Time-averaged Maximum Velocity Research Articles

Echo-Doppler ultrasonographic assessment of resistance and velocity of blood flow in the ductus venosus throughout gestation in fetal lambs

It has been postulated that during fetal hypoxia, the blood flow shunted through the ductus venosus increases and may account for upto 70% of the total umbilical flow. The objectives of the present study were to use ultrasonography to determine the velocities and waveform indices of blood flow in the ductus venosus in the fetal lamb. The ductus venosus of 15 lamb fetuses was evaluated weekly from Days 45 to 143 of gestation (Day 0=day of AI). The Doppler indices measured were: S/D, the systole/diastole ratio; RI, the resistance index; and PI, the pulsatility index. The velocity waveforms studied were: SV, the peak velocity during ventricular systole; D, the peak velocity during ventricular diastole; aV, the lowest forward velocity during atrial contraction; and TAMV, the time-averaged maximum velocity. Doppler indices from Days 52 to 143 were highly correlated: S/D versus PI (r=0.96, P<0.0001), and versus RI (r=0.93, P<0.0001); and PI versus RI (r=0.97, P<0.0001). Velocity indices were also positively correlated: velocity SV versus D (r=0.87, P<0.0001), versus aV (r=0.79, P<0.05), and versus TAMV (r=0.98, P<0.0001); D versus aV (r=0.88, P<0.05), and versus TAMV (r=0.87, P<0.05); and aV versus TAMV (r=0.82, P<0.05). Doppler indices were negatively correlated with SV (r=-0.22, P<0.03); D (r=-0.37, P<0.0001); TAMV (r=-0.32, P<0.05) and with aV (r=-0.67, P<0.05). The mean value of each Doppler index decreased 40% from Days 52 to 73 (e.g., PI from 0.82+/-0.08 to 0.51+/-0.10; P<0.05), with no significant changes thereafter. Mean (+/-S.E.M.) values of velocity indices SV, D, aV, and TAMV rose twofold from Days 60 to 115 of gestation (e.g., SV from 54.4+/-8.8cm/s to 104.9+/-19.7 and aV from 24.8+/-6.9 to 54.9+/-5.9; P<0.05). In conclusion, Doppler ultrasonography facilitated assessment of the blood flow pattern in the ductus venosus in lamb fetuses between Days 52 and 143.

Gray and Color Doppler Ultrasonography in Differentiation Between Chronic Viral Hepatitis and Compensated Early Stage Cirrhosis

To assess the value of Gray scale (GS) and Colour Doppler Ultrasonography (CDU) in differentiating the progression of chronic viral hepatitis (CVH) and compensated liver cirrhosis (CIR).Seventy-two patients and 32 normal individuals used as controls were studied. Forty-four patients suffered from CVH and 28 from CIR. All patients underwent liver biopsy. Multiple qualitative and quantitative variables were studied with GS and CDU in the Liver, Portal Vein (PV), Hepatic Artery (HA) and spleen. On the basis of the obtained Doppler data several known indexes were calculated. Alternative indexes [PV diameter (D)/time average maximum velocity (Vmax), PV diameter/time average mean velocity (VTAM), HA/PV VTAM ratio] derived from them were calculated.ROC analysis showed that PV Congestion Index, PV D/VTAM and HA/PV VTAM indexes had the best sensitivity and specificity in discriminating CVH from CIR. Stepwise discriminant analysis selected as significant predictors 3 qualitative and 4 quantitative variables that correctly classify 88.9% of the original grouped cases. In CVH patients that underwent biopsy we found statistically significant changes in those at fibrotic stage 5 compared to fibrotic stages 1-4.We found significant differences in haemodynamic parameters and indexes for CVH patients at fibrosis stage 5 compared to all other stages. Simple GS and CDU parameters may discriminate CVH from CIR. The alternative Doppler indexes suggested that accurate differentiation between CVH and CIR is possible. These indexes could be useful for monitoring CVH and avoiding unnecessary biopsies.

