Feasibility of two-dimensional ultrasound shear wave elastography of human fetal lungs and liver: A pilot study

Review of shear wave elastography in placental function evaluations

Background: Ultrasound is key to evaluating placental function. However, traditional ultrasound examinations cannot evaluate the changes in the biomechanical properties of the placenta in vivo. As a non-invasive technique, shear wave elastography (SWE) can be used analyze the physiological and biomechanical properties of the placenta. Moreover, it can evaluate the pathological changes in early placental insufficiency in a more direct and sensitive manner.Objective: This study aimed to systematically introduce SWE in placental function evaluations.Materials and methods: The terms 'placenta', 'ultrasound', and 'elastography' were searched on Pubmed, Embase, and CNKI databases (Apr 2023); this review was limited to results including placental sonoelastography.Results: Twenty-six studies satisfied the inclusion criteria and were included in this review. Herein, we introduce the basic principle of SWE, analyze the factors affecting placental measurements, and summarize the prospects of clinical applications of SWE in the field of obstetrical diseases.Conclusion: The SWE technology demonstrates excellent clinical application value and research prospects in obstetrics, particularly in placental function evaluation, owing to its objective and repeatable quantitative operation.

Virtual touch IQ elastography in the evaluation of fetal liver and placenta in pregnancies with gestational diabetes mellitus

OBJECTIVES

Elastography is considered a novel technique in the assessment of placenta parenchymal elasticity and very few data present the feasibility of elastography on human fetal tissue. This study aims to investigate the feasibility of fetal liver and placenta elastography and differences in pregnancies with GDM.

METHODS

Fifty-five women with GDM and 40 women with uncomplicated pregnancy as the control group was enrolled prospectively in this case-control study. Fetal liver VTIQ and placenta VTIQ elastography were performed between 25 and 39 weeks of pregnancy.

RESULTS

Mean placenta thickness at the level of umbilical cord insertion was significantly higher in the GDM group than in the control group (p=0.034). VTIQ elastography elasticity velocity (kPa) examinations revealed similar mean placenta and mean fetal liver stiffness in both groups. A weak to moderate correlation was observed between the mean elasticity of the placenta and the mean elasticity of the fetal liver (r=0.310; p=0.004).

CONCLUSIONS

Elastography may provide valuable information of especially on fetal tissue development and pathology. While placenta and fetal liver VTIQ elastography are feasible in pregnancy, the diagnostic value of these examinations in GDM is not certain and it seems to be that significant differences in SWE examinations that reflect structural changes in fetal tissue or placenta are more prominent in more chronic conditions such as type 1 and type 2 diabetes mellitus.

Use of Virtual Touch Tissue Quantification Elastography Technique in Fetal Lung Maturation: A Preliminary Study

ABSTRACT

This study is an analysis of fetal lung stiffness by virtual touch tissue quantification (VTTQ) elastography to predict fetal lung maturation. Evaluation of fetal lungs was first performed in B mode, and fetal lungs were analyzed at 3 different periods at third trimester in each pregnant woman, at 28 to 31, 32 to 36, and 37 to 41 weeks. Fetal lung elastography was performed at regions with the least acoustic shadow and far from ribs and heart. Each fetal lung assessment were done by taking mean lung stiffness obtained by measuring stiffness of both left and right fetal lungs. T test analysis showed no significant difference in fetal lung stiffness between male and female fetuses among 3 gestational periods. Analysis of variance was performed to evaluate fetal lung stiffness of the fetuses at 3 different gestational periods (28-31, 32-36, and 37-41 weeks). This analysis showed significant difference ( P < 0.01). Duncan multiple comparison analysis did not show significant difference in fetal lung stiffness between 28 and 31 weeks and 32 and 36 weeks, whereas fetal lung stiffness of fetuses at 37 to 41 weeks were significantly greater ( P < 0.01). This study is first step to analyze fetal lung maturation noninvasively using VTTQ elastography technique by measuring fetal lung stiffness.

