Trends in diagnostic ultrasound acoustic output from data reported to the US Food and Drug Administration for device indications that include fetal applications

Prenatal ultrasound use and risk of autism spectrum disorder: Findings from the case-control Study to Explore Early Development

BACKGROUND

Studies evaluating the association between prenatal ultrasounds and autism spectrum disorder (ASD) have largely produced negative results. Concern remains due to the rising identification of children with ASD and ultrasound use.

OBJECTIVE

To evaluate the association between prenatal ultrasound use and ASD.

METHODS

We used data from the Study to Explore Early Development, a multisite case-control study of preschool-aged children with ASD implemented during 2007-2012. We recruited cases from children receiving developmental disability services and randomly selected population controls from birth records. ASD case status was based on in-person standardised assessments. We stratified analyses by pre-existing maternal medical conditions and pregnancy complications associated with increased ultrasound use (ultrasound indications) and used logistic regression to model case status by increasing ultrasound counts. For pregnancies with medical record data on ultrasound timing, we conducted supplementary tests to model associations by trimester of exposure.

RESULTS

Among 1524 singleton pregnancies, ultrasound indications were more common for ASD cases than controls; respectively, for each group, no indications were reported for 45.1% and 54.2% of pregnancies, while ≥2 indications were reported for 26.1% and 18.4% of pregnancies. The percentage of pregnancies with multiple ultrasounds varied by case status and the presence of ultrasound indications. However, stratified regression models showed no association between increasing ultrasound counts and case status, either for pregnancies without (aOR 1.01, 95% CI 0.92, 1.11) or with ultrasound indications (aOR 1.01, 95% CI 0.95, 1.08). Trimester-specific analyses using medical record data showed no association in any individual trimester.

CONCLUSIONS

We found no evidence that prenatal ultrasound use increases ASD risk. Study strengths included gold-standard assessments for ASD case classification, comparison of cases with controls, and a stratified sample to account for conditions associated both with increased prenatal ultrasound use and ASD.

In vitro characterisation of ultrasound-induced heating effects in the mother and fetus: A clinical perspective

INTRODUCTION

The quantification of heating effects during exposure to ultrasound is usually based on laboratory experiments in water and is assessed using extrapolated parameters such as the thermal index. In our study, we have measured the temperature increase directly in a simulator of the maternal-fetal environment, the 'ISUOG Phantom', using clinically relevant ultrasound scanners, transducers and exposure conditions.

METHODS

The study was carried out using an instrumented phantom designed to represent the pregnant maternal abdomen and which enabled temperature recordings at positions in tissue mimics which represented the skin surface, sub-surface, amniotic fluid and fetal bone interface. We tested four different transducers on a commercial diagnostic scanner. The effects of scan duration, presence of a circulating fluid, pre-set and power were recorded.

RESULTS

The highest temperature increase was always at the transducer-skin interface, where temperature increases between 1.4°C and 9.5°C were observed; lower temperature rises, between 0.1°C and 1.0°C, were observed deeper in tissue and at the bone interface. Doppler modes generated the highest temperature increases. Most of the heating occurred in the first 3 minutes of exposure, with the presence of a circulating fluid having a limited effect. The power setting affected the maximum temperature increase proportionally, with peak temperature increasing from 4.3°C to 6.7°C when power was increased from 63% to 100%.

CONCLUSIONS

Although this phantom provides a crude mimic of the in vivo conditions, the overall results showed good repeatability and agreement with previously published experiments. All studies showed that the temperature rises observed fell within the recommendations of international regulatory bodies. However, it is important that the operator should be aware of factors affecting the temperature increase.

