Assessment of normal fetal liver blood flow using quantitative three-dimensional power Doppler ultrasound

Fetal liver blood flow is very important for fetal hemodynamics. To assess the development of fetal liver vascularization and blood flow in normal gestation, we measured the fetal liver vascularization and blood flow in normal fetuses using the three-dimensional (3-D) power Doppler ultrasound (US) and quantitative 3-D power Doppler histogram analysis. This study was undertaken with a prospective, cross-sectional design. In total, 196 normal singletons with gestational age between 20 and 40 weeks were included. The 3-D power Doppler US and the quantitative histogram analysis were used to assess the fetal liver vascularization index (VI), flow index (FI), vascularization-flow index (VFI) and mean greyness in each case. Our results showed that all the fetal liver VI, FI and VFI increased significantly with gestational age (GA), whereas, fetal liver mean greyness decreased with GA. Using GA as the independent variable, the linear regression equations for fetal liver VI, FI, VFI and mean greyness were VI = 0.5746 x GA - 5.8264 (r = 0.86, p < 0.0001), FI = 0.3291 x GA + 35.624 (r = 0.35, p < 0.001), VFI = 0.2905 x GA - 3.4871 (r = 0.82, p < 0.0001) and mean greyness = -0.2034 x GA + 42.315 (r = -0.20, p < 0.0001). In addition, fetal liver VI, FI, VFI and nean greyness were all significantly correlated with common fetal growth indexes, such as biparietal diameter, occipitofrontal diameter, head circumference, abdominal circumference, femur length and estimated fetal weight. Our study indicates that normal fetal liver vascularization and blood flow change significantly with the advancement of GA as well as fetal growth indexes. We believe our data may serve as a reference for further studies of fetal liver blood flow in abnormal conditions.     

Evaluation of fetal regional cerebral blood perfusion using power Doppler ultrasound and the estimation of fractional moving blood volume.

OBJECTIVE: To standardize the evaluation of regional fetal brain blood perfusion, using power Doppler ultrasound (PDU) to estimate the fractional moving blood volume (FMBV) and to evaluate the reproducibility of this estimation. METHODS: Brain blood perfusion was evaluated in 35 normally grown fetuses at 28-30 weeks of gestation, using PDU. The following cerebral regions were included in the PDU color box: anterior sagittal, complete sagittal, basal ganglia, and cerebellar. Ten consecutive good-quality images of each anatomical plane were recorded and the delimitation of the region of interest (ROI) was performed off-line. FMBV was quantified in the ROI of all images and the mean considered as the final value. Differences between regions, variability, reproducibility and agreement between observers were assessed. RESULTS: Power Doppler images of the described anatomical planes were obtained in all cases, regardless of fetal position. The median time for the acquisition of the images was 7 (range 4-12) min. Mean (range) FMBV values were: anterior sagittal, 16.5 (10.7-22.8)%, inter-patient coefficient of variation (CV) 0.22; complete sagittal, 13.5 (8.8-16.1)%, CV 0.27; basal ganglia, 18.3 (10.7-27.6)%, CV 0.27; and cerebellar, 6.6 (3.0-11.0)%, CV 0.38. There were statistically significant differences in FMBV between cerebellar and complete sagittal ROIs with the frontal and basal ganglia regions. Reproducibility analyses showed an intraclass correlation coefficient of 0.91 (95% CI 0.67-0.97) and an interclass correlation coefficient of 0.87 (95% CI 0.70-0.94). Interobserver agreement showed a mean difference between observers of -0.2 (SD 2.7) with 95% limits of agreement -5.6 to 5.2. CONCLUSIONS: When the regions of interest are well defined, the FMBV estimate offers a method to quantify blood flow perfusion in different fetal cerebral areas. There appear to be regional differences in FMBV within the fetal brain.     

