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Die Sicherheit des Ultraschalls ist bei der Untersuchung der Lunge von besonderer Bedeutung, da spezifische Wechselwirkungsmechanismen an der alveolaren Luft-Gewebegrenze auftreten. Lungengewebe ist dabei deutlich empfindlicher als solides Gewebe gegenüber mechanischen Kräften. Die ursächlichen biologischen Effekte basierend auf Totalreflektion von Schallwellen sind zudem nur unzureichend untersucht. Andererseits ist der klinische Nutzen des Lungenultraschalls beträchtlich und hat Aufgrund der Pandemiesituation erheblichen Stellenwert dazugewonnen. Dabei erweist sich dieser bisweilen dem anderer radiologischer Bildgebungsverfahren ebenbürtig. Deshalb widmet sich diese Arbeit, basierend auf derzeit verfügbaren Literaturquellen, dem Einfluss von Schalleffekten auf das Lungenparenchym und evaluiert bestehende Empfehlungen zur Schalldruckreduzierung bei der Durchführung der Lungensonographie. Es wird ein Vorgehen empfohlen, um klinisch relevante Bilder zu erhalten und gleichzeitig die Ultraschallsicherheit zu gewährleisten. Ein besonderes Augenmerk liegt auf der Sicherheit neuer Ultraschall Modalitäten, welche zum Zeitpunkt früherer Empfehlungen noch nicht berücksichtigt waren. Abschließend werden notwendige Forschungs- und Ausbildungsschritte empfohlen, um Wissenslücken auf dem Gebiet des Lungenultraschalls in Zukunft schließen zu können. Diese Empfehlungen für die Praxis wurden von ECMUS, dem Sicherheitskommittee der EFSUMB, unter Mitwirkung von international Experten auf dem Gebiet der Lungensonographie und biologischer Ultraschallwechselwirkung erstellt. The safety of ultrasound is of particular importance when examining the lungs, due to specific bioeffects occurring at the alveolar air-tissue interface. Lung is significantly more sensitive than solid tissue to mechanical stress. The causal biological effects due to the total reflection of sound waves have also not been investigated comprehensively. On the other hand, the clinical benefit of lung ultrasound is outstanding. It has gained considerable importance during the pandemic situation, showing comparable diagnostic value with other radiological imaging modalities. Therefore, based on currently available literature, this work was dedicated determining possible ultrasound effects on the lung parenchyma and evaluating existing recommendations for acoustic output power limits when performing lung sonography. This work recommends a stepwise approach to obtain clinically relevant images while ensuring lung ultrasound safety. A special focus was set on the safety of new ultrasound modalities, which had not yet been introduced at the time of previous recommendations. Finally, necessary research and training steps are recommended in order to close knowledge gaps in the field of lung ultrasound safety in the future. These recommendations for practice were prepared by ECMUS, the safety committee of the EFSUMB, with participation of international experts in the field of lung sonography and ultrasound bioeffects.

This first position paper of the European Federation of Societies for Ultrasound in Medicine and Biology (EFSUMB) on professional standards presents a common position across the different medical professions within EFSUMB regarding optimal standards for the performing and reporting of ultrasound examinations by any professional ultrasound operator. It describes general aspects of professionality that ensure procedure quality, effectiveness, efficiency, and sustainability in virtually all application fields of medical ultrasound. Recommendations are given related to safety and indication of ultrasound examinations, requirements for examination rooms, structured examination, systematic reporting of results, and management, communication and archiving of ultrasound data. The print version of this article is a short version. The long version is published online.Dieses erste Positionspapier der European Federation of Societies for Ultrasound in Medicine and Biology (EFSUMB) zu professionellen Standards beschreibt eine gemeinsame Position der verschiedenen medizinischen Berufe innerhalb der EFSUMB zu optimalen Standards, wie Ultraschall-Untersuchungen von jedem professionellen Untersucher durchgeführt und befundet werden sollten. Beschrieben werden allgemeine Aspekte der Professionalität, die die Qualität, Effektivität, Effizienz und Nachhaltigkeit in praktisch allen Anwendungsbereichen des medizinischen Ultraschalls gewährleisten. Empfehlungen werden gegeben zur Sicherheit und Indikationsstellung von Ultraschall-Untersuchungen, zu Anforderungen an Untersuchungsräume, zur strukturierten Untersuchung und systematischen Befundung sowie zur Verarbeitung, Kommunikation und Archivierung von Ultraschalldaten. Die gedruckte Version dieses Artikels ist eine kurze Version. Die lange Version wird online veröffentlicht.

