Liu G, Sobering G, Olson A W, van Gelderen P, Moonen C T
In Vivo NMR Research Center, BEIP, NCRR, National Institutes of Health, Bethesda, MD 20892.
Magn Reson Med. 1993 Jul;30(1):68-75. doi: 10.1002/mrm.1910300111.
The principles of a fast T2*-sensitized MR imaging method (Moonen et al., Magn. Reson. Med. 26, 184 (1992)) are extended to further increase T2* sensitivity. It is shown that the period of T2*-weighting can be lengthened by n TR-periods by appropriate gradient schemes without RF refocusing resulting in progressively delayed gradient-recalled echoes. This extension of the echo-shifting concept thus introduces large flexibility in the choice of T2*-weighting without changing total imaging time. The coherence pathway formalism is used to evaluate and describe the selection of the desired echo and the attenuation of unwanted coherences. The new techniques are demonstrated for tracking a bolus of susceptibility contrast agent in cat brain. Relative blood-volume maps are derived with expected contrast between white and gray matter.
一种快速T2敏感磁共振成像方法（Moonen等人，《磁共振医学》26卷，184页（1992年））的原理得到扩展，以进一步提高T2敏感性。结果表明，通过适当的梯度方案，在不进行射频重聚焦的情况下，T2加权期可以延长n个重复时间（TR）期，从而产生逐渐延迟的梯度回波。因此，这种回波移位概念的扩展在不改变总成像时间的情况下，为T2加权的选择引入了很大的灵活性。相干路径形式主义用于评估和描述所需回波的选择以及不需要的相干性的衰减。新技术用于在猫脑中追踪一团顺磁性造影剂。得出了具有预期白质和灰质对比度的相对血容量图。