定量三维能量多普勒超声监测正常中晚孕期胎盘血流的临床价值

目的：探讨应用三维能量多普勒超声评价正常中晚孕期胎盘血流灌注的临床价值.方法：观察150例胎盘位于子宫前壁或宫底的正常孕妇,孕周22～40周,取得胎盘三维能量多普勒指数,包括血管化指数（Ⅵ）,血流指数（FI）,血管化-血流指数（VFI）,并与孕龄作相关分析.结果：正常胎盘血流的三维能量图呈现立体血管树的特征,随着孕周的增加,胎盘内血管增多、增粗.胎盘的三维能量多普勒指数与孕龄呈直线相关,以孕龄为自变量,胎盘的三维能量多普勒指数为因变量的直线回归公式为VI =0.905 ×GA-16.15 （r=0.940,n=150,P＜O.000 1）,FI=0.284×GA＋42.961（r=0.341,n=150,P＜0.001）,VFI=0.502×GA-9.350（r=0.951,n=150,P＜0.000 1）.结论：三维能量多普勒超声能定量分析正常中晚孕期胎盘血流灌注情况,为产前准确评价胎盘功能提供重要的辅助诊断依据.     

三维超声评价胎儿小脑体积

目的应用三维超声建立不同孕周胎儿小脑体积正常范围参考值。方法对16～40周正常单胎胎儿283例进行小脑三维超声容积扫查,采用VOCAL程序30°旋转法测定小脑体积,应用相关回归分析拟合小脑体积随孕周增长的回归模型。结果正常妊娠胎儿小脑体积三维超声测量值与孕周高度相关(r=0.924,P<0.0001)。小脑体积随孕周增长的最适方程为幂曲线方程(R2=0.975,F=10751.86,P<0.0001)。结论三维超声不同孕周胎儿小脑体积正常值的建立将为产前判断小脑发育不良及相关异常,准确推算孕周提供有价值的参考。     

Assessment of fetal cerebellar volume using three-dimensional ultrasound

The purposes of this study were to assess the fetal cerebellar volume during normal gestation using three-dimensional (3-D) ultrasound (US) and to establish a normal chart of fetal cerebellar volume using Altman's model of statistics. In total, 231 healthy fetuses were studied for assessment of cerebellar volume using a 3-D US volume scanner. The fetuses to be studied were selected to give a cross-sectional series (i.e., each fetus was examined only once). Polynomial regression analysis was calculated to find the best-fit model using gestational age as the independent variable and cerebellar volume as the dependent variable. Altman's model was used to calculate the age-related reference centiles for the variance of cerebellar volume. In addition, common fetal growth indices, such as biparietal diameter, occipitofrontal diameter, head circumference, abdominal circumference, femur length and estimated fetal weight, were also measured for the correlation between cerebellar volume and these indices. Our results indicated that the fetal cerebellar volume was highly correlated with gestational age in normal pregnancies with the best-fit polynomial regression equation of a second-order (r = 0.91, p < 0.0001). In addition, fetal cerebellar volume in normal gestation is also highly correlated with common fetal growth indices, such as biparietal diameter, occipitofrontal diameter, head circumference, abdominal circumference, femur length and estimated fetal weight (all p < 0.0001). Following the Altman's model, a normal growth chart of fetal cerebellar volume was established for clinical reference. In conclusion, with 3-D US, the assessment of fetal cerebellar volume becomes feasible. We believe that fetal cerebellar volume assessed by 3-D US may be useful in detecting cerebellar hypoplasia and relevant syndromes prenatally.     

Validation of fractional moving blood volume measurement with power Doppler ultrasound in an experimental sheep model.

