Obstetric Ultrasound Biological Effects and Safety

Evaluation and patient experience of wireless noninvasive fetal heart rate monitoring devices

INTRODUCTION

In clinical practice, fetal heart rate monitoring is performed intermittently using Doppler ultrasound, typically for 30 minutes. In case of a non-reassuring heart rate pattern, monitoring is usually prolonged. Noninvasive fetal electrocardiography may be more suitable for prolonged monitoring due to improved patient comfort and signal quality. This study evaluates the performance and patient experience of four noninvasive electrocardiography devices to assess candidate devices for prolonged noninvasive fetal heart rate monitoring.

MATERIAL AND METHODS

Non-critically sick women with a singleton pregnancy from 24 weeks of gestation were eligible for inclusion. Fetal heart rate monitoring was performed during standard care with a Doppler ultrasound device (Philips Avalon-FM30) alone or with this Doppler ultrasound device simultaneously with one of four noninvasive electrocardiography devices (Nemo Fetal Monitoring System, Philips Avalon-Beltless, Demcon Dipha-16 and Dräger Infinity-M300). Performance was evaluated by: success rate, positive percent agreement, bias, 95% limits of agreement, regression line, root mean square error and visual agreement using FIGO guidelines. Patient experience was captured using a self-made questionnaire.

RESULTS

A total of 10 women were included per device. For fetal heart rate, Nemo performed best (success rate: 99.4%, positive percent agreement: 94.2%, root mean square error 5.1 BPM, bias: 0.5 BPM, 95% limits of agreement: -9.7 - 10.7 BPM, regression line: y = -0.1x + 11.1) and the cardiotocography tracings obtained simultaneously by Nemo and Avalon-FM30 received the same FIGO classification. Comparable results were found with the Avalon-Beltless from 36 weeks of gestation, whereas the Dipha-16 and Infinity-M300 performed significantly worse. The Avalon-Beltless, Nemo and Infinity-M300 closely matched the performance of the Avalon-FM30 for maternal heart rate, whereas the performance of the Dipha-16 deviated more. Patient experience scores were higher for the noninvasive electrocardiography devices.

CONCLUSIONS

Both Nemo and Avalon-Beltless are suitable devices for (prolonged) noninvasive fetal heart rate monitoring, taking their intended use into account. But outside its intended use limit of 36 weeks' gestation, the Avalon-Beltless performs less well, comparable to the Dipha-16 and Infinity-M300, making them currently unsuitable for (prolonged) noninvasive fetal heart rate monitoring. Noninvasive electrocardiography devices appear to be preferred due to greater comfort and mobility.

Simulation-Based Ultrasound Training in Obstetrics and Gynecology: A Systematic Review and Meta-Analysis

OBJECTIVE

 The purpose of this systematic review and meta-analysis was to examine the effects of simulation-based ultrasound training (SIM-UT) in obstetrics and gynecology compared to non-SIM-UT on trainee learning, clinical performance, patient-relevant outcomes, and cost of training.

METHODS

 A systematic search was performed in June 2019 in PubMed, Embase, and Scopus using search terms for the topic and the intervention as well as certain MESH terms. Inclusion criteria were defined in accordance with the PICO question. Studies published in any language involving SIM-UT in obstetrics and gynecology compared to non-SIM-UT or no training were included. The outcomes included effects on health care provider learning and clinical performance, patient-relevant outcomes, and cost of training. Two authors evaluated the study quality with the MERSQI instrument and the Oxford Quality Scoring System. A meta-analysis was planned for the included randomized controlled trials.

RESULTS

 15 studies were included, and 11 studies were eligible for meta-analysis. SIM-UT was significantly superior to clinical training only and theoretical teaching with standard mean differences (SMD) of 0.84 (0.08-1.61) and 1.20 (0.37-2.04), respectively. However, SIM-UT was not superior to live model training; SMD of 0.65 (-3.25-4.55). Of all studies included in the meta-analysis, 91 % favored SIM-UT over clinical training alone, theoretical teaching, or in some cases live model training.

CONCLUSION

 In the field of obstetrics and gynecology, SIM-UT in addition to clinical training markedly improves trainee learning, clinical performance, as well as patient-perceived quality of care.

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.

