Time-averaged Maximum Velocity Research Articles

Fetal cerebral blood flow velocity during labor and the early neonatal period.

This study was performed to elucidate circulatory changes in the fetal cerebral circulation during uncomplicated labor and in early neonatal life. Eighteen healthy term singleton fetuses were followed longitudinally during labor. Using the transabdominal approach, and the color Doppler technique, the middle cerebral artery was identified and Doppler flow velocity waveforms recorded between and during uterine contractions. Neonatal recordings were made by insonating the middle cerebral artery from the temporal region before and immediately after the cutting of the umbilical cord, and at 1 hour and 1 day after birth. The recorded Doppler signals were evaluated for pulsatility index, heart rate, peak systolic flow velocity, end-diastolic flow velocity and time-averaged maximum velocity. There was no change in the pulsatility index between and during contractions (1.39 +/- 0.36 and 1.40 +/- 0.39, respectively, mean +/- SD). A significant decrease in the pulsatility index compared to fetal values was seen 4 min after birth (1.06 +/- 0.30, p < 0.01). One hour after birth, the pulsatility index values increased significantly (1.52 +/- 0.25, p < 0.001), to fall again between I hour and 1 day after birth (0.95 +/- 0.26, p < 0.001). Mechanical compression of the skull, blood gas changes and a decrease in ductal shunting may all have contributed to these changes. The present study has shown physiological neonatal circulatory adaptation and onset of breathing to cause manifest changes in cerebral blood flow velocity.

Endometrial thickness and Doppler velocimetry of the uterine arteries as discriminators of endometrial status in women with postmenopausal bleeding: A comparative study

Our purpose was to compare the ability of transvaginal Doppler ultrasonographic examination with that of gray-scale ultrasonographic examination to discriminate between benign and malignant and between normal and pathologic endometrium in women with postmenopausal bleeding. One hundred thirty-eight consecutive women scheduled for curettage because of postmenopausal bleeding underwent transvaginal ultrasonography, including color and spectral Doppler techniques, within 8 days preceding the operation. The thickness of the endometrium was measured. Doppler signals of the maximum blood flow velocity obtained from the two main uterine arteries and subendometrial and intraendometrial arteries were evaluated for pulsatility index and time-averaged maximum velocity. The results of the examinations were compared with the histologic diagnosis of the curettage specimen. Receiver-operator characteristic curves showed endometrial thickness to be a better discriminator between normal and pathologic and between benign and malignant endometrium than any Doppler variable, 14 mm being the optimal threshold value for differentiating between benign and malignant endometrium (sensitivity 88%, specificity 81%). Measurement of endometrial thickness with transvaginal ultrasonography is a better method for discriminating between benign and malignant or normal and pathologic endometrium than is Doppler velocimetry of the uterine arteries.

Quantitative flow measurements for classification of ovarian tumors by transvaginal color Doppler sonography in postmenopausal patients.

Color Doppler and Duplex measurements were obtained in 83 (42 benign, 41 malignant) ovarian tumors in postmenopausal patients. An ATL UM9/HDI was used. The following flow criteria were analyzed: lowest resistance index (RI) and pulsatility index (PI), total number of arteries and number of central arteries and the maximum, mean and sum of systolic, end-diastolic and time-averaged maximum velocities of all intratumoral vessels. In 98% of malignant and in 85% of benign lesions, vessels were detected. All flow criteria showed highly significant differences between benign and malignant tumors (p < 0.0001). However, there was a considerable overlap between benign and malignant tumors (e.g. the median of the lowest RI was 0.62 (range 0.26-1.0) for benign and 0.40 (0.22-0.66) for malignant tumors; the median of the maximum systolic velocity was 17.5 cm/s (range 5.2-61.5 cm/s) for benign and 47.05 cm/s (14.6-105.0 cm/s) for malignant tumors). Differentiation of malignant tumors by the lowest RI and PI, number of arteries and maximum of systolic flow velocities gave a sensitivity of 77-85%, specificity of 77-83% and accuracy of 80-84%. Differentiation was superior by calculation of the maximum end-diastolic velocities and by the summation of the systolic, end-diastolic and time-averaged maximum flow velocities: sensitivity 90-9.5% specificity 83-86% and accuracy 87-91%. This study confirms that a single measurement is not sufficient for an accurate differentiation of ovarian lesions and, besides the measurement of minimum RI and PI, the measurements of flow velocities as Doppler criteria play an important role.

