Color Doppler examination of the outflow tracts of the fetal heart: a technique for identification of cardiovascular malformations.

The objective was to describe a technique using color Doppler to identify the outflow tracts of the fetal heart by directing the ultrasound transversely through the fetal chest. One hundred second- and third-trimester control fetuses were examined with real-time and color Doppler ultrasound. The ultrasound beam was directed cephalad, in the same transverse plane used to image the four-chamber view, and the outflow tracts were examined. Four fetuses with abnormal cardiovascular anatomy were examined using the above approach, to study the anatomical relationships of the outflow tracts identified with color Doppler ultrasound in normal fetuses.When the ultrasound beam was directed immediately cephalad to the four-chamber view, the aorta was identified as it exited the left ventricle. Further movement of the ultrasound beam cephalad identified the following vessels in a single plane: the main pulmonary artery perpendicular to the ascending aorta; the left pulmonary artery branching from the main pulmonary artery; the full length of the ductus arteriosus; and the transverse arch of the aorta. The ascending aorta, main pulmonary artery, ductus arteriosus and transverse aortic arch were identified in 100% of fetuses. Four fetuses with abnormalities of the outflow tracts (aortic stenosis, aortic regurgitation, pulmonary stenosis and premature constriction of the ductus arteriosus) were imaged using this approach in which pathology was readily identified.This technique enables rapid identification of the outflow tracts in second- and third-trimester fetuses using color Doppler and accurately identifies abnormalities of these vessels.     

Sonographic assessment of normal fetal palate using three-dimensional imaging: a new technique.

OBJECTIVES: The aim of this study was to describe a novel three-dimensional (3D) ultrasound rendering technique to examine the normal fetal posterior palate and to assess its correspondence with the real fetal anatomy. METHODS: A prospective longitudinal study was conducted from January to October 2005 and included 100 fetuses in a low-risk population. Fetal ultrasound examinations were performed at 17, 22, 27 and 32 weeks' gestation to determine the normal 3D ultrasound view of the fetal palate at different gestational ages. The ultrasound scans were performed using the strict anterior axial plane of the starting reconstruction volume and the underside 3D view of the fetal palate. The 3D view of the fetal palate was compared with the normal anatomical view of the fetal palate obtained by surgical fetopathological examination of fetuses at the same gestational ages. The sonographic visualization rates of seven defined anatomical landmarks of the fetal palate were computed for each gestational age. The visualization rates across gestational ages were compared by use of the Cochrane Q test. The reliability of detection of each anatomical landmark across gestational ages was determined by Cronbach's Alpha. RESULTS: In all cases a 3D ultrasound view of the fetal maxilla and secondary palate was obtained at each period of gestation and corresponded well to the fetal anatomical specimens. The seven defined anatomical landmarks of the fetal palate were identified in 42-100% of cases. The visualization rates across gestational ages were significantly different in five of these anatomical landmarks. These differences can be explained by different developmental processes of these anatomical structures. The overall reliability of visualization across the gestational ages for the anatomical landmarks was medium to very high (0.73-0.96), except for the landmark interpalatal suture which was low (0.48). CONCLUSIONS: This technique of anterior axial 3D view reconstruction of the fetal palate seen by an underside view can provide unique diagnostic information on the integrity of the secondary palate. This innovative, simple and rapid technique may become the reference technique in ultrasound investigation of the fetal palate, and should be of value in diagnosing isolated secondary cleft palate or palatal involvement when cleft lip and alveolus are diagnosed.     

The size of the fetal thoracolumbar spine: a three-dimensional ultrasound study.

OBJECTIVE: To evaluate three-dimensional sonographic measurements of the thoracolumbar spine in the 16-37 week fetus. DESIGN: Prospective cross-sectional study. SUBJECTS: Two hundred and eighty-nine patients between 16 and 37 weeks of gestation were enrolled at the time of their anomaly scan or routine third trimester scan if fetal size was appropriate for gestational age and if no fetal anomalies were apparent. METHODS: Three-dimensional (3D) volume calculation of the first and fifth lumbar vertebral body, the 12th thoracic vertebral body and the whole lumbar spine was performed in the transverse plane of the multiplanar mode while lumbar spine length was determined in the sagittal plane. RESULTS: All volumetric measurements were significantly correlated with gestational age and estimated fetal weight. For each examined parameter regression analysis was performed to describe the 'best-fit' equation. CONCLUSIONS: 3D sonography allows volume calculation of the fetal spine. Our study provides further data relating to volume changes in the developing fetal spine between 16 and 37 weeks of gestation.     

