Three-dimensional ultrasound fetal lung volume measurement: a systematic study comparing the multiplanar method with the rotational (VOCAL) technique

Clinical assessment of the fetal right Quantitative Lung Index

OBJECTIVES

We have previously described gestational-age-independent sonographic indices to assess fetal lung size in the right and left lungs: The Quantitative Lung Index for the right lung (QLI-R) and for the left lung (QLI-L), respectively. The purpose of this study was to evaluate the clinical cutoff point of the QLI-R to predict pulmonary hypoplasia and neonatal death.

MATERIALS AND METHODS

Retrospective assessment of the QLI-R in patients with left-sided congenital diaphragmatic hernia (CDH-L) and other fetal conditions at risk for fetal pulmonary hypoplasia. Cross-section and longitudinal assessment of the behavior of the QLI-R in untreated and treated patients. ROC curve analysis to determine the optimal cutoff point of the QLI-R in predicting neonatal death.

RESULTS

One hundred eighteen patients with CDH-L and other fetal conditions at risk for pulmonary hypoplasia had QLI-R measurements done. Seventeen patients were excluded for various reasons. Eleven patients with conditions other than CDH-L but at risk for pulmonary hypoplasia were used for intraclass coefficient measurements of the QLI-R. Ninety patients had CDH-L, of which 78 did not undergo antenatal intervention and in which the cutoff point for pulmonary hypoplasia and neonatal demise was assessed. Stent tracheal occlusion was performed in the remaining 12 patients with CDH-L, in which the behavior of the QLI after surgery was assessed. Analysis of the ICC showed an overall intra-rater reliability of 0.985 (Cronbach's Alpha-based). There was no correlation between gestational age and QLI-R (-0.73, Pearson correlation, p = .72). Twenty-six of the 78 patients (33%) with CDH-L managed expectantly had a neonatal demise. A QLI-R equal to or less than 0.45 was significantly predictive of neonatal demise (area under the curve 0.64, p = .046, sensitivity 77%). Nine of the 12 patients (75%) that underwent tracheal occlusion had neonatal survival. Of these, 10 had serial assessments of the QLI-R after surgery. An increase in the QLI-R of 0.11 was associated with a tendency for neonatal survival (p = .056).

CONCLUSION

Our study confirms that the QLI-R is a gestational-age-independent measurement of fetal lung size, with a high degree of reproducibility. In a population of expectantly managed CDH-L patients, a cutoff value of the QLI-R of 0.45 or lower is predictive of neonatal death from pulmonary hypoplasia. The QLI-R can be used to monitor fetal lung growth after tracheal occlusion, and an increase in the QLI-R is suggestive of neonatal survival. Further prospective studies are needed to confirm these findings and to explore the use of the QLI in other populations at risk for pulmonary hypoplasia and consequent neonatal demise.

Validation of an automatic software in assessing fetal brain volume from three dimensional ultrasonographic volumes: Comparison with manual analysis

OBJECTIVE

This study was aimed to test the agreement between a manual and an automatic technique in measuring fetal brain volume (FBV) from three-dimensional (3D) fetal head datasets.

METHODS

FBV were acquired independently by two operators from low risk singleton pregnancies at a gestational age between 19 and 34 weeks. FBV measurements were obtained using an automatic software (Smart ICV™) and manually by Virtual Organ Computer-aided AnaLysis (VOCAL™). Intraclass correlation coefficient (ICC) were calculated to assess reliability, while bias and agreement were evaluate by examining Bland-Altman plots. The time spent in measuring volumes was calculated and values obtained compared.

RESULTS

Sixty-three volumes were considered for the study. In all the included volumes successful volume analysis were obtained with both techniques. Smart ICV™ showed a high intra-observer (0.996; 95% CI 0.994-0.998) and inter-observer (ICC 0.995; 95% CI 0.991-0.997). An excellent degree of reliability was found when the two techniques were compared (ICC 0.995; 95% CI 0.987-0.998). The time required to perform FBV was significantly lower for Smart ICV™ than VOCAL™ (8.2 ± 4.5 vs. 121.3 ± 19.0 s; p < 0.0001).

CONCLUSIONS

The measurement of FBV is feasible with both manual and automatic techniques. Smart ICV™ showed an excellent intra- and inter-observer reliability associated with a valuable agreement with volume measurements obtained manually with VOCAL™. Volumes may be measured significantly faster with smart ICV™ than manually and this automatic software has the potential to become the preferred methods for the assessment of FBV.

Assessment of the fetal lungs in utero

Antenatal diagnosis of abnormal pulmonary development has improved significantly over recent years because of progress in imaging techniques. Two-dimensional ultrasound is the mainstay of investigation of pulmonary pathology during pregnancy, providing good prognostication in conditions such as congenital diaphragmatic hernia; however, it is less validated in other high-risk groups such as those with congenital pulmonary airway malformation or preterm premature rupture of membranes. Three-dimensional assessment of lung volume and size is now possible using ultrasound or magnetic resonance imaging; however, the use of these techniques is still limited because of unpredictable fetal motion, and such tools have also been inadequately validated in high-risk populations other than those with congenital diaphragmatic hernia. The advent of advanced, functional magnetic resonance imaging techniques such as diffusion and T2* imaging, and the development of postprocessing pipelines that facilitate motion correction, have enabled not only more accurate evaluation of pulmonary size, but also assessment of tissue microstructure and perfusion. In the future, fetal magnetic resonance imaging may have an increasing role in the prognostication of pulmonary abnormalities and in monitoring current and future antenatal therapies to enhance lung development. This review aims to examine the current imaging methods available for assessment of antenatal lung development and to outline possible future directions.

3D ultrasound as a surgical quality control of conization in patients with severe dysplasia: a prospective study

Purpose

To compare the techniques for cone measurement with ultrasound to determine the size of the resected tissue and to evaluate parameters which may be relevant for stratifying women at risk who need surveillance when pregnant.

Methods

The present study included women with a pathological cervical biopsy. Cervical length and volume were determined by transvaginal ultrasound prior to conization. The pathologist measured the volume of the removed tissue by the fluid displacement technique and using a ruler. A repeat transvaginal ultrasound was performed during a follow-up visit. Factors affecting cone volume as well as the correlation between measurement techniques were analyzed.

Results

A total of 28 patients underwent cervical excision treatment. The mean cervical volumes measured sonographically before and after the operation were 17.72 ± 7.34 and 13.21 ± 5.43 cm³, respectively. The proportion of volume excised was 25.50 ± 17.43%. A significant correlation was found between the cone depth and the cone volume measured by the fluid displacement technique, and histopathologically and sonographically measured difference in cervical volume. The interobserver reliability coefficient was > 0.9. Analyzing influential parameters, only age affected the extent of cone volume and the correlation between the three measurement techniques.

Conclusion

Commonly applied techniques of cervical and cone measurement are equivalent and interchangeable. Our ultrasound data show variety in the volume and length of the cervix, and in the proportion of the volume excised at conization. Ultrasound measurements may help the surgeon to estimate not only the dimension of the remaining cervix but also its function.

The role of three-dimensional ultrasonography fetal lung volume measurement in the prediction of neonatal respiratory function outcome

BACKGROUND

Respiratory distress is commonly encountered among premature babies immediately after birth resulting in significant neonatal morbidity or mortality.

OBJECTIVES

To evaluate the possible correlation between three dimensional fetal lung volumes (FLVs) and neonatal respiratory outcomes.

