Center for Magnetic Resonance Research and Department of Radiology, University of Minnesota Medical School, Minneapolis, Minnesota, USA.
Magn Reson Med. 2024 Jan;91(1):149-161. doi: 10.1002/mrm.29839. Epub 2023 Aug 15.
To develop a new MRI method, entitled alternating Look-Locker (aLL), for quantitative , , and 3D mapping.
A Look-Locker scheme that alternates magnetization from +Z and -Z axes of the laboratory frame is utilized in combination with a 3D Multi-Band Sweep Imaging with Fourier Transformation (MB-SWIFT) readout. The analytical solution describing the spin evolution during aLL, as well as the correction required for segmented acquisition were derived. The simultaneous and mapping are demonstrated on an agar/saline phantom and on an in-vivo rat head. relaxation was achieved by cyclically applying magnetization preparation (MP) modules consisting of two adiabatic pulses. values in the rat brain in-vivo and in a gadobenate dimeglumine (Gd-DTPA) phantom were compared to those obtained with a previously introduced steady-state (SS) method.
The accuracy and precision of the analytical solution was tested by Bloch simulations. With the application of MP modules, the aLL method provides simultaneous and maps. Conversely, without it, the method can be used for simultaneous and mapping. values were similar with both aLL and SS techniques. However, the aLL method resulted in more robust quantitative mapping compared to the SS method. Unlike the SS method, the aLL method does not require additional scans for generating maps.
The proposed method offers a new flexible tool for quantitative mapping of , , and . The aLL method can also be used with readout schemes different from MB-SWIFT.
开发一种新的 MRI 方法，称为交替 Look-Locker（aLL），用于定量、 和 3D 映射。
利用实验室框架中交替的+Z 和-Z 轴的 Look-Locker 方案与 3D 多带扫频成像与傅里叶变换（MB-SWIFT）读取相结合。推导了描述 aLL 期间自旋演化的解析解，以及分段采集所需的校正。在琼脂/盐水体模和体内大鼠头部上演示了同时的 和 映射。通过周期性地施加由两个绝热脉冲组成的磁化准备（MP）模块来实现 弛豫。将体内大鼠脑和钆喷替酸二葡甲胺（Gd-DTPA）体模中的 值与先前介绍的稳态（SS）方法获得的值进行比较。
通过 Bloch 模拟测试了解析解的准确性和精度。通过应用 MP 模块，aLL 方法提供同时的 和 图谱。相反，如果没有它，则可以使用该方法同时进行 和 映射。两种 aLL 和 SS 技术的 值相似。然而，与 SS 方法相比，aLL 方法的定量映射更稳健。与 SS 方法不同，aLL 方法不需要生成 图谱的额外扫描。
所提出的方法为定量 、 和 映射提供了一种新的灵活工具。aLL 方法也可与不同于 MB-SWIFT 的读取方案一起使用。
