Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Boston, MA 02114, USA.
J Magn Reson. 2010 Apr;203(2):283-93. doi: 10.1016/j.jmr.2010.01.010. Epub 2010 Jan 28.
The purpose of this work was to design and implement constant adiabaticity gradient modulated pulses that have improved slice profiles and reduced artifacts for spectroscopic imaging on 3T clinical scanners equipped with standard hardware. The newly proposed pulses were designed using the gradient offset independent adiabaticity (GOIA, Tannus and Garwood[13]) method using WURST modulation for RF and gradient waveforms. The GOIA-WURST pulses were compared with GOIA-HSn (GOIA based on nth-order hyperbolic secant) and FOCI (frequency offset corrected inversion) pulses of the same bandwidth and duration. Numerical simulations and experimental measurements in phantoms and healthy volunteers are presented. GOIA-WURST pulses provide improved slice profile that have less slice smearing for off-resonance frequencies compared to GOIA-HSn pulses. The peak RF amplitude of GOIA-WURST is much lower (40% less) than FOCI but slightly higher (14.9% more) to GOIA-HSn. The quality of spectra as shown by the analysis of lineshapes, eddy currents artifacts, subcutaneous lipid contamination and SNR is improved for GOIA-WURST. GOIA-WURST pulse tested in this work shows that reliable spectroscopic imaging could be obtained in routine clinical setup and might facilitate the use of clinical spectroscopy.
这项工作的目的是设计和实现恒绝热梯度调制脉冲，以改善在配备标准硬件的 3T 临床扫描仪上进行光谱成像的切片轮廓并减少伪影。新提出的脉冲使用梯度偏移独立绝热性（GOIA，Tannus 和 Garwood[13]）方法设计，使用 WURST 调制 RF 和梯度波形。将 GOIA-WURST 脉冲与具有相同带宽和持续时间的 GOIA-HSn（基于 n 阶双曲正割的 GOIA）和 FOCI（频率偏移校正反转）脉冲进行了比较。在体模和健康志愿者中进行了数值模拟和实验测量。与 GOIA-HSn 脉冲相比，GOIA-WURST 脉冲提供了改善的切片轮廓，对于离频频率的切片模糊程度较小。与 FOCI 相比，GOIA-WURST 的峰值 RF 幅度要低得多（低 40％），但比 GOIA-HSn 略高（高 14.9％）。线形状、涡流伪影、皮下脂质污染和 SNR 的分析表明，GOIA-WURST 的光谱质量得到了改善。本工作中测试的 GOIA-WURST 脉冲表明，在常规临床设置中可以获得可靠的光谱成像，并且可能有助于临床光谱学的应用。