STUDY DESIGN

A cohort study included 100 pregnant women who participated in the study and were divided into two groups; group A (n: 50 - women pregnant ±34-37 weeks) and group B (n: 50 - women pregnant ±37⁺¹ to 40 weeks). A three dimensional measurement of the right fetal lung was made using virtual organ computer-aided analysis (VOCAL) software then correlated to neonatal respiratory functions namely Apgar score at birth and the occurrence of respiratory distress syndrome (RDS).

RESULTS

In group A, FLV was negatively correlated with Apgar score and the occurrence of RDS. In group B, FLV showed no statistical correlation with Apgar score and the occurrence of RDS.

CONCLUSIONS

Three dimensional fetal lung volumes might be an accurate noninvasive predictor for the development of RDS among preterm fetuses.

Sonographic Measurement of Cervical Volume in Pregnant Women at High Risk of Preterm Birth Using a Geometric Formula for a Frustum Versus 3-Dimensional Automated Virtual Organ Computer-Aided Analysis

OBJECTIVES

To compare cervical volume measurements by 3-dimensional (3D) sonography using Virtual Organ computer-aided analysis (VOCAL; GE Healthcare, Milwaukee, WI) versus a manual method using a geometric formula for a frustum.

METHODS

We included 142 asymptomatic pregnant women at 16 to 24 weeks gestation at high risk for preterm birth. With a Voluson 730 Expert system (GE Healthcare), they underwent 2-dimensional (2D) transvaginal sonographic cervical length measurements and 3D cervical volume acquisition. The stored volumes were processed by VOCAL on a surface tablet. Cervical volume was manually calculated from the 2D images by using the formula V = 1/3 × π × h × (r1²  + r2²  + r1 × r2), where V represents cervical volume; π was approximated as 3.14159; h, cervical length; r1, radius at the internal os; and r2, radius at the external os.

RESULTS

Cervical volume was lower when obtained manually than by VOCAL, with a coefficient of variation of 30%, a mean difference of 10.1 ± 14.9 cm³ (P < .0001), and a poor interclass correlation coefficient of 0.62 (95% confidence interval [CI], 0.31 to 0.78). Both methods had good reproducibility; however, VOCAL had wider limits of agreement. A positive correlation was found between both methods (r = 0.63; P < .0001). No correlation was found between cervical length by 2D transvaginal ultrasound and cervical volume by the VOCAL technique (r = 0.06; 95% CI, -0.10 to 0.22) or cervical volume by the manual method (r = 0.2; 95% CI, 0.08 to 0.39).

CONCLUSIONS

The cervix represents a frustum (truncated cone, r1 is not equal to r2) in shape rather than a cylinder. Both methods are reproducible; VOCAL is less reliable but provides higher values of cervical volume.

Prenatal prediction of pulmonary hypoplasia

Pulmonary hypoplasia, although rare, is associated with significant neonatal morbidity and mortality. Conditions associated with pulmonary hypoplasia include those which limit normal thoracic capacity or movement, including skeletal dysplasias and abdominal wall defects; those with mass effect, including congenital diaphragmatic hernia and pleural effusions; and those with decreased amniotic fluid, including preterm, premature rupture of membranes, and genitourinary anomalies. The ability to predict severe pulmonary hypoplasia prenatally aids in family counseling, as well as obstetric and neonatal management. The objective of this review is to outline the imaging techniques that are widely used prenatally to assess pulmonary hypoplasia and to discuss the limitations of these methods.

[Congenital anomalies of poor prognosis. Genetics Consensus Committee]

INTRODUCTION

The Genetic Branch of the Chilean Society of Paediatrics, given the draft Law governing the decriminalisation of abortion on three grounds, focusing on the second ground, which considers the "embryo or foetus suffering from a congenital structural anomaly or a genetic disorder incompatible with life outside the womb", met to discuss the scientific evidence according to which congenital anomalies (CA) may be included in this draft law.

METHODOLOGY

Experts in clinical genetics focused on 10 CA, reviewed the literature evidence, and met to discuss it.

RESULTS

It was agreed not to use the term "incompatible with life outside the womb", as there are exceptions and longer survivals, and change to "congenital anomaly of poor prognosis (CAPP)". Ten CA were evaluated: serious defects of neural tube closure: anencephaly, iniencephaly and craniorachischisis, pulmonary hypoplasia, acardiac foetus, ectopia cordis, non-mosaic triploidy, "limb body wall" complex, "body stalk" anomaly, trisomy 13, trisomy 18, and bilateral renal agenesis. Findings on the prevalence, natural history, prenatal diagnostic methods, survival, and reported cases of prolonged survival were analysed. Post-natal survival, existence of treatments, and outcomes, as well as natural history without intervention, were taken into account in classifying a CA as a CAPP.

CONCLUSION

A CAPP would be: anencephaly, severe pulmonary hypoplasia, acardiac foetus, cervical ectopia cordis, non-mosaic triploidy, limb body wall complex, body stalk anomaly, non-mosaic trisomy 13, non-mosaic trisomy 18, and bilateral renal agenesis. For their diagnosis, it is required that all pregnant women have access to assessments by foetal anatomy ultrasound and occasionally MRI, and cytogenetic and molecular testing.

Assessing the accuracy and reliability of ultrasonographic three-dimensional parathyroid volume measurement in a patient with secondary hyperparathyroidism: a comparison with the two-dimensional conventional method

Purpose

The purpose of this study was to investigate the accuracy and reliability of the semi-automated ultrasonographic volume measurement tool, virtual organ computer-aided analysis (VOCAL), for measuring the volume of parathyroid glands.

Methods

Volume measurements for 40 parathyroid glands were performed in patients with secondary hyperparathyroidism caused by chronic renal failure. The volume of the parathyroid glands was measured twice by experienced radiologists by two-dimensional (2D) and three-dimensional (3D) methods using conventional sonograms and the VOCAL with 30°angle increments before parathyroidectomy. The specimen volume was also measured postoperatively. Intraclass correlation coefficients (ICCs) and the absolute percentage error were used for estimating the reproducibility and accuracy of the two different methods.

Results

The ICC value between two measurements of the 2D method and the 3D method was 0.956 and 0.999, respectively. The mean absolute percentage error of the 2D method and the 3D VOCAL technique was 29.56% and 5.78%, respectively. For accuracy and reliability, the plots of the 3D method showed a more compact distribution than those of the 2D method on the Bland-Altman graph.

Conclusion

The rotational VOCAL method for measuring the parathyroid gland is more accurate and reliable than the conventional 2D measurement. This VOCAL method could be used as a more reliable follow-up imaging modality in a patient with hyperparathyroidism.

Volume of intracranial structures on three-dimensional ultrasound in fetuses with congenital heart disease

OBJECTIVE

To investigate the volume of intracranial structures in fetuses with congenital heart disease (CHD).

METHODS

Total intracranial volume, frontal lobes volume, thalamus volume and cerebellar volume were prospectively evaluated and compared in 73 fetuses with CHD and 168 normal fetuses using three-dimensional ultrasound combined with post-processing software at 20 + 0 to 36 + 6 weeks of gestation. Multiple regression analyses were performed to identify risk factors for reduced volume of intracranial structures.

RESULTS

From the 28th week of gestation onwards, total brain volumes and those of specific structures became progressively smaller in fetuses with CHD relative to those in controls (P < 0.05). The decrease was largest in frontal lobes volume, followed by total intracranial volume and cerebellar volume, and the smallest decrease was in thalamus volume (P < 0.05). Multivariable analysis showed that the diagnostic category (P < 0.001) was independently associated with smaller brain volumes in fetuses with CHD. The largest differences from controls occurred in hypoplastic left heart syndrome (HLHS), followed by aortic hypoplasia, transposition of the great arteries (TGA) and tetralogy of Fallot (TOF).