Uterine blood flow and perfusion in mares with uterine cysts: effect of the size of the cystic area and age

Transrectal color and power Doppler ultrasonography was used to study uterine blood flow and perfusion in mares with and without uterine cysts. Vascular perfusion of the uterus and blood flow velocities, vascular perfusion, diameter, circumference, and area of a cross section of the mesometrial attachment were evaluated. To study the effect of internal cysts, two matched groups (cystic and control, n=21 mares/group) were used. Uterine vascular perfusion in mares with cysts was less (P<0.0001) in the cystic than the noncystic region and less (P<0.0009) than that for controls. Mares with cysts had lower (P<0.04) pulsatility index (PI) and greater end diastolic velocity (EDV; P<0.03) and time-averaged maximum velocity (TAMV; P<0.05) of the mesometrial vessels than the controls. To study the effect of the size of internal uterine cystic area, paired mares were arranged in four groups (n=8-11/group): small uterine cystic area (< or =275 mm(2)) versus controls and large uterine cystic area (>410 mm(2)) versus controls. A small uterine cystic area did not affect uterine hemodynamics. Mares with large uterine cystic area had lower PI (P<0.05) and greater peak systolic velocity (P< or =0.05), EDV (P<0.009), and TAMV (P<0.005). To study the effect of age, old versus young mares without cysts were compared (n=11/group). Old mares had greater EDV (P<0.02) and TAMV (P<0.01) than young mares. Results demonstrated, for the first time in any species, reduced uterine vascular perfusion in mares with uterine cysts and a positive association between size of the cystic area and disturbed uterine hemodynamics.

Ductus venosus Doppler velocimetry in the first trimester: a new finding

To establish reference curves for ductus venosus blood flow velocities during the first trimester and compare them with previously published curves. This was a cross-sectional and retrospective study performed between January 1998 and January 2003. The following inclusion criteria were used: singleton pregnancy, velocity measurements taken when the crown-rump length (CRL) was between 34 and 84 mm, absence of fetal anomalies, full-term pregnancy and newborn birth weight appropriate for gestational age. The following variables of the ductus venosus were measured: peak velocity during ventricular systole (S-wave) and diastole (D-wave), nadir during atrial contraction in late diastole (A-wave), time-averaged maximum velocity (TAMXV) and pulsatility index for veins (PIV). A total of 843 fetuses were included. The mean CRL was 62 (range, 34-84) mm. The S-wave, D-wave, TAMXV and PIV were normally distributed, and logarithmic transformation was performed to achieve a normal distribution for the A-wave. S-wave, D-wave and A-wave and TAMXV increased with CRL. PIV increased up to a CRL of 63 mm and decreased thereafter. Regression analysis revealed a significant quadratic relationship between PIV and CRL. S-wave, D-wave, A-wave velocities and TAMXV in the ductus venosus increase with CRL between 34 and 84 mm. The reference range for PIV has a biphasic pattern, with an initial non-significant increase up to a CRL of 63 mm and a fall thereafter.

The ‘lead vessel’: a vascular ultrasound feature of metastasis in the ovaries

To investigate, in a series of metastatic and primary invasive ovarian lesions examined by color Doppler, the prevalence of a main peripheral vessel penetrating into the central part of the ovarian mass with a tree-shaped morphology, defined as the 'lead vessel'. This was a retrospective study of 31 patients with histopathologically confirmed metastatic involvement of the ovary and 106 patients with confirmed primary invasive ovarian carcinoma, who had undergone standardized ultrasound examination, with established definitions of ultrasound characteristics. We retrieved sonographic images and videoclips, focusing on the detection of the lead vessel. The presence of the lead vessel was detected in 11/31 (35.4%) metastatic ovarian tumors, and in only two (0.01%) cases of primary ovarian carcinoma (P = 0.0001). At color Doppler analysis, metastatic ovarian lesions were characterized by significantly lower pulsatility index (P = 0.0001) and resistance index (P = 0.0001) values, and significantly higher peak systolic velocity (P = 0.0002) and time-averaged maximum velocity (P = 0.04) values, when compared with primary ovarian carcinomas. The lead vessel was detected in 11/21 (52%) solid metastatic lesions and in no cases of multilocular or multilocular-solid lesions (P = 0.008). The lead vessel is a novel sonographic feature of vascular morphology in solid ovarian metastases. The more frequent observation of this feature in metastatic ovarian tumors compared with primary invasive ovarian carcinomas warrants further investigation in order to explore its potential role in the diagnosis of metastatic ovarian masses.

