PARACEST MRI with improved temporal resolution.
PARACEST MRI with improved temporal resolution.
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DOI：
10.1002/mrm.21863
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发表时间：
2009-02
影响因子：
3.3
通讯作者：
Pagel MD
中科院分区：
文献类型：
--
作者：
Liu G;Ali MM;Yoo B;Griswold MA;Tkach JA;Pagel MD
顺磁化学交换饱和转移 (PARACEST) 是一种新颖的 MRI 对比机制。分子成像的体内 MRI 应用非常需要具有高时间分辨率的 PARACEST MRI 方法。为了满足这一需求，我们开发了一种策略，其中包括在每次重复弛豫增强快速采集 (RARE) 脉冲序列之前有一个较长的选择性饱和期。该策略适用于将 PARACEST 造影剂应用于 T1 弛豫时间较长的环境。另一种策略是在采集每个 k 空间轨迹之前使用短的选择性饱和周期来维持稳态条件，这可以通过快速低角度发射 (FLASH) 脉冲序列来实现。与第一种方法相比，这些短的饱和周期延长了总扫描时间，但补偿了与 T1 弛豫相关的 PARACEST 对比度损失。与传统的梯度回波 PARACEST 方法相比，这两种方法均已在体外和体内证明具有显着提高的时间分辨率，且不牺牲 CNR 效率。这些演示还采用了测量 PARACEST 效应的策略，仅需要在单个 MR 频率下选择性饱和，这进一步提高了 PARACEST 检测的时间分辨率。
PARAmagnetic Chemical Exchange Saturation Transfer (PARACEST) is a novel contrast mechanism for MRI. A PARACEST MRI methodology with high temporal resolution is highly desired for in vivo MRI applications of molecular imaging. To address this need, a strategy has been developed that includes a long selective saturation period before each repetition of a Rapid Acquisition with Relaxation Enhancement (RARE) pulse sequence. This strategy is suitable for the application of PARACEST contrast agents to environments with long T1 relaxation times. An alternative strategy uses short selective saturation periods before the acquisition of each k-space trajectory to maintain steady state conditions, which can be implemented with a Fast Low Angle Shot (FLASH) pulse sequence. These short saturation periods lengthen the total scan time as compared to the first approach but compensate for the loss in PARACEST contrast related to T1 relaxation. Both approaches have been demonstrated in vitro and in vivo with significantly improved temporal resolutions as compared to a conventional gradient-echo PARACEST method without sacrificing CNR efficiency. These demonstrations also adopted a strategy for measuring the PARACEST effect that only requires selective saturation at a single MR frequency, which further improves temporal resolution for PARACEST detection.