CONCLUSIONS

The volume of intracranial structures is smaller in fetuses with CHD, particularly in those with HLHS, aortic hypoplasia or TGA. This study highlights the need for routine brain screening and early intervention to improve neurodevelopmental outcomes in fetuses with CHD.

Prediction of lethal pulmonary hypoplasia by means fetal lung volume in skeletal dysplasias: a three-dimensional ultrasound assessment

OBJECTIVE

The aim of this study was to assess the capacity of three-dimensional ultrasound (3DUS) for predicting lethality in fetuses with skeletal dysplasia.

METHODS

Twenty-four fetuses between 20 and 32 weeks of gestation were assessed. Bilateral lung volume scans were performed three times in each fetus during one ultrasound session. The virtual organ computer-aided analysis method was used to obtain a sequence of six sections of each lung around a fixed axis, and a rotation angle of 30° was adopted. Fetal lung volume measurements were analyzed according to the reference range. After birth, lung hypoplasia was diagnosed considering clinical and radiological criteria.

RESULTS

Of all cases of skeletal dysplasia, 18 (75%) were lethal. Among the lethal cases, after postnatal diagnosis, four were osteogenesis imperfecta type II, three were thanatophoric dysplasia and two were campomelic dysplasia. The remaining nine cases remained without a definitive diagnosis. The accuracy of 3DUS in predicting lethality in fetuses with skeletal dysplasia was high, with a sensitivity of 83.3%, specificity of 100%, positive predictive value of 100% and negative predictive value of 66.7%. The kappa index of 0.174 showed a good agreement between the possibility of lethality when the 3DUS volume measurement was altered and real lethality after birth (p < 0.001).

CONCLUSION

This study suggests that the 3DUS lung volume measurement is a good predictor of lethal pulmonary hypoplasia in fetuses with skeletal dysplasia, with high accuracy.

True Reproducibility of UltraSound Techniques (TRUST): systematic review of reliability studies in obstetrics and gynecology

OBJECTIVES

To examine the quality of methods used and the accuracy of the interpretation of agreement in existing studies that examine the reliability of ultrasound measurements and judgments in obstetrics and gynecology.

METHODS

A systematic search of MEDLINE was performed on 25 March 2014, looking for studies that examined the reliability of ultrasound measurements and judgments in obstetrics and gynecology with evaluation of concordance (CCC) or intraclass (ICC) correlation coefficients or kappa as a main objective.

RESULTS

Seven hundred and thirty-three records were examined on the basis of their title and abstract, of which 141 full-text articles were examined completely for eligibility. We excluded 29 studies because they did not report CCC/ICC/kappa, leaving 112 studies that were included in our analysis. Two studies reported both ICC and kappa and were counted twice, therefore, the number used as the denominator in the analyses was 114. Only 16/114 (14.0%) studies were considered to be well designed (independent acquisition and blinded analysis) and to have interpreted the results properly. Most errors occurring in the studies are likely to overestimate the reliability of the method examined.

CONCLUSIONS

The vast majority of published studies examined had important flaws in design, interpretation and/or reporting. Such limitations are important to identify as they might create false confidence in the existing measurements and judgments, jeopardizing clinical practice and future research. Specific guidelines aimed at improving the quality of reproducibility studies that examine ultrasound methods should be encouraged.

Role of 3-D ultrasound in clinical obstetric practice: evolution over 20 years

The use of 3-D ultrasound in obstetrics has undergone dramatic development over the past 20 years. Since the first publications on this application in clinical practice, several 3-D ultrasound techniques and rendering modes have been proposed and applied to the study of fetal brain, face and cardiac anatomy. In addition, 3-D ultrasound has improved calculations of the volume of fetal organs and limbs and estimations of fetal birth weight. And furthermore, angiographic patterns of fetal organs and the placenta have been assessed using 3-D power Doppler ultrasound quantification. In this review, we aim to summarize current evidence on the clinical relevance of these methodologies and their application in obstetric practice.

Estimation of uterine volume: A comparison between Viewpoint and 3D ultrasound estimation in women undergoing laparoscopic hysterectomy

Objectives: To assess the three‐dimensional (3D) tool, Virtual Organ Computed‐aided AnaLysis™ (VOCAL) in the calculation of pre‐operative uterine volume and to correlate the measurements with those obtained with Viewpoint, using uterine dry weight (UDW) as the gold standard.

Methods: Prospective observational study of women consented for a laparoscopic hysterectomy (LH) at Nepean Hospital between October 2008 and November 2011. All women underwent detailed transvaginal scan (TVS) at the pre‐operative assessment. Two‐dimensional (D) images of the uterus were obtained both in the mid‐sagittal and transverse planes. 3D volumetric acquisitions were also obtained for each uterus in the mid‐sagittal plane. 2D measurements of the uterus in millimetres (Anterio‐Posterior, longitudinal and transverse) were recorded in Viewpoint software package (GE Healthcare ViewPoint, Germany); which then generated an estimated uterine volume (ml) using the ellipsoid formula. The 3D uterine volumetric datasets were reviewed using SonoView Pro and uterine volumes were estimated with off‐line processing using VOCAL™. The gold standard for comparison was UDW in grams (g), measured by the histopathologist at the time of analysis of the LH specimens. The relationship between the estimated uterine volumes and actual UDW was evaluated using correlation analysis. P‐values were calculated to ascertain the significance of these findings; P values &< 0.05 represented statistical significance.

Results: 76 women underwent LH during the study period. Complete data were available in 96% (74/76) of cases. The mean age of the women was 43.7 years and 92% were multiparous. The mean Viewpoint uterine volume was 283 ml, the mean VOCAL™ uterine volume was 249 ml and the mean UDW was 295 g. There was a significant correlation between UDW and estimated uterine volumes both for Viewpoint (R = 0.83, P < 0.001) and VOCAL™ (R = 0.97, P < 0.001), respectively. Viewpoint systematically overestimated weight by 43.1 g, whereas VOCAL™ underestimated by an average of 42.4 g, and this difference was statistically significant (P < 0.001). In terms of absolute values, the mean prediction error for VOCAL™ was −18.0 g and for Viewpoint it was 27.6 g (P &< 0.0001). Conclusion: VOCAL™ was found to be significantly more accurate than Viewpoint in the estimation of uterine volumes, and it was better correlated with UDW.

Fetal cardiac interventricular septum: volume assessment by 3D/4D ultrasound using spatio-temporal image correlation (STIC) and virtual organ computer-aided analysis (VOCAL)

OBJECTIVE

To determine reference values for fetal interventricular septum (IVS) volume by 3D/4D ultrasound using spatio-temporal image correlation (STIC) and virtual organ computer-aided analysis (VOCAL).

METHODS

A prospective cross-sectional study was conducted on 200 consecutive normal low-risk pregnant women at a gestational age ranging from 18w0d to 33w6d. The volume data sets of the fetal heart were acquired by applying STIC to a four-chamber plane. IVS volume was calculated offline using VOCAL with rotation of 30° (six planes). To assess the correlation of fetal IVS volume as a function of gestational age (GA), Pearson's correlation coefficient (r) and polynomial regression models with adjustments through the coefficient of determination (R(2)) were calculated. The intra-class coefficient (ICC) was used to evaluate intra- and inter-observer reproducibility.

