Rodriguez Rosendo A, Rodriguez Carlos D, Mesana Thierry, Nathan Howard J
Department of Surgery, Division of Cardiac Surgery, University of Ottawa Heart Institute, Ottawa, Ontario, Canada.
J Neuroimaging. 2007 Jul;17(3):211-8. doi: 10.1111/j.1552-6569.2007.00107.x.
To compare the ability of the signal relative-intensity and sample-volume-length (SVL) to discriminate air bubbles from solid spheres in an in-vitro model using two different carrier frequencies of the Doppler transducer.
A gel ultrasound phantom was connected to a circuit in which blood-mimicking fluid circulated. Air bubbles (100-140 microm) and latex spheres (125 +/- 10 microm) were injected into the circuit and interrogated using 1- and 2-MHz transducers. High-intensity-transient-signals (HITS) were recorded with a dual-gated transcranial Doppler (TCD) system. Receiver-Operating-Characteristic curves determined the best cut-off points that would distinguish between embolic materials.
HITS from air bubbles had higher intensities and longer SVL than solid spheres with either transducer (P < .0001). Air bubbles (P < .0001) and microspheres (P= .049) showed higher intensities with the 1-MHz relative to the 2-MHz transducer. The intensity increase with the 1-MHz transducer was greater for air bubbles than microspheres (P < .0001). The discriminating efficacy of both the relative-intensity and SVL was similar between transducers (intensity, P= .201; SVL, P= .98).
The relative-intensity and SVL are equally effective to distinguish solid from air emboli using 1- and 2-MHz transducers. Our study indicates that using a lower carrier frequency does not improve the discrimination of air from solid emboli.
在体外模型中，使用两种不同载波频率的多普勒换能器，比较信号相对强度和样本体积长度（SVL）区分气泡与实心球体的能力。
将凝胶超声体模连接到血液模拟流体循环的电路中。将气泡（100 - 140微米）和乳胶球体（125±10微米）注入电路，并使用1兆赫和2兆赫的换能器进行检测。用双门控经颅多普勒（TCD）系统记录高强度瞬态信号（HITS）。通过绘制受试者工作特征曲线来确定区分栓塞物质的最佳临界点。
使用任何一种换能器时，气泡产生的HITS强度均高于实心球体，且SVL更长（P < 0.0001）。相对于2兆赫换能器，1兆赫换能器检测到的气泡（P < 0.0001）和微球体（P = 0.049）强度更高。1兆赫换能器使气泡强度增加的幅度大于微球体（P < 0.0001）。两种换能器在相对强度和SVL的鉴别效能上相似（强度，P = 0.201；SVL，P = 0.98）。
使用1兆赫和2兆赫换能器时，相对强度和SVL在区分固体栓子与空气栓子方面同样有效。我们的研究表明，使用较低的载波频率并不能提高区分空气栓子与固体栓子的能力。