Zwar kommt die Sonographie ohne ionisierende Strahlung aus, wahrend der Untersuchung wird das Gewebe aber dennoch mit Energie beaufschlagt. Der Anwender muss deshalb Wirkungsmechanismen und mogliche Risiken kennen und bewerten. Thermische und nichtthermische Wirkungen (z. B. Kavitation) stehen in Beziehung mit Intensitat und Schalldruck der Ultraschallwellen und hangen somit auch ab vom eingesetzten Verfahren (B-Bild, Farbdoppler/Pulsed-wave[pw]-Doppler). Im B‑Mode sind keine gefahrlichen thermischen Effekte zu erwarten. Vorsicht ist bei Embryonen und Feten sowie bei fiebernden Patienten geboten. Im pw-Doppler-Modus konnen Temperaturspitzen entstehen, deren Risiko mit der Dauer der Einwirkung steigt. Ultraschallkontrastmittel stellen Kavitationskeime dar und sollten bis zu 24 h vor einer Stoswellenlithotripsie vermieden werden. Insbesondere bei Anwendungsmodi mit hoher lokaler Leistung sollte man die angezeigten Werte fur den thermischen und mechanischen Index (TI und MI) beachten und dem ALARA(„as low as reasonably achievable“)-Prinzip folgen.

This first position paper of the European Federation of Societies for Ultrasound in Medicine and Biology (EFSUMB) on professional standards presents a common position across the different medical professions within EFSUMB regarding optimal standards for the performing and reporting of ultrasound examinations by any professional ultrasound operator. It describes general aspects of professionality that ensure procedure quality, effectiveness, efficiency, and sustainability in virtually all application fields of medical ultrasound. Recommendations are given related to safety and indication of ultrasound examinations, requirements for examination rooms, structured examination, systematic reporting of results, and management, communication and archiving of ultrasound data. The print version of this article is a short version. The long version is published online.Dieses erste Positionspapier der European Federation of Societies for Ultrasound in Medicine and Biology (EFSUMB) zu professionellen Standards beschreibt eine gemeinsame Position der verschiedenen medizinischen Berufe innerhalb der EFSUMB zu optimalen Standards, wie Ultraschall-Untersuchungen von jedem professionellen Untersucher durchgeführt und befundet werden sollten. Beschrieben werden allgemeine Aspekte der Professionalität, die die Qualität, Effektivität, Effizienz und Nachhaltigkeit in praktisch allen Anwendungsbereichen des medizinischen Ultraschalls gewährleisten. Empfehlungen werden gegeben zur Sicherheit und Indikationsstellung von Ultraschall-Untersuchungen, zu Anforderungen an Untersuchungsräume, zur strukturierten Untersuchung und systematischen Befundung sowie zur Verarbeitung, Kommunikation und Archivierung von Ultraschalldaten. Die gedruckte Version dieses Artikels ist eine kurze Version. Die lange Version wird online veröffentlicht.

