Thomas David L, Lythgoe Mark F, Gadian David G, Ordidge Roger J
RCS Unit of Biophysics, Institute of Child Health, University College London, 30 Guilford Street, London WC1N 1EH, United Kingdom.
Neuroimage. 2002 Apr;15(4):992-1002. doi: 10.1006/nimg.2001.1042.
A new MRI sequence for the rapid simultaneous measurement of T2 and T2* is presented. The technique uses the multiple acquisition of spin and gradient echoes with interleaved echo planar imaging (MASAGE-IEPI). IEPI data sets are sampled during and between a pair of short and long echo time spin echoes, allowing the reconstruction of a set of images with different combinations of T2 and T2* weighting and the calculation of T2 and T2* maps. In the context of neuroimaging, these maps can provide information on cerebral hemodynamics and oxygenation status, either via the deoxyhemoglobin-based BOLD signal or by the effect of exogenous paramagnetic contrast agents. MASAGE-IEPI benefits from the inherent advantages of the IEPI approach, i.e., high time resolution and minimal image distortion, and also has good time efficiency due to the acquisition of multiple image data sets following each excitation pulse. The accuracy of the sequence for the measurement of T2 and T2* is verified on phantoms, and the technique is applied to monitor changing hemodynamics in the rat brain during episodes of hypoxia. Data for the generation of maps of T2 and T2* are acquired with a time resolution of 12 s to accurately define the rapidly changing time course. As increasing emphasis is placed on the role of T2 and T2* in the direct measurement of physiological parameters such as cerebral metabolic rate of oxygen consumption and blood vessel sizes, MASAGE-IEPI offers an efficient method for the measurement of these two important MRI parameters.
本文介绍了一种用于快速同时测量T2和T2的新型磁共振成像（MRI）序列。该技术采用多采集自旋回波和梯度回波并结合回波平面成像（MASAGE-IEPI）。在一对短回波时间和长回波时间自旋回波期间及之间对IEPI数据集进行采样，从而能够重建具有不同T2和T2加权组合的一组图像，并计算T2和T2图谱。在神经成像领域，这些图谱可通过基于脱氧血红蛋白的血氧水平依赖（BOLD）信号或外源性顺磁性造影剂的作用，提供有关脑血流动力学和氧合状态的信息。MASAGE-IEPI受益于IEPI方法的固有优势，即高时间分辨率和最小的图像失真，并且由于在每个激发脉冲后采集多个图像数据集，还具有良好的时间效率。该序列测量T2和T2的准确性在体模上得到验证，并将该技术应用于监测大鼠脑在缺氧发作期间血流动力学的变化。以12秒的时间分辨率采集生成T2和T2图谱的数据，以准确界定快速变化的时间进程。随着对T2和T2在直接测量诸如脑氧代谢率和血管大小等生理参数方面作用的日益重视，MASAGE-IEPI为测量这两个重要的MRI参数提供了一种有效的方法。