Serial fetal lung volume measurement using three-dimensional ultrasound.

OBJECTIVE: To establish reference intervals for fetal lung growth. DESIGN: Longitudinal observational study. SUBJECTS: Fifty-eight women with initially uncomplicated singleton pregnancies were recruited from the antenatal population of a teaching hospital. Four women were excluded from the final analysis because of complications arising in their pregnancy. METHODS: Each subject was serially scanned at monthly intervals. At each visit lung volume was measured using an ultrasound-based computerized three-dimensional imaging system. Multilevel models were used to determine conditional and unconditional reference intervals. RESULTS: Reference intervals for fetal lung growth were derived. Fetal lung volume increases in a non-linear way with gestation. CONCLUSIONS: Our computerized system has the capacity to be used in conjunction with any standard two-dimensional ultrasound scanner in order to measure volume. Lung volume measurement may be useful in predicting pulmonary hypoplasia.     

A novel three-dimensional endoscopic ultrasound technique for the freehand examination of the oesophagus

This study details the development and evaluation of a freehand radial three-dimensional endoscopic ultrasound (3D-EUS) technique for use in the upper gastro-intestinal tract. It comprised of a commercial EUS system, a custom acquisition system to simultaneous acquire radial B-mode images and corresponding incremental changes in position of the scope as it was withdrawn and a custom 3D-EUS package written in Matlab™, to reconstruct and analyse the volume. This technique was evaluated using an EUS phantom with embedded objects of known dimensions and volumes and with clinical images acquired during routine cancer staging. For the phantom measurements, average Z-dimensional error was <1% and volume errors were 1.4% (volume₁ = 48930 mm³) and 4.5% (volume₂ = 5100 mm³). Application of this technique to EUS acquired clinical images produced excellent characterisation of oesophageal structures and accurate dimension and volume measurements. It also enabled the endoscopist to review “off-line” the EUS examination in case important information was missed.     

Artifacts and the visualization of fetal distal extremities using three-dimensional ultrasound.

OBJECTIVES: To demonstrate that acoustic shadowing in 3D US may give rise to artifacts simulating limb defects and provide a solution to eliminate its occurrence. METHODS: Twenty second trimester fetuses (gestational age 15-24 weeks) were scanned with three-dimensional ultrasound (3D US) using a sagittal acquisition plane. Fetal tibia/fibula and radius/ulna pairs were assessed for completeness of imaging. A further 20 fetuses (gestational age 20-26 weeks) were scanned in both axial and sagittal planes and the results compared to verify clear visualization of both bones. RESULTS: Shadowing from adjacent structures produced an apparent limb defect in 55% of the first 20 fetuses imaged only sagittally (18% of limb pairs). Acquiring data from more than one orientation avoided this artifact. CONCLUSIONS: The 3D US is subject to the same artifacts as two-dimensional (2D US) in terms of acoustic shadowing, although their presentation may be different. Awareness of this fact is essential for correct interpretation of 3D US studies. Three-dimensional scanning protocols should be modified to ensure that fetal structures are adequately visualized by acquiring volume data in more than one acquisition orientation.     

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.     

Prenatal diagnosis of fetal acrania using three-dimensional ultrasound

Fetal acrania is uniformly lethal and termination is suggested whenever the diagnosis is made. Traditionally, the diagnostic tool was 2-D ultrasound (US). In this series, we report our work of detecting acrania using 3-D US. We reviewed our medical records of prenatal diagnosis on fetal acrania in National Cheng Kung University Hospital from May 1997 to December 2002. All the cases were scanned by a 3-D US scanner. In total, 29 cases of fetal acrania were diagnosed. The range of gestational age at prenatal diagnosis by US was between 11 and 21 weeks and 44% were depicted in the first trimester. Among them, 93.1% were isolated findings, and one was associated with trisomy 18. Comparing with previous literature, 3-D US can detect fetal acrania as early as 2-D US, and it also can provide additional vivid illustration after various modes of reconstruction, which 2-D US cannot. In conclusion, 3-D US may contribute to early detection of fetal acrania and provide a novel visual depiction of this defect after reconstruction; thus, assists substantially in diagnosis as well as consultation.     