Doppler assessment of the aortic isthmus and perinatal outcome in preterm fetuses with severe intrauterine growth restriction

To evaluate the characteristics and association with perinatal outcome of the aortic isthmus (AoI) circulation as assessed by Doppler imaging in preterm growth-restricted fetuses with placental insufficiency. This was a prospective cross-sectional study. Fifty-one fetuses with intrauterine growth restriction (IUGR) and either an umbilical artery (UA) pulsatility index (PI) > 95(th) centile or a cerebroplacental ratio < 5(th) centile were examined at 24-36 weeks' gestation. AoI impedance indices (PI and resistance index) and absolute velocities (peak systolic (PSV), end-diastolic and time-averaged maximum (TAMXV) velocities), were measured in all cases and compared with reference ranges by gestational age. Furthermore, fetuses were stratified into two groups according to the direction of the diastolic blood flow in the AoI: those with antegrade flow (n = 41) and those with retrograde flow (n = 10). Clinical surveillance was based on gestational age and Doppler assessment of the UA, middle cerebral artery and ductus venosus (DV). Adverse perinatal outcome was defined as stillbirth, neonatal death and severe morbidity (respiratory distress syndrome, bronchopulmonary dysplasia, Grade III/IV intraventricular hemorrhage, necrotizing enterocolitis and a neonatal intensive care unit stay > 14 days). Adverse perinatal outcome was significantly associated with an increased AoI-PI (area under the curve 0.77; 95% CI, 0.63-0.92; P < 0.005). A significant correlation (P < 0.001) was found between retrograde blood flow in the AoI and adverse perinatal outcome, the overall perinatal mortality being higher in the retrograde group (70% vs. 4.8%, P < 0.001). In 4/5 (80%) fetuses the reversal of flow in the AoI preceded that in the DV by 24-48 h. AoI-PSV and AoI-TAMXV were < 5(th) centile in 40/51 (78%) and 48/51 (94%) cases, respectively, whereas AoI-PI was > 95(th) centile in 21/51 (41%) cases. Retrograde flow in the AoI in growth-restricted fetuses correlates strongly with adverse perinatal outcome. Absolute velocities in the AoI are decreased in growth-restricted fetuses. The data suggest a potential role for Doppler imaging of the AoI in the clinical surveillance of fetuses with severe IUGR, which should be confirmed in larger prospective studies.

The left portal vein as an indicator of watershed in the fetal circulation: development during the second half of pregnancy and a suggested method of evaluation

The left portal vein represents a watershed area in the fetal circulation and the change of flow direction is a suggested marker of circulatory compromise. Our aim was to study the left portal vein of uncompromised human pregnancies and establish reference ranges. One hundred and sixty low-risk pregnant women were recruited to a longitudinal study that included four to five Doppler measurements at monthly intervals during the second half of pregnancy. Based on 554 Doppler recordings we found time-averaged maximum flow velocities increasing from a mean of 10.6 cm/s to 14.2 cm/s during 21-31 weeks of gestation, remaining stable until 37 weeks and decreasing towards term. Intermittent flow reversal occurred during fetal respiratory movements, and continuous flow reversal was seen in 2/160 fetuses close to delivery. We propose time-averaged maximum blood velocity measurement for quantification of the watershed phenomenon in the left portal branch, and have provided reference ranges for single observations and serial measurements.

