CEREBRAL PERFUSION IMAGING

使用核磁共振成像脑血流是一项令人兴奋的发展 临床核磁共振检查。由于核磁共振信号可以被精确地敏感于 通过在磁场中应用梯度来实现分子运动，这 这项技术被称为“扩散加权成像”(DWI)。然而，在那里 有几种技术不能给出一致的结果。一组位于 美国国立卫生研究院发现，大脑中的水的DWI与脑部 微血管水平。这一结果遭到了麻省理工学院的一个小组的反驳。在……里面 每种情况下，还不清楚哪种技术可以可靠地区分 来自血管外的水。我们的实验使用的是含氟血液 代用品(FBS)，严格地说是血管内的。因为FBS现在不是 这些实验被批准用于人类，只能在动物身上进行。我们的 初步实验表明，弥散加权成像显示信号丢失 FBS的比例远远超过了已知的 分子扩散；也就是说，我们已经证实了一种对血流灌注敏感的MR。 图像。然而，我们的结果与美国国立卫生研究院的结果在数量上不一致。 并需要更多的研究来澄清和描述这种影响。 此外，我们希望了解已知因素的影响 血管扩张剂二氧化碳及其对L-精氨酸合成一氧化氮的影响 这会选择性地改变大脑的灌注量。我们的核磁共振技术可以 区分相干和非相干流型；一个主要问题是 毛细管流在多长时间间隔内模拟非相干(随机) 流。我们还可以有选择地对接收的信号进行加权 动脉或静脉血管，以澄清它们对 效果。澄清这些观点将提高科学基础。 用于多种病理状态的诊断，如脑梗塞、肿瘤、动静脉畸形、 等质子弥散加权成像在临床上应用于人体。

The use of MRI to image cerebral perfusion is an exciting development in clinical MRI. Since the NMR signal can be made exquisitely sensitive to molecular motion by applying gradients in the magnetic field, this technique is called "diffusion weighted imaging" (DWI). However, there are several techniques which do not give consistent results. A group at NIH found that a DWI of water in the brain was related to perfusion at the microvascular level. This result was contradicted by a group at MGH. In each case, it is not clear which technique can reliably distinguish intra- from extra-vascular water. Our experiments utilize fluorinated blood substitutes (FBS), which are strictly intravascular. Since FBS is not now approved for human use, the experiments are done only in animals. Our preliminary experiments have demonstrated that DWI shows a loss of signal of the FBS far in excess of what is known to occur as a result of molecular diffusion; i.e., we have demonstrated a perfusion sensitive MR image. However, our results disagree quantitatively with those of the NIH group and require more study to clarify and characterize the effect. Furthermore, it is desirable to understand the influence of the known vasodilator CO2 as well as the influence of NO synthesis from L-Argine, which alters cerebral perfusion in a selective way. Our MRI technique can distinguish coherent from incoherent flow patterns; a major question is over what time interval does capillary flow mimic incoherent (random) flow. We can also selectively weight the received signal towards the arterial or venus vessels to clarify their relative contributions to the effect. Clarification of these points will improve the scientific basis for diagnosis of many pathologic states, such as infarction, tumor, AVM, etc. when proton DWI is used clinically in humans.