An Automated ALARA Method for Ultrasound: An Obstetric Ultrasound Feasibility Study

OBJECTIVES

Ultrasound users are advised to observe the ALARA (as low as reasonably achievable) principle, but studies have shown that most do not monitor acoustic output metrics. We developed an adaptive ultrasound method that could suggest acoustic output levels based on real-time image quality feedback using lag-one coherence (LOC).

METHODS

Lag-one coherence as a function of the mechanical index (MI) was assessed in 35 healthy volunteers in their second trimester of pregnancy. While imaging the placenta or the fetal abdomen, the system swept through 16 MI values ranging from 0.15 to 1.20. The LOC-versus-MI data were fit with a sigmoid curve, and the ALARA MI was selected as the point at which the fit reached 98% of its maximum.

RESULTS

In this study, the ALARA MI values were between 0.35 and 1.03, depending on the acoustic window. Compared to a default MI of 0.8, the pilot acquisitions suggested a lower ALARA MI 80% of the time. The contrast, contrast-to-noise ratio, generalized contrast-to-noise ratio, and LOC all followed sigmoidal trends with an increasing MI. The R2 of the fit was statistically significantly greater for LOC than the other metrics (P < .017).

CONCLUSIONS

These results suggest that maximum image quality can be achieved with acoustic output levels lower than the US Food and Drug Administration limits in many cases, and an automated tool could be used in real time to find the ALARA MI for specific imaging conditions. Our results support the feasibility of an automated, LOC-based implementation of the ALARA principle for obstetric ultrasound.

Management of ureteric stone in pregnancy: a review

Background

Urolithiasis in pregnancy is a major health concern and is one of the most common causes for non-obstetrical abdominal pain and subsequent hospital admission during pregnancy. The incidence of urinary calculi during pregnancy varies in the range of 1/200 to 1/2000. Acute ureteric colic in pregnancy is associated with significant potential risks to both mother and fetus. Significant anatomic and functional changes occur in pregnancy which not only lead to stone formation but also create diagnostic dilemma. The diagnosis of ureteric calculi can be incorrect in about 28% of pregnant patients.

Main body

Management of ureteric stone during pregnancy is remaining to be a challenge for the treating urologist. Because of the inability to use good imaging options for the diagnosis confirmation and more invasive approach for the treatment, management continues to be difficult. The main threats are preterm labor with delivery and premature rupture of membranes. Other pregnancy complications are obstructive uropathy, gestational diabetes mellitus, recurrent abortions and pre-eclampsia. Management of diagnosed ureteric stone is unique in the pregnant population and requires multi-disciplinary care. It should be individualized for each patient and moves preferably from conservative to invasive approaches sequentially. With continued advancements in endourological techniques, few definitive treatment options are also available for such patients.

Conclusion

There are several lacunae related with the diagnostic imaging, medical expulsive therapy, reliability of ureteral stent/percutaneous nephrostomy insertions and safety of ureteroscopy during pregnancy. Herein, we review the management of ureteric stone during pregnancy, the various diagnostic modalities and treatment options with their advantages and disadvantages. We also proposed our management algorithm to deal with such clinical scenario in this particular population.

Doppler Ultrasound Technology for Fetal Heart Rate Monitoring: A Review

Fetal well-being is commonly assessed by monitoring the fetal heart rate (fHR). In clinical practice, the de facto standard technology for fHR monitoring is based on the Doppler ultrasound (US). Continuous monitoring of the fHR before and during labor is performed using a US transducer fixed on the maternal abdomen. The continuous fHR monitoring, together with simultaneous monitoring of the uterine activity, is referred to as cardiotocography (CTG). In contrast, for intermittent measurements of the fHR, a handheld Doppler US transducer is typically used. In this article, the technology of Doppler US for continuous fHR monitoring and intermittent fHR measurements is described, with emphasis on fHR monitoring for CTG. Special attention is dedicated to the measurement environment, which includes the clinical setting in which fHR monitoring is commonly performed. In addition, to understand the signal content of acquired Doppler US signals, the anatomy and physiology of the fetal heart and the surrounding maternal abdomen are described. The challenges encountered in these measurements have led to different technological strategies, which are presented and critically discussed, with a focus on the US transducer geometry, Doppler signal processing, and fHR extraction methods.

