Importance of angle correction in the measurement of blood flow velocity with transcranial Doppler sonography.

BACKGROUND AND PURPOSE: The angle of insonation cannot be assessed with conventional transcranial Doppler sonography. Findings in healthy control subjects suggest that the angle is relatively small in routine clinical practice. Data regarding the angle in middle cerebral artery (MCA) stenosis are scarce. In this study, the angle and its effect on flow velocity measurements were assessed with transcranial color Doppler sonography in patients with MCA stenosis. METHODS: Eighteen patients (median age, 53 y; age range, 22-72 y) who satisfied qualifying criteria (eg, angiographically revealed unilateral MCA stenosis of > or =50%) were selected from 149 consecutive patients enrolled in a prospective study of transcranial color Doppler sonography and cerebral digital subtraction angiography. All had active neurologic symptoms. The angle of insonation and peak systolic and mean flow velocities in both MCAs were measured from videotapes generated at sonography. RESULTS: The mean angle of insonation was 47 +/- 11 degrees (range, 19-64 degrees ) on the stenotic side and 34 +/- 18 degrees on the contralateral side (P <.05). Angle-corrected velocities were higher than uncorrected ones. Differences between angle-corrected and uncorrected peak systolic and mean flow velocities on the stenotic side were 46.6% and 45.9%, respectively, of uncorrected values. Differences between corrected and uncorrected peak systolic and mean velocities were larger on the stenotic side compared with those on the contralateral side (P <.05). CONCLUSION: In patients with moderate or severe MCA stenosis, the angle of insonation can be substantial and cause large errors when flow velocities are measured without angle correction.     

Cerebral blood flow velocity and psychomotor performance during acute hypoxia

INTRODUCTION: The physiological effects of hypoxic environments can help determine safe limits for workers where cognitive and motor performance is important. We investigated the effects of a PIO2 of 15 kPa and 10 kPa on medial cerebral artery blood flow velocity (CBFV) and psychomotor performance. METHODS: Over 3 sessions, each involving 3 separate test batteries, 13 subjects breathed either 21 kPa PIO2 (control), 15 kPa PIO2, or 10 kPa PIO2. The tests measured reaction time, spatial orientation, voluntary repetitive movement, and fine manipulation. CBFV, PETCO2, PETO2, Sa02, and BP were recorded throughout. RESULTS: ANOVA analysis showed that 15 kPa PIO2 did not significantly change psychomotor test performance. The mean number of incorrect responses in the reaction time test significantly increased to 5.6 (SD - 4.0) while breathing 10 kPa PIO2, as did the mean number of errors (7.7 +/- 5.0) in the fine manipulation test. Only 10 kPa PIO2 affected CBFV, causing a significant increase in flow from 50 +/- 6.5 cm x s(-1) to 55 +/- 10.3 cm x s(-1). CBFV significantly increased during three psychomotor tests while breathing air; however, it did not increase further during psychomotor testing in hypoxia. DISCUSSION: A PIo2 of 15 kPa did not affect subject performance, and should not cause operational risk. At 10 kPa PIO2, accuracy and vigilance were slightly affected; however, the reduction in oxygenation was not great enough to cause major decrements. CBFV was not a good indicator of mental stress during hypoxia.     

Assessment of blood flow velocity and diameter of the middle cerebral artery during the acetazolamide provocation test by use of transcranial Doppler sonography and MR imaging

BACKGROUND AND PURPOSE: Our purpose was to show changes in the diameter of the M1 segment of the middle cerebral artery (MCA) by using high-resolution MR imaging in patients with chronic internal carotid artery occlusion after IV administered acetazolamide challenge. Changes in blood flow velocity of the basal cerebral arteries are thought to correlate with changes of cerebral blood flow. Changes in the diameter of the basal cerebral arteries, however, might influence the validity of transcranial Doppler measurements. METHODS: Eight patients with internal carotid artery occlusion who were undergoing acetazolamide testing for assessment of cerebrovascular vasomotor reactivity were included in the study. Blood flow velocities of both MCAs were measured with transcranial Doppler sonography before and 25 minutes after the administration of acetazolamide. Before and 15 minutes after the administration of medication, MR imaging was performed contralateral to the occlusion side. A T2-weighted turbo-gradient spin-echo sequence was chosen to show a cross section of the M1 segment in high resolution (pixels, 0.27 x 0.29 mm). Based on interpolated data, the smallest and greatest MCA diameters were determined. RESULTS: We did not find changes in the diameter of the MCA after acetazolamide provocation testing with high-resolution MR imaging in patients with occlusive extracranial carotid artery disease. CONCLUSION: The results of our study support the hypothesis that changes in MCA flow velocity measured by transcranial Doppler sonography reflect relative changes in cerebral blood flow after acetazolamide provocation testing.     