OBJECTIVE: To compare fractional moving blood volume (FMBV) estimation using power Doppler ultrasound (PDU) with blood flow estimation using radioactive microspheres (RMS) for evaluation of fetal organ blood perfusion. METHODS: Blood flow was measured in the adrenal gland of nine exteriorized fetal lambs. Five fetal lambs underwent total umbilical cord occlusion in order to induce changes in the adrenal blood flow (asphyxia group). Four lambs were used as sham controls (control group). Three RMS injections, with coincident PDU recordings of the adrenal gland, were performed in each lamb. In the asphyxia group, measurements were taken before the cord occlusion, 5 min later and when the mean blood pressure decreased below 25 mmHg. In the control group, the measurements were done with an interval of 5 min. FMBV normalized for attenuation of PDU signals, and mean pixel intensity (MPI) were estimated offline. After completion of the study, adrenal blood perfusion was calculated according to the reference sample microsphere technique, using the isotope activity and expressed in mL/min/100 g. The correlation between RMS and FMBV and MPI, respectively, was analyzed individually for each lamb. RESULTS: In the asphyxia group, all lambs showed a marked reduction in the adrenal blood perfusion towards the third RMS injection. In the control group, the adrenal perfusion showed small variations throughout the experiment. In the total material, there was a higher correlation between FMBV and RMS (median, r = 0.90; range, 0.43-0.99) than between MPI and RMS (median, r = 0.55; range, -0.53 to 0.99). CONCLUSION: The FMBV method of quantifying PDU signals correlates highly with blood flow perfusion estimation using RMS in the fetal lamb adrenal gland.     

Estimation of fractional moving blood volume in fetal lung using Power Doppler ultrasound, methodological aspects

Perfusion estimation of the fetal lung is an important predictor of its maturity and function after birth. Ultrasound (US) power Doppler has previously been used to assess the perfusion of the fetal lung, based on the mean pixel intensity (MPI) over a region-of-interest (ROI). The drawback is that the MPI is not only dependent on the amount of flowing blood, but also depth, gain and attenuation in overlying tissue layers. In this study, power Doppler images have been analysed according to a previously published method that attempts to compensate for such unwanted variations, resulting in a measure termed fractional moving blood volume (FMBV). A total of 29 singleton pregnancies with normally grown fetuses were evaluated after 35 weeks of gestation. For reliable interpatient comparisons, we found it always necessary to use a well-defined section of the fetal lung. Therefore, all scans were performed in a transverse plane of the fetal thorax with a four-chamber view of the heart, through the intercostal space. ROIs in 12 left and 17 right fetal lungs were defined (the fetal lung closest to the transducer was always examined). No differences in estimated FMBV or MPI were found between left and right lungs. Similarly, there was no significant difference between images acquired during systole and diastole. FMBV is compensated for depth and, also, for other sources of power variation, as reflected in the coefficient of variation: 0.14 for FMBV and 0.24 for MPI. A scan on a test phantom reveals that the power in dB is linearly related to velocity over a limited range, suggesting that FMBV might be useful for discriminating between normal and decreased fetal lung perfusion.     

Assessment of fetal adrenal gland volume using three-dimensional ultrasound

To assess the normal fetal adrenal gland volume during normal gestation, we performed a prospective study on 119 normal fetuses with gestational age ranging from 21 to 40 weeks using a 3-D ultrasound (US) volume scanner with a pure cross-sectional design. Polynomial regression analysis was calculated to find the best-fit model between gestational age (GA) and adrenal gland volume. In addition, estimated fetal weight (EFW) was also measured to demonstrate the correlation between adrenal gland volume and fetal weight. Our results showed that fetal adrenal gland volume is highly correlated with GA. Furthermore, using GA as the independent variable and adrenal gland volume as the dependent variable, the best-fit regression equation was adrenal glands volume (mL) = -0.2683 x GA + 0.0082 x GA(2) + 3.1927 (r = 0.93, n = 119, p < 0.0001). For clinical use, a chart of normal growth centiles of fetal adrenal gland volume in utero was then calculated based on this equation. In addition, fetal adrenal gland volume during normal gestation is also highly correlated with EFW (p < 0.0001). In conclusion, our data of fetal adrenal gland volume assessed by 3-D US can serve as a useful reference in evaluating fetal growth status during gestation.     