Ultrasound safety is of particular importance in fetal and neonatal scanning. Fetal tissues are vulnerable and often still developing, the scanning depth may be low, and potential biological effects have been insufficiently investigated. On the other hand, the clinical benefit may be considerable. The perinatal period is probably less vulnerable than the first and second trimesters of pregnancy, and ultrasound is often a safer alternative to other diagnostic imaging modalities. Here we present step-by-step procedures for obtaining clinically relevant images while maintaining ultrasound safety. We briefly discuss the current status of the field of ultrasound safety, with special attention to the safety of novel modalities, safety considerations when ultrasound is employed for research and education, and ultrasound of particularly vulnerable tissues, such as the neonatal lung. This CME is prepared by ECMUS, the safety committee of EFSUMB, with contributions from OB/GYN clinicians with a special interest in ultrasound safety. Die Sicherheit des Ultraschalls ist bei der Untersuchung von Foten und Neugeborenen von besonderer Bedeutung. Fetales Gewebe ist empfindlich und befindet sich meist noch in der Entwicklung, die Eindringtiefe kann gering sein und mogliche biologische Effekte sind nur unzureichend untersucht worden. Andererseits kann der klinische Nutzen betrachtlich sein. In der Perinatalperiode ist der Fotus wohl weniger gefahrdet als im ersten und zweiten Trimester der Schwangerschaft, und Ultraschall ist haufig eine sicherere Alternative verglichen mit anderen diagnostischen bildgebenden Verfahren. Hier stellen wir Schritt fur Schritt das Vorgehen vor, um klinisch relevante Bilder zu erhalten und gleichzeitig die Ultraschallsicherheit zu gewahrleisten. Wir erortern kurz den aktuellen Stand auf dem Gebiet der Ultraschallsicherheit, mit besonderem Augenmerk auf der Sicherheit neuer Modalitaten, Uberlegungen zur Sicherheit beim Einsatz von Ultraschall in Forschung und Ausbildung sowie die Sonografie besonders gefahrdeter Gewebe, wie z. B. der neonatalen Lunge. Diese CME-Arbeit wurde von ECMUS, dem Sicherheitsausschuss der EFSUMB, unter Mitwirkung von Gynakologen mit besonderem Interesse an der Ultraschallsicherheit erstellt.

B‑mode and color Doppler ultrasound are standard radiological methods to quantify tissue echo texture and tissue perfusion. Microstructure and composition of tissue influence echo texture parameters and acoustic parameters, such as speed of sound, attenuation and backscatter and quantitative color Doppler image parameters are influenced by the hemodynamics in depictable vessels. Dynamic contrast-enhanced ultrasound enables quantification of tissue perfusion and ultrasound elastography assists in assessing tissue stiffness. B‑mode texture analysis, analysis of high-frequency echo signals and quantitative color Doppler image analysis are able to contribute to the assessment of tissue microstructure but have so far not been implemented clinically due to their complexity. Dynamic contrast-enhanced ultrasound and ultrasound elastography have proven to be robust under clinical conditions.

Der Ultraschall fand zunachst in den technischen Disziplinen Anwendung, bevor er zu medizinischen Zwecken genutzt wurde. Er diente bereits zu Beginn des 20. Jahrhunderts zur Echolotung in der Schifffahrt und findet bis in die Gegenwart z. B. in der Materialprufung Anwendung. Grundlage dafur war die Entdeckung des piezoelektrischen Effektes durch die Bruder Curie und der damit verbundenen Moglichkeit, durch Umwandlung elektrischer in mechanische Energie Ultraschallwellen zu erzeugen. Seit Anfang der 1940er Jahre, ausgehend von den Gebrudern Dussik (1942), fanden Ultraschallverfahren schnell Anwendung in der Medizin und haben sich seitdem in eindrucksvoller Weise als bildgebendes Verfahren in Erganzung der bekannten herkommlichen Techniken der Rontgendiagnostik etabliert. Die Sonographie entwickelte sich in nahezu allen klinischen Fachdisziplinen zur Methode der ersten Wahl und stellt inzwischen das am haufigsten eingesetzten Verfahren der Bildgebung dar. Zu diagnostischen Ultraschalluntersuchungen des Urogenitaltraktes erfolgten bereits in den 60’er Jahren des vorigen Jahrhunderts erste Anwendungen (Holmes 1966 und Goldberg et al. 1968), die masgebend fur die „Uro-Sonographie“ in ihrer weiteren Entwicklung waren. Nahezu sensationell war die Einfuhrung der transrektalen Sonographie zur Beurteilung der Prostata (Watanabe et al. 1973) als endosonographische Untersuchungsmethode ebenso wie die Nutzung der Duplex-Sonographie in Zusammenhang mit der Farbgebung (FKDS: farbcodierte Duplexsonographie), die uber die Wiedergabe der morphologischen Strukturen der Bildgebung hinaus auch die Beurteilung der Durchblutung im Bereich der „region of interest“ ermoglicht. Damit ist die Uro-Sonographie zu einem integralen unersetzbaren Bestandteil im Spektrum der sonographischen Moglichkeiten in der Humanmedizin geworden.