RESULTS

A good correlation between GA and fetal IVS volume (r = 0.827) was observed. The mean fetal IVS volume ranged from 0.13 ± 0.03 cm(3) (0.08-0.18 cm(3)) at 18wd0 of gestation to 1.33 ± 0.37 cm(3) (0.41-1.98 cm(3)) at 33w6d. The best correlation between fetal IVS volume and GA was exponential: fetal IVS volume = 0.11e(0.139×GA) (R(2 )= 0.785). A good intra- and inter-observer reliability were observed, with ICC = 0.999 and 0.991, respectively.

CONCLUSIONS

Reference values for fetal IVS volume using STIC and VOCAL by 3D/4D ultrasound between 18w0d and 33w6d of gestation were determined and showed to be reliable and concordant.

Volumetric growth of the lungs in human fetuses: an anatomical, hydrostatic and statistical study

Purpose

The prenatal assessment of lung volume is becoming increasingly important in determining survival in both preterm infants and newborns affected by pulmonary hypoplasia. This study aimed to examine the lung volumes in the human fetus at varying gestational ages.

Materials and methods

Using anatomical, hydrostatic (water displacement according to Archimedes’ patent) and statistical methods (one-way ANOVA test for paired data and post-hoc Bonferroni test, Kolmogorov–Smirnov test, Levene’s test, Student’s t test, regression analysis), volumes of the right and left lungs were measured in 67 human fetuses of both sexes (35 males, 32 females) aged 16–25 weeks, derived from spontaneous abortions and stillbirths.

Results

No male–female differences concerning the right and left pulmonary volumes were found. The mean volume of the right lung increased from 1.43 ± 0.25 to 8.45 ± 2.66 cm³, according to the cubic function y = –1.592 + 0.0007 × age³ ± 0.851 (R² = 0.84). The volumetric growth of the left lung, from 1.24 ± 0.22 to 6.78 ± 3.03 cm³, followed the cubic model y = –1.110 + 0.0005 × age³ ± 0.794 (R² = 0.78). The total pulmonary volume increased from 2.67 ± 0.47 to 15.22 ± 5.58 cm³, in accordance with the cubic model y = –2.729 + 0.0012 × age³ ± 1.598 (R² = 0.83). The mean volumes of the right and left lungs accounted for 54.9 ± 2.0 and 45.1 ± 2.0 %, respectively, of the total lung volume.

Conclusions

No sex differences are found between the lung volumes in the fetus. The growth of fetal lung volume follows a three-degree polynomial function. Throughout the analyzed period the two lungs grow proportionately to each other, with the volumetric predominance of the right lung. The lung volumes in the fetus are of great relevance in the evaluation of the normal pulmonary growth and the diagnosis of pulmonary hypoplasia.

Prediction of mortality and the need for neonatal extracorporeal membrane oxygenation therapy by 3-dimensional sonography and magnetic resonance imaging in fetuses with congenital diaphragmatic hernias

OBJECTIVES

To compare different rotation angles for assessment of fetal lung volume by 3-dimensional (3D) sonography with magnetic resonance imaging (MRI) regarding prediction of mortality and the need for neonatal extracorporeal membrane oxygenation (ECMO) therapy in fetuses with congenital diaphragmatic hernias.

METHODS

One hundred patients with fetal congenital diaphragmatic hernias between 22 and 39 weeks' gestation were examined by 3D sonography and MRI. Sonographic contralateral fetal lung volumes were assessed by the rotational technique (virtual organ computer-aided analysis) at 3 different rotation angles: 6°, 15°, and 30°. The MRI fetal lung volumes were calculated based on multiplanar T2-weighted MRI. To eliminate the influence of gestational age, the observed to expected contralateral fetal lung volume on sonography and the observed to expected fetal lung volume on MRI were calculated. Receiver operating characteristic (ROC) curves were calculated for the statistical prediction of survival and need for ECMO therapy by the observed to expected contralateral fetal lung volume (sonography) and observed to expected fetal lung volume (MRI).

RESULTS

One hundred cases were assessed for survival and 89 for ECMO necessity (11 neonates were not eligible for ECMO). For prediction of postpartum survival and ECMO necessity, the areas under the ROC curves (AUCs) showed very similar results for MRI and 3D sonography: observed to expected fetal lung volume by MRI, 0.819 (95% confidence interval, 0.730-0.909) and 0.835 (0.748-0.922), respectively; 6° sonography, 0.765 (0.647-0.883) and 0.820 (0.734-0.905); 15° sonography, 0.784 (0.672-0.896) and 0.811 (0.719-0.903); and 30° sonography, 0.732 (0.609-0.855) and 0.772 (0.671-0.872). Comparisons between the AUCs revealed no statistical differences.

CONCLUSIONS

We have shown the good prognostic value of 3D sonography in fetuses with congenital diaphragmatic hernias compared with MRI, particularly when using small rotation angles. Therefore, it can be an appropriate diagnostic tool when counseling patients for congenital diaphragmatic hernias.

Cervical length vs VOCAL cervical volume for predicting pre-term delivery in asymptomatic women at 20-22 weeks' pregnancy

We conducted a prospective observational study of 306 asymptomatic women at 20-22 weeks of pregnancy to compare 3-dimensional ultrasound measurements of cervical volume with 2-dimensional ultrasound measurements of cervical length to evaluate the performance of cervical volume as a predictor of pre-term delivery, compared with the current standard, cervical length. Participants underwent transvaginal ultrasound measurements of cervical length (mm) and cervical volume (cm(3)). Cervical volume as measured by 3-dimensional ultrasound was found to be a useful tool for predicting pre-term delivery; however, due to the high correlation between cervical length and cervical volume and the lack of differences in the sensitivity, specificity, positive predictive value, negative predictive value and relative risk between the two methods, replacing cervical length measurements with cervical volume calculations does not seem to be justified for this purpose, because of increased difficulty in volume acquisition.

New anatomical landmarks to study the relationship between fetal lung area and thoracic circumference by three-dimensional ultrasonography

OBJECTIVE

To evaluate the relation between total lung area (TLA) and thoracic circumference (TC) ratio by three-dimensional (3D) ultrasonography applying new anatomical landmarks as the fetal aorta and inferior angle of the scapula.

METHODS

A longitudinal prospective study was conducted with 56 uncomplicated pregnancies between 24 and 32 weeks of gestation. Polynomial regressions were used to evaluate the correlation between TC and gestational age (GA) as well as TC and estimated fetal weight (EFW). A simple linear regression was used to evaluate the correlation between TLA and Total thoracic area (TTA) and GA. The intraclass correlation coefficient (ICC) was used to assess the intra and interobserver variability.

RESULTS

127 examinations were performed. TC values ranged from 150 to 174 mm (mean 166 mm) at 24 weeks and 215-248 mm (mean 231 mm) at 32 weeks. The TLA/TC ratio ranged from a mean of 0.64 at 24 weeks (range 0.56-0.70) to 0.90 at 32 weeks gestation (range 0.79-1.01). The intraobserver variability using the ICC was of 0.919 for TC; 0.916 for TTA; 0.860 for right lung area (RLA) and 0.910 for left lung area (LLA). Interobserver reproducibility was with an ICC of 0.970 for TC; 0.984 for RLA and 0.910 for LLA.

CONCLUSIONS

Measurement of fetal TC and the relationship between TLA and TC by 3D-ultrasonography applying new anatomical landmarks shows good reproducibility and allows a new assessment of thoracic and lung growth.

Assessment of lung volume by 3-dimensional sonography and magnetic resonance imaging in fetuses with congenital diaphragmatic hernias

OBJECTIVES

The purpose of this study was to evaluate the influence of different rotation angles in assessment of the contralateral lung volume by 3-dimensional (3D) sonography in comparison to magnetic resonance imaging (MRI) in fetuses with congenital diaphragmatic hernias.