Imaging of the basal cerebral arteries and measurement of blood velocity in adults by using transcranial real-time color flow Doppler sonography

We report an attempt to obtain images of the basal cerebral arteries and to measure the quantitative flow velocity in these arteries from outside the skull via the color Doppler imaging method. In 25 healthy volunteers, 22-41 years old, the transducer was positioned just superior to the zygomatic arch and anterior to the external ear canal. The absolute flow velocity was calculated by dividing the measured velocity by the cosine of the incident angle. The middle cerebral artery was readily identified in all subjects, but the anterior cerebral artery was seen in only 7/50, and the posterior cerebral artery in 27/50. The corrected mean velocity of the horizontal middle cerebral artery was 86 +/- 17 cm/sec at an average incident angle of 49 degrees. However, it was difficult to calculate the absolute flow velocity in the anterior and posterior cerebral arteries because the length of those arteries delineated was too short to read the incident angle. The reproducibility of the mean blood velocity in the middle cerebral artery was tested by two examiners on two different occasions, and showed a linear regression with a correlation coefficient of 0.93 (p less than .001) when the correction with the incident angle was made. Transcranial real-time color-flow Doppler imaging permits more accurate noninvasive quantification of cerebral hemodynamic consequences than previous methods do.     

TCD与彩色多普勒超声对椎动脉流速减慢的对比研究

目的:对比分析椎动脉血流速度减慢患者经颅多普勒(TCD)与彩色多普勒超声(CDFI)检测结果,探讨其有无差异。方法:应用TCD和CDFI分别检测82例椎动脉血流速度减慢患者的椎动脉血流动力学指标及二维结构。结果:TCD与CDFI所测椎动脉血流速度和阻力指数(RI)值比较无差异(P0.05)。结论:TCD与CDFI联合检测椎动脉血流速度减慢患者,可证实椎动脉血液循环障碍的客观存在及病变部位所在,揭示了椎动脉血流速度减慢的病理基础。     

下体负压联合旋转床模拟推拉效应的心率变化特征

目的 建立下体负压联合旋转床模拟推拉效应的方法,观察不同预先-Gz作用后Gz时心率反应的变化特征.方法 8名健康男性志愿者,利用旋转床或联合下体负压随机暴露于预先0°(0 Gz)、-30°(-0.5 Gz)和-90°(-1 Gz),分析在模拟推拉动作时-Gz或0 Gz、"拉"时相及与单纯+1 Gz时相同时间段的平均心率,比较在不同倾斜角度即不同预先-Gz作用或联合下体负压模拟推拉动作时"拉"时相的心率反应.结果 利用旋转床模拟推拉动作时,在"推"时相即头低位时心率显著降低,随倾斜角度的增大降低更加显著,"拉"时相的心率随预先倾斜角度增大回升更明显.下体负压联合旋转床模拟推拉动作时,心率变化与单纯旋转床模拟推拉动作时基本一致.后者在"拉"时相与单纯+1 Gz作用时相比心率变化更大,提示心率回升更加缓慢.结论 旋转床或联合下体负压可以模拟推拉效应,其心率反应随预先-Gz值的增大在"拉"时相回升明显,并且受随后模拟+Gz负荷大小的影响.     

