体外模拟实验研究心脏运动对频谱多普勒血流速度测定的影响

目的：通过体外模拟实验,研究心脏运动对频谱多普勒血流速度测定的影响。方法：设计一套仪器,使它模拟心脏运动的速度和频率并使在其内流动的模拟血液的流速和频率及这两种运动的开启和停止时间都分别可控,观察模拟血流的频谱多普勒在模拟心脏运动影响下的变化及它们之间量的关系。结果：在模拟心脏运动作用下,原来的模拟血流波形已不存在,代之以模拟心脏运动和模拟血流控速度矢量相加规律所组成的复合波,而模拟心脏运动所产生的多普勒频移信号的振幅和频率都未改变且与上述血流信号并存于频谱中,结论：通常所谓的血流速度频谱实际上是血细胞在心脏内流动速度和心脏运动速度的矢量和。即两项运动的复合频谱。所以,为减少误差,在用多普勒血流速度频谱测定血流参数时,应考虑校正问题。     

人体心脏运动对多普勒血流速度频谱测定的影响

目的 观察多普勒血流速度频谱上的心脏运动性多普勒频移信号的幅度是否有真正代表心脏局部运动的速度,进而为纠正血流速度频谱中血流速度测量误差提供方法。方法 以心尖部为探测点,主动脉瓣环处M型超声心动图不同相位的最大运动速度为标准,观察主动脉瓣口多普勒血流速度频谱中相应相位的心脏运动性多普勒频移信号的峰值速度是否与M型测得者相关。结果 心脏运动性多普勒频谱领带不同相位的峰值运动速度与M型超声心动图所测得的相应相位的最大运动速度相关非常显著,r＝0．99。结论 根据本研究和体外模拟实验研究,血液通过各瓣口的真实峰值血流速度为血流速度频谱显示的最大血流速度与心脏运动性多普勒频移信号的峰值速度之和。     

心脏运动对多普勒血流速度频谱分析的影响

本文对37例正常人及16例心脏病人的12对心内及心外取样点上的超声多普勒频谱进行了拟同步分析,发现心内取样点上记录到的所谓血流速度频谱中.有一部分规律出现的频移信号是因心脏本身运动产生的,并非真正的血流信号。本文研究了这些频移信号各波产生的机理、命名,测定了其正常范围的幅度、宽度及与心电图各波间的距离,用模拟实验证实了其产生机理,讨论了这些信号对血流速度频谱测定的影响,为深入理解多普勒血流速度频谱提供了新信息。     

心脏运动对血流速度时间积分测定影响的模拟实验研究

目的 探讨体外模拟心脏运动对多普勒血流流速曲线速度时间积分(VTI)测定的影响。方法用自行设计的TD-3型心底运动模拟仪和血流模拟器，记录两者在不同速度状态下分别运动和同步运动时多普勒流速曲线的特点．观察模拟心脏运动对模拟血流流速曲线VTI测定的影响及其定量关系。结果在模拟心脏运动作用下，模拟血流改变了原有的流速曲线波形，两者同向运动时，模拟血流流速曲线VTI为两者单独运动时的VTI之和．反向运动时为两者单独运动的VTI之差．而模拟心腔运动所产生的多普勒频移信号的速度和频率没有变化。结论模拟心脏运动对模拟血流流速曲线VTI测值有明显影响，在用多普勒方法测量血流量时应当考虑到心脏运动对多普勒测值的影响并加以校正。     