METHODS

A total of 126 measurements by 3D sonography and MRI were conducted in 81 patients between 18 and 39 weeks' gestation. The 3D sonographic volumes of the contralateral fetal lung were calculated by the rotational technique (virtual organ computer-aided analysis) with rotation angles of 6°, 15°, and 30°. Transverse multiplanar T2-weighted MRI was performed for the MRI measurements. To compare the accuracy of 3D sonographic volumetry using different rotation angles, MRI assessment was taken as the reference method, and percentage errors and limits of agreement were calculated for each angle.

RESULTS

Three-dimensional sonographic volume measurements showed a high correlation with MRI (6° angle, R(2) = 0.86; 15° angle, R(2) = 0.78; 30° angle, R(2) = 0.68). The mean percentage error showed no systematic error. With regard to random error, the 6° step had significantly lower values than the larger angles 30° step (R = 0.472) and the narrowest limits of agreement.

CONCLUSIONS

Especially when using a small rotation angle, assessment of the contralateral fetal lung volume by 3D sonography in congenital diaphragmatic hernias is a reliable alternative to MRI.

In vitro models of the fetal lung: comparison of lung volume measurements with 3-dimensional sonography and magnetic resonance imaging

OBJECTIVES

Three-dimensional (3D) sonography is an established volumetric method in gynecology and obstetrics. The aim of this study was to investigate the variability of 3D sonographic measurements and their accuracy in comparison with magnetic resonance imaging (MRI) for assessing fetal lung volume using in vitro lung models.

METHODS

Twenty-three in vitro lung models with randomly defined volumes ranging from 1 to 60 mL were made from gelatin with plastic sheaths, manually molded into the shape of fetal lungs. The models were measured using 3D sonography and MRI. The 3D sonographic volumes were calculated using the rotational technique with angles of 6° and 30°. Multiplanar T2-weighted sequences were used for the MRI measurements. The percentage error and absolute percentage error were calculated for each method, and intraobserver and interobserver variability in 3D sonographic measurements was assessed with intraclass correlation coefficients (ICCs). Agreement between calculated and real volumes using the limits of agreement method was also evaluated.

RESULTS

The ICCs for the rotation angles indicated very good intraobserver and interobserver variability (6°, 0.995 and 0.996; 30°, 0.997 and 0.985). No systematic errors were observed in the mean percentage errors for 3D sonographic measurements or MRI volumetry. The lowest median absolute percentage error (1.76) was obtained with MRI volumetry, significantly lower than the values for sonography (6°, 5.00; P < .001; 30°, 5.49; P < .001). There were no significant differences in absolute percentage errors between the rotation angles (P = .82) and no significant differences in limits of agreement between 3D sonography and MRI (6°, P = .76; 30°, P = .39).

CONCLUSIONS

Three-dimensional sonographic volumetry was almost as accurate as MRI in this in vitro model and can be regarded as a good alternative method. Further research is needed to confirm these findings in vivo and to assess the prognostic value in fetuses with lung hypoplasia (eg, congenital diaphragmatic hernias).

Influence of different rotation angles in assessment of lung volumes by 3-dimensional sonography in comparison to magnetic resonance imaging in healthy fetuses

OBJECTIVES

Three-dimensional (3D) sonographic volumetry is established in gynecology and obstetrics. Assessment of the fetal lung volume by magnetic resonance imaging (MRI) in congenital diaphragmatic hernias has become a routine examination. In vitro studies have shown a good correlation between 3D sonographic measurements and MRI. The aim of this study was to compare the lung volumes of healthy fetuses assessed by 3D sonography to MRI measurements and to investigate the impact of different rotation angles.

METHODS

A total of 126 fetuses between 20 and 40 weeks' gestation were measured by 3D sonography, and 27 of them were also assessed by MRI. The sonographic volumes were calculated by the rotational technique (virtual organ computer-aided analysis) with rotation angles of 6° and 30°. To evaluate the accuracy of 3D sonographic volumetry, percentage error and absolute percentage error values were calculated using MRI volumes as reference points. Formulas to calculate total, right, and left fetal lung volumes according to gestational age and biometric parameters were derived by stepwise regression analysis.

RESULTS

Three-dimensional sonographic volumetry showed a high correlation compared to MRI (6° angle, R(2) = 0.971; 30° angle, R(2) = 0.917) with no systematic error for the 6° angle. Moreover, using the 6° rotation angle, the median absolute percentage error was significantly lower compared to the 30° angle (P < .001). The new formulas to calculate total lung volume in healthy fetuses only included gestational age and no biometric parameters (R(2) = 0.853).

CONCLUSIONS

Three-dimensional sonographic volumetry of lung volumes in healthy fetuses showed a good correlation with MRI. We recommend using an angle of 6° because it assessed the lung volume more accurately. The specifically designed equations help estimate lung volumes in healthy fetuses.

Three-dimensional ultrasound fetal lung volumes and infant respiratory outcome: a prospective observational study

OBJECTIVE

To determine if fetal lung volumes (FLVs), determined by three-dimensional rotational ultrasound and virtual organ computer-aided analysis software (vocal), correlated with neonatal respiratory outcomes in surviving infants who had a high risk [fetuses with congenital diaphragmatic hernia (CDH)], lower risk [fetuses with anterior wall defects (AWDs)] and no risk (controls) of abnormal antenatal lung growth.

DESIGN

Prospective observational study.

SETTING

Tertiary fetal medicine and neonatal intensive care units.

POPULATION

Sixty fetuses (25 with CDH, 25 with AWDs and ten controls).

METHODS

FLVs were measured and expressed as the percentage of the observed compared with the expected for gestational age.

MAIN OUTCOME MEASURES

Neonatal respiratory outcome was determined by the duration of supplemental oxygen, mechanical ventilation and dependencies, and assessment of lung volume using a gas dilution technique to measure functional residual capacity (FRC).

RESULTS

The infants with CDH had lower FLV results than both the infants with AWDs (P=0.05) and the controls (P<0.05). The infants with CDH had longer durations of mechanical ventilation (P<0.001) and supplementary oxygen (P<0.001) dependence, compared with infants with AWDs. The infants with CDH had a lower median FRC than both the infants with AWDs (P<0.001) and the controls (P<0.001). FLV results correlated significantly with the durations of dependency on ventilation (r= -0.744, P<0.01) and oxygen (r= -0.788, P<0.001), and with FRC results (r=0.429, P=0.001).

CONCLUSIONS

These results suggest that FLVs obtained using three-dimensional rotational ultrasound might be useful in predicting neonatal respiratory outcome in surviving infants who had varying risks of abnormal lung growth. Larger and more comprehensive studies are needed to clarify the role that lung volume measurements have in assessing lung function and growth.

Three-dimensional ultrasound in evaluating the fetus

In recent years three-dimensional (3D) ultrasound has made a place in clinical practice and has become a major field of research in obstetrics. In this article we will review the diagnostic performance of the most widely used 3D ultrasound applications in the assessment of fetal anomalies, explain the technique to gain correct 3D images and offer some practical advice for their efficient use. Examples are given to demonstrate the applicability and vividness of 3D in daily routine.

Comparison of inter- and intraobserver agreement and reliability between three different types of placental volume measurement technique (XI VOCAL, VOCAL and multiplanar) and validity in the in-vitro setting

OBJECTIVES

To compare XI VOCAL (eXtended Imaging Virtual Organ Computer-aided AnaLysis) for three-dimensional (3D) ultrasound volumetry of the placenta and of phantom objects with a rotational method using VOCAL and with the multiplanar method.

