First-trimester sonography: is the fetus exposed to high levels of acoustic energy?

Ultrasound Used for Diagnostic Imaging Facilitates Dendritic Branching of Developing Neurons in the Mouse Cortex

Neuronal differentiation and synaptogenesis are regulated by precise orchestration of intrinsic and extrinsic chemical and mechanical factors throughout all developmental steps critical for the assembly of neurons into functional circuits. While ultrasound is known to alter neuronal migration and activity acutely, its chronic effect on neuronal behavior or morphology is not well characterized. Furthermore, higher-frequency (3–5 MHz) ultrasound (HFU) is extensively used in gynecological practice for imaging, and while it has not been shown harmful for the developing brain, it might be associated with mild alterations that may have functional consequences. To shed light on the neurobiological effects of HFU on the developing brain, we examined cortical pyramidal cell morphology in a transgenic mouse model, following a single and short dose of high-frequency ultrasound. Layer V neurons in the retrosplenial cortex of mouse embryos were labeled with green and red fluorescent proteins by in utero electroporation at the time of their appearance (E14.5). At the time of their presumptive arrival to layer V (E18.5), HFU stimulation was performed with parameters matched to those used in human prenatal examinations. On the third postnatal day (P3), basic morphometric analyses were performed on labeled neurons reconstructed with Neurolucida. Low-intensity HFU-treated cells showed significantly increased dendritic branching compared to control (non-stimulated) neurons and showed elevated c-fos immunoreactivity. Labeled neurons were immunopositive for the mechanosensitive receptor TRPC4 at E18.5, suggesting the role of this receptor and the associated signaling pathways in the effects of HFU stimulation.

Evaluation of the Scan Duration and Mechanical and Thermal Indices Applied for the Diagnostic Ultrasound Examinations

OBJECTIVE

Although epidemiological studies have failed to show the harmful effects of ultrasound in humans, as a form of energy, ultrasound has the potential to cause bio-effects in tissues. Therefore, clinical guidelines have been established for ultrasound technology related to human safety, which include Thermal (TI) and mechanical (MI) indices. The appropriate TI and MI ranges for embryonic examinations are between 0-1.0 and 0-0.4, respectively. The accepted TI and MI ranges are 0-2.0 and 0-1.9, respectively, for general ultrasound examinations. In addition, the scan duration should be kept as low as possible. Therefore, the present study aimed at evaluating the scan duration, TI, and MI as measures of acoustic output during ultrasound studies.

METHODS

A cross-sectional descriptive study was conducted for patients undergoing pregnancy checkups, routine checkups, and initial diagnosis ultrasound examinations. Samples were selected from imaging departments of 4 educational hospitals based on convenience sampling and 321 checklists completed by direct observation of ultrasound examinations.

RESULTS

For pregnancy scans, the mean TI and MI were obtained as 0.32 ± 0.27 and 1.15 ± 0.13, respectively. For non-pregnancy examinations, the mean value of TI and MI were 0.30 ± 0.29 and 1.07 ± 0.35, respectively. Therefore, mean TI for pregnancy and non-pregnancy examinations and mean MI for non-pregnancy studies obtained lower than the permitted values, while the mean MI was higher than the permitted level for first trimester of pregnancy. Also, relatively suitable scan durations were seen in reviewed studies.

CONCLUSION

From this study, it may be concluded that the reported ultrasound scans were safe.

First-trimester screening model for small-for-gestational-age using maternal clinical characteristics, serum screening markers, and placental volume: prospective cohort study

OBJECTIVE

To examine predictive value of first trimester placental volume, maternal clinical characteristics, and serum biomarkers in predicting small-for-gestational-age (SGA) singleton pregnancy.

METHODS

We conducted a prospective study to determine whether SGA is associated with maternal clinical factors. Between November 2016 to May 2018, 351 women were enrolled. We included pregnant women who underwent an integrated test for aneuploidy screening. Placental volume, maternal clinical characteristics, and maternal serum pregnancy-associated plasma protein A (PAPP-A) levels in the first trimester (at 10⁺⁰-13⁺⁶weeks) and maternal serum biomarkers after 15⁺⁰-22⁺⁶weeks were measured. We measured the width, height, and thickness of the placenta and calculated the placental volume using an established mathematical formula; then, we analyzed the association between SGA at delivery, estimated placental volume (EPV), maternal clinical characteristics, and maternal serum biomarkers by multiple logistic regression analysis.