Reference ranges for fetal venous and atrioventricular blood flow parameters.

This cross-sectional study establishes reference ranges with gestation for Doppler parameters of fetal venous and atrioventricular blood flow. Color flow Doppler was used to examine 143 normal singleton pregnancies at 20-40 weeks' gestation. Flow velocity waveforms were recorded from the ductus venosus, right hepatic vein and inferior vena cava. The waveforms are triphasic, reflecting ventricular systole, early diastole and atrial contraction. Peak velocities for these parameters were measured with pulsed Doppler and a new index, the peak velocity index for veins (PVIV), was calculated. Similarly, time-averaged maximum velocities for the whole cardiac cycle were measured and the pulsatility index for veins (PIV) was calculated. Flow velocity waveforms were also recorded at the level of the atrioventricular valves and the ratios of peak velocities at early diastolic filling (E) and atrial contraction (A) were calculated. Regression analysis was used to define the association of each measured and calculated Doppler parameter with gestational age. Blood flow velocities in the fetal veins and velocities and E/A ratios across the atrioventricular valves increased significantly with gestation, whereas PVIV and PIV decreased. Blood flow velocities were highest in the ductus venosus and lowest in the right hepatic vein, and PVIV and PIV were highest in the hepatic vein and lowest in the ductus venosus. In the ductus venosus, there was always forward flow throughout the heart cycle, whereas in the inferior vena cava and hepatic vein during atrial contraction, flow was away from or towards the heart or there was no flow. Pulsatility of flow velocity waveforms in the venous system is the consequence of changes in pressure difference between the venous system and the heart during the heart cycle. The finding that PVIV and PIV decrease with gestation is consistent with decreasing cardiac afterload and maturation of diastolic ventricular function.

Estimation of cerebral blood flow through color duplex sonography of the carotid and vertebral arteries in healthy adults.

To noninvasively estimate cerebral blood flow volume, a prospective study of color duplex sonography of the common, external, and internal carotid arteries and vertebral arteries of healthy adults was done. Cerebral blood flow was calculated with the sum of flow volumes in the internal carotid and vertebral arteries of both sides. Using a 7.0-MHz linear transducer of a computed sonography system, cervical arteries of 48 volunteers (23 women, 25 men; mean age, 35 +/- 12 years) were examined. We measured angle-corrected time-averaged velocities and the diameter of the vessels and calculated the flow volumes of all arteries. In addition, peak systolic, maximum end-diastolic, and time-averaged maximum velocities and the resistance, pulsatility, and spectral broadening indexes were determined. Furthermore, we analyzed the side-to-side difference, age dependence, and long-term reproducibility of these parameters. The mean +/- SD values of flow volumes in the common, internal, and external carotid and vertebral arteries were 470 +/- 120, 265 +/- 62, 160 +/- 66, and 85 +/- 33 mL/min on either side, respectively. Total cerebral blood flow was 701 +/- 104 mL/min (corresponding to 54 +/- 8 mL/100 g per minute), with no variation in age or sex. Long-term reproducibility of cerebral blood flow and flow volumes in all vessels was significant (P < .01). We conclude that color duplex sonography of cervical arteries is potentially a practical method for estimating total cerebral blood flow. This noninvasive technique may be ideally suited for bedside and follow-up examinations of the critically ill patient. In future studies it should be compared with established radionuclide techniques.

Transcranial color duplex sonography in childhood and adolescence. Age dependence of flow velocities and waveform parameters.