经颅多普勒对活血通窍刺灸法治疗椎动脉型颈椎病的血流动力学观察

目的:通过经颅多普勒(TCD)观察活血通窍刺灸法对椎动脉型颈椎病椎-基底动脉血流动力学的影响。方法:椎动脉型颈椎病患者176例,随机分为活血通窍组和西比灵组,分别于治疗前后行TCD检查,观察2组患者TCD有关指标的变化。结果:2组均能改善椎-基底动脉的血流动力学。结论:活血通窍刺灸法治疗椎动脉型颈椎病具有可靠的依据。     

血管内多普勒超声测定血流速度的可行性研究

目的探讨利用多普勒微探头在血管内多普勒超声(IVDS)测定血流速度的可能性。方法利用一直径为0.3mm的多普勒微探头,先对40例常规脑血管造影的45条不同血管进行插管及波形记录研究,再利用IVDS对14例股-动脉狭窄进行经皮血管成形术(PTA)前后血流速度的对比研究。结果IVDS在健康血管中应用成功率达95.6%(43/45),并记录到与经皮测量相似的典型的动脉血流频谱图;14例股-动脉狭窄中,12例经IVDS证实狭窄病变经球囊成功扩张后血流显著增加,PTA前后血流速度比较,统计学上有非常显著性差异（t=4.01,P<0.01）。结论IVDS测定血流速度是可行的;对于经皮能直接探查到的血管,经皮多普勒超声仍为最佳选择;对于经皮无法直接探查到的血管,IVDS可以作为一种选择。     

经颅多普勒超声动态监测重型颅脑损伤后脑血流动力学变化的临床意义

目的 探讨经颅多普勒超声（ＴＣＤ）动态监测重型颅脑损伤后脑血流动力学变化的临床意义。方法 ６０例重型颅脑损伤患者为观察组,２５名健康体检者为对照组,于重型颅脑损伤后３天、７天、１０天、１４天动态监测ＴＣＤ大脑中动脉（ＭＣＡ）收缩期峰血流速度（Ｖｓ）、平均血流速度（Ｖｍ）和脉动指数（ＰＩ）的变化。结果 重型颅脑损伤后３天,ＭＣＡ－Ｖｍ已明显下降,与对照组相比有明显差异（Ｐ〈０．０５）。ＭＣＡ－Ｖｓ,     

颅内动脉经颅彩色多普勒血流成像研究

目的探讨不同年龄正常人颅内动脉的显示率和内径变化。方法256例正常成人按年龄、性别分6组,采用经颅彩色多普勒血流成像(TCCDFI)、能量多普勒(CDE)及超声造影(ECE)技术,观察颅内动脉走行及血流方向,并测量其血管内径。结果①TCCDFI和CDE颅内动脉成功显示率在男女各组中均随年龄增长而下降。三组女性间差异有显著性意义,老年女性明显低于男性(P<0.05),Willis环完全未显示的老年组被检者行ECE仍有85%可清晰显示;②血管内径随年龄增加而变小且男女间差异有显著性意义(P<0.05)。结论TCCDFI、CDE及ECE能实时动态观测颅内动脉,可作为颅内动脉检查的有效方法。     

The effect of contrast material on transcranial Doppler evaluation of normal middle cerebral artery peak systolic velocity

BACKGROUND AND PURPOSE: Several recent studies have shown that sonographic contrast agents may affect transcranial Doppler evaluation of the arterial peak systolic velocity (PSV). Some investigators reported an increase in PSV, and others reported no change in PSV compared with baseline values. This study was conducted to determine the effect of sonographic contrast agent on PSV measured in normal middle cerebral arteries. METHODS: Continuous spectral Doppler sonography was performed on the right middle cerebral artery of 20 participants with angiographically proven normal intracranial vasculature. Videotaping was performed in each case from the initiation of the administration of contrast medium until the effect of the contrast agent on the PSV subsided. The PSV values were normalized for each participant, were pooled, and were plotted as a function of time. RESULTS: PSV increased in all participants after the administration of contrast material; the mean maximum increase was 24+/-7.4% (mean +/- standard deviation) (range, 15-36%). The mean duration of PSV increase was 320+/-97 s (range, 165-465 s). CONCLUSION: The middle cerebral artery PSV increased substantially after the administration of contrast material. This effect needs to be considered if velocity thresholds developed for disease detection without the use of contrast materials are used when contrast agents are administered.     