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。     

Measuring engagement of the fetal head: validity and reproducibility of a new ultrasound technique.

OBJECTIVE: Fetal head engagement can be assessed by translabial ultrasound and has been shown to be predictive of delivery mode. We attempted to validate the technique by comparing ultrasound with abdominal and vaginal palpation. Reproducibility was tested in a blinded test-retest series. METHODS: In a prospective clinical study, 139 nulliparous women between 35 + 3 and 40 + 4 weeks' gestation were assessed by translabial ultrasound, abdominal palpation of the fetal head (n = 139) and vaginal examination (n = 112). Ultrasound was performed using two methods, with the symphysis pubis as reference. A test-retest series was performed in 90 women. RESULTS: Ultrasound of head engagement correlated strongly with abdominal palpation, full Bishop scores and vaginal assessment (all P < 0.001 for Kendall's tau-b). Intraclass correlation coefficients (n = 90) for the two methods were 0.75 and 0.92, signifying excellent interobserver agreement. Reproducibility was higher for the method using the central symphyseal axis as reference. CONCLUSION: Quantitation of head engagement by translabial ultrasound is highly reproducible and correlates strongly with clinical measures of head engagement. We are now undertaking a prospective study to assess the predictive value of this new parameter for intrapartum events.     

Three-dimensional multiplanar time-motion ultrasound or anatomical M-mode of the fetal heart: a new technique in fetal echocardiography.

OBJECTIVE: To assess the application of a three-dimensional multiplanar rendering technique for examination of the fetal heart. MATERIAL AND METHODS: Free-hand acquisition of a three-dimensional volume was performed without moving or tilting the transducer. While the anatomical plane shows the four cardiac chambers, the two other orthogonal planes show vertical and horizontal time-axis planes as M-mode traces. Because off-line plane positioning is possible on three-dimensional multiplanar reconstruction, M-mode traces can be obtained from different stored cardiac structures independently of the fetal position. Fifty-two women with normal singleton pregnancies at 22-40 weeks underwent transabdominal ultrasound examination and five women with singleton fetuses between 13 and 15 weeks were assessed transvaginally. Clinical application of the echocardiographic technique was tested in a further two fetuses with arrhythmia. RESULTS: Off-line M-mode traces from atrioventricular valve excursions and myocardial contractions were possible in 45/52 (86.5%) cases examined at 22-40 weeks. Among the 32 fetuses in which visualization of the outflow tracts was attempted, M-mode traces of the aortic and pulmonary valves were possible in 22 (68.7%) and 20 (62.5%) cases, respectively. In three of five cases examined transvaginally, M-mode traces could be registered. Both cases with supraventricular extrasystoles (26 and 31 weeks) were easily diagnosed using this technique. CONCLUSION: The new technique presented here enables the easy acquisition of optimal M-mode traces from different fetal heart structures. Based on our promising findings we would recommend that, in the future, three-dimensional multiplanar imaging should not be limited to automatic volume acquisition but should include the free-hand technique.     

三维超声容积自动测量技术评价胎儿小脑蚓部发育

目的 应用三维超声容积自动测量技术检测胎儿小脑蚓部的发育,为产前筛查胎儿小脑发育异常提供理论依据.方法 选择20～36孕周正常胎儿387例,应用经腹三维容积自动测量技术(VOCAL)测量小脑蚓部体积,观察胎儿小脑蚓部发育规律.结果 应用VOCAL软件测量胎儿小脑蚓部体积成功率为98%.胎儿小脑蚓部体积与孕周及小脑横径呈正相关,r分别为0.98、0.98(P<0.0001).以孕周为自变量X,小脑蚓部体积测量值为因变量Y,直线回归分析认为X与Y之间有直线关系,方程为Y=-2.17 0.12X.以小脑横径为自变量,小脑蚓部体积测量值为因变量,直线回归分析认为X与Y之间有直线关系,方程为Y=-0.94 0.06X.结论 三维超声容积自动测量技术测量胎儿小脑蚓部体积有助于评价胎儿小脑蚓部的发育.     