三维彩色能量成像评价正常妊娠胎盘血流灌注

目的探讨三维彩色能量成像(3DCPA)测量胎儿胎盘的三维能量多普勒指数与孕龄的相关关系及其临床意义。方法采用Voluson730expert三维超声成像系统的3DCPA测量130例20～40周的胎儿胎盘的血管化指数(VI),血流指数(FI),血管化血流指数(VFI),并与孕龄比较分析。结果胎儿胎盘的三维能量多普勒指数与孕龄呈直线相关,以孕龄为自变量,胎儿胎盘的三维能量多普勒指数为因变量的直线回归公式为VI=0.297×GA-3.428(r=0.59,n=130,P<0.0001)FI=0.23×GA 27.516(r=0.32,n=130,P<0.0001),VFI=0.115×GA-1.509(r=0.59,n=130,P<0.0001)。结论3DCPA可以作为妊娠中观察胎盘血管树发育的工具,胎儿胎盘的三维能量多普勒指数与孕龄的增长以及胎儿各生长参数积极相关。     

Assessment of postoperative postvoid residual bladder volume using three-dimensional ultrasound volumetry

The aim of our prospective study was to assess the concordance between postvoid residual volumes (PVR) of the urinary bladder obtained by two different three-dimensional (3-D) ultrasound (US) volumetric methods (VOCAL and XI VOCAL) and with measurement by the catheter in postoperative patients who have undergone radical hysterectomy. The 3-D sonographic volume-determination of PVR with both methods correlated significantly with the actual amount of PVR by the catheter. The accuracy of both 3-D US volumetric methods was significantly higher under 300 mL of PVR. Bland-Altman plots were generated to examine limits of agreement. Both noninvasive 3-D sonographic methods are appropriate for the correct volume-determination of PVR following radical hysterectomy. Thus, we may avoid routine, albeit often unnecessary, catheterization to measure postoperative residual bladder volumes and subsequently the incidence of lower urinary tract infection may be reduced and better postoperative comfort for patients may be permitted. (E-mail: szabolcs.bozsa@aok.pte.hu)     

三维能量多普勒超声在急诊科领域的应用

1999年Pairleitner等第一次提出运用三维彩色能量多普直方图的测算软件获取血管化指数（VI）,血流指数（FI）,血管化血流指数（VFI）三个参数,用于定量评估目标器官的血流灌注情况。血管化指数（VI）为血管内彩色体素/（总的体素-背景体素）值,代表感兴趣区内单位容积内的血管数目,表示该组织内血管的丰富或稀疏程度。血流指数（FI）为加权平均彩色体元/彩色体元,是所有血流的平均彩色值或血流密度,代表目标容积内血流信号的平均强度,表示三维扫查的瞬间有多少血细胞。血管化血流指数（VFI）为加权彩色体元/（彩色体元-背景体元）,是感兴趣区域内加权的彩色值（振幅的加权）,是存在的血管信息和血流信息的结合。     

Fractional moving blood volume estimation in the fetal lung using power Doppler ultrasound: a reproducibility study.

OBJECTIVE: To evaluate the reproducibility of fractional moving blood volume (FMBV) estimation in the fetal lung using power Doppler ultrasound (PDU). METHODS: The lung blood perfusion of 20 normally grown singleton fetuses at 32-35 weeks of gestation was evaluated by two experienced observers using PDU. Each observer recorded two consecutive sequences of images from the posterior part of the fetal lung and calculated FMBV offline. FMBV expresses the percentage of blood movement within a defined region of interest (ROI). Repeatability and agreement were evaluated by means of the intraclass (intraCC) and interclass (interCC) correlation coefficients. RESULTS: FMBV was successfully evaluated in 17/20 fetuses by both observers (kappa index 0.82; 95% CI 0.51-0.93). The intraCC for repeatability for Observer A was 0.92 (95% CI 0.78-0.96), and for Observer B 0.90 (95% CI 0.74-0.96). The mean difference between the first and the second measurement was 0.7% (SD 4.5%). The interCC for repeatability over time and between the operators was 0.70 (95% CI 0.56-0.76) and the mean difference between the observers was 0.6% (SD 4.65%). The interCC for agreement was 0.92 (95% CI 0.84-0.95) and the mean difference in FMBV results when both observers analyzed the same sequences offline was 0.6% (SD 3.85%). CONCLUSION: In the hands of experienced operators, using a well-defined ROI and standard settings, FMBV estimation is a reproducible method of quantifying power Doppler signals recorded from fetal lung blood perfusion.     