多普勒超声血流测量中仪器因素对速度测量影响的实验研究

目的　探讨不同彩色多普勒超声诊断仪对流速测定的可能影响 ,以及不同仪器测定流速与实际流速的差异和相关性。方法　利用体外模拟血流实验装置模拟 10种流速 ,在控制影响流速测定的主要因素的情况下 ,记录 5台不同类型的多普勒超声仪测定的流速。并使用其中 4台仪器测定 11名健康人的双侧颈总动脉收缩期峰值流速。比较多普勒测速与实际流速的相关性 ,以及不同仪器间流速测定的差异性。结果　体外模拟血流实验中多普勒测定的流速多数高于实际流速 ,但与实际流速之间有很好的相关性 (r=0 .96 4～ 0 .992 ,P<0 .0 0 0 5 )。 5台仪器的测定流速之间无显著性差异 ,但对流速大于 33.0 0 cm/s的数据进行分析可见其中 1台仪器与其他 4台仪器的测定流速两两之间存在显著性差异 (P<0 .0 5 )。进行人体颈总动脉的流速检测的 4台仪器中 ,该台仪器与其余 3台仪器的测速之间均有显著性差异 (P<0 .0 1)。结论　多普勒测量的流速与实际流速之间有很好的相关性 ,是评价血流动力学的有效手段。不同的多普勒超声仪器的流速测定可能存在一定差异 ,在评价正常或疾病情况下的血流速度时应当考虑到仪器因素 ,比较不同的研究结果应以已知测量的其他条件为前提。     

多普勒超声测定家兔颈总动脉血流速度及影响血流速度因素的实验研究

本文应用Doppler超声对20只兔颈总动脉血流速度的测量进行了实验研究,并对有关影响因素进行了探讨。实验结果表明:用Doppler超声探测颈部血流速度的变化基本反映体内血流量的变化。在血液动力学变化不大情况下,血流速度和血流量变化密切相关。经皮肤无创测量血流速度与经颈总动脉壁测量血流速度的相关性良好。从体外无创测得的血流速度变化大体可以正确反映血管内血流的实际流速变化。本研究表明应用Doppler超声法测定小动脉(直径1.5～2.0mm)血流速度变化是可行的。该技术在口腔颌面部血管血流方面的基础研究和临床疾病诊断及有关应用,将具有很大潜力。     

多普勒角度校正功能对血流速度测量的影响

目的：为了强调正确使用多普勒角度校正功能在外周血管血流速度测量的重要性，我们测量不同角度下正常人颈总动脉血流速度频谱，分析了不同角度对多普勒血流测量影响。资料与方法：仪器应用美国Ａｃｕｓｏｎ１２８ＸＰ１０型彩色电脑声像仪，检测正常人不同取样角度下颈总动脉最大血流速度、速度时间积分及计算每分血流量。结果：当改变角度校正线时，测量数据产生明显变化，角度在２０°以内，每变化１０°，最大血流速度变化平均１－２ｃｍ／ｓ，每分血流量变化平均１０～２２ｍｌ；同样１０°变化，角度从５０°～６０°，最大血流速度则由平均７９～１０２ｃｍ／ｓ，每分血流量平均７１６～９１２ｍｌ。结论：在外周血管血流检测中，要注意精确地将角度校正线调整到与血流方向平行的位置上，尽量减小声束与血流方向夹角，以便获得可信的血流动力学信息     

彩色多普勒超声检测腮腺血流的研究

目的:探讨彩色多普勒超声检测腮腺血流的临床价值。方法:采用彩色多普勒超声检测40名健康人的腮腺血流,并观测酸刺激前后血流动力学的变化。结果:彩色多普勒超声可清楚了解血管的类型、分支及伴行方式。酸刺激前腮腺腺体小动脉最高流速、最低流速、阻力指数分别为20.1±6.9cm/sec,0.2±1.5cm/sec及1.0±0.1;酸刺激后则分别为25.2±6.6cm/sec,2.5±2.8cm/sec及0.9±0.1,酸刺激前后各项指标有显著性差别(P<0.01)。结论:彩色多普勒超声是检测腮腺血流的良好临床检查手段。     

