ARTIFACTS IN T1P-WEIGHTED IMAGING

这个子项目是许多研究子项目中的一个 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH来源获得了主要资金， 因此可以在其他CRISP条目中表示。所列机构为 研究中心，而研究中心不一定是研究者所在的机构。 磁共振（MR）组织对比度取决于组织弛豫时间T1和T2、扩散加权、磁化传递（MT）或灌注效应的差异，以区分健康组织和患病组织。除了这些传统的对比技术，一个强大的方法来创建组织对比是旋转旋转坐标系中的晶格弛豫时间（T1 ρ）。 理想情况下，为了实现最大T1 q加权对比度，自旋锁定幅度应该与所涉及的物理过程的频率相对应，尽管在实践中，可能的自旋锁定幅度受到B 0场梯度伪影和传递到组织的辐射的高比吸收率（SAR）的影响。旋转回波或绝热激发结合高振幅自旋锁定可从B1和B 0场中的梯度中去除伪影，然而，增加RF场以减少伪影并减少RF场以降低SAR是一种缺点，将1.5 T和3 T临床扫描仪上可接受的自旋锁定振幅限制为400600 Hz，以获得T1 rho加权图像。此外，随着扫描仪的场强继续增加至7 T，可能没有可接受的射频场幅度范围。 一种拓宽可接受的自旋锁范围的技术是必要的，特别是在低频区，在脑代谢或静态偶极子研究中，1H和17 O之间的标量耦合产生有用的临床对比偶极或1H交换动力学。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Magnetic resonance (MR) tissue contrast depends on differences in tissue relaxation times T1 and T2, diffusion weighting, magnetization transfer (MT) or perfusion effects to distinguish healthy and diseased tissues. In addition to these conventional contrast techniques, a powerful method to create tissue contrast is the spinlattice relaxation time in the rotating frame (T1rho). Ideally, to achieve maximum T1q-weighted contrast, the spin locking amplitude should coincide with the corresponding with the frequency of the physical process involved, although, in practice, possible spin lock amplitudes are compromised by B0 field gradient artifacts and the high specific absorption rate (SAR) of radiation delivered to tissues. Rotary echoes or adiabatic excitation combined with a high amplitude spin lock remove artifacts from gradients in the B1 and B0 field, however, increasing the RF field to reduce artifacts and decreasing the RF field to reduce SAR is a vice, limiting the acceptable spin lock amplitude on 1.5 and 3 T clinical scanners to 400600 Hz to obtain a T1rho-weighted image. Also, as scanners continue to increase in field strength to 7 T, there may be no range over which the RF field amplitude is acceptable. A technique to widen the acceptable spin lock range is necessary, particularly in the low-frequency regime where useful clinical contrast is generated by the scalar coupling between 1H and 17O in studies of brain metabolism or static dipoledipole or 1H exchange dynamics in human cartilage.