Comparison of the two-dimensional and multiplanar methods and establishment of a new constant for the measurement of fetal lung volume

Prenatal prediction of respiratory distress syndrome by multimodality approach using 3D lung ultrasound, lung-to-liver intensity ratio tissue histogram and pulmonary artery Doppler assessment of fetal lung maturity

OBJECTIVE

Studying the correlation of different lung parameters, using three-dimensional ultrasound (3D US) with fetal lung maturity (FLM) to predict the development of neonatal respiratory distress syndrome (RDS).

METHODS

Three-dimensional ultrasound was done to record the fetal lung volume (FLV), fetal lung-to-liver intensity ratio (FLLIR) and the main pulmonary artery (MPA) blood flow parameters; pulsatility index (PI), resistive index (RI) and acceleration time-to-ejection time ratio (At/Et), to 218 women between 32 and 40 weeks gestational age within 24 h from labor.

RESULTS

Of 218 fetuses examined, final analysis was done for 143 fetuses. Thirty eight (26.5%) were diagnosed with RDS. The MPA PI and RI were significantly higher in fetuses diagnosed with RDS compared with those without (2.51 ± 0.33 and 0.90 ± 0.03 cm/s versus 1.96 ± 0.20 and 0.84 ± 0.01 cm/s; p value < 0.001 and <0.001 respectively). MPA At/Et was significantly lower (0.24 ± 0.04 vs 0.35 ± 0.04; p value < 0.001). FLLIR was significantly lower (1.04 ± 0.07 vs 1.18 ± 0.11; p value < 0.001), and the mean FLV was significantly smaller (28.23 ± 5.63, vs 38.87 ± 4.68 cm³; p value < 0.001).

CONCLUSION

Main pulmonary artery (PI, RI, At/Et ratio), FLIIR, and mean FLV can be used as reliable predictors of neonatal RDS.

ADVANCES IN KNOWLEDGE

3D ultrasound VOCAL technique, ultrasound tissue histogram and pulmonary artery Doppler are reliable tools for prenatal prediction of fetal lung maturity.

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.

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.

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.

A review of fetal volumetry: the need for standardization and definitions in measurement methodology

Volume charts of fetal organs and structures vary considerably among studies. This review identified 42 studies reporting normal volumes, namely for fetal brain (n = 3), cerebellum (n = 4), liver (n = 6), femur (n = 2), lungs (n = 15), kidneys (n = 3) and first-trimester embryo (n = 9). The differences among median volumes were expressed both in percentage form and as standard deviation scores. Wide discrepancies in reported normal volumes make it extremely difficult to diagnose pathological organ growth reliably. Given its magnitude, this variation is likely to be due to inconsistencies in volumetric methodology, rather than population differences. Complicating factors include the absence of clearly defined anatomical landmarks for measurement; inadequate assessment and reporting of method repeatability; the inherent difficulty in validating fetal measurements in vivo against a reference standard; and a multitude of mutually incompatible three-dimensional (3D) imaging formats and software measuring tools. An attempt to standardize these factors would improve intra- and inter-researcher agreement concerning reported volumetric measures, would allow generalization of reference data across different populations and different ultrasound systems, and would allow quality assurance in 3D fetal biometry. Failure to ensure a quality control process may hamper the wide use of 3D ultrasound.

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.

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.