RESULTS

In this study, 12.3% (43/351) neonates were delivered before 37 weeks of gestation, and the birth weight of 23.6% (83/351) was below the 10th percentile according to gestational age. On multivariate logistic regression, the MSAFP multiples of the median (MoM) showed the strongest association with SGA in singleton pregnancy (p < .01), and the PAPP-A MoM showed a weaker association in the multiple logistic regression than in the univariate regression (p = .0073 and .0068, respectively). Our prediction model using maternal age, maternal smoking, PAPP-A, and EPV achieved an area under the curve of 0.668 in singleton pregnancy.

CONCLUSION

During the first trimester, maternal clinical characteristics, serum biomarkers, and EPV may be used for predicting the risk of SGA in singleton pregnancy.

Obstetric ultrasound: where are we and where are we going?

Diagnostic ultrasound (DUS) is, arguably, the most common technique used in obstetrical practice. From A mode, first described by Ian Donald for gynecology in the late 1950s, to B mode in the 1970s, real-time and gray-scale in the early 1980s, Doppler a little later, sophisticated color Doppler in the 1990s and three dimensional/four-dimensional ultrasound in the 2000s, DUS has not ceased to be closely associated with the practice of obstetrics. The latest innovation is the use of artificial intelligence which will, undoubtedly, take an increasing role in all aspects of our lives, including medicine and, specifically, obstetric ultrasound. In addition, in the future, new visualization methods may be developed, training methods expanded, and workflow and ergonomics improved.

Written Feedback on Thermal Index During the First-Trimester Nuchal Translucency Examination Does Not Improve Compliance With the “as Low as Reasonably Achievable” Principle

Objective: The null hypothesis was that there would be no change in as low as reasonably achievable (ALARA) behavior based on feedback from comments on the nuchal translucency quality review (NTQR) image submissions. Methods: A review of the Perinatal Quality Foundation Database found 206 practitioners who failed their first credential attempt and received ALARA comments as feedback. The second submissions of the same subjects were reviewed to determine if compliance with ALARA improved following written feedback. Results: Seventeen percent of all second submissions addressed ALARA. Sixty-one percent of second submissions passed, however only 18.4 % of those addressed ALARA. Among those who submitted thermal index at bone values on both first and second submissions, the mean values on the second submission were 0.20 lower compared to the first submission ( P = .0288). Second submission mean thermal index at bone values were 0.68 lower among those submissions with ALARA concerns addressed compared to those not addressing these concerns ( P < .001). Conclusions: Written feedback without consequences on the ALARA principle did not improve compliance.

Safety Indices during Fetal Echocardiography at the Time of First-Trimester Scan Are Machine Dependent

The aim of our study was to evaluate the thermal index (TI) and mechanical index (MI), during the assessment of the fetal heart at the time of first-trimester scan, with different ultrasound machines. This was part of an observational study conducted in patients undergoing routine first-trimester screening. Cases were examined with Voluson E8 or 730Pro scanners using 2–8 MHz transabdominal probes. TI and MI were retrieved from the saved displays while in gray mode, color flow mapping and pulsed-wave (PW) Doppler examinations of the fetal heart and also from the ductus venosus (DV) assessment. We evaluated 552 fetal cardiac examinations, 303 (55%) performed with Voluson E8 and 249 (45%) with Voluson 730Pro ultrasound machines. The gray-scale exam of the heart and the PW Doppler DV assessment had TI values significantly lower for the Voluson E8 group (median, 0.04 vs. 0.2 and 0.1 vs. 0.2, respectively). The MI values from gray-scale and color flow mapping of the heart were significantly lower (median, 0.6 vs, 1.2 and 0.7 vs. 1) and for PW Doppler exam of the tricuspid flow were significantly higher (median 0.4 vs. 0.2) in the Voluson E8 group. The TI values from Doppler examinations of the heart, either color flow or PW imaging and MI values from DV assessment were not significantly different between the two groups. A different (newer) generation of ultrasound equipment provides lower or at least the same safety indices for most of the first-trimester heart examinations.