OP15.02: Intertwin disparity in crown–rump length, gestational sac and yolk sac size and fetal heart rate at 7 weeks'gestation

Objectives: To compare (1) absolute and (2) weight-specific blood flow volume of uterine arteries (UtA) in normal twin pregnancies to normal singleton pregnancies. Methods: Twelve twin pregnancies (10 dichorionic, two monochorionic) with normal UtA PI and normal weight at birth were included. UtA diameter and time-averaged maximum velocity were obtained to calculate flow (mL/min) and UtA flow/EFW (mL/min/kg) in each UtA. UtA flow was estimated by the formula Q = hV · πD2/4; a patient-specific coefficient, h, was obtained by an ad hoc mathematical model. Total UtA flow was calculated as a sum of right and left vessel flow volume. Twins’ UtA flow was expressed per unit EFW considering the sum of the two EFWs. Twins were compared to 48 normal age-matched singletons. Results: Gestational age at exam was similar in twins and in singletons (25.9 ± 6.4 vs. 25.2 ± 6.2 weeks, NS). UtA flow (mL/min) was significantly increased in twins (509.3 ± 240.7 mL/min) compared to singletons (337.2 ± 257.0 mL/min) (P = 0.04). UtA flow (mL/min) exponentially increased along gestation in twins and in singletons. The twins’ trend was above the third interquartile range of singletons’ reference values. UtA diameter was significantly increased in twins (0.33 ± 0.07 cm) than in singletons (0.28 ± 0.05 cm), while no differences in UtA mean velocity were observed (77.5 ± 29.9 vs. 76.7 ± 29.1 cm/sec, respectively, NS). UtA flow per EFW did not differ between twins and singletons (384.4 ± 198.6 vs. 460.9 ± 302.9 mL/min/kg, respectively, NS). Conclusions: (1) UtA flow volume (mL/min) in twin pregnancies was significantly increased. This was determined by larger vessel diameter, compared to singletons. (2) Each twin proved to share an amount of UtA flow per unit estimated fetal weight not significantly different from singletons.

OP15.01: Absolute uterine artery blood flow volume is increased in twin human pregnancies compared to singletons

Objectives: To compare (1) absolute and (2) weight-specific blood flow volume of uterine arteries (UtA) in normal twin pregnancies to normal singleton pregnancies. Methods: Twelve twin pregnancies (10 dichorionic, two monochorionic) with normal UtA PI and normal weight at birth were included. UtA diameter and time-averaged maximum velocity were obtained to calculate flow (mL/min) and UtA flow/EFW (mL/min/kg) in each UtA. UtA flow was estimated by the formula Q = hV · πD2/4; a patient-specific coefficient, h, was obtained by an ad hoc mathematical model. Total UtA flow was calculated as a sum of right and left vessel flow volume. Twins’ UtA flow was expressed per unit EFW considering the sum of the two EFWs. Twins were compared to 48 normal age-matched singletons. Results: Gestational age at exam was similar in twins and in singletons (25.9 ± 6.4 vs. 25.2 ± 6.2 weeks, NS). UtA flow (mL/min) was significantly increased in twins (509.3 ± 240.7 mL/min) compared to singletons (337.2 ± 257.0 mL/min) (P = 0.04). UtA flow (mL/min) exponentially increased along gestation in twins and in singletons. The twins’ trend was above the third interquartile range of singletons’ reference values. UtA diameter was significantly increased in twins (0.33 ± 0.07 cm) than in singletons (0.28 ± 0.05 cm), while no differences in UtA mean velocity were observed (77.5 ± 29.9 vs. 76.7 ± 29.1 cm/sec, respectively, NS). UtA flow per EFW did not differ between twins and singletons (384.4 ± 198.6 vs. 460.9 ± 302.9 mL/min/kg, respectively, NS). Conclusions: (1) UtA flow volume (mL/min) in twin pregnancies was significantly increased. This was determined by larger vessel diameter, compared to singletons. (2) Each twin proved to share an amount of UtA flow per unit estimated fetal weight not significantly different from singletons.