Ultrasound biosafety: Knowledge and opinions of health practitioners who perform obstetric scans in South Africa

BACKGROUND

Diagnostic ultrasound is generally considered as a safe test in pregnancy. To date there is no evidence that ultrasound has caused harm to the developing foetus. However, with the number of obstetric scans on the rise and the steep increase in acoustic output achieved by modern machines, the lack of evidence of absolute safety remains a concern. Acoustic output is under the direct control of the operator and is therefore the operator's responsibility to keep the intensity as low as reasonably achievable. A situation analysis in the South African context was deemed necessary to determine end user knowledge and opinions on safe antenatal ultrasound practice.

AIM

The aim of this quantitative descriptive, cross-sectional study was to evaluate the knowledge and practice of health practitioners who perform antenatal scans regarding safety aspects of diagnostic ultrasound.

SETTING

A self-administered questionnaire was distributed at two national congresses, hosted by the South African Society of Ultrasound and Obstetrics (SASUOG) and South African Society of Obstetricians (SASOG) committees.

METHOD

Quota non-probability sampling allowed for the identification of professional categories capable of providing information relevant to the study objectives. The sample represented a population with experience in obstetric ultrasound.

RESULTS

Compared to international studies, South African end users demonstrated better knowledge of safety indices than their international counterparts. It is, however, discouraging that end users still demonstrate insufficient knowledge regarding factors contributing to adverse biological effects.

CONCLUSION

With room for improvement, an effort should be made to comply with international standards through increased training efforts and raising awareness.

Fetal Heart Rate Monitoring Implemented by Dynamic Adaptation of Transmission Power of a Flexible Ultrasound Transducer Array

Fetal heart rate (fHR) monitoring using Doppler Ultrasound (US) is a standard method to assess fetal health before and during labor. Typically, an US transducer is positioned on the maternal abdomen and directed towards the fetal heart. Due to fetal movement or displacement of the transducer, the relative fetal heart location (fHL) with respect to the US transducer can change, leading to frequent periods of signal loss. Consequently, frequent repositioning of the US transducer is required, which is a cumbersome task affecting clinical workflow. In this research, a new flexible US transducer array is proposed which allows for measuring the fHR independently of the fHL. In addition, a method for dynamic adaptation of the transmission power of this array is introduced with the aim of reducing the total acoustic dose transmitted to the fetus and the associated power consumption, which is an important requirement for application in an ambulatory setting. The method is evaluated using an in-vitro setup of a beating chicken heart. We demonstrate that the signal quality of the Doppler signal acquired with the proposed method is comparable to that of a standard, clinical US transducer. At the same time, our transducer array is able to measure the fHR for varying fHL while only using 50% of the total transmission power of standard, clinical US transducers.

Health professionals' experiences and views on obstetric ultrasound in Rwanda: A cross-sectional study

OBJECTIVES

Implementation of ultrasound in antenatal care (ANC) in low-income countries has been shown to increase pregnant women's compliance with ANC visits, and facilitate detection of high-risk pregnancies. In Rwanda, as in other low-income countries, access to ultrasound has increased significantly, but lack of training is often a barrier to its use. The aim of this study was to investigate Rwandan health professionals' experiences and views of obstetric ultrasound in relation to clinical management, resources and skills.

METHODS

A cross-sectional questionnaire study was undertaken between November 2016 and March 2017, as part of the CROss Country UltraSound Study (CROCUS). Data were collected at 108 health facilities located in both rural and urban areas of Rwanda, including provincial, referral, district and private hospitals as well as health centres. Participants were obstetricians (n = 29), other physicians (n = 222), midwives (n = 269) and nurses (n = 387).

RESULTS

Obstetricians/gynecologists/other physicians commonly performed ultrasound examinations but their self-rated skill levels implied insufficient training. Access to ultrasound when needed was reported as common in hospitals, but available to a very limited extent in health centres. The vast majority of participants, independent of health profession, agreed that maternity care would improve if midwives learned to perform basic ultrasound examinations.

CONCLUSIONS

Barriers to provision of high quality ultrasound services include variable access to ultrasound depending on health facility level and insufficient skills of ultrasound operators. Physicians in general need more training to perform ultrasound examinations. Implementation of a general dating ultrasound examination seems to be a relevant goal as most health professionals agree that pregnant woman would benefit from this service. To further improve maternity care services, the possibility of educating midwives to perform ultrasound examinations should be further explored.

