Eicke B M, Tegeler C H, Dalley G, Myers L G
Department of Neurology, Bowman Gray School of Medicine, Winston-Salem, NC 27157-1078.
J Neuroimaging. 1994 Jan;4(1):29-33. doi: 10.1111/jon19944129.
Since the introduction of transcranial Doppler sonography in the early 1980s, flow velocity estimates have assumed a 0- to 30-degree angle of insonation. Based on limited radiological and anatomical studies, such as assumption appeared justified, and seemed to confer only minimal potential for error due to the cosine function in the Doppler formula. The introduction of transcranial color duplex sonography allows the direct evaluation of this assumption and the effect on flow velocities. Fifteen healthy volunteers were studied bilaterally using a unilateral transtemporal approach from the right. Velocity measurements were taken from the middle, anterior, and posterior cerebral arteries. Flow velocities were obtained with and without angle correction (0 degree). After completion of the color duplex study, velocities were obtained with a conventional, "blind" Doppler transducer at corresponding depths. For all insonated vessels the average angle of insonation was around 30 degrees. However, there was a wide variability of individual angles of insonation (0-70 degrees) in specific vessels. In 74.5% of all vessels, the angle-corrected flow velocity did not exceed the uncorrected velocity by more than 25%. In 14.5% the angle-corrected velocity was 25 to 50% higher and in 10.8% it was more than 50% higher as compared to the uncorrected velocity. Thus, the angle of insonation was unpredictable and often higher than originally expected. Angle-corrected velocities were higher than uncorrected values, and were more than 25% higher in about one-fourth of the vessels studied. Understanding of the clinical importance of such differences requires further study.
自20世纪80年代初经颅多普勒超声检查问世以来，血流速度估计一直假定入射角度为0至30度。基于有限的放射学和解剖学研究，这样的假设似乎是合理的，并且由于多普勒公式中的余弦函数，似乎只会带来极小的误差可能性。经颅彩色双功超声检查的引入使得可以直接评估这一假设以及对血流速度的影响。对15名健康志愿者采用从右侧进行单侧经颞部的方法进行双侧研究。从大脑中动脉、前动脉和后动脉进行速度测量。在有和没有角度校正（0度）的情况下获取血流速度。在完成彩色双功检查后，使用传统的“盲”多普勒换能器在相应深度获取速度。对于所有被探测的血管，平均入射角度约为30度。然而，特定血管的个体入射角度存在很大差异（0至70度）。在所有血管的74.5%中，角度校正后的血流速度比未校正的速度高出不超过25%。在14.5%的血管中，角度校正后的速度比未校正的速度高25%至50%，在10.8%的血管中，角度校正后的速度比未校正的速度高出50%以上。因此，入射角度是不可预测的，而且往往比最初预期的要高。角度校正后的速度高于未校正的值，并且在所研究的约四分之一的血管中高出超过25%。要理解这种差异的临床重要性还需要进一步研究。