Quantitative three-dimensional power Doppler ultrasound predicts the outcome of placental chorioangioma.

The relationship of large and vascularized chorioangiomas to adverse pregnancy outcome is well recognized. We present a patient with a large placental tumor and signs of impending fetal cardiac failure. The angioarchitecture of the tumor depicted by three-dimensional (3D) power Doppler ultrasound enabled us to accurately diagnose a placental chorioangioma. During the follow-up period, quantitative flow data obtained using 3D power Doppler indicated altered hemodynamics in the tumor and concomitant improvement in the condition of the fetus, enabling us to manage the mother conservatively. Spontaneous delivery occurred at 38 weeks without any complications. This report demonstrates the potential value of 3D power Doppler in prenatal diagnosis and monitoring of pregnancies complicated by large, vascularized chorioangioma.     

三维能量多普勒超声评估子宫内膜异位症患者在位内膜血流分布

目的 探讨三维能量多普勒超声在子宫内膜异位症患者在位内膜血流分布评估中的应用价值.方法 对44例子宫内膜异位症患者和51例正常对照者在增殖期或者分泌期行三维能量多普勒超声检查,测定子宫在位内膜的内膜容积、血管化指数(VI)、血流指数(FI)、血管化血流指数(VFI),比较两组各参数的差异.结果 病例组增殖内膜VI为(5.499±5.153)％,FI为(28.832±4.279)dB,VFI为(1.769±1.981)dB,均高于对照组增殖期内膜VI[(1.135±1.333)％,P＜0.001]、FI[(25.544±3.465) dB,P=0.006]、VFI[(0.321±0.397)dB,P=0.002].病例组分泌内膜VI为(8.693±5.940)％,FI为(30.689±3.632)dB,VFI为(2.753±2.044) dB,均高于对照组分泌期内膜VI[(1.014±0.968)％,P＜0.001]、FI[(24.748±3.811)dB,p＜0.001]、VFI[(0.27±0.293) dB,P=0.001].病例组与对照组增殖期内膜容积、分泌期内膜容积相比差异均无明显统计学意义(P =0.108和0.068).结论 三维能量多普勒超声可评估子宫内膜异位症患者在位内膜血流分布情况,为抗血管生成治疗提供临床依据.     

Assessment of normal fetal upper arm volume by three-dimensional ultrasound

Fetal upper arm volume (UAV) is closely related to fetal growth and nutrition status. In the past, 2-D ultrasound (US) has shown limitations in assessing fetal UAV. With the recent advancement of 3-D US, the limitation in assessing fetal UAV by 2-D US can be overcome. To establish a reference chart of fetal UAV for clinical use, a prospective and cross-sectional study using 3-D US was undertaken to assess the fetal UAV in normal pregnancy. In total, 206 singleton fetuses ranging between 20 and 40 weeks of gestation that fit the criteria of normal pregnancies were enrolled in this study. Our results showed that fetal UAV is highly correlated with the gestational age. Furthermore, using gestational age (GA) as the independent variable and UAV as the dependent variable, the best-fit regression equation was UAV (mL) = 43.546 - 4.530 x GA + 0.133 x GA(2) (r = 0.913, n = 206, p < 0.0001). For further clinical use, a chart of normal growth centiles of fetal UAV in utero was then calculated based on this equation. In conclusion, we believe our data of fetal UAV assessed by 3-D US can serve as a useful reference in evaluating fetal growth and nutrition status during gestation.     