METHODS

We acquired 3D volume datasets from 32 fetuses at 11-14 weeks' gestation. Placental volume was calculated twice by each of two observers using XI VOCAL (with 5, 10, 15 and 20 slices), multiplanar (1-mm interval) and VOCAL (with 12 degrees, 18 degrees and 30 degrees rotation) methods. In addition, validity was assessed using the in-vitro setting with three phantom objects of known volume.

RESULTS

Both inter- and intraobserver reliabilities were very high for all three methods. There was no systematic bias between any two methods except between XI VOCAL (10 slices) and the multiplanar (1-mm interval) method, with a smaller volume using the former method. The limits of agreement were wide between any two of the three methods. In the in-vitro setting, there was a trend towards less valid measurements with the XI VOCAL technique and fewer slices. With the same number of steps, measurements made with VOCAL (12 degrees and 18 degrees) were more valid than were those made with XI VOCAL (15 and 10 slices, respectively).

CONCLUSION

XI VOCAL cannot be used interchangeably with VOCAL or multiplanar techniques in measuring placental volume at 11-14 weeks' gestation.

Reliability and validity of in vitro volume calculations by 3-dimensional ultrasonography using the multiplanar, virtual organ computer-aided analysis (VOCAL), and extended imaging VOCAL methods

OBJECTIVE

The purpose of this study was to assess the reliability and validity of in vitro volume calculations by 3-dimensional ultrasonography.

METHODS

This observational study was performed by 2 examiners to obtain volumes of 3 objects of different shapes and sizes filled with ultrasound gel and immersed in water. The examiners used the multiplanar (5-mm interval), virtual organ computer-aided analysis (VOCAL, 30 degrees) and extended imaging (XI) VOCAL (5, 10, 15, and 20 planes) methods to estimate the volumes of each object. A paired Student t test (P) and intraclass correlation coefficients (ICCs) were used to assess reproducibility of the methods. Validity was assessed comparing the percent differences between the estimated and the real volumes using the P value, mean differences, and ICC for each method.

RESULTS

All methods were highly reliable and valid. There were no significant differences in interobserver variability; there was a strong interobserver correlation. There were no significant differences in the percent differences between the estimated and real volumes of the objects using the 3 methods. The XI VOCAL method was superior to the multiplanar and VOCAL methods in the measurement of irregularly shaped objects. The XI VOCAL method with 10 planes estimated volumes closest to the real volumes.

CONCLUSIONS

All 3 methods were reliable and valid; however, XI VOCAL was superior to the other methods in the measurement of irregularly shaped objects.

Three-dimensional ultrasound imaging

This review is about the development of three-dimensional (3D) ultrasonic medical imaging, how it works, and where its future lies. It assumes knowledge of two-dimensional (2D) ultrasound, which is covered elsewhere in this issue. The three main ways in which 3D ultrasound may be acquired are described: the mechanically swept 3D probe, the 2D transducer array that can acquire intrinsically 3D data, and the freehand 3D ultrasound. This provides an appreciation of the constraints implicit in each of these approaches together with their strengths and weaknesses. Then some of the techniques that are used for processing the 3D data and the way this can lead to information of clinical value are discussed. A table is provided to show the range of clinical applications reported in the literature. Finally, the discussion relating to the technology and its clinical applications to explain why 3D ultrasound has been relatively slow to be adopted in routine clinics is drawn together and the issues that will govern its development in the future explored.

Validation of volume measurements for fetal echocardiography using four-dimensional ultrasound imaging and spatiotemporal image correlation

OBJECTIVES

To assess the accuracy and reliability of four-dimensional (4D) ultrasound imaging using spatiotemporal image correlation (STIC) employing three different techniques to measure volumes in vitro.

METHODS

Customized miniature balloons attached to a pump system were used to mimic fetal cardiac chambers. After the balloon model had been immersed in a bath filled with viscous gel, 4D datasets were acquired and three methods were used for volume analysis: three dimensional (3D) slice method, Virtual Organ Computer-aided AnaLysis (VOCAL) and VOCAL combined with inversion mode. Accuracy and measurement error were measured as the difference between the volume measurements and the actual volumes. Intraobserver reliability was assessed by computing coefficients of variation (CV) and intraclass correlation (ICC).

RESULTS

Measurement of 76 different volumes, ranging from 0.30 to 4.95 mL, resulted in a total of 912 measurements. The 3D slice method had a mean error of -3.3%, the inversion method underestimated the volumes with a mean error of -6.1%, and VOCAL had a mean error of -2.9%. The 3D slice method had the best agreement (95% limits of agreement (LOA), -11.2 to 4.7%), followed by VOCAL (95% LOA, -14.1 to 8.3%); the inversion mode demonstrated the worst agreement (95% LOA, -21.4 to 9.2%). All three methods were reliable with CV < 10% and ICC > 0.95.

CONCLUSIONS

4D ultrasonography with STIC is a feasible and accurate method for calculating volumes of 0.30 mL upwards. In an in-vitro model the 3D slice method proved accurate, was the least time consuming, had the best reliability and had the smallest LOA. This method may prove useful when applied to in-vivo investigations.

Fetal lung volume in fetuses with urinary tract malformations: comparison by 2D-, 3D-sonography and magnetic resonance imaging

OBJECTIVE

To evaluate the concordance between two-dimensional ultrasonography (2DUS), three-dimensional ultrasonography (3DUS) and magnetic resonance imaging (MRI) in the assessment of lung volume in fetuses with urinary tract malformations (UTM).

METHODS

This was a cross-sectional study involving 12 pregnancies between 19 and 34 weeks, with various fetal UTM. Pulmonary volume was obtained by 2DUS using the following equation: total lung volume = [right lung antero-posterior diameter (X) x transverse diameter (Y) x cranial-caudal diameter x 0.152 + left lung (X1) x (Y1) x (Z1) x 0.167]. Pulmonary volume by 3DUS was obtained using the virtual organ computer-aided analysis (VOCAL) method with a 30 degrees (VOL30), 18 degrees (VOL18) and 12 degrees (VOL12) rotation. A fast sequence of transverse lung section was also obtained by MRI. The intraclass correlation coefficient was used to evaluate the correlation between the three methods. The paired student t-test was used to compare the means.

RESULTS

There was a strong correlation between the three methods, and the highest correlations were between MRI and VOL18 for the right (ICC = 0.913) and left (ICC = 0.947) lungs. A strong correlation was also found between the lung volumes obtained through MRI and VOL12 as well as VOL18 (p = 0.544 and 0.286, respectively). However, for the left lung there was only a correlation between MRI and VOL12 (p = 0.49).

CONCLUSIONS

There is a good concordance between 3DUS (VOL12) and MRI in the evaluation of lung volume in fetuses with UTM.