Transcranial color duplex sonographic examinations in children and adolescents without cerebrovascular disease were evaluated retrospectively. Flow velocities and waveform parameters were determined and their side-to-side differences and age dependence analyzed and, finally, compared with analogous data of a previously described group of healthy adults. With a 2.0-MHz sector transducer of a computed sonographic system, the anterior, middle, and posterior cerebral arteries were examined in 64 children and adolescents between 1.5 and 17.5 years of age. Angle-corrected systolic peak, end-diastolic maximum, time-averaged, and time-averaged maximum velocities, and the resistance, pulsatility, and spectral broadening indexes were determined in all vessels. Mean +/- SD values for time-averaged maximum velocity (and time-averaged velocity) were 92.2 +/- 13.0, 79.9 +/- 17.7, and 63.9 +/- 13.6 (55.3 +/- 11.7, 40.4 +/- 10.4, and 34.2 +/- 9.2) cm/s, respectively, in the middle, anterior, and posterior cerebral arteries in children under 10 years of age; values were 83.2 +/- 11.9, 69.4 +/- 13.8, and 55.6 +/- 10.1 (50.8 +/- 9.0, 39.9 +/- 10.5, and 33.1 +/- 6.3) cm/s, respectively, in children 10 years of age and older. Time-averaged maximum velocity decreased significantly with age in all vessels (P < .001). Although time-averaged velocity did not change significantly during childhood and adolescence, a clear decline occurred from adolescence to adulthood (P < .0001 in the middle and posterior cerebral arteries; P < .01 in the anterior cerebral artery). The spectral broadening index decreased significantly from childhood to adolescence in the anterior and posterior cerebral arteries (P < .0001). The resistance and pulsatility indexes remained stable throughout childhood. Transcranial color duplex sonography allows angle-corrected measurements of "true" flow velocities in basal cerebral arteries. Additional determination of time-averaged velocity permits more detailed evaluation of flow characteristics for all age groups. The transcranial color duplex technique may provide deeper insights on normal cerebral perfusion and its disorders.

Blood flow velocity in the uterine and ovarian arteries during the normal menstrual cycle.

Twelve healthy women with regular menstrual cycles were examined with a combination of two-dimensional real-time ultrasound and color and spectral Doppler techniques on cycle days 4 and 8 and daily from cycle day 12 until follicular rupture, then days + 1, +2, +5, +7 and +12 after follicular rupture. The uterine and subendometrial arteries, arteries in the ovarian stroma and hilum, in the wall of the largest follicle of each ovary, and in the wall of the corpus luteum were examined. The pulsatility index and the time-averaged maximum velocity were calculated. In the uterine arteries the pulsatility index was highest on day + 2, after which it decreased successively to its lowest value, whereas the time-averaged maximum velocity reached its highest value on day + 12. Similar changes were observed in the subendometrial arteries. In the non-dominant ovary, neither the pulsatility index nor the time-averaged maximum velocity manifested any consistent changes during the cycle. In the dominant ovary, the time-averaged maximum velocity increased and the pulsatility index decreased after follicular rupture, being significantly higher and lower, respectively, in the luteal than in the follicular phase. These changes were seen in the ovarian hilum, stroma and follicular wall, but were most obvious in the wall of the dominant follicle and of the corpus luteum. We conclude that the blood circulation in the uterus and in the dominant ovary changes considerably during the menstrual cycle, whereas that in the non-dominant ovary shows no unequivocal changes.

Evaluation of the vertebrobasilar-posterior system by transcranial color duplex sonography in adults.

The transcranial color duplex sonography technique was applied to the vertebrobasilar-posterior system to provide normal data for clinical application. The intracranial posterior circulation was studied in 49 healthy volunteers (mean +/- SD age, 35 +/- 12 years) by a transcranial and suboccipital approach with a 2.0-MHz sector transducer of a computed sonography system. The posterior cerebral artery and the vertebrobasilar system were depicted clearly in the color Doppler mode. Pulsed Doppler signals could be recorded in the posterior cerebral (100%), basilar (92%), and vertebral arteries (89%). The following normal values were provided for all vessels: systolic peak, end-diastolic maximum, time-averaged, and time-averaged maximum velocities; resistance and pulsatility indexes; and a spectral broadening index. Mean +/- SD values were 45.9 +/- 9.6, 45.5 +/- 10.8, and 39.2 +/- 10.6 cm/sec for time-averaged maximum velocity, and 28.3 +/- 6.5, 30.6 +/- 7.2, and 24.7 +/- 8.4 cm/sec for time-averaged velocity in the posterior cerebral, basilar, and vertebral arteries, respectively. In a reproducibility study, duplex measurements of the posterior cerebral arteries were repeated in 27 subjects. The correlation between the two examiners was high (r = 0.56, p less than or equal to 0.0001 for time-averaged maximum velocity). Color duplex sonography of the vertebrobasilar-posterior system is a new, noninvasive, bedside investigative technique. It permits visualization of artery flow in real time, relating these to adjacent brain and cranial structures, as well as angle-corrected duplex measurement of "true" flow velocities at defined sites of the vessels. Thus, it will open new diagnostic possibilities in disorders of the posterior circulation.

