PHASE ROBUST PULSE PAIRS FOR CHEMICAL SHIFT SELECTIVE SPIN ECHOES

用于化学位移选择性自旋回波的相位鲁棒脉冲对

• 批准号: 6309982
• 负责人: SIMON TOPP
• 金额: $ 1.55万
• 依托单位: STANFORD UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-01-01 至 2000-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6309982
• 关键词: Mammalia; bioimaging /biomedical imaging; biomedical resource; magnetic resonance imaging; radiology; technology /technique

Introduction: An important side effect of applying a frequency selective pulse is the introduction of a phase gradient across the spectrum. Flip angle deviations on the order of 5-10% significantly change the phase profile across the passband of the pulse. Methods: The frequency response of a spin-echo is calculated from the Cayley-Klein parameters for the two pulses in a 90-180 spin-echo pair. To design the pulses we first establish a goal profile which defines the ideal profile for a pair of amplitude-modulated pulses subject to B1 inhomogeneity. Least squares optimization by simulated annealing is then used to find the pulse pair that minimizes the deviation between the actual profile and the goal profile, for +/-20% variation in B1. Results: The pulses were implemented as spatial-spectral pulses for use in a fast spectroscopic imaging experiment. Measurements of phase variations over the volume of interest confirmed the stability of the phase profile. Conclusions: A joint design of 90-180 spin-echo pairs offers frequency profiles that are immune to up to 20% variation in RF homogeneity.

简介：应用频率的重要副作用 选择性脉冲是跨整个相位梯度的引入 光谱。 5-10％阶的翻转角度偏差显着 在脉冲的整个通过带上更改相位轮廓。 方法： 自旋回波的频率响应是根据 90-180旋转回波对中两个脉冲的Cayley-Klein参数。 为了设计脉冲，我们首先建立一个定义的目标概况 一对振幅调节的脉冲的理想轮廓 B1不均匀性。 通过模拟退火优化最小二乘 然后用于查找最小化偏差的脉冲对 在实际轮廓和目标曲线之间，对于+/- 20％变化 在B1中。 结果：脉冲被实现为空间谱 用于快速光谱成像实验中的脉冲。 确认的兴趣量的相位变化的测量 相位轮廓的稳定性。 结论：联合设计 90-180旋转回波对提供免疫的频率轮廓 RF同质性变化为20％。