ppm 时 5 μT 与 7 μT，增加了 B 的鲁棒性）。随着带宽的增加，FOCI 脉冲甚至在最大 B 强度的 50%时也能实现强大的脂肪抑制，而 HS 脉冲则需要最大 B 强度的>75%。与标准的 3D TSE-STIR 采用 HS 脉冲相比，FOCI 脉冲在 3T 时实现了均匀的脂肪抑制（P<0.05）、更好的神经可视化（P<0.05）和最小的阴影伪影（P<0.01）。
与 HS 脉冲相比，FOCI 脉冲对 B 和 B 不均匀性的鲁棒性更强，并且能够在 3T 时实现臂丛神经的均匀脂肪抑制。
1 技术功效：阶段 1 J. Magn. Reson. Imaging 2018;48:1104-1111.