Ultrasonographic velocimetry of the fetal ductus venosus

In fetal lambs, the ductus venosus shunts well-oxygenated blood directly to the heart, a pattern expected to be found also in the human fetus. We aimed to describe the human ductus venosus in a longitudinal sonographic study of two-dimensional imaging, colour flow mapping, and pulsed doppler velocimetry every 3-4 weeks during the second half of pregnancy. The fetuses of 29 healthy women were studied. The ductus venosus and its blood flow were identified and recorded for later analysis that included maximum velocity tracing. In the 184 examinations analysed, the ductus venosus appeared as a narrow vessel projecting a high-velocity jet posteriorly to reach the foramen ovale. The mean peak velocity in the ductus venosus increased from 65 cm/s in week 18 to 75 cm/s at term. Low values of the time-averaged maximum velocity were found in 2 fetuses with cardiovascular abnormalities (1 supraventricular tachycardia, 1 congestive heart failure), as a result of reversed flow in the ductus venosus during atrial systole. The high peak velocity in the ductus venosus, which is comparable with arterial velocities, probably gives the blood sufficient momentum to reach the foramen ovale without extensive mixing with deoxygenated blood. Velocimetry of the ductus venosus carries new diagnostic possibilities.

Fetal and preterm newborn cerebral blood flow velocity

Using Doppler ultrasound, cerebral blood flow velocities (CBFV) in the first month of life of normoxemic preterm infants born in the 28th gestational week with stable circulatory conditions were examined. The results were compared with fetal CBFV in the 28th to 32nd weeks of pregnancy. Peak systolic (PSV), end-diastolic (EDV) and time averaged maximum velocities (TAMV) were evaluated from the Doppler shifts recorded from the middle cerebral artery (MCA). Cerebral circulatory changes in neonates in the first 4 weeks of life were much more pronounced than in fetuses at the corresponding gestational age (28–32 weeks). After the rapid increase in neonatal CBFV in the first 3 weeks of life, our results appear to indicate a stabilisation between the 3rd and 4th week (corresponding to the 32 gestational weeks). The significance of, and possible mechanisms for, these changes are discussed.

Use of duplex scanning in the diagnosis of arteria profunda femoris stenosis

To evaluate the accuracy of duplex scanning in diagnosing arteria profunda femoris stenoses in patients with concomitant superficial femoral artery occlusions, 123 femoral artery bifurcations were examined in 103 patients. Peak systolic and time-averaged maximal flow velocity parameters were measured in the arteria profunda femoris and compared with independently performed angiography. For detecting stenoses greater than 30% diameter reduction (50% by area) of the arteria profunda femoris, duplex scanning had a sensitivity of 91% and 96%, a specificity of 85% and 98%, a positive predictive value of 86% and 98%, and a negative predictive value of 91% and 96%, for a peak systolic velocity of 180 cm/sec and more, and for a time-averaged maximal velocity of 50 cm/sec and more in the arteria profunda femoris, respectively. The day-to-day variability for peak systolic and time-averaged maximal velocity parameters was low with correlation coefficients between velocity measurements on both days of 0.96 and 0.98(n = 20), respectively. In 10 patients with arteria profunda femoris stenoses and superficial femoral artery occlusions, undergoing percutaneous transluminal angioplasty of arteria profunda femoris stenosis, the duplex scan revealed a reduction in stenotic peak systolic velocity from 330 ± 84 to 163 ± 50 cm/sec and a decrease in stenotic time-averaged maximal velocity from 156 ± 47 to 54 ± 17 cm/sec after the interventional procedure. These results show that peak systolic and time-averaged maximal velocities are accurate parameters to detect significant arteria profunda femoris stenosis in patients with superficial femoral artery occlusions. Their day-to-day variability is sufficiently low to warrant their continued use for quantification of the hemodynamic improvement as a result of catheter or surgical revascularizations of the arteria profunda femoris.