Cerebral pulsatility index by transcranial Doppler sonography predicts the prognosis of patients with fulminant hepatic failure

AimCerebral hemodynamic derangement is well known in patients with fulminant hepatic failure. The advent of transcranial Doppler sonography (TCD) enabled noninvasive observation of cerebral hemodynamics. To evaluate its clinical usefulness, we examined longitudinal cerebral hemodynamic parameters in patients with fulminant hepatic failure and severe acute hepatitis.MethodsThe six subjects were four patients with fulminant hepatic failure, one with severe acute hepatitis and one with severe acute exacerbation on chronic hepatitis. The pulsatility indices of the right middle cerebral artery were used as parameters of cerebral hemodynamics.ResultsThe pulsatility indices of the two patients with a deteriorating course had elevated to >1.00, whereas those of the two patients undergoing recovery were within normal limits, as well as of the patients with acute hepatitis or acute exacerbation on chronic hepatitis.ConclusionCerebral pulsatility measured by TCD may be a real-time and useful tool to assess and monitor patients with fulminant hepatic failure.     

Doppler sonography of hepatic arterial blood flow velocity after percutaneous transhepatic portal vein embolization

OBJECTIVE: This study was conducted to elucidate the changes in hepatic arterial blood flow after portal vein embolization. SUBJECTS AND METHODS: We prospectively measured the flow velocity and resistive index of the common, right, and left hepatic arteries, using Doppler sonography, in 21 patients who underwent embolization of the right portal vein. The measurements were performed before and 1, 3, 5, 7, and 14 days after embolization. We assessed the changes in liver volume with a volumetric study using CT. RESULTS: After embolization, flow velocity in the common hepatic artery increased significantly (p < 0.0001). Flow velocity in the right hepatic artery also increased significantly (p < 0.0001), with a significant decrease in resistive index (p < 0.0001). The flow velocity and resistive index of the left hepatic artery were unchanged. The increase in flow velocity in the right hepatic artery significantly correlated with that in the common hepatic artery (r = 0.514, p < 0.05). The calculated volume of the embolized right hepatic lobe significantly (p < 0.0001) decreased, from 685 +/- 32 cm(3) before embolization to 568 +/- 28 cm(3) after embolization. The atrophy rate of the right hepatic lobe significantly correlated with the increase in flow velocity in the right hepatic artery (r = 0.700, p < 0.0005). CONCLUSION: Portal vein embolization induces an increase in hepatic arterial blood flow velocity in the embolized hepatic segments, resulting from an increase in common hepatic arterial flow, but not from a steal phenomenon due to decreased hepatic arterial blood flow in the nonembolized hepatic segments. This observation may be explained by the simple mechanical effect of interposing a slower flowing stream (portal flow) in the path of a faster flowing stream (arterial flow).     

经颅多普勒检测血透病人脑血流动力学改变结果分析

将３０例尿毒症血透病人的经颅多普勒超声检测结果与对照组作对比分析。结果观察组脑动脉收缩峰值速和平均流速显著增快、血管痉挛，与正常对照组比较。大脑中、前动脉搏动指数减低，与正常对照组比较Ｐ＜０．０１。提示尿素症血透病人有脑动脉的血流动力不显著异常和顺应性、弹性减退。这对血液透析并发症的防治有指导意义。     

Cerebral blood flow during acceleration in flight measured with SPECT

INTRODUCTION: Positive pressure breathing for G-protection (PBG) reduces the need for fighter pilots to use the fatiguing anti-G straining maneuver (AGSM) so that they can better endure high acceleration (+Gz). The aim of the study was to determine the differences in cerebral blood flow during flight with an extended-coverage anti-G suit (ECGS) with AGSM or with PBG. METHODS: Subjects were eight male members of the Finnish Air Force. Each was studied in the laboratory at +1 Gz and then during two identical flights in the back seat of the BAe Hawk Mk 51 jet trainer at +6 Gz, first with AGSM and second with PBG (24 mmHg). Regional cerebral blood flow (rCBF) was measured by injecting (99 m) Tc-ECD for deposition at +6 Gz, then scanning the subject in the laboratory an hour later using single photon emission computed tomography (SPECT). RESULT: The rCBF was 30% below baseline for both the AGSM and PBG. CONCLUSIONS: PBG maintained CBF at +6 Gz without the need for the fatiguing AGSM.