Assessment of changes in endometrial and subendometrial volume and vascularity during the normal menstrual cycle using three-dimensional power Doppler ultrasound.

OBJECTIVES: To describe changes in endometrial and subendometrial volume and vascularity during the normal menstrual cycle using three-dimensional (3D) power Doppler ultrasonography. METHODS: Fourteen healthy volunteers, 24-44 years old with regular menstrual cycles, underwent serial transvaginal 3D power Doppler ultrasound examinations of the uterus on cycle day 2, 3 or 4, then daily from cycle day 9 until follicular rupture and 1, 2, 5, 7 and 12 days after follicular rupture. Endometrial and subendometrial volume (cm3), vascularization index (VI), flow index (FI) and vascularization flow index (VFI) were calculated using the VOCAL (Virtual Organ Computer-aided AnaLysis) software. RESULTS: Endometrial and subendometrial vascularity indices increased throughout the follicular phase, decreased to a nadir 2 days after follicular rupture and then increased again during the luteal phase. Endometrial and subendometrial volume increased rapidly during the follicular phase and then remained almost unchanged during the luteal phase. CONCLUSIONS: Substantial changes occur in endometrial volume and vascularization during the normal menstrual cycle. There is the potential for 3D power Doppler ultrasonography to become a useful tool for assessing pathological changes associated with female subfertility and abnormal uterine bleeding.     

A double beam doppler ultrasound method for quantitative blood flow velocity measurement

A method for measuring the absolute blood flow velocity waveform is reported. Two independent beams of ultrasound illuminate a vessel simultaneously, producing complementary Doppler signals. The two Doppler frequency shift signals are processed by subtraction and addition at the receiver. The optimum probe position where blood flow velocity is detected can be found as the position where the subtractor output reaches zero. At this position the blood flow velocity is the output from the adder. By this means the influence of the angle between the probe and blood flow is eliminated so that a quantitative measurement is obtained. Both in vitro and clinical results are reported.     

Computerized evaluation of blood flow measurement indices using doppler ultrasound

The study involved computer-assisted analysis of Doppler blood flow signals from an in vitro experimental system utilizing a calibrated occlusive pulsatile pump, vinyl tubings of various dimensions, and human blood. The power spectra of these signals were obtained using the Fast Fourier Transform, and the peak and mean frequencies along with the first moments of the Fourier spectra around the zero-frequency axis were computed. These indices were evaluated using different flow rates and tubal dimensions. It was experimentally verified that the first moment provided a more linear measure of volume flow rate than that estimated by peak and mean velocities. Although the first moment cannot measure the absolute flow rate, it may serve as a better indicator of relative flow changes than the other two indices.     

Subsample volume processing of doppler ultrasound signals

Processing of Doppler signals produced by pulsed Doppler systems is based on the assumption that the phase of the received high frequency ultrasound signals changes linearly with depth. However, the random spatial distribution of scatterers is not in accordance with this basic assumption. Consequently, averaging of the demodulated signal over an observation window, covering a few periods of the received signal, does not improve the estimate for the instantaneous quadrature components of the Doppler signal originating from a given depth. Hence, the accuracy of the Doppler velocity estimate is independent of the length of the observation window employed. However, splitting the observation window in subsample volumes, each with a length of one period at the emission frequency, and combining the Doppler signals of the subsample volumes at the last stage of signal processing, i.e., mean Doppler frequency estimation using the autocorrelation technique, results in a considerable reduction of the variance of the velocity estimate. Using a computer simulation of the signal processing involved, it is demonstrated that with subsample volume processing the variance of the velocity estimate attains the same variance as is expected for the RF cross correlation technique.