Study of normal Chinese vertebral–basilar arteries with transcranial color Doppler flow imaging

The aim of this study was to evaluate the blood flow characteristics of intracranial vertebral-basilar artery (V-BA) in healthy Chinese adults with transcranial color Doppler flow imaging (TCDFI) and provide reference values of healthy people of different ages and genders. Three hundred healthy Chinese adults were divided into three groups based on their ages: Group I: 20-39 years, Group II: 40-59 years, Group III: >/=60 years. Each group was subdivided into two subgroups according to their gender. Peak systolic velocity (Ps), end-diastolic velocity (Vd), time average maximum velocity (TAMAX), pulsatility index (PI), and resistance index (RI) were measured from intracranial V-BA scanning. Ps, Vd, and TAMAX decreased with age, while PI and RI increased in all groups. Flow velocity in women was slightly higher than that of men, and there was significant differences in group III between men and women (P<.05). However, no difference was found in the flow parameters between left and right vertebral arteries. This study offered reference values of intracranial V-BA flow parameters in healthy Chinese adults and indicated that these parameters varied with age and gender.

Middle cerebral artery blood flow velocities and pulsatility index and the cerebroplacental pulsatility ratio: longitudinal reference ranges and terms for serial measurements

To establish reference ranges suitable for serial assessments of the fetal middle cerebral (MCA) and umbilical (UA) artery blood flow velocities, pulsatility index (PI) and cerebroplacental pulsatility ratio and to provide terms for calculating conditional reference intervals suitable for individual serial measurements. This was a longitudinal study of 161 singleton pregnancies. Using Doppler ultrasound, MCA and UA blood velocities and PI were determined three to five times at 3-5-week intervals over a gestational age range of 19-41 weeks. Polynomial regression lines for the 95th, 50th and 5th percentiles were calculated for the peak systolic velocity (PSV), time-averaged maximum velocity (TAMXV), PI and cerebroplacental ratio. Terms for calculating conditional reference intervals were established. Based on 566 observations our new longitudinal reference ranges for fetal middle cerebral PSV, TAMXV and PI provided terms for calculating conditional reference intervals (i.e. predicting expected 95% confidence limits based on a previous measurement), and correspondingly for the cerebroplacental ratio (n = 550). The reference ranges were at some variance with those of previous cross-sectional studies. The narrow 95% confidence limits for the 5(th) and 95(th) percentiles ensured reliable ranges. We have established longitudinal reference ranges appropriate for the serial assessment of MCA blood velocities and PI and cerebroplacental ratio. Particularly the terms for calculating conditional ranges based on a previous observation make this system more appropriate for longitudinal monitoring than are cross-sectional data.

Doppler changes in the main fetal brain arteries at different stages of hemodynamic adaptation in severe intrauterine growth restriction

To evaluate changes in the temporal evolution and regional distribution of arterial brain Doppler parameters in relation to different stages of hemodynamic adaptation in fetuses with severe intrauterine growth restriction (IUGR). Thirty-six fetuses with severe IUGR (<or= 32 weeks of gestation) and abnormal umbilical artery (UA) pulsatility index (PI) (mean > 2 SD) were evaluated longitudinally with pulsed Doppler ultrasound at four different hemodynamic stages: Stage 1 (n = 36), mean UA-PI > 2 SD or absent UA end-diastolic flow; Stage 2 (n = 34), abnormal middle cerebral artery (MCA) PI (mean < 2 SD); Stage 3 (n = 30), reversed UA end-diastolic flow; Stage 4 (n = 12), absent or reversed atrial flow in the ductus venosus. In addition, 36 normally grown fetuses were studied for comparison. PI and time-averaged maximum velocity (TAMXV) in the MCA and the anterior cerebral (ACA), pericallosal (PER) and posterior cerebral (PCA) arteries were measured. In IUGR fetuses, PI values from all arteries were significantly reduced at Stage 2. At Stages 3 and 4, ACA-PI and PCA-PI did not change further, whereas MCA-PI and PER-PI showed a slight increase. In the ACA, MCA and PER, TAMXV in Stage 2 increased significantly. In Stages 3 and 4, ACA and PER-TAMXV remained unchanged, whereas MCA-TAMXV showed a slight decrease, mirroring the PI values. PCA-TAMXV values were similar to controls at all stages. In IUGR fetuses, the brain arteries differ in the magnitude and time sequence of Doppler parameters in relation to systemic hemodynamic adaptation, suggesting the existence of regional brain redistribution processes.

