What Does 2‐Dimensional Imaging Add to 3‐ and 4‐Dimensional Obstetric Ultrasonography?

OBJECTIVE: The purpose of this study was to determine whether 2-dimensional (2D) ultrasonography adds diagnostic information to that provided by the examination of 3-dimensional/4-dimensional (3D/4D) volume data sets alone. METHODS: Ninety-nine fetuses were examined by 3D/4D volume ultrasonography. Volume data sets were evaluated by a blinded independent examiner who, after establishing an initial diagnostic impression by 3D/4D ultrasonography, performed a 2D ultrasonographic examination. The frequency of agreement and diagnostic accuracy of each modality to detect congenital anomalies were calculated and compared. RESULTS: Fifty-four fetuses with no abnormalities and 45 fetuses with 82 anomalies diagnosed by 2D ultrasonography were examined. Agreement between 3D/4D and 2D ultrasonography occurred for 90.4% of the findings (123/136; intraclass correlation coefficient, 0.834; 95% confidence interval, 0.774-0.879). Six anomalies were missed by 3D/4D ultrasonography when compared to 2D ultrasonography (ventricular septal defect [n = 2], interrupted inferior vena cava with azygous continuation [n = 1], tetralogy of Fallot [n = 1], horseshoe kidney [n = 1], and cystic adenomatoid malformation [n = 1]). There were 2 discordant diagnoses: transposition of the great arteries diagnosed as a double-outlet right ventricle and pulmonary atresia misinterpreted as tricuspid atresia on 3D/4D ultrasonography. One case of occult spinal dysraphism was suspected on 3D ultrasonography but not confirmed by 2D ultrasonography. When compared to diagnoses performed after delivery (n = 106), the sensitivity and specificity of 3D/4D ultrasonography (92.2% [47/51] and 76.4% [42/55], respectively) and 2D ultrasonography (96.1% [49/51] and 72.7% [40/55]) were not significantly different (P = .233). CONCLUSIONS: Information provided by 2D ultrasonography is consistent, in most cases, with information provided by the examination of 3D/4D volume data sets alone.     

Quality of 2‐ and 3‐Dimensional Fast Acquisition Fetal Cardiac Imaging at 18 to 22 Weeks

Objective. The purpose of this study was to evaluate the frequency with which 6 different fetal cardiac views taken during a fetal ultrasound examination at 18 to 22 weeks' gestation can be obtained satisfactorily for cardiac anomaly screening using either a 2‐dimensional (2D) static or 3‐dimensional (3D) fast acquisition technique. Methods. A prospective study of 100 low‐risk women undergoing an anatomic survey was performed. Standard static 2D and 3D fast acquisition volumes were obtained on all patients. The 2D and 3D images were assigned, in a random order, to be independently graded by 3 reviewers. The degree of inter‐reviewer agreement was assessed through the use of the Cohen κ statistic. The factors contributing to satisfactory imaging were evaluated by random effects logistic regression. Results. A significant proportion of both 2D and 3D images were judged unsatisfactory for screening purposes. However, 2D images were significantly more likely, for all cardiac views, to be judged satisfactory (P < .05). The odds ratios for the 2D technique's being more likely than the 3D technique to provide images satisfactory for screening were 2.6 for the 4‐chamber view, 2.4 for the right ventricular outflow tract, 4 for the left ventricular outflow tract, 3.2 for the 3‐vessel view, 8.6 for the aortic arch, and 2.2 for the ductal arch. Conclusions. In this prospective study, static 2D imaging was significantly more likely than fast acquisition 2D imaging to yield cardiac views of high enough quality to satisfactorily screen for anomalies.     

Evaluation of the Development of the Fetal Anal Sphincter with Tomography Ultrasonography Imaging

The aim of the study described here was to examine the potential of tomography ultrasonography imaging (TUI) in evaluation of the fetal anal sphincter. In this prospective cross-sectional study of the fetal anal sphincter with TUI, 326 singleton pregnancies (mean age = 28 y, range: 22–38 y) were scanned at 19–40 wk of gestation. The fetal anal region and ischium were revealed in 320 of 326 patients (98.2%). The normal fetal anal sphincter diameter and ischial space reached maximums of 15 and 39 mm, respectively. The normal fetal anal sphincter diameter and the ischial space were plotted as a function of gestational age (GA) on a linear curve, and the regression equations for normal fetal anal sphincter diameter and ischial space as a function of GA in weeks were obtained. A scatterplot was also created that revealed a significant positive relationship between normal fetal anal sphincter diameter and ischial space. On the basis of these criteria, imperforate anus was diagnosed in one fetus. Ultrasonographic assessment of the fetal anal sphincter and the ischium with TUI is feasible. The reference values reported in this article may be useful in prenatal diagnosis of fetal anal sphincter abnormalities.     