Acoustic output measured by thermal and mechanical indices during fetal echocardiography at the time of the first trimester scan

We measured acoustic output, expressed as the thermal index (TI) and mechanical index (MI), during fetal echocardiography at the time of the first trimester scan. TI and MI were retrieved from the saved displays during gray-mode, high-definition color flow Doppler and pulsed-wave Doppler (tricuspid flow) ultrasound examinations of the fetal heart and from the ductus venosus assessment. A total of 399 fetal cardiac examinations were evaluated. There was a significant increase in TI values from B-mode studies (0.07 ± 0.04 [mean ± SD]) to color flow mapping (0.2 ± 0.0) and pulsed-wave Doppler studies (0.36 ± 0.05). The TI from ductus venosus assessment (0.1 ± 0.01) was significantly lower than those from Doppler examinations of the heart. MI values from B-mode scans (0.65 ± 0.12) and color flow mapping (0.71 ± 0.11) were comparable, although different, and both values were higher than those from pulsed-wave Doppler tricuspid evaluation (0.39 ± 0.03). There were no differences in MI values from power Doppler assessment between the tricuspid flow and ductus venosus. Safety indices were remarkably stable and were largely constant, especially for color Doppler (TI), tricuspid flow (MI) and ductus venosus assessment (TI, MI). We acquired satisfactory Doppler images and/or signals at acoustic levels that were lower than the actual recommendations and never reached a TI of 0.5.

Transvaginal 3-d power Doppler ultrasound evaluation of the fetal brain at 10-13 weeks' gestation

The objective of this study was to measure the fetal brain volume (FBV) and vascularization and blood flow using transvaginal 3-D power Doppler (3DPD) ultrasound late in the first trimester of pregnancy. 3DPD ultrasound examinations with the VOCAL imaging analysis program were performed on 36 normal fetuses from 10-13 weeks' gestation. FBV and 3DPD indices related to the fetal brain vascularization (vascularization index [VI], flow index [FI] and vascularization flow index [VFI]) were calculated in each fetus. Intra- and interclass correlation coefficients and intra- and interobserver agreements of measurements were assessed. FBV was curvilinearly correlated well with the gestational age (R2 = 0.861, p < 0.0001). All 3-D power Doppler indices (VI, FI and VFI) showed no change at 10-13 weeks' gestation. FBV and all 3-D power Doppler indices (VI, FI and VFI) showed a correlation > 0.82, with good intra- and interobserver agreement. Our findings suggest that 3-D ultrasound is a superior means of evaluating the FBV in utero, and that 3-D power Doppler ultrasound histogram analysis may provide new information on the assessment of fetal brain perfusion.

Fetal reflex movement in twin pregnancies late in the first trimester: 4-D sonographic study

The objective of this study was to evaluate reactions to touch in utero between twin fetuses using 4-D sonography late in the first trimester of pregnancy. Six monochorionic diamniotic (MD) and eight dichorionic diamniotic (DD) pregnancies were studied for 30 min with transabdominal 4-D sonography at 12-13 weeks' gestation. The frequencies of no reaction (twins appear to touch each other but there is no clear reaction) and reaction (twins appear to touch each other and there is a clear reaction by the co-twin) movements were evaluated. There was no significant difference in the rate of reaction movements between MD (median, 33.6%) and DD (median, 33.9%) twins. The median rate of reaction movements in all 14 twins was 33.9% (range, 27 to 64.1%). Our findings suggest that the incidence of reflex movement of the co-twin on being touched by the other twin late in the first trimester is more frequent than that assessed by conventional 2-D ultrasound.

Four-dimensional sonographic assessment of inter-twin contact late in the first trimester

OBJECTIVE

To evaluate the total number of inter-twin contacts between monochorionic diamniotic (MD) and dichorionic diamniotic (DD) twins using four-dimensional (4D) sonography late in the first trimester of pregnancy.

METHOD

Six MD and 8 DD pregnancies were studied for 30 minutes with 4D sonography at 10-11 and 12-13 weeks of gestation. A total of 10 types of inter-twin contact was evaluated.

RESULTS

There was a significant difference in the total number of all contacts between MD and DD twins at the 10-11 weeks of gestation (P<0.05). There was also a significant difference in the total number of contacts between 10-11 and 12-13 weeks of gestation in DD twins (P<0.05).

CONCLUSION

Four-dimensional sonography provides a means of evaluating inter-twin contact in the first trimester of pregnancy and could be an accurate and reliable tool in studies of inter-twin behavior.