The Power Doppler Velocity Index, Pulsatility Index, and Resistive Index Can Assist in Making a Differential Diagnosis of Primary Ovarian Carcinoma and Krukenberg Tumors

The aim of this study was to compare the effectiveness of transvaginal power Doppler sonography with spectral Doppler analysis as an aid in preoperatively distinguishing primary ovarian carcinoma and metastatic carcinoma to the ovary (Krukenberg tumors). Fifty women with ovarian disease were preoperatively examined with transvaginal power Doppler sonography. Six basic parameters were measured, including intratumoral peak systolic velocity, end-diastolic velocity, time-averaged maximum velocity, pulsatility index (PI), resistive index (RI), and velocity index (VeI). Blood flow analyses were detectable in all patients. Twelve patients with metastatic carcinoma to the ovary were classified as group 1; 38 patients with primary ovarian carcinoma were classified as group 2. Comparison of intratumoral blood flow analyses between the two groups was performed. The PI, RI, and VeI were significantly lower in patients with metastatic carcinoma to the ovary than those with primary ovarian carcinoma (P < .05). There were no significant differences in the peak systolic velocity (P = .871), end-diastolic velocity (P = .508), and time-averaged maximum velocity (P = .850) between the two groups. Transvaginal power Doppler sonography with spectral Doppler analysis is an effective method in evaluating intratumoral blood flow of Krukenberg tumors. Low impedance (PI, RI, and VeI) might assist us in making differential diagnoses between primary ovarian carcinoma and Krukenberg tumors according to our preliminary results.

The fetal portal vein: normal blood flow development during the second half of human pregnancy

The umbilical vein is the major source of blood for the fetal liver, but portal blood, which has not been measured directly in human fetuses, probably constitutes a physiologically important contribution. We aimed to establish a method for measuring blood flow in the fetal portal vein and to produce longitudinal reference ranges for diameter, blood flow velocities and volume blood flow during the second half of pregnancy. After a pilot project to develop the measuring technique, 160 low-risk pregnant women were recruited to a longitudinal study that included ultrasound examinations at 4-5-week intervals starting at 20-22 weeks of gestation. The inner diameter (D) of the vessel was measured with a perpendicular insonation angle, and the time-averaged maximum blood velocity (TAMXV) and weighted mean velocity (VWMEAN) were recorded with an insonation directed along the long axis of the vessel. Portal flow was calculated as: Q = pi(D/2)(2) x h x TAMXV (where h is a velocity profile parameter and equals 0.5). Portal flow was normalized for estimated fetal weight based on birth-weight percentiles. The portal vein could be visualized and measured in 558/593 (94%) cases. Blood flow was pulsatile. D and TAMXV doubled during the second half of pregnancy (21-39 weeks), from 1.5 to 3.4 mm and from 8.4 to 14.9 cm/s, respectively. Correspondingly, the portal flow increased from 5 to 41 mL/min, and from 10 to 13 mL/min/kg when normalized for fetal weight. Similar results were achieved for VWMEAN. Portal flow can be measured with a standardized technique. It increases during the second half of pregnancy, even when normalized for fetal weight, suggesting that it has increasing importance in the fetal liver circulation.

