Russell David, Brucher Rainer
Department of Neurology, the National Hospital, Oslo, Norway.
Stroke. 2002 Aug;33(8):1975-80. doi: 10.1161/01.str.0000022809.46400.4b.
The aim of this study was to assess the first multifrequency transcranial Doppler system that was specially developed to automatically detect and discriminate between solid and gaseous cerebral microemboli.
The multifrequency transcranial Doppler instrumentation insonates simultaneously with 2.5 and 2.0 MHz. Differentiation between solid and gaseous microemboli is based on the principle that solid microemboli reflect more ultrasound at the higher than at the lower frequency, whereas the opposite is the case for gaseous microemboli. In the in vitro studies, 159 plastic spheres (50 or 80 micro m in diameter) and 105 gas bubbles (8 to 25 micro m) were studied in a pulsatile closed-loop system containing irodinium or pig blood. In vivo studies were carried out for 1 hour in 15 patients with mechanical heart valves and in 45 patients with carotid stenosis. This gave a total of 60 hours of online automatic monitoring in patients.
In the in vitro studies, 152 of the 159 (95.6%) plastic spheres were classified as solid, and 7 (4.4%) were classified as uncertain solid. Of the 105 gas bubbles, 99 (94.3%) were classified as gaseous and 6 (5.7%) as uncertain gaseous. Thus, correct classification was made for 251 (95.1%) of the 264 embolic events studied. A comparison between the automatic multifrequency discrimination and the known embolic classification gave a kappa value of 0.897 (P<0.0001). The multifrequency Doppler classified 433 (84.2%) of the 514 emboli detected in the mechanical heart valve patients as gaseous, 74 (14.4%) as solid, and 7 (1.4%) as uncertain (3 uncertain solid, 4 uncertain gas). Thirty-two emboli were detected in 17 (38%) of the 45 carotid stenosis patients; 30 (93.7%) were classified as solid and 2 (6.3%) as uncertain solid.
This study has shown that multifrequency transcranial Doppler can be used to automatically differentiate between solid and gaseous microemboli online. Most detected microemboli in this initial study of mechanical heart valves were classified as gaseous, whereas most were classified as solid in the patients with carotid stenosis.
本研究旨在评估首个专门开发用于自动检测和区分实性与气态脑微栓子的多频经颅多普勒系统。
多频经颅多普勒仪器同时以2.5MHz和2.0MHz进行超声探测。实性与气态微栓子的区分基于这样的原理：实性微栓子在较高频率下比在较低频率下反射更多超声，而气态微栓子情况则相反。在体外研究中，在含有伊洛定或猪血的脉动闭环系统中研究了159个塑料球（直径50或80μm）和105个气泡（8至25μm）。对15例机械心脏瓣膜患者和45例颈动脉狭窄患者进行了1小时的体内研究。这为患者提供了总共60小时的在线自动监测。
在体外研究中，159个塑料球中有152个（95.6%）被归类为实性，7个（4.4%）被归类为不确定实性。105个气泡中，99个（94.3%）被归类为气态，6个（5.7%）被归类为不确定气态。因此，在所研究的264个栓塞事件中，251个（95.1%）得到了正确分类。自动多频鉴别与已知栓塞分类之间的比较得出kappa值为0.897（P<0.0001）。多频多普勒将机械心脏瓣膜患者中检测到的514个栓子中的433个（84.2%）归类为气态，74个（14.4%）归类为实性，7个（1.4%）归类为不确定（3个不确定实性，4个不确定气态）。在45例颈动脉狭窄患者中的17例（38%）中检测到了32个栓子；30个（93.7%）被归类为实性，2个（6.3%）被归类为不确定实性。
本研究表明多频经颅多普勒可用于在线自动区分实性与气态微栓子。在这项对机械心脏瓣膜的初步研究中，检测到的大多数微栓子被归类为气态，而在颈动脉狭窄患者中大多数被归类为实性。