Doppler Ultrasonography of Malignant Melanomas of the Uvea

Doppler shifts were detected using duplex and color Doppler scanning in 41 of 42 patients with malignant melanomas of the uvea. Mean maximum tumor systolic velocity was 18.8 +/- 7.6 cm/s. Time-averaged maximum velocity in the tumor vessels was 12.3 +/- 5.3 cm/s. Maximum tumor velocity increased in four of eight tumors and was unchanged or had diminished in the other four 2 to 3 days after ruthenium plaque irradiation. Doppler shifts were undetectable in three tumors, markedly reduced in three tumors, and unchanged in one tumor 1 to 4 months after treatment. We detected minimal non-pulse-synchronized Doppler shifts in one of three tumors, and no shifts in the remaining two tumors 1 1/2 to 4 years after therapy. Color duplex scanning allowed a rapid overview of tumor vasculature and facilitated study of individual vessels.

The relationship between time averaged intensity weighted mean velocity, and time averaged maximum velocity in neonatal cerebral arteries

It is usual practice to calculate the mean velocity of blood flow in neonatal cerebral vessels from the intensity weighted mean (IWM) Doppler shift signal. Theoretically however the maximum frequency envelope could be used for similar purposes, and indeed may have certain advantages. The purpose of this study was to confirm the suitability of the maximum frequency method. Good quality Doppler recordings from the anterior cerebral and middle cerebral arteries of both term and very low birth weight babies were analyzed by both methods and compared. A small number of recordings were then deliberately degraded, either by the addition of noise or by the use of inappropriate filters, and reanalyzed. The results of these comparisons suggest that the maximum frequency follower should be the follower of choice for neonatal cerebral blood flow studies.

Failure of autoregulation of cerebral blood flow in neonates studied by pulsed Doppler ultrasound of the internal carotid artery.

To reveal the influence of therapeutically induced changes of arterial blood pressure on cerebral circulation, pulsed Doppler measurements of blood velocity in the right internal carotid artery were performed in 23 neonates. A positive correlation between mean arterial blood pressure and time-averaged maximum blood velocity (change more than 0.5%/torr) could be noticed in 16 infants. These infants were supposed to have loss of autoregulation. The main characteristics in this non-autoregulating group were: gestational age less than 31 weeks, birth weight less than 1501 g and mean carotid blood velocity less than 20 cm/s. In accordance with animal experiments we assume that autoregulation does not work below a definite lower limit of brain perfusion, which is reflected by carotid blood velocity in our study. Patients below/equal 1500 g or 30 gestational weeks very often do not exceed this limit and thus do not reach the "range of autoregulation".

Fodrin: axonally transported polypeptides associated with the internal periphery of many cells.

Fodrin (formerly designated 26 and 27) comprises two polypeptides (250,000 and 240,000 mol wt) that are axonally transported at a maximum time-averaged velocity of 40 mm/d--slower than the most rapidly moving axonally transported proteins, but faster than at least three additional groups of proteins. In this communication, we report the intracellular distribution of fodrin. Fodrin was purified from guinea pig brain, and a specific antifodrin antibody was produced in rabbit and used to localize fodrin in tissue sections and cultured cells by means of indirect immunofluorescence. Fodrin antigens were highly concentrated in the cortical cytoplasm of neurons and also nonneuronal tissues (e.g., skeletal muscle, uterus, intestinal epithelium). Their disposition resembles a lining of the cell: hence, the designation fodrin (from Greek fodros, lining). In cultured fibroblasts, immunofluorescently labeled fodrin antigens were arranged in parallel arrays of bands in the plane of the plasma membrane, possibly reflecting an exclusion of labeled fodrin from some areas occupied by stress fibers. The distribution of fodrin antigens in mouse 3T3 cells transformed with simian virus 40 was more diffuse, indicating that the disposition of fodrin is responsive to altered physiological states of the cell. When mixtures of fodrin and F-actin were centrifuged, fodrin cosedimented with the actin, indicating that these proteins interact in vitro. We conclude that fodrin is a specific component of the cortical cytoplasm of many cells and consider the possibilities: (a) that fodrin may be indirectly attached to the plasma membrane via cortical actin filaments; (b) that fodrin may be mobile within the cortical cytoplasm and that, in axons, a cortical lining may be in constant motion relative to the internal cytoplasm; and (c) that fodrin could serve to link other proteins and organelles to a submembrane force-generating system.