CEREBRAL PERFUSION IMAGING

使用MRI对脑灌注成像是一个令人兴奋的发展， 临床MRI 由于核磁共振信号可以对 通过在磁场中施加梯度来进行分子运动， 这种技术被称为“扩散加权成像”（DWI）。 但 有几种技术不能给出一致的结果。 的一个小组 NIH发现，脑内水的DWI与脑组织的灌注有关。 微血管水平 这一结果与MGH的一个小组相矛盾。 在 在每种情况下，尚不清楚哪种技术可以可靠地区分内部， 血管外的水 我们的实验使用氟化血液 替代品（FBS），这是严格的血管内。 由于FBS现在不是 虽然这些药物被批准用于人类，但实验只能在动物身上进行。 我们 初步实验已经证明DWI显示信号损失 的FBS远远超过什么是已知发生的结果， 分子扩散;即，我们已经证明了灌注敏感MR 形象 然而，我们的结果与NIH的结果在数量上不一致 组和需要更多的研究，以澄清和特点的影响。 此外，希望了解已知的影响。 血管扩张剂CO2以及从L-精氨酸合成NO的影响， 从而选择性地改变脑灌注。 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 在什么时间间隔内毛细流动模拟非相干（随机） 流 我们还可以选择性地将接收到的信号加权到 动脉或静脉血管，以阐明它们对 效果 澄清这些要点将改善科学基础 用于诊断许多病理状态，如梗塞、肿瘤、AVM， 等质子弥散加权成像在临床上用于人体时，

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.