Fetal cerebellar volume and symmetry on 3-d ultrasound: volume measurement with multiplanar and vocal techniques

The purpose of this prospective longitudinal study was to evaluate the growth of the fetal cerebellar volume by means of 3-D ultrasound to evaluate whether there is a difference between the volumes of the left and right cerebellar hemispheres, and to evaluate the intra- and interobserver reliability of two different techniques of volume measurement. Three-dimensional ultrasound examinations were performed every two to three weeks on 27 fetuses between 20 and 40 weeks' gestation. Measurements of the total cerebellar volume and of the left and right cerebellar hemispheres were done using the multiplanar technique. Multilevel analysis was used to determine the growth of cerebellar volume based on individual developmental trajectories and compare the volume of the right and left hemispheres of the cerebellum. The intra- and interobserver reliability was calculated for the multiplanar and VOCAL techniques in a subgroup of 10 fetuses. A nonlinear growth curve of cerebellar volume in normal pregnancy was generated. The cerebellar growth per two-week decreased from a gain of 51% of the first measurement at 20 weeks to a gain of 16% of the first measurement at 38 weeks. The left cerebellar hemisphere was significantly larger (12.3%, p < 0.01) than the right. The intraclass correlation coefficient for the measurements by the two techniques was 0.99. Intraobserver reliability: the intraclass correlation coefficient for the measurements using the multiplanar technique was 0.96 and 0.97 and for VOCAL it was 0.98 and 0.97 for the two observers, respectively. Interobserver reliability: the intraclass correlation coefficient for the measurements using the multiplanar technique was 0.97 and for VOCAL 0.98. Longitudinal growth curves based on individual developmental trajectories were generated for the cerebellar volume. The left fetal cerebellar hemisphere was found to be significantly larger than the right. Both multiplanar and VOCAL techniques had a good intra- and interobserver reliability and yielded very similar results.

Three-dimensional ultrasonographic bladder volume measurement: reliability of the Virtual Organ Computer-Aided Analysis technique using different rotation steps

OBJECTIVE

The purpose of this study was to investigate the reliability of Virtual Organ Computer-Aided Analysis (VOCAL; GE Healthcare, Kretztechnik, Zipf, Austria) using the 4 standard rotation steps to measure the bladder volume with 3-dimensional (3D) ultrasonography.

METHODS

Using the 4 standard rotation steps of VOCAL, 2 independent observers made 3D volume measurement data sets from the urinary bladder (n = 180). Sets of 30, 20, 12, and 6 planes were obtained from the sequential rotations of 6 degrees, 9 degrees, 15 degrees, and 30 degrees, respectively. The internal contours of the bladders were determined manually. Reliability was evaluated with the intraclass correlation coefficient (ICC), and Bland-Altman plots were generated to examine bias and agreement. One-way analysis of variance was used to compare bladder volume measurements between the angles. P < .05 was considered statistically significant.

RESULTS

A high degree of reliability was observed between pairs of different rotation angles (ICC, 0.994-0.999). There was good agreement between all pairs of different rotation angles, with percentages of the mean difference ranging from -0.9% to 1.8%. No significant difference was found for bladder volume measurements by the VOCAL technique with varying rotation steps. Intraobserver and interobserver reliabilities were high (ICC, 0.994-0.998).

CONCLUSIONS

Urinary bladder volume measurement by the VOCAL technique using different rotation steps is highly reliable. A plane rotation of 30 degrees produces the fastest result.

Three-dimensional sonographic calculation of the volume of intracranial structures in growth-restricted and appropriate-for-gestational age fetuses

OBJECTIVES

To evaluate the feasibility and reproducibility of volume segmentation of fetal intracranial structures using three-dimensional (3D) ultrasound imaging, and to estimate differences in the volume of intracranial structures between intrauterine growth-restricted (IUGR) and appropriate-for-gestational age (AGA) fetuses.

METHODS

Total intracranial, frontal, thalamic and cerebellar volumes were measured using 3D ultrasound imaging and Virtual Organ Computer-aided AnaLysis (VOCAL) in 39 IUGR and 39 AGA fetuses matched for gestational age, at 28-34 weeks of gestation. Volumes of, and ratios between, structures were estimated, and differences between IUGR and AGA fetuses were calculated. Volume measurements were performed by two observers, and interobserver and intraobserver intraclass correlation coefficients (ICCs) were calculated for each structure.

RESULTS

Volumes were satisfactorily obtained in all fetuses. All net volumes except those for the thalamus (P = 0.23) were significantly smaller (P = 0.001) in IUGR fetuses. After adjusting volumes for biparietal diameter the frontal volume was significantly smaller (P = 0.02) and the thalamic volume significantly greater (P = 0.03) in IUGR fetuses than in AGA fetuses. Significant intergroup differences in the ratios between structures were found only in those involving the frontal region. Interobserver ICCs were as follows: total intracranial 0.97 (95% CI, 0.92-0.98), cerebellar 0.69 (95% CI, 0.44-0.75), frontal 0.66 (95% CI, 0.42-0.79) and thalamic 0.54 (95% CI, 0.37-0.72).

CONCLUSIONS

IUGR fetuses show differences in the volume of intracranial structures compared with AGA fetuses, with the largest difference found in the frontal region. These differences might be explained by in-utero processes of neural reorganization induced by chronic hypoxia.

Fetal cardiac function assessed with four-dimensional ultrasound imaging using spatiotemporal image correlation

OBJECTIVES

The goal of this study was to use spatiotemporal image correlation (STIC) to provide reference values for left and right ventricle volumes, and indices of fetal cardiac function.

METHODS

In this prospective longitudinal study, STIC volumes were acquired periodically from 12 weeks of gestation onwards. The STIC volumes were frozen in end-systole and end-diastole, and volumetric data were measured by manual tracing and summation of multiple slices. These ventricle volumes were used to calculate stroke volume, ejection fraction and cardiac output.

RESULTS

Some 202 STIC volumes of 63 fetuses were included in the analysis. Mean left and right ventricle stroke volume increased from 0.02 mL at 12 weeks to 1.41 mL and 1.46 mL, respectively, at 30 weeks, while the mean right to left stroke volume ratio remained stable at around 1.2. Mean left and right ventricle cardiac output increased from 2.40 mL/min and 2.60 mL/min at 12 weeks to 197.74 mL/min and 204.81 mL/min, respectively, at 30 weeks. Both left and right mean ejection fraction remained constant at around 0.45 with advancing gestational age. Bland-Altman analysis showed a coefficient of variation for measured stroke volume of 13.7%.

CONCLUSIONS

This study establishes reference values for fetal cardiac volumes and indices for fetal cardiac function from 12 to 30 weeks of gestation using STIC. STIC seems to overcome many of the pitfalls of conventional ultrasound methods and has the potential to become the method of choice.

Comparison of inter- and intraobserver agreement between three types of fetal volume measurement technique (XI VOCAL, VOCAL and multiplanar)

OBJECTIVES

To compare the new XI VOCAL (eXtended Imaging Virtual Organ Computer-aided Analysis) for three-dimensional (3D) ultrasound measurement of fetal volume with the conventional multiplanar technique and a rotational method using VOCAL.

METHODS

We acquired 3D volume datasets from 30 fetuses at 11-14 weeks of gestation using a commercially available ultrasound system. Fetal volume was calculated using XI VOCAL (with 5, 10, 15 and 20 slices), multiplanar (1-mm interval) and VOCAL (with 12 degrees, 18 degrees and 30 degrees rotation) techniques. The level of agreement for interobserver and intraobserver variability was determined and evaluated for all methods and reliability was assessed.

RESULTS

Fetal volume measurements obtained using XI VOCAL (10 slices) showed good correlation with those obtained using VOCAL (18 degrees) (r = 0.940, P = 0.076; intraclass correlation coefficient (ICC), 0.962 (95% CI, 0.920-0.982), P = 0.182), and XI VOCAL (15 slices) showed good correlation with VOCAL (12 degrees ) (r = 0.961, P = 0.092; ICC, 0.979 (95% CI, 0.957-0.990), P = 0.190). The mean difference between paired measurements by the XI VOCAL (10 slices) and VOCAL (18 degrees ) methods was 1.00 mL, while that by the XI VOCAL (15 slices) and VOCAL (12 degrees) methods was 0.90 mL. 95% limits of agreement were - 2.80 to 4.80 between XI VOCAL (10 slices) and VOCAL (18 degrees) and - 1.90 to 3.70 between XI VOCAL (15 slices) and VOCAL (12 degrees). There was a small difference in the time required to complete the fetal volume measurement between XI VOCAL and VOCAL when a similar number of slices or rotational steps was used (P < 0.05), XI VOCAL taking less time.