Effects of 2D-Shear Wave Elastography on Brain-Derived Neurotrophic Factor (BDNF) in the Brains of Neonatal Mice and Exploration of the Mechanism

BACKGROUND The aim of this study was to explore the effect and duration of 2-dimensional shear wave elastography (2D-SWE) irradiation on the expression of brain-derived neurotrophic factor (BDNF) in the brains of neonatal mice and to preliminarily investigate whether its mechanism is neuronal apoptosis. MATERIAL AND METHODS Neonatal mice (within 48 hours of birth) were subjected to 2D-SWE irradiation of the brain for 10 minutes (group S1), 20 minutes (group S2), and 30 minutes (group S3). The mice were sacrificed immediately after irradiation or 24 hours after irradiation. Brains were collected for real-time polymerase chain reaction (RT-PCR) and western blot experiments to determine the expression of BDNF in each group. TdT-mediated dUTP nick-end labeling (TUNEL) was performed to observe neuronal apoptosis in the brain. RESULTS The results of PCR and western blots from the brains of neonatal mice that were sacrificed immediately after irradiation show that S1, S2, and S3 were significantly different from those in the control group. The PCR and western blot results of brain tissues from neonatal mice sacrificed at 24 hours after irradiation showed that there was no significant difference between the S1, S2, S3, and control groups. The results of TUNEL experiments showed that there was no statistically significant difference in the number of apoptotic neurons between the S1, S2, S3, and control groups. CONCLUSIONS 2D-SWE irradiation of neonatal mice for more than 10 minutes downregulated the expression of BDNF. This effect disappeared within 24 hours after the irradiation, and the 2D-SWE scan seemed not to induce neuronal apoptosis.

Biological Effect of Modern Fetal Ultrasound Techniques on Human Dermal Fibroblast Cells

Background:

Diagnostic ultrasound has been used to detect human disease especially fetus abnormalities in recent decades. Although the harmful effects of diagnostic ultrasound on human have not been established so far, several researchers showed it has had bioeffects in cell lines and in experimental animals. Three-dimensional (3D), four-dimensional (4D), and color Doppler sonography are new techniques which are widely used in diagnostic fetal ultrasonography.

Objective:

The study aims to evaluate some bioeffects of 3D, 4D, and color Doppler sonography in different exposure times according to the acoustic output which is set as ultrasound scanner’s default for fetal sonography in the second trimester on human dermal fibroblast (HDF) cells.

Material and Methods:

Exposure times selected consist of 10, 40, 70, and 100 seconds for 3D sonography, 10, 20, and 30 minutes for 4D sonography, and 10, 30, and 50 seconds for color Doppler. Cell viability, cell proliferation, and apoptosis induction on HDF cells were assessed using MTT assay, immunocytochemistry of Ki-67, and Terminal Transferase-mediated dUTP End-labeling (TUNEL) assay, respectively.

Results:

Exposure of cells to 3D, 4D, and color Doppler modes led to decreased cell viability and increased proliferation rate of HDF. None of the diagnostic ultrasound modes induced cell apoptosis. .

Conclusion:

The results indicated that 3D, 4D, and color Doppler techniques may affect the cell viability and proliferation of HDF cells, however, have no effects on the induction of apoptosis probability. Further long-term studies with other molecular endpoints are required.

Safety of Ultrasound Exposure: Knowledge, Attitudes, and Practices of Australasian Sonographers

Introduction:

While perceived as safe, diagnostic ultrasound has the potential to cause biological effects on the body tissues. The aim of this study was to evaluate knowledge, attitudes, and practices of Australasian sonographers on bioeffects and safety of ultrasound scanning.

Methods:

Focus groups were used to develop a questionnaire to explore knowledge, attitudes, and practices of ultrasound safety, which was then distributed to Australasian sonographers. Thematic (focus groups) and descriptive (questionnaires) analyses were undertaken.

Results:

A 37-item questionnaire addressed knowledge, attitudes, and practices of ultrasound safety. In 47 collected responses, sonographers demonstrated good familiarity of thermal index (TI) (79%), mechanical index (MI) (68%), and “as low as reasonably achievable” (ALARA) principle (85%). However, most sonographers could not accurately define TI (13%) and had poor knowledge of safety guidelines relating to TI (19%) and MI (14%). Over 30% were uncertain about their attitudes to ultrasound safety issues. While 52% always and 30% most of the time adhere to ALARA, 37% of sonographers reported never monitoring TI and MI.

