Wilke N, Jerosch-Herold M, Stillman A E, Kroll K, Tsekos N, Merkle H, Parrish T, Hu X, Wang Y, Bassingthwaighte J
Center for Bioengineering, University of Washington, Seattle.
Magn Reson Q. 1994 Dec;10(4):249-86.
Based on the major innovations in ultrafast magnetic resonance (MR) imaging in recent years, myocardial perfusion imaging with MR has become the focus of many investigators. Two major approaches to myocardial perfusion imaging involve either exogenous or endogenous contrast agents. For the first category of perfusion experiments, we review the characteristics of the common contrast agents and MR techniques for experimental and clinical first-pass studies and in particular address the question of extracting quantitative estimates for myocardial blood flow (milliliters per minute per gram) and volume (milliliters per gram). We demonstrated quantitative perfusion analysis using intravascular relaxation agents and heavily T1-weighted ultrafast gradient echo sequences. Signal time curves need to be transformed to content time curves and the resulting residue functions were analyzed with a multiple-pathway, axially distributed perfusion model. These preliminary results suggest that quantitative assessment of myocardial perfusion is feasible, but additional studies should provide further confidence for this novel MR approach. The exact sensitivity and specificity of MR first-pass imaging in conjunction with extracellular contrast agents in patient studies and its diagnostic accuracy as judged against coronary angiography and scintigraphic perfusion imaging remain yet undefined. The second category of perfusion experiments does not require exogenous contrast agents and has not yet been tested in patient studies. Progress is reported on several MR perfusion-sensitive methods that use the tissue water as an endogenous contrast agent in combination with magnetization transfer techniques as well as paramagnetic deoxyhemoglobin for measuring tissue oxygenation using heavily T2*-weighted sequences for blood oxygen-level-dependent contrast. Possible future directions and developments toward further improvements for MR myocardial perfusion measurements and contraction-perfusion matching are also addressed.
基于近年来超快磁共振（MR）成像的重大创新，MR心肌灌注成像已成为众多研究者关注的焦点。心肌灌注成像的两种主要方法涉及外源性或内源性对比剂。对于第一类灌注实验，我们回顾了用于实验和临床首过研究的常见对比剂和MR技术的特点，特别探讨了提取心肌血流量（每分钟每克毫升数）和血容量（每克毫升数）定量估计值的问题。我们展示了使用血管内弛豫剂和重T1加权超快梯度回波序列进行定量灌注分析。信号时间曲线需要转换为含量时间曲线，并使用多途径、轴向分布的灌注模型分析所得的残差函数。这些初步结果表明，心肌灌注的定量评估是可行的，但进一步的研究应为此新型MR方法提供更大的可信度。在患者研究中，结合细胞外对比剂的MR首过成像的确切敏感性和特异性，以及与冠状动脉造影和闪烁灌注成像相比的诊断准确性仍未明确。第二类灌注实验不需要外源性对比剂，尚未在患者研究中进行测试。本文报道了几种MR灌注敏感方法的进展，这些方法使用组织水作为内源性对比剂，结合磁化传递技术以及顺磁性脱氧血红蛋白，利用重T2 *加权序列进行血氧水平依赖对比以测量组织氧合。还讨论了未来可能的方向以及为进一步改进MR心肌灌注测量和收缩 - 灌注匹配而进行的发展。