Abnormal Number of Fetal Ribs on 3‐Dimensional Ultrasonography

Objective. The purpose of this study was to describe the clinical importance of an abnormal number of fetal ribs. Methods. A retrospective study of all fetuses that were found to have an abnormal number of ribs during routine ultrasonographic examinations was performed. Volume data sets of the fetal ribs were acquired by either static 3‐ or 4‐dimensional volume contrast imaging in plane C. In all cases, a meticulous survey of the fetal anatomy was performed, and prenatal and postnatal records were reviewed. Results. Seventy‐five fetuses were found retrospectively to have an abnormal number of ribs. Ultrasonographic examinations were done between 14 and 31 weeks' gestation (mean, 21.8 weeks; median, 23 weeks). More than 24 ribs were found in 28 fetuses (37%), and fewer than 24 ribs were found in 47 (63%). Additional anomalies were found in 22 fetuses (29%). Cardiovascular anomalies were detected in 10 fetuses. Seven fetuses had renal anomalies. Two fetuses had mild ventriculomegaly, and 1 fetus had holoprosencephaly. Lung dysplasia was found in 2 cases. One fetus had enlarged nuchal translucency with wormian bones. Termination of pregnancy was performed in 3 cases because of major malformations. The other 19 fetuses with associated abnormalities and the 53 without associated anomalies were born alive with only minor anomalies. Conclusions. An abnormal number of fetal ribs is an isolated finding in most cases. It may also be seen with major anomalies; however, more frequently the anomalies are minor, and the overall prognosis is good.     

Multislice Display of the Fetal Face Using 3‐Dimensional Ultrasonography

Objective. Multislice 3‐dimensional ultrasonography (3DUS) allows ultrasonographic volume data to be presented in parallel slices. Our aim was to develop a technique using a multislice display to specifically differentiate the maxilla (primary palate) from the mandible and to display the orbits in a single image in fetuses with normal anatomy and cleft lip/palate. Methods. Three‐dimensional ultrasonographic volumes of the fetal face were acquired in 142 patients (49 prospective and 93 retrospective). Fifteen patients had a confirmed diagnosis of cleft lip with or without cleft palate. Three readers manipulated volumes in a standardized fashion to show the orbits, maxilla, and mandible. The best interslice distance was determined. Image quality was assessed. Results. The mean gestational age of the fetuses was 23 weeks (range, 11–38 weeks). The mean interval distance used varied from 3 to 3.7 mm (range, 1–5.8 mm). The interval distance correlated with gestational age (Spearman ρ = 0.66; P < .0001). Image quality obtained through multislice evaluation of the orbits, maxilla, and mandible was high and did not vary with gestational age, interval distance, retrospective versus prospective acquisition, or 3DUS versus 4‐dimensional volumes. A higher image quality rating was associated with axial and sagittal planes of acquisition as opposed to coronal and oblique planes (Wilcoxon P < .002). All cases of cleft lip with or without cleft palate were correctly identified retrospectively. Conclusions. Multislice 3DUS evaluation of the fetal face can be performed successfully with high image quality. This technique can be used to consistently and accurately differentiate the fetal primary palate and mandible. Fetuses with cleft lip with or without cleft palate can be identified with confidence.     

Evaluation of the Fetal Secondary Palate by 3‐Dimensional Ultrasonography

Objective. Diagnosis of cleft lip and palate remains a challenge with 2‐dimensional ultrasonography, particularly when clefting involves only the secondary palate. The utility of 3‐dimensional ultrasonography (3DUS) has enhanced our ability to detect clefts. We report our experience with a modification of the flipped face technique to aid in the diagnosis of clefting of the secondary palate. Methods. Ninety‐two volumes of 92 fetal faces were evaluated. Thirty‐six volumes were acquired prospectively. Fifty‐six volumes had previously been acquired and included 8 with clefting of the secondary palate. Volumes were obtained on 3DUS systems and reviewed by 4 blinded readers on personal computer workstations. Volumes were manipulated so that an upright profile was visualized. The palate was then rendered using a thin, curved render box. Statistical analysis was performed using the Fisher exact test for categorical data. Intraclass correlations were computed to assess inter‐rater agreement. Results. The mean gestational age at image acquisition ± SD was 22 ± 5 weeks. Image quality of the secondary palate was obtained and rated as adequate by at least 2 reviewers in 34% (31 of 92) of volumes. The sensitivity of cleft detection ranged from 33% to 63%, and the specificity ranged from 84% to 95%. The low sensitivity was mainly due to artifacts/shadowing. The inter‐rater reliability was 0.62 (95% confidence interval, 0.47–0.76). Conclusions. Three‐dimensional ultrasonography can be used to diagnose clefts of the secondary palate. This evaluation is limited by the fetal position and artifacts from shadowing of adjoining structures. Pseudoclefts can be created, and optimal imaging cannot be obtained in all fetuses.     