胎儿二尖瓣口血流速度的多普勒超声研究

报告孕龄在２１～３８周的孕妇６８例，按孕龄将胎儿分为三个组：２１～２６周，２７～３２周，３３～３８周。测量胎儿二尖瓣口的血流速度Ｅ、Ａ、Ｅ／Ａ、ＥＩ、ＡＩ、ＥＩ／ＡＩ、ＴＩ、ＳＶ＝ＴＩ·Ａｒｅａ。结果显示：①Ｅ、ＥＩ随胎龄的增加而显著增加；②Ａ峰随胎龄的增加而轻度降低，这种变化没有显著性差异；③Ｅ／Ａ、ＥＩ／ＡＩ随胎龄而增加，具有显著性；④ＳＶ胎龄而增加，在每二组间都有显著性；⑤ＨＲ变化不大。     

血流动力学对能量多普勒显像的影响：血流速度的影响

目的：在实验模型中观察血流速度对能量多普勒显像（ＰＤＩ）的影响。方法：在３ｍｍ内径硅胶管中模拟不同血流速度（２．０～３３．２ｃｍ／ｓｅｃ）的血流。记录ＰＤＩ血流图,用计算机分析血流的彩色像素面积（ＣＰＡ）和彩色亮度（ＣＶ）。结果：血流速度与ＰＤＩ血流的ＣＰＡ和ＣＶ呈正相关,其中ＣＰＡ：ｒ＝０．８３４,Ｐ＜０．０１;ＣＶ：ｒ＝０．８４８,Ｐ＜０．０１,尤其在血流速度为８．３ｃｍ／ｓｅｃ以下时变化最明显。结论：血流速度对ＰＤＩ血流的血流面积和亮度均有影响。     

On the measurement of the mean velocity of blood flow over the cardiac cycle using Doppler ultrasound

A number of modern duplex scanners now have facilities for determining volumetric blood flow through intact vessels. The methods these machines use to arrive at an answer must presuppose a number of conditions which may not be met in practice. This paper examines the effect that nonuniform insonation of the target blood vessel (using continuous wave or wide-gate pulsed ultrasound) has on the mean velocity, as determined using mean, root mean square (RMS) and maximum frequency processors. It is shown that for a given beam/vessel geometry the error is dependent only on the shape of the mean component of the velocity profile which, depending on the arterial site, may be flat, parabolic or intermediate. Mean processors may overestimate the mean velocity of established flow by up to 33%, but this could be turned to advantage when it is impracticable to insonate a vessel uniformly. Maximum frequency processors are of value when either plugflow or fully established flow of low pulsatility is present in the target vessel. In the first case the mean flow is the same as the maximum flow, while in the second the mean flow is half the time averaged maximum flow, irrespective of the size and shape of the ultrasound beam. RMS processors are probably best avoided in volumetric flow measurement applications.     

Effect of microbubble contrast on intracranial blood flow velocity assessed by transcranial Doppler

Purpose

Ultrasound contrast agents (UCA) salvage a considerable number of transcranial Doppler (TCD) exams which would have failed because of poor bone window. UCA bolus injection causes an undesirable increase in measured blood flow velocity (BFV). The effect of UCA continuous infusion on measured BFV has not been investigated, and some in vitro experiments suggest that gain reduction during UCA administration may also influence measured BFV. This study aimed to investigate the effect of UCA continuous infusion on BFV measured by TCD and the influence of gain reduction on these measurements in a clinical setting.

Methods

The right middle cerebral artery of ten patients with optimal bone window was insonated using a 2 MHz probe. UCA were administered using an infusion pump. BFV was measured (1) at baseline, (2) during UCA infusion, (3) during UCA infusion with gain reduction, and (4) after UCA wash-out phase. Gain reduction was based on the agreement between two neurosonographers on the degree of gain reduction necessary to restore baseline Doppler signal intensity (DSI). Actual DSI was estimated offline by analysis of raw data.

