Markus H
Division of Clinical Neuroscience St George's Hospital Medical School, London, UK.
Stroke. 1993 Aug;24(8):1246-50. doi: 10.1161/01.str.24.8.1246.
The identification of gaseous emboli using Doppler ultrasound was described as early as the 1960s. Recently it has been demonstrated that this method can also detect solid emboli such as thrombi and platelet aggregates. This may make this technology useful in a large number of patients with, or at risk of, embolic stroke.
Emboli appear as short-duration, high-intensity signals in the Doppler spectrum. The intensity of the Doppler signal from an artery containing an embolus depends on the density difference between the embolic material and blood. This difference is greatest for gaseous emboli, which are therefore the most easy to detect. Gaseous emboli have been demonstrated during deep-sea diving, and their presence correlates with the occurrence of decompression sickness. Similar signals have been detected during cardiopulmonary bypass. A relation has been demonstrated between the number of emboli detected by transcranial Doppler and a decline in neuropsychological function after cardiopulmonary bypass. Solid emboli such as thrombi and platelet aggregates result in less intense signals than air emboli. Their detection, using Doppler ultrasound, has recently been described in patients with prosthetic heart valves, atrial fibrillation, and carotid artery disease. It may also help in the detection and localization of embolic sources in patients with stroke. Studies in in vitro and in vivo models demonstrate that this technique provides information on the size and type of emboli. Larger emboli produce signals of greater intensity and duration. Practical patient monitoring will require automatic emboli detectors incorporated into the Doppler machine; such programs are being developed.
Detection of solid emboli using Doppler techniques offers an exciting new diagnostic tool. It has been demonstrated that the technique can detect solid emboli. The prognostic significance of such emboli remains to be determined. It is hoped that the technique will allow detection of patients at high risk of embolic stroke in whom appropriate prophylactic treatment can then be instituted.
早在20世纪60年代就有人描述了使用多普勒超声识别气体栓子。最近已证实，该方法还可检测血栓和血小板聚集体等固体栓子。这可能使该技术对大量患有栓塞性中风或有栓塞性中风风险的患者有用。
栓子在多普勒频谱中表现为持续时间短、强度高的信号。含有栓子的动脉的多普勒信号强度取决于栓塞物质与血液之间的密度差异。气体栓子的这种差异最大，因此最容易检测到。气体栓子已在深海潜水中得到证实，其存在与减压病的发生相关。在体外循环期间也检测到了类似的信号。经颅多普勒检测到的栓子数量与体外循环后神经心理功能下降之间已证实存在关联。血栓和血小板聚集体等固体栓子产生的信号强度低于空气栓子。最近在人工心脏瓣膜、心房颤动和颈动脉疾病患者中描述了使用多普勒超声检测它们的情况。它还可能有助于检测中风患者的栓子来源并对其进行定位。体外和体内模型研究表明，该技术可提供有关栓子大小和类型的信息。较大的栓子产生强度和持续时间更大的信号。实际的患者监测将需要将自动栓子探测器集成到多普勒机器中；此类程序正在开发中。
使用多普勒技术检测固体栓子提供了一种令人兴奋的新诊断工具。已证实该技术可检测固体栓子。此类栓子的预后意义仍有待确定。希望该技术能够检测出有栓塞性中风高风险的患者，然后对其进行适当的预防性治疗。