Tomographic ultrasound imaging of the fetal heart: a new technique for identifying normal and abnormal cardiac anatomy.

OBJECTIVE: In 2003 and 2004, the American College of Radiology, the American Institute of Ultrasound in Medicine, and the American College of Obstetricians and Gynecologists published guidelines for the standard ultrasound examination of the fetus. Each group recommended that the outflow tracts of the fetal heart be examined if technically feasible. One method to accomplish this task is to perform a free-hand sweep of the transducer beam directed in a transverse plane from the 4-chamber view to the fetal neck. One problem with this approach is that the examiner may not direct the beam transversely and, therefore, may not accurately identify the outflow tract anatomy. METHODS: A new technology, tomographic ultrasound imaging (TUI), allows the examiner to obtain a volume data set that simultaneously displays multiple images at specific distances from the 4-chamber view. This study examined TUI technology for identifying normal and abnormal fetal cardiac anatomy with the use of either static or spatiotemporal image correlation volume data sets. RESULTS: The 4 views used in the screening examination of the outflow tracts of the fetal heart (4-chamber, 5-chamber, 3-vessel, and tracheal views) could be identified with the use of TUI technology in fetuses between 13 and 40 weeks' gestation. Examples of fetuses with abnormal cardiac anatomy of the outflow tracts (tetralogy of Fallot, transposition of the great vessels, and pulmonary stenosis) all showed abnormal anatomy on TUI. CONCLUSIONS: Tomographic ultrasound imaging technology enables the fetal examiner to evaluate the 4-chamber view and the outflow tracts in a systematic manner to identify normal and abnormal cardiac anatomy.     

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.     

Volumetric assessment of normal fetal lungs using three-dimensional ultrasound

We attempted to construct normal reference centiles of fetal lung volume (LV) for clinical application by using three-dimensional (3-D) ultrasound (US) during normal gestation. A prospective study was performed on 195 healthy fetuses with gestational age (GA) ranging from 20 to 40 weeks for the assessment of fetal LV using a 3-D US volume scanner with a mixture of cross-sectional and serial measurements. Polynomial regression analysis was calculated to find the best-fit model between GA, right lung volume (RLV), left lung volume (LLV) and total lung volume (TLV). In addition, common fetal growth parameters, such as biparietal diameter (BPD), occipitofrontal diameter (OFD), head circumference (HCi), abdominal circumference (ACi), femur length (FL) and estimated fetal weight (EFW) were also measured to demonstrate the correlations between RLV, LLV, TLV and these parameters. Our results showed that RLV, LLV and TLV were highly correlated with GA. Using GA as the independent variable and RLV, LLV and TLV as the dependent variable, the best-fit regression equations were: RLV (mL) = 0.067 GA(2) - 1.2464 GA + 2.7825 (r = 0.95, n = 173, p < 0.0001), LLV (mL) = 0.0573 GA(2) - 1.599 GA + 12.454 (r = 0.95, n = 159, p < 0.0001) and TLV (mL) = 0.1263 GA(2) - 2.982 GA + 17.448 (r = 0.96, n = 152, p < 0.0001). For clinical use, a chart of normal growth centiles of fetal LV in utero was then calculated based on this equation. Furthermore, RLV, LLV and TLV were also highly correlated with the common fetal growth parameters during normal gestation (all p < 0.0001). In conclusion, the 3-D US nomograms of the fetal lung volume established in this study can be utilized as useful references in prenatal detection of fetal pulmonary pathologic status and relevant abnormalities.     