Results

BFV measured during UCA infusion with no gain adjustment was significantly higher than baseline BFV [peak systolic velocity (PSV): 85.1 ± 19.7 vs. 74.4 ± 19.7 cm/s, p < 0.0001; Mean velocity (MV): 56.5 ± 11.8 vs. 50.2 ± 12.3 cm/s, p < 0.0001]. BFV measured during UCA infusion with gain reduction was not significantly higher than baseline BFV (PSV: 74.3 ± 18.9 vs. 74.4 ± 19.4 cm/s, p = 0.8; MV: 49.4 ± 11.0 vs. 50.2 ± 12.3 cm/s, p = 0.8). Actual DSI during UCA infusion with gain reduction was not significantly higher than baseline DSI (13 ± 1 vs. 13 ± 1 dB).

Conclusion

This study shows that UCA continuous infusion leads to an increase in measured BFV which may be counteracted by reducing Doppler gain thus restoring pre-contrast DSI.     

正常青年人汉语认知活动与脑血流速度变化的相关性研究

目的:探讨汉语认知任务的完成对脑血流速度的影响。方法:在进行汉语词语联想、句子重建、近意词辨别认知任务时及其先前的休息期,对45个正常的志愿者(右利手)用经颅超声多普勒监测其双侧大脑中动脉血流速度的变化。结果:完成认知任务时与休息时期相比,所有认知任务的完成均诱导出双侧大脑中动脉血流速度的显著增加(P<0.01):词语联想任务左侧相对增加14.2±4.7,右侧8.5±2.8,句子重建左侧相对增加13.8±3.2,右侧8.6±2.2,近意词辨别左侧相对增加13.0±6.4,右侧7.3±3.1;并显现出显著的左侧半球偏侧化。性别对部分认知活动诱导的脑血流速度变化产生影响,但男女性别间偏侧化倾向无显著差异。结论:词语联想、句子重建、近意词辨别任务可诱导脑血流速度的左侧偏侧化。     

Blood flow velocity changes in migraine attacks-a transcranial Doppler study

A pulsed Doppler device was used to measure blood flow velocities in the common carotid artery, the extracranial part of the internal carotid artery, the external carotid artery, the middle cerebral artery, and the anterior cerebral artery in 31 migraineurs without aura (n = 27) and with aura (n = 4), both during and outside an attack. The aims were to compare blood flow velocity during and between migraine attacks and to study asymmetries of the blood flow velocity. Compared with blood flow velocity values obtained in the attack-free interval, blood flow velocity was lower during attacks without aura in both common carotid arteries, but not in the other extra- and intracranial vessels which were examined. However, during attacks of migraine with aura, blood flow velocity tended to be lower in all examined vessels. There were no asymmetries of the blood flow velocity. We suggest that during migraine attacks without aura there is a dissociation in blood flow regulation in the common carotid and middle cerebral arteries.     

Effect of hypertension and candesartan on the blood flow velocity of the extraocular vessels in hypertensive patients