Advances in the clinical application of ultrasound elastography in uterine imaging

Changes in tissue stiffness by physiological or pathological factors in tissue structure are identified earlier than their clinical features. Pathological processes such as uterine fibrosis, adenomyosis, endometrial lesions, infertility, and premature birth can manifest as tissue elasticity changes. In clinical settings, elastography techniques based on ultrasonography, optical coherence tomography, and magnetic resonance imaging are widely used for noninvasive measurement of mechanical properties in patients, providing valuable tool and information for diagnosis and treatment. Ultrasound elastography (USE) plays a critical role in obstetrics and gynecology clinical work because of its simplicity, non-invasiveness, and repeatability. This article reviews the recent progress of USE in uterine tumor diagnosis (especially early diagnosis and treatment effect evaluation), prediction of preterm birth, and intrauterine insemination. We believe that USE, especially shear wave elastography, may serve as a potential means to assess tissue stiffness, thereby improving the diagnosis and treatment of adenomyosis, fibroids, endometrial lesions, cervical cancer, and precise management of preterm birth and intrauterine insemination monitoring.

Prenatal quantification of human foetal lung and liver elasticities between 24 and 39 weeks of gestation using 2D shear wave elastography

Objectives

To quantify and model normal foetal lung and liver elasticities between 24 and 39 weeks of gestation (WG) using two-dimensional shear wave elastography (2D-SWE). To assess the impact of the distance between the probe and the target organ on the estimation of elasticity values.

Methods

Measurements of normal foetal lungs and liver elasticity were prospectively repeated monthly between 24 and 39 WG in 72 foetuses using 2D-SWE. Elasticity was quantified in the proximal lung and in the region inside the hepatic portal sinus. The distance between the probe and the target organ was recorded. Trajectories representing foetal lung and liver maturation from at least 3 measurements over time were modelled.

Results

The average elasticity for the lung and liver was significantly different from 24 WG to 36 WG (p < 0.01). Liver elasticity increased during gestation (3.86 kPa at 24 WG versus 4.45 kPa at 39 WG). From 24 WG to 32 WG, lung elasticity gradually increased (4.12kPa at 24 WG, 4.91kPa at 28 WG, 5.03kPa at 32 WG, p < 0.002). After 32 WG, lung elasticity decreased to 4.54kPa at 36 WG and 3.94kPa at 39 WG. The dispersion of the average elasticity values was greater for the lung than for the liver (p < 0.0001). Variation in the elasticity values was less important for the liver than for the lung. The values were considered valid and repeatable except for a probe-lung distance above 8cm.

Conclusion

Foetal lung and liver elasticities evolve differently through gestation. This could reflect the tissue maturation of both organs during gestation.

Trial registration

clinicaltrials.gov identifier: NCT03834805

Key Points

• Prenatal quantification of foetal lung elasticity using 2D shear wave elastography could be a new prenatal parameter for exploring foetal lung maturity.

• Liver elasticity increased progressively from 24 weeks of gestation (WG) to 39 WG, while lung elasticity increased first between 24 and 32 WG and then decreased after 32 WG.

• The values of elasticity are considered valid and repeatable except for a probe-lung distance above 8cm.

Imaging during pregnancy: What the radiologist needs to know

During the last decades, there has been a growing demand for medical imaging in gravid women. Imaging of the pregnant woman is challenging as it involves both the mother and the fetus and, consequently, several medical, ethical, or legal considerations are likely to be raised. Theoretically, all currently available imaging modalities may be used for the evaluation of the pregnant woman; however, in practice, confusion regarding the safety of the fetus often results in unnecessary avoidance of useful diagnostic tests, especially those involving ionizing radiation. This review article is focused on the current safety guidelines and considerations regarding the use of different imaging modalities in the pregnant population; also presented is an imaging work-up for the most common medical conditions of pregnant women, with emphasis on fetal and maternal safety.