CONCLUSION

XI VOCAL (with 10, 15 and 20 slices) can be used interchangeably with the multiplanar technique (1-mm interval) for the measurement of fetal volume. XI VOCAL (10 slices) and VOCAL (18 degrees) can be used interchangeably, as can XI VOCAL (15 slices) and VOCAL (12 degrees), for the measurement of fetal volume.

MR lung volume in fetal congenital diaphragmatic hernia: logistic regression analysis--mortality and extracorporeal membrane oxygenation

PURPOSE

To prospectively assess the results of logistic regression analysis that were based on magnetic resonance (MR) image fetal lung volume (FLV) measurements to predict survival and the corresponding need for extracorporeal membrane oxygenation (ECMO) therapy in fetuses with congenital diaphragmatic hernia (CDH) before and after 30 weeks gestation.

MATERIALS AND METHODS

Written informed consent was obtained and the study was approved by the local research ethics committee. FLV was measured on MR images in 95 fetuses (52 female neonates, 43 male neonates) with CDH between 22 and 39 weeks gestation by using multiplanar T2-weighted half-Fourier acquired single-shot turbo spin-echo MR imaging. On the basis of logistic regression analysis results, mortality and the need for ECMO therapy were calculated for fetuses before and after 30 weeks gestation.

RESULTS

Overall, higher FLV was associated with improved survival (P < .001) and decreasing probability of need for ECMO therapy (P = .008). Survival at discharge was 29.2% in neonates with an FLV of 5 mL, compared with 99.7% in neonates with an FLV of 25 mL. The corresponding need for ECMO therapy was 56.1% in fetuses with an FLV of 5 mL and 8.7% in fetuses with an FLV of 40 mL. Prognostic power was considerably lower before 30 weeks gestation.

CONCLUSION

Beyond 30 weeks gestation, logistic regression analysis that is based on MR FLV measurements is useful to estimate neonatal survival rates and ECMO requirements. Prior to 30 weeks gestation, the method is not reliable and the FLV measurement should be repeated, particularly in fetuses with small lung volumes, before a decision is made about therapeutic options.

Three- and four-dimensional ultrasound: new methods for evaluating fetal thoracic anomalies

OBJECTIVE

To study three- (3D) and four-dimensional (4D) ultrasound applications for the evaluation of fetal thoracic anomalies.

METHODS

Volume datasets of 23 fetuses with thoracic anomalies were acquired with static 3D and cine 4D ultrasound, i.e. spatiotemporal image correlation (STIC) mode. The volumes were analyzed and displayed by multiplanar and tomographic ultrasound imaging (TUI) modes and static volume contrast imaging (VCI). Color Doppler was added to the volumes acquired, and various rendering modes were used to display the volume datasets.

RESULTS

The mean gestational age at evaluation was 22 (range, 14-34) weeks. The anomalies were identified as: diaphragmatic hernia (n = 5), lung dysplasia (n = 11), skeletal dysplasia with small thorax/thanatophoric dysplasia (n = 2), abnormal situs (n = 2), hydrothorax (n = 2) and esophageal atresia (n = 1). The TUI mode achieved optimal display of the thorax, thereby aiding the diagnosis of diaphragmatic hernia and lung dysplasia. In right diaphragmatic hernias, the VCI mode proved invaluable as it distinguished liver from lung tissue. High-definition color Doppler with glass-body rendering significantly contributed to the detection of abnormal vascularization in lung dysplasia. Maximal transparent mode with a transvaginal transducer provided accurate diagnosis of skeletal dysplasia in the first trimester. Situs abnormalities were best viewed with a minimal transparent mode, in which abnormal organs and positions of vessels were clearly identified. Pleuroamniotic shunt localization was monitored precisely by 3D in a fetus with hydrothorax, and inversion mode added important information regarding the size of an esophageal pouch in a fetus with esophageal atresia.

CONCLUSION

The 3D-4D technique is a novel, useful sonographic tool for evaluating the fetal thorax. It enhances precise diagnosis and provides better spatial visualization of the anomalies involved.

Three-dimensional ultrasound in prenatal diagnosis

PURPOSE OF REVIEW

Several technological advances have greatly improved three-dimensional sonography, which have improved acquisition and display capabilities. This review describes these technical changes as well as current applications of 3D sonography in prenatal diagnosis.

RECENT FINDINGS

Recently published papers have emphasized the potential of getting a precise 'any plane of choice' from a three-dimensional volume, as a new way of scanning, based on the off-line analysis of a volume dataset. Surface mode has been used to demonstrate malformations and genetic diseases. The maximum rendering mode, which highlights bones, has great potential for imaging the nasal bones and the frontal bones with the metopic suture. Organ volume can be measured, but the utility of this in clinical practice remains to be determined. Three-dimensional ultrasound needs to be standardized.

SUMMARY

Three-dimensional ultrasonography is the most rapidly developing technique in fetal imaging. New features will permit the transition from the era of 'sonography in two-dimensional planes' to 'volume ultrasound'.

[Fetal lung imaging]

Exponential improvements in imaging techniques over the last ten years, through patients' and physicians' wishes for less invasive fetal work-up, now allow us to better explore and understand fetal lung physiology during pregnancy. Diagnostic and prognostic consequences at stake are huge, especially for fetuses at risk of pulmonary hypoplasia. We will decline in three parts (normal lung, malformative lung and pulmonary hypoplasia), through a review of the literature and at the light of our experience, the potentialities and limitations of all imaging modalities (Ultrasound, Doppler, 3D, MRI). Then, we will dwell on future leads and the need for large-scale collaborative studies.

Reproducibility of sonographic assessment of fetal liver length in diabetic pregnancies

OBJECTIVES

Assessing fetal liver size might be useful in monitoring the effectiveness of the treatment of diabetes in pregnancy. We aimed to assess the reproducibility of fetal liver-length measurement in pregnant women with diabetes.

METHODS

From 3 April 2006 to 5 December 2006, we assessed intraobserver and interobserver variation of fetal liver-length measurements on 55 sonograms in 44 pregnant women with diabetes, 34 of whom had gestational diabetes. The mean maternal age was 33 years, the mean maternal weight was 92 kg and the mean body mass index (BMI) was 33.7 kg/m(-2). The effect of covariates BMI, gestational age and maternal age on the reproducibility of fetal liver length was assessed by calculating intraobserver SD ratios. We compared liver length with abdominal circumference and gestational age. Nine of 12 sonographers scanned, on average, six women (range, 3-12) as the first sonographer, and all 12 sonographers scanned, on average, four women (range, 1-10) as the second sonographer. The data were analyzed using a hierarchical linear model.

RESULTS

Measurement of fetal liver length was reproducible. The intraobserver SD was 3.06 (95% CI, 2.68-3.59) mm; the interobserver SD was 2.17 (95% CI, 0.59-4.83) mm; the intraobserver correlation was 0.77 (95% CI, 0.63-0.87), and the interobserver correlation was 0.84 (95% CI, 0.51-0.99). The covariate effects were minimal, the SD for a 1-unit increase in the covariate was 1.06 for gestational age, 0.98 for BMI, and 0.97 for maternal age.

CONCLUSIONS

Measurement of fetal liver length in the diabetic pregnancy is reproducible. It is worthy of further investigation as a parameter for monitoring the effectiveness of treatment of the diabetic pregnancy.