Automatic Measurement of Thalamic Diameter in 2-D Fetal Ultrasound Brain Images Using Shape Prior Constrained Regularized Level Sets

We derived an automated algorithm for accurately measuring the thalamic diameter from 2-D fetal ultrasound (US) brain images. The algorithm overcomes the inherent limitations of the US image modality: nonuniform density; missing boundaries; and strong speckle noise. We introduced a "guitar" structure that represents the negative space surrounding the thalamic regions. The guitar acts as a landmark for deriving the widest points of the thalamus even when its boundaries are not identifiable. We augmented a generalized level-set framework with a shape prior and constraints derived from statistical shape models of the guitars; this framework was used to segment US images and measure the thalamic diameter. Our segmentation method achieved a higher mean Dice similarity coefficient, Hausdorff distance, specificity, and reduced contour leakage when compared to other well-established methods. The automatic thalamic diameter measurement had an interobserver variability of -0.56 ± 2.29 mm compared to manual measurement by an expert sonographer. Our method was capable of automatically estimating the thalamic diameter, with the measurement accuracy on par with clinical assessment. Our method can be used as part of computer-assisted screening tools that automatically measure the biometrics of the fetal thalamus; these biometrics are linked to neurodevelopmental outcomes.

Measurement of Thermal Effects of Doppler Ultrasound: An In Vitro Study

Objective

Ultrasound is considered a safe imaging modality and is routinely applied during early pregnancy. However, reservations are expressed concerning the application of Doppler ultrasound in early pregnancy due to energy emission of the ultrasound probe and its conversion to heat. The objective of this study was to evaluate the thermal effects of emitted Doppler ultrasound of different ultrasound machines and probes by means of temperature increase of in-vitro test-media.

Methods

We investigated the energy-output of 5 vaginal and abdominal probes of 3 ultrasound machines (GE Healthcare, Siemens, Aloka). Two in-vitro test objects were developed at the Center for Medical Physics and Biomedical Engineering, Medical University Vienna (water bath and hydrogel bath). Temperature increase during Doppler ultrasound emission was measured via thermal sensors, which were placed inside the test objects or on the probes’ surface. Each probe was emitting for 5 minutes into the absorbing test object with 3 different TI/MI settings in Spectral Doppler mode.

Results

During water bath test, temperature increase varied between 0.1 and 1.0°C, depending on probe, setting and focus, and was found highest for spectral Doppler mode alone. Maximum temperature increase was found during the surface heating test, where values up to 2.4°C could be measured within 5 minutes of emission.

Conclusions

Activation of Doppler ultrasound in the waterbath model causes a significant increase of temperature within one minute. Thermally induced effects on the embryo cannot be excluded when using Doppler ultrasound in early pregnancy.

Study of the association between the incidences of congenital anomalies and hydrocephalus in Sudanese fetuses

This study was designed with an aim to detect the congenital anomalies appear to be linked to and in conjunction with hydrocephalus fetuses in Sudan, when ultrasound is used to exam fetuses in the second and third trimesters of pregnancy. This prospective cohort study was performed from December 2011 to December 2013, in a group consists of 5000 single gestation pregnant Sudanese women. In all cases, maternal ages were 35 years up to 48 years; mean age of 42.5 years. Pelvic; obstetric ultrasound scanning protocol used should meet the standards established by the American Institute of Ultrasound in Medicine (AIUM) for scanning in the second and third trimesters of pregnancy. Statistical Package for the Social Sciences (SPSS) was used to analyze the results. Diagnosed hydrocephalus cases (0.4%) were found to be associated with other fetal anomalies as aqueduct stenosis (45%), spina bifida (30%), Arnold-Chiari malformation (20%) and Dandy-Walker malformation (5%). The incidence of congenital anomalies and hydrocephalus in Sudanese fetuses showed considerable variation among different regions of Sudan. Hydrocephalus is associated with certain congenital anomalies. In agreement with previous studies, hydrocephalus is predominantly in male rather than female fetuses. The prevalence of fetal anomalies and hydrocephalus are within previously reported ranges.