Equilibration of Two-Dimensional Double-Diffusive Intrusions

Abstract This paper considers the equilibration of lateral intrusions in a doubly diffusive fluid with uniform unbounded basic-state gradients in temperature and salinity. These are density compensated in the horizontal direction and finger favorable in the vertical direction. Previous nonlinear studies of this effect have qualitative and quantitative limitations because of their fictitious parameterizations of the weak “turbulence” that arises. Here, two-dimensional direct numerical simulations (DNS) that resolve scales from the smallest to the intrusive are used to predict the equilibrium state. This is achieved by numerically tilting the x–z computational box so that the mean intrusion is represented by a mode with no lateral variation, but smaller-scale 2D eddies comparable to the intrusion thickness are resolved. The DNS show that the initial plane wave intrusion evolves to an equilibrium state containing both a salt finger interface and a diffusive interface, surrounded by well-mixed layers. The inversion of the horizontally averaged density in the mixed layer is negligibly small, but the salt finger buoyancy flux produces large transient density inversions that drive the mixed layer convection. For the considered values of horizontal/vertical gradients, the calculations yield small Cox numbers and buoyancy Reynolds numbers [comparable to those measured in staircases during the Caribbean-Sheets and Layers Transects (C-SALT) program]. An important testable result is the time-averaged maximum velocity of the fastest-growing intrusion Umax = 18.0 (Σ*z/Σ*x)+1/2KT(gΘ*z/νKT)1/4. Here Θ*z is the undisturbed vertical temperature gradient in buoyancy units, Σ*z and Σ*x are the corresponding vertical and horizontal salinity gradients, g is the gravity acceleration, and ν and KT are the respective values of the molecular viscosity and heat diffusivity. The paradoxical inverse dependence on the horizontal gradient results from the assumption that the latter is unbounded.

Doppler sonography evaluation of flow velocity and volume of the extracranial internal carotid and vertebral arteries in healthy adults

To measure with Doppler sonography the velocity and volume of blood flow in the extracranial internal carotid artery (ICA) and vertebral artery (VA) of healthy adults and to calculate total cerebral blood flow volume (tCBFV). Bilateral ICA and VA were examined sonographically in 180 healthy adults. Angle-corrected peak systolic (Vps), end-diastolic (Ved), and time-averaged maximum blood flow velocity (TAV) were measured in pulsed Doppler mode, and the resistance index (RI) and pulsatility index (PI) were calculated. The cross-sectional area (A) was measured on gray-scale images. Volume flow was calculated as FV = TAV x A, and tCBFV was calculated as the sum of the right and left ICA and VA volume flow. tCBFV was 651 +/- 96 ml/min for the entire population. There was a significant decrease in Vps, Ved, TAV, and tCBFV with age in all arteries. RI and PI values initially declined and then increased with age. Cross-sectional area increased with age in ICA but not in VA. PI and RI were higher in men than in women. Blood flow velocity and volume were higher, and RI was lower in the left than in the right VA. The Doppler sonographic assessment of extracranial ICA and VA blood flow volume may be useful for the study of cerebral hemodynamic changes in patients with cerebrovascular disorders. Age-dependent changes should be considered, for instance, in the management of intensive care patients with impaired cerebral perfusion.

Longitudinal reference ranges for ductus venosus flow velocities and waveform indices

Serial Doppler measurements of the ductus venosus are used increasingly for monitoring fetuses at risk of hemodynamic compromise, but existing reference ranges are based on cross-sectional studies and thus are less suitable for comparison with serial measurements. We aimed to establish longitudinal reference ranges for ductus venosus flow velocities and waveform indices and to provide the necessary terms for calculating conditional reference ranges for serial measurements. This was a longitudinal study of 160 low-risk pregnancies. Pulsed Doppler ultrasound was used to record ductus venosus blood flow velocities at 4-week intervals from 20-22 weeks of gestation onwards. With a success rate of 93%, 547 measurements (four or five in each fetus) were used to establish reference ranges. The time-averaged maximum velocity was 50 cm/s at 21 weeks of gestation, increased to 60 cm/s at 32 weeks, and remained so until term. Similarly, the peak systolic velocity increased from 59 cm/s at 21 weeks to 71 cm/s at 31 weeks and remained so until term. The end-diastolic velocity showed a continuous increase from 31 cm/s at 21 weeks to 43 cm/s at 40 weeks. The pulsatility index for veins decreased from 0.57 at 21 weeks to 0.44 at 40 weeks. When conditioned by a previous measurement, the reference ranges for the next observation became narrower and commonly shifted compared with those of the entire population. The new longitudinal reference ranges presented here reflect the development of the ductus venosus flow velocities and velocity indices and are thus appropriate for serial measurements, particularly if conditional terms are included.