OBJECTIVE: To define alterations in the blood flow velocities of the ophthalmic artery (OA), central retinal artery (CRA), posterior ciliary artery (PCA) in essential hypertension and to evaluate the effect of a new antihypertensive drug, candesartan which is an angiotensin II receptor antagonist, on the blood flow velocity in hypertensive patients. METHODS: Blood flow velocity and resistive index (RI) of the OA, CRA, and PCA were measured in 22 hypertensive patients off medication and 15 controls by color Doppler imaging. After treatment with candesartan, blood flow velocity and RI were again measured in the hypertensive patients. RESULTS: In controls (n=15), the OA had a mean peak systolic flow velocity (PSFV) of 48.1+/-2.6 cm/s, mean end diastolic flow velocity (EDFV) of 16+/-1.0 cm/s, and RI of 0.65+/-0.01; the CRA had a PSFV of 20.8+/-0.4 cm/s, EDFV of 9.4+/-0.3 cm/s, and RI of 0.54+/-0.01; the PCA had a PSFV of 23.6+/-0.7 cm/s, EDFV of 11.2+/-0.3 cm/s, and RI of 0.52+/-0.01. There was a significant decrease in the PSFV and EDFV of the vessels in the medication free hypertensive patients when compared with controls (P<0.05). In the hypertensive patients off medication (n=22), the OA had a PSFV of 29.4+/-1.2 cm/s, EDFV of 10.4+/-0.5 cm/s, and RI of 0.71+/-0.01; the CRA had a PSFV of 15.1+/-0.6 cm/s, EDFV of 5.4+/-0.3 cm/s, and RI of 0.65+/-0.02; the PCA had a PSFV of 17.2+/-0.6 cm/s, EDFV of 6.7+/-0.3 cm/s, and RI of 0.61+/-0.01. RI measured in the OA, CRA, PCA were significantly increased in the hypertensive patients when compared with the controls (P<0.05). In hypertensive patients after medication (n=22), OA had a PSFV of 38.3+/-2.5 cm/s, EDFV of 12.3+/-0.7 cm/s, and RI of 0.68+/-0.01; CRA had a PSFV of 19.2+/-0.5 cm/s, EDFV of 7.8+/-0.3 cm/s, and RI of 0.59+/-0.01; PCA had a PSFV of 20.8+/-0.8 cm/s, EDFV of 9.2+/-0.4 cm/s, and RI of 0.56+/-0.01. There was a significant increase in the blood flow velocities of the OA, CRA, PCA (P<0.05) and significant decrease in the RI values in the treated hypertensive patients when compared with the controls (P<0.05). But blood flow velocities and RI values did not reach the control level. CONCLUSION: The increase in the RI values and the decrease in the blood flow velocity of extraocular vessels in the hypertensive patients are thought to be caused by increased peripheral resistance in the vessels of the eye and orbit. Although, it increases blood flow velocity and decreases RI significantly, candesartan treatment in the hypertensive patients cannot increase blood flow velocity and decrease RI to the control level.     

Color and conventional image-directed Doppler ultrasonography: accuracy and sources of error in quantitative blood flow measurements.

Accuracy of two systems--conventional (DRF 400, Diasonics) and color-coded (Angiodynograph, Quantum/Phillips) image-directed Doppler ultrasonography--was investigated using an in vitro model that generated both monophasic and triphasic pulsatile flow patterns. Estimated and actual blood volume flow rates showed good correlations, but the sampling with a hand-held transducer led to wide variations in measurement error for the conventional (-69.2% to 50%) and the color-coded (-79.3% to 265.7%) systems. By performing multiple measurements, one could improve accuracy considering only the maximal values of a series instead of the mean values. Accuracy was impaired by interposed muscular or fatty tissue due to false low time-average velocity measurements caused by a loss of Doppler signal. Comparison of both systems revealed significant differences between pulsatility index values (p less than 0.001), blood flow velocities (p less than 0.001), and blood volume flow rates (p less than 0.05 for program flow, p less than 0.001 for manual and automatic flow program of the color-coded system).     

Carotid artery flow volume and velocity by duplex sonography in men with chronic low thoracic and lumbar spinal cord injury

OBJECTIVE: To investigate the common carotid blood flow volume and velocity in men with chronic low thoracic and lumbar spinal cord injury (SCI), using duplex sonography. DESIGN: Experimental control study. SETTING: University laboratory in a department of rehabilitation medicine. PARTICIPANTS: Twenty men with SCI between the T7 and L1 segments and 15 age- and sex-matched control subjects. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Common carotid artery flow volume and velocity. RESULTS: The mean carotid artery time-averaged flow velocity of subjects with SCI was significantly lower than that of control subjects. Moreover, the mean carotid flow volume of subjects with SCI was significantly lower than that of control subjects (right side: SCI, .52+/-.14 L/min; controls, .67+/-.10 L/min; P <.05; left side: SCI, .54+/-.15 L/min; controls, .72+/-.14 L/min; P <.05). CONCLUSIONS: There are reduced common carotid artery flow volumes and flow velocities in men with chronic SCI. The reduction may result from disturbances of blood distribution induced by reduced vasoconstriction tone below the level of SCI lesion.