ACR Appropriateness Criteria® Acute Pelvic Pain in the Reproductive Age Group

Premenopausal women who present with acute pelvic pain frequently pose a diagnostic dilemma, exhibiting nonspecific signs and symptoms, the most common being nausea, vomiting, and leukocytosis. Diagnostic considerations encompass multiple organ systems, including obstetric, gynecologic, urologic, gastrointestinal, and vascular etiologies. The selection of imaging modality is determined by the clinically suspected differential diagnosis. Thus, a careful evaluation of such a patient should be performed and diagnostic considerations narrowed before a modality is chosen. Transvaginal and transabdominal pelvic sonography is the modality of choice when an obstetric or gynecologic abnormality is suspected, and computed tomography is more useful when gastrointestinal or genitourinary pathology is more likely. Magnetic resonance imaging, when available in the acute setting, is favored over computed tomography for assessing pregnant patients for nongynecologic etiologies because of the lack of ionizing radiation. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed every two years by a multidisciplinary expert panel. The guideline development and review include an extensive analysis of current medical literature from peer reviewed journals and the application of a well-established consensus methodology (modified Delphi) to rate the appropriateness of imaging and treatment procedures by the panel. In those instances where evidence is lacking or not definitive, expert opinion may be used to recommend imaging or treatment.

ACR Appropriateness Criteria® assessment of gravid cervix

It is well recognized that preterm birth is the leading cause of perinatal mortality and morbidity. There is a significant association between cervix length and preterm birth risk. Most authorities consider a cervical length <3 cm as the lower limit of normal. A cervical length >3 cm has a high negative predictive value for delivery less than 34 weeks. A cervical length of <15 mm is moderately predictive (∼ 70%) of preterm birth within 48 hours. Cervical length is normally distributed and should remain relatively constant until the third trimester. Transabdominal US is the least reliable method of cervical length assessment. The most reliable method of documenting cervical length is transvaginal ultrasound (TVUS). Transperineal US is an alternative for imaging if TVUS is contraindicated, such as with premature rupture of membranes. However, the resolution is decreased compared to TVUS. Short cervix length is the single most important predictive finding for premature delivery. This observation should prompt consultation for high risk obstetrical care and consideration of other management options such as cerclage or activity restriction.The ACR Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed biennially by a multidisciplinary expert panel. The guideline development and review include an extensive analysis of current medical literature from peer reviewed journals and the application of a well-established consensus methodology (modified Delphi) to rate the appropriateness of imaging procedures by the panel. In those instances where evidence is lacking or not definitive, expert opinion may be used to recommend imaging.

Colour Doppler ultrasound of spiral artery blood flow in the prediction of pre-eclampsia and intrauterine growth restriction

Pre-eclampsia and intrauterine growth restriction are responsible for significant maternal and fetal morbidity and mortality worldwide. Identifying pregnancies at highest risk for their development would allow increased surveillance in individual pregnancies and also allow therapeutic trials to decrease their incidences in the future. To date, multiple attempts to develop a screening test for these disorders have met with limited success. Proposed screening methods have included maternal serum biochemical parameters as well as ultrasonographic markers. Uterine artery Doppler, direct evaluation of the spiral arteries using colour and spectral Doppler, three-dimensional placental volume analysis and, most recently, three-dimensional power Doppler angiography have all been suggested. Although an adequate screening method remains elusive, advances in ultrasound technology have improved our ability to observe the pathophysiologic changes that occur with these conditions early in pregnancy, bringing us closer to a reproducible screening model.

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

PURPOSE

As a form of energy, diagnostic ultrasound has bioeffects on living tissues. The thermal index (TI), TIS (TI for soft tissue), TIB (TI for bone), TIC (TI for cranial bone) expresses the potential for rise in temperature at the ultrasound beam's focal point. The mechanical index (MI) indicates the potential for the ultrasound beam to induce inertial cavitation in tissues. The goal of this study was to characterize the acoustic output of clinical ultrasound instruments, as expressed by TI and MI, during routine first-trimester sonographic examinations.

METHODS

A prospective observational study was conducted. First-trimester patients were randomly selected from those scheduled for viability scans. An obstetrician collected data. Sonographers were blinded to the data being sought, which included gestational age, duration of the examination, and every variation in the MI and TI during each sonographic examination.

RESULTS

A total of 52 first-trimester examinations were evaluated. The mean gestational age was 8.9 +/- 1.9 weeks. The mean duration of the sonographic examinations was 8.1+/- 1.4 minutes. During the examinations, there were 178 MI variations (mean +/- SD, 0.9 +/- 0.3) and 167 TI variations (mean +/- SD, 0.2 +/- 0.1).

CONCLUSION

First-trimester sonographic examinations are associated with a negligible rise in TI.