Discussion:

While familiar with safety terms, knowledge of safety guidelines was lacking. Many sonographers were uncertain about their attitudes to the safety of scans, and safety practices involving monitoring for bioeffects were not a high priority.

Association of Prenatal Ultrasonography and Autism Spectrum Disorder

Importance

The prevalence of autism spectrum disorder (ASD) has been increasing rapidly, with current estimates of 1 in 68 children affected. Simultaneously, use of prenatal ultrasonography has increased substantially, with limited investigation into its safety and effects on brain development. Animal studies have demonstrated that prenatal ultrasonography can adversely affect neuronal migration.

Objective

To quantify prenatal ultrasound exposure by the frequency, timing, duration, and strength of ultrasonographic scans in children with later ASD, developmental delay, and typical development.

Design, Setting, and Participants

This case-control study included 107 patients with ASD, 104 control individuals with developmental delay, and 209 controls with typical development. Participants were identified from medical records based on prenatal care and delivery at Boston Medical Center, a diverse, academic, safety-net medical center, from July 1, 2006, through December 31, 2014, with a gestational age at birth of at least 37 weeks. Data were analyzed from May 1, 2015, through November 30, 2017.

Exposures

Ultrasonographic exposure was quantified by the number and timing of scans, duration of exposure, mean strength (depth, frame rate, mechanical index, and thermal index), and time of Doppler and 3- and 4-dimensional imaging.

Main Outcomes and Measures

Among participants with ASD and controls with developmental delay and typical development, ultrasound exposure was quantified and compared per trimester and for the entire pregnancy, with adjustment for infant sex, gestational age at birth, and maternal age.

Results

A total of 420 participants were included in the study (328 boys [78.1%] and 92 girls [21.9%]; mean age as of January 1, 2016, 6.6 years; 95% CI, 6.5-6.8 years). The ASD group received a mean of 5.9 scans (95% CI, 5.2-6.6), which was not significantly different from the 6.1 scans (95% CI, 5.4-6.8) in the developmental delay group or the 6.3 scans (95% CI, 5.8-6.8) in the typical development group. Compared with the typical development group, the ASD group had shorter duration of ultrasound exposure during the first (290.4 seconds [95% CI, 212.8-368.0 seconds] vs 406.4 seconds [95% CI, 349.5-463.3 seconds]) and second (1687.6 seconds [95% CI, 1493.8-1881.4 seconds] vs 2011.0 seconds [95% CI, 1868.9-2153.1 seconds]) trimesters but no difference in the number of scans. The ASD group had greater mean depth of ultrasonographic penetration than the developmental delay group in the first trimester (12.5 cm [95% CI, 12.0-13.0 cm] vs 11.6 cm [95% CI, 11.1-12.1 cm]). The ASD group had greater mean depth than the typical development group during the first (12.5 cm [95% CI, 12.0-13.0 cm] vs 11.6 cm [95% CI, 11.3-12.0 cm]) and the second (12.9 cm [95% CI, 12.6-13.3 cm] vs 12.5 cm [95% CI, 12.2-12.7 cm]) trimesters.

Conclusions and Relevance

This study found significantly greater mean depth of ultrasonographic penetration in the ASD group compared with the developmental delay group in the first trimester and compared with the typical development group in the first and second trimesters. Further research is needed to determine whether other variables of ultrasound exposure also have adverse effects on the developing fetus.

Multifunctional hard-shelled microbubbles for differentiating imaging, cavitation and drug release by ultrasound

Polymeric microbubbles bearing a hard shell exhibit prominent stability and tunable acoustical properties that serve the purposes of biomedical imaging and ultrasound (US)-triggered cavitations.