新的腹围测量方法在超声胎儿体重估计中的应用价值

目的探索一种新的腹围测量方法在超声胎儿体重估计中的准确性,及临床应用价值。方法对226例孕妇采用相同的胎儿双顶径,头围,股骨测量方法,同时对同一胎儿用两种方法进行腹围测量,并分别估计胎儿体重,并与出生体重对比分析。结果两种腹围测量方法对不同分组胎儿体重的估计准确性无明显差异。并且两种腹围测值统计学分析亦无差异。结论实际工作中可根据情况选择更方便、更清晰、更易于显示的腹围层面进行测量,以便估计胎儿体重,新的腹围测量方法具有较好的临床应用价值。     

Three-dimensional targeting: a new three-dimensional ultrasound technique to evaluate needle position during breast biopsy.

OBJECTIVE: To evaluate the role of three-dimensional (3D) ultrasound (US) following needle breast biopsy under two-dimensional (2D) needle guidance. METHODS: A total of 188 core-needle biopsies and 24 fine-needle aspiration biopsies were 3D US correlated after typical 'freehand' US needle guidance. All cases were examined with a linear 3D US volume scanner (5-13 MHz, Voluson 530D, Medison-Kretztechnik, Zipf, Austria). After core-needle stroke or localization of fine needle, a 3D US data volume set was acquired and a multiplanar analysis performed. This needle position check in all three planes is called '3D targeting'. 66 women with a mean age of 51 years (range, 27-80 years) showed 77 breast lesions (55 solid lesions, 22 cysts) with a mean diameter of 1.5 (range, 0.3-5.0) cm. RESULTS: In 49 women with 55 solid breast lesions, 16 lesions were malignant and 39 lesions benign. In 53 solid breast lesions 188 core-needle biopsies were performed (mean 3.6 biopsies/lesion). After core-needle biopsy 23 lesions (16 malignant, seven benign) were surgically removed. In 22 cases final histology confirmed results of the core-needle specimen. In one case a core-needle specimen of a 5 mm lesion showed atypical lobular hyperplasia. The definitive histology after surgery was invasive lobular carcinoma. Twenty-two cysts and two benign solid lesions were punctured with a fine needle followed by aspiration biopsy. The overall sensitivity of core-needle results in this study was 94% (specificity 100%, accuracy 0.98, positive predictive value 1, negative predictive value 0.97). In 117 core-needle strokes of benign (21) and malignant (12) lesions 3D targeting prospectively revealed 95 lesion hits, Twelve marginal lesion hits and nine out-of-lesion hits. In one case after the initial large core-needle path a 5-mm lesion was disguised by air bubbles, therefore 3D targeting failed during the second biopsy procedure. CONCLUSION: 3D US combined with 3D targeting technique is a reliable and objective tool demonstrating exact spatial positioning of core and fine needle during biopsy procedure.     

Accuracy in estimating fetal urinary bladder volume using a modified ultrasound technique.

OBJECTIVE: Fetal urine production at different gestational ages has been evaluated using ultrasound in several previous studies. In a recent study, we investigated the accuracy when estimating the bladder volume using the conventional ultrasound technique and found a total variability of 17.3-10.9% for bladder volumes of 5-40 mL. The variability is mainly caused by: (i) inappropriate image selection (the 'freezing error') and (ii) limitations when measuring on the frozen image (the 'frozen error'). The aim of this study was to reduce the total error by reducing the 'freezing' and the 'frozen error'. To this end, we used a modified manual ultrasound technique (adding a 'rocking' motion to the conventional method) and digitized the selected image. METHODS: Two patients for each gestational week from 24 to 40 weeks were selected. The fetal urinary bladder was examined with ultrasound three times within 1 min and documented on videotape. The volume, as assessed by the longitudinal section of the recorded bladder images, stored in digitized form, was evaluated on three occasions with > 24 h in between. The mean and variability (standard deviation, SD) were estimated. RESULTS: For fetal bladder volumes between 5 and 40 mL, the 'freezing error' (SD), the 'frozen error' and the 'total error' were 11.7-5.1%, 8.0-3.0% and 14.2-5.9%, respectively. Comparing the present with a previous study, when selecting images and assessing bladder volumes repeatedly within 1 min, SD was 12.9-5.5% vs. 17.3-10.9%. CONCLUSIONS: Using a modified ultrasound technique, the variability in fetal bladder volume estimation can be reduced.