Middle cerebral artery pulsatility index: reliability at different sampling sites

To analyze the interobserver reliability of measurement of the middle cerebral artery (MCA) pulsatility index (PI) at two different sampling sites. This study included 100 consecutive singleton pregnancies between 24 and 40 weeks with normal fetal growth. The PI was calculated by two independent operators at proximal and distal sampling sites of the near-field MCA. Reliability analyses were performed between observers at each sampling site by means of the intraclass correlation coefficient (ICC) for agreement. Differences between observers were explored and agreement limits calculated by means of the Bland-Altman test. Satisfactory flow velocity waveforms were obtained successfully in each fetus at both sampling sites. Peak systolic, end-diastolic and time-averaged maximum velocities were significantly higher at the proximal compared with the distal sampling site. Conversely, PI was significantly higher at the distal compared with the proximal site. ICCs for PI were 0.3 and 0.33 at the proximal and the distal sampling sites, respectively. The 95% interval of the PI differences between observers were +0.91 and -1.14 at the proximal and +1.03 and -1.08 at the distal sampling sites. In about 30% of the cases the PI difference between observers was greater than 0.5 at both sampling sites. Moderate interobserver reliability in the measurement of end-diastolic and time-averaged maximum MCA flow velocities results in limited agreement of the PI calculation at both proximal and distal sampling sites. These results may preclude its clinical applicability.

Transcranial Doppler ultrasonography in adults with sickle cell disease

Transcranial Doppler (TCD) is used to select children with sickle cell disease (SCD) for primary stroke prevention using regular blood transfusion. Whether it can also identify high stroke risk in adults with SCD is not known. The authors examined 112 adult patients from two convenience population samples with SCD and 53 healthy control subjects to compare velocities in adults to those reported in children with SCD and to evaluate the influence of age and hematocrit on TCD. Adults with SCD had a higher mean time-averaged maximum mean velocity (110.9 +/- 25.7 cm/s) compared with healthy controls (71.1 +/- 12.0 cm/s), and the difference is approximately proportional to their anemia. No cases with velocities >/=200 cm/s (the threshold used in children for prophylactic treatment) were found in this sample. Transcranial Doppler velocities in adults with sickle cell disease (SCD) are lower than those in children with SCD. Velocity criteria used in children cannot be used to stratify risk of stroke in adults.

Transrectal Doppler sonography for evaluation of uterine blood flow throughout pregnancy in 13 cows

Once weekly from 30 to 270 days of gestation in 13 cows, Doppler ultrasound scanning (triplex Doppler system) was done to assess blood-flow parameters of both median uterine arteries. Resistance, velocity and volume indices were measured. Resistance index values were negatively correlated to all other blood-flow parameters ( P < 0.05), but there were positive correlations between velocity and volume indices ( P < 0.05). Resistance indices were lower, and velocity and volume indices were significantly higher in the median uterine artery ipsilateral versus contralateral to the fetus. Resistance indices decreased continuously during the first 36 weeks of pregnancy. Velocity values rose three-fold, whereas the area increased 20-fold and the volume increased 17-fold by the end of gestation ( P < 0.05). Birth weight of calves was positively correlated with blood-flow volume ( r = 0.34) but negatively correlated with the resistance index ( r = −0.45). There were no significant differences between male versus female calves (at any stage of gestation) in the resistance, time-average maximum velocity, and volume indices ( P > 0.05). In conclusion, arterial blood flow was monitored with transrectal Doppler sonography in both median uterine arteries weekly throughout pregnancy in cattle; this could be very valuable for monitoring pregnancies at high risk for abnormalities of the placenta, fetus or both, e.g. cloned calves.