Collaborative Study on 4‐Dimensional Echocardiography for the Diagnosis of Fetal Heart Defects

Objective. Congenital anomalies are the leading cause of infant mortality in the United States, and congenital heart defects (CHDs) are the most common type of birth defects. Recently, 4‐dimensional ultrasonography (4DUS) with spatiotemporal image correlation (STIC) has been introduced for fetal echocardiography. Accumulating evidence indicates that 4DUS with STIC may facilitate the examination of the fetal heart. Our objectives were to determine the accuracy of 4DUS for the diagnosis of CHDs and the agreement among centers. Methods. This study included 7 centers with expertise in 4D fetal echocardiography. Fetuses with and without confirmed heart defects were scanned between 18 and 26 weeks, and their volume data sets were uploaded onto a centralized file transfer protocol server. Intercenter agreement was determined using a κ statistic for multiple raters. Results. Ninety volume data sets were randomly selected for blinded analysis. Overall, the median (range) sensitivity, specificity, positive and negative predictive values, and false‐positive and ‐negative rates for the identification of fetuses with CHDs were 93% (77%–100%), 96% (84%–100%), 96% (83%–100%), 93% (79%–100%), 4.8% (2.7%–25%), and 6.8% (5%–22%), respectively. The most frequent CHDs were conotruncal anomalies (36%). There was excellent intercenter agreement (κ = 0.97). Conclusions. (1) Four‐dimensional volume data sets can be remotely acquired and accurately interpreted by different centers. (2) Among centers with technical expertise, 4DUS is an accurate and reliable method for fetal echocardiography.     

Applications of 3‐Dimensional Ultrasonography in the Neck,Excluding the Thyroid

Ultrasonography (US) of the neck is an accepted, useful imaging modality for many applications beyond its usefulness in thyroid disease. Two‐dimensional US has been effectively used for evaluation of many types of neck conditions, and now, 3‐dimensional US can be added to the imaging armamentaria. Three‐dimensional US is useful in the evaluation of cervical lymph nodes, recurrent/residual thyroid neoplasia, parathyroid glands, parotid and submandibular glands, as well as thyroglossal duct cysts and other assorted palpable and visible abnormalities because of its unique capabilities, including multiplanar reconstruction, accessibility of the coronal view, volume calculation, and regularly spaced incremental slice evaluation.     

Feasibility of Automated 3‐Dimensional Fetal Cardiac Screening in Routine Ultrasound Practice

Objective. The purpose of this study was to prospectively assess the clinical feasibility of an automated 3‐dimensional (3D) software tool for extended basic cardiac screening in routine ultrasound practice. Methods. During the 2‐month study period, all gravidas fitting our inclusion criteria were consecutively included. Cardiac 3D volumes were acquired within the time slot allocated for the usual 2‐dimensional fetal examination. All volumes were assessed on their quality, based on display of the 4‐chamber view, and on the ability to sufficiently display diagnostic cardiac planes (left ventricular outflow tract [LVOT], right ventricle outflow tract [RVOT], and stomach location) with Sonography‐Based Volume Computer‐Aided Diagnosis software (SonoVCAD; GE Healthcare, Milwaukee, WI). Results. Volume acquisition was successful in 107 of 126 cases (85%). For each sonographer, more than 70% of the acquired cardiac volumes were of high or sufficient quality. Separately analyzed, diagnostic planes of the LVOT, RVOT, and stomach location were visible in 62.1%, 81.6%, and 92.2%, respectively. An extended basic fetal cardiac examination based on retrieval of all diagnostic cardiac planes from a single volume using SonoVCAD could be performed in 46.6% of the cases. Conclusions. This study shows that cardiac volume acquisition can be incorporated in a routine ultrasound screening program without much difficulty. However, currently, SonoVCAD software still lacks the consistency to be clinically feasible for cardiac screening purposes. Further advances in ultrasound technology and familiarization with 3D ultrasound might improve its performance.     

Three‐Dimensional Ultrasonography of the Fetal Vermis at 18 to 26 Weeks' Gestation

Objective. The purpose of this study was to establish the normality of the fetal vermis, ie, the time of appearance of the primary fissure, as well as its measurements between 18 and 26 weeks' gestation, using 3‐dimensional (3D) ultrasonography. Methods. A prospective cross‐sectional study of normal singleton pregnancies was conducted. Examinations were performed with high‐resolution transabdominal ultrasonography using the axial plane in 173 fetuses between 18 and 26 weeks' gestation. Postprocessing measurements of the fetal vermis were done with 4‐dimensional software using static volume contrast imaging and tomographic ultrasound imaging in the C‐plane. Detection of the primary fissure was evaluated in all cases, and the time of appearance was documented. Results. Adequate vermis measurements were obtained in 173 fetuses. Vermian length as a function of gestational age was expressed by regression equations, and the correlation coefficients were found to be highly statistically significant (P < .001). The normal mean ± 2 SD for each gestational week was defined. The primary fissure was observed at 24 weeks' gestation in all cases, at 22 weeks in 94% of cases, and as early as 18 weeks in 40%. Conclusions. This 3D study documents the appearance of the primary fissure and presents the normal range of vermian measurements, confirming normal development of the fetal vermis starting as early as 18 weeks' gestation. It also shows an easy method for visualizing the vermis with 3D ultrasonography at every gestational week regardless of fetal presentation.