The “Ordinance on Protection Against the Harmful Effects of Non-Ionizing Radiation in Human Applications” will go into effect at the beginning of 2021 1. § 10 of this ordinance prohibits non-medical fetal ultrasound exposure thereby resulting in uncertainty, particularly among affected patients, with respect to the generally accepted theory regarding the lack of ultrasound side effects. Although not a single study has shown a detrimental effect on fetal or child development following exposure to ultrasound, the Federal Ministry for the Environment, Nature Conservation and Nuclear Safety has justified the ban with the purely hypothetical possibility of an unidentified side effect. The first part of the following study shows which ultrasound-induced biophysical effects are known and which dose-dependent threshold values must be taken into consideration. In particular, the study focuses on the well-researched heat effect with some in vivo measurements in humans showing that the actual temperature increase is less than the theoretically calculated values. The planned second part of this study will discuss the non-thermal effects and present the most important epidemiological studies.

The first part of this CME article (issue 5/20) provided a detailed examination of the biophysical effects of ultrasound waves, the exposure values, and in particular the thermal effect. In vivo and in vitro measurements have shown that the temperature increase in tissue associated with B-mode ultrasound is far too low to pose a potential risk. Even experiments with exposure values in the range of pulsed Doppler have shown that temperature increases of over 1.5 °C can only occur in areas in direct contact with the probe, thus making a limited exposure time particularly in the case of transvaginal application advisable. The second part of this CME article describes various laboratory and animal experiments for evaluating non-thermal effects and also presents the most important epidemiological studies in the last 30 years in the form of an overview and review. In addition to direct insonation of isolated cells to examine possible mutagenic effects, the blood of patients exposed in vivo to ultrasound was also analyzed in multiple experiments. Reproducible chromosome aberrations could not be found in any of the studies. In contrast, many experiments on pregnant rodents showed some significant complications, such as abortion, deformities, and behavioral disorders. As in the case of thermal effects, the results of these experiments indicate the presence of an intensity- or pressure-dependent effect threshold. Numerous epidemiological studies examining possible short-term and long-term consequences after intrauterine ultrasound exposure are available with the most important studies being discussed in the following. In contrast to information presented incorrectly in the secondary literature and in the lay press, health problems could not be seen in the children observed in the postpartum period in any of these studies. Im ersten Teil dieses CME-Artikels (Heft 5/20) waren die biophysikalischen Effekte von Ultraschallwellen, die Expositionsgrößen und insbesondere die Wärmewirkung ausführlich behandelt worden. In-vivo- und In-vitro-Messungen hatten gezeigt, dass insbesondere die mit dem B-Modus einhergehende Temperaturerhöhung im Gewebe weit unterhalb jeglichen Gefährdungspotenzials lag. Selbst aus Versuchen mit Expositionen im Leistungsbereich gepulster Doppler war hervorgegangen, dass lediglich im direkten Kontaktbereich der Sonden Temperaturerhöhungen von über 1,5 °C auftreten können – Erwärmungen, die insbesondere bei transvaginaler Applikation eine zeitliche Befristung der Expositionsdauer nahelegen. Dieser zweite Teil des CME-Artikels beschreibt zum einen verschiedene Labor- und Tierversuche zur Evaluierung von nichtthermischen Effekten und stellt des Weiteren die wichtigsten epidemiologischen Studien der letzten 30 Jahre in Form eines Überblicks und Reviews vor. Neben der direkten Beschallung von isolierten Zellen zur Untersuchung eventueller mutagener Folgen war in mehreren Versuchen auch das Blut von in vivo exponierten Patienten analysiert worden. In keiner der Studien konnte reproduzierbar eine Chromosomenaberration gefunden werden. Demgegenüber zeigten viele Versuche an trächtigen Nagern teils signifikante Komplikationen, wie Aborte und Fehlbildungen der Nachkommen sowie Verhaltensauffälligkeiten. Die Ergebnisse dieser Versuche deuten – vergleichbar mit den thermischen Effekten – auf das Vorhandensein einer leistungs- oder druckabhängigen Wirkungsschwelle hin. Epidemiologische Studien zur Untersuchung etwaiger Kurz- und Langzeitfolgen nach intrauterinen Ultraschallexpositionen stehen in großer Vielzahl zur Verfügung, wobei die wichtigsten Arbeiten nachfolgend besprochen werden. Anders als in der Sekundärliteratur und in der Laienpresse teilweise verfälscht wiedergegeben, konnte in keiner dieser Studien eine gesundheitliche Beeinträchtigung der post partum beobachteten Kinder gefunden werden. Publication Date: 09 April 2021 (online) © 2021. Thieme. All rights reserved. Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, Germany

Background: This study assesses the effects of the ‘Radiant’ image enhancement technique on fetal nuchal translucency (NT) measurements during first-trimester sonographic exams. Methods: A retrospective analysis of 263 ultrasound images of first-trimester midsagittal sections was conducted. NT measurements were obtained using a semi-automatic tool. Statistical methods were applied to compare NT measurements with and without ‘Radiant’ enhancement. An in vitro setup with predefined line distances provided additional data. Results: Incremental increases in NT measurements were observed with varying levels of ‘Radiant’ application: an average increase of 0.19 mm with ‘Radiant min’, 0.24 mm with ‘Radiant mid’, and 0.30 mm with ‘Radiant max.’ The in vitro results supported these findings, showing consistent effects on line thickness and measurement accuracy, with the smallest mean deviation occurring at the ‘Radiant mid’ setting. Conclusions: ‘Radiant’ image enhancement leads to significant increases in NT measurements. To avoid systematic biases in clinical assessments, it is advisable to disable ‘Radiant’ during NT measurement procedures. Further studies are necessary to corroborate these findings and to consider updates to the NT reference tables based on this technology.

Background: This study assesses the effects of the ‘Radiant’ image enhancement technique on fetal nuchal translucency (NT) measurements during first trimester sonographic ex-ams. Methods: A retrospective analysis of 263 ultrasound images of first trimester midsagittal sections was conducted. NT measurements were obtained using a semi-automatic tool. Statistical methods were applied to compare NT measurements with and without ‘Radi-ant’ enhancement. An in-vitro setup with predefined line distances provided additional data. Results: Incremental increases in NT measurements were observed with varying levels of ‘Radiant’ application: An average increase of 0.19 mm with ‘Radiant min’, 0.24 mm with ‘Radiant mid’ and 0.30 mm with ‘Radiant max.’ The in-vitro results supported these findings, showing consistent effects on line thickness and measurement accuracy, with the smallest mean deviation occurring at the ‘Radiant mid’ setting. Conclusions: ‘Radiant’ image enhancement leads to significant increases in NT measure-ments. To avoid systematic biases in clinical assessments, it is advisable to disable ‘Radi-ant’ during NT measurement procedures. Further studies are necessary to corroborate these findings and to consider updates to the NT reference tables based on this technology.