The use of high-intensity focused ultrasound (HIFU) to heat polymer films is getting more in focus of interest in the industry due to some advantages e.g. low damages of thin polymer films during film processing or cost reduction of the processing tool. The capability to heat thin polymer films using a solid waveguide transducer was already reported in the literature. However, some significant hurdles persist: the physical principles responsible for the heating of thin polymer films are not fully understood. This study aims to investigate the sound field occurring in thin polymer films between a solid waveguide transducer (having a resonance frequency of 1.1 MHz) and a solid counterpart and compared it to the sound field in mm-thick polymer sample. An analogy between the sound field measured in water and the sound field inside polymer films during the heating process is done. The sound field between counterpart and solid waveguide is analyzed by means of membrane hydrophone sound field measurements and finite element simulations. The impact of the transducer-counterpart gap size is studied. This investigation reveals that the behavior and characteristics of the sound field in water in a transducer-counterpart gap differ considerably from each other depending on the gap size. When the gap is smaller than a wavelength, the sound cannot be focused within the waveguide-counterpart gap and complex interferences occur inside the small gap. Furthermore, the investigation showed that similarities occur between the sound field measured in water and the sound field calculated in polymer. These findings are relevant for the understanding of HIFU-based processes involving thin polymer films.

This document is the updated 2019 revision of the EFSUMB Clinically Safety Statement. A Safety Statement has been published by EFSUMB annually since 1994 by the Safety Committee (ECMUS) of the federation. The text is deliberately brief and gives a concise overview of safety in the use of diagnostic ultrasound.Dieses Dokument ist die 2019 aktualisierte Revision des EFSUMB-Clinically-Safety-Statements. Diese Stellungnahme zur Sicherheit wird von der EFSUMB seit 1994 jährlich durch das Sicherheitskomitee (ECMUS) der EFSUMB veröffentlicht. Der Text ist bewusst kurz gehalten und gibt einen prägnanten Überblick über die Sicherheit bei Anwendung des diagnostischen Ultraschalls.

This article presents the study of the thermal and acoustic effects occurring in polymer samples of different thicknesses receiving high-intensity focused ultrasound (HIFU). Whereas the heating mechanisms in polymer plates immersed in water are well known, the physical mechanisms enabling the heating of polymer films using a solid waveguide transducer remain not fully understood. A coupled acoustothermal finite-element simulation is conducted to model the sound field and the heat generation inside polymer samples of different thicknesses. To validate the acoustic model, the acoustic particle velocities at the transducer waveguide tip are measured by vibrometry and compared with the simulation results. The heating effects in the samples are monitored using an infrared thermography system and compared with the measured particle velocities and with the acoustic and thermal simulation results. Correlations among particle velocities, sound intensity, and polymer heating are investigated. A qualitative and quantitative correlation between the simulation and the measurement results is found. Experiments show that the heating effects depend on the sample thickness. In samples thinner than 1 mm, the maximum temperature is lower than the one observed in samples thicker than 1 mm but rises faster. The simulation shows that the sound intensity in polymer samples thinner than 1 mm decreases sharply with the decrease in the thickness of the sample. This study contributes to the understanding of the challenges in heating thin polymer films by HIFU in a dry environment, using only a force to couple the transducer to the polymer films.

Michiel Postema, Spiros Kotopoulis, Klaus-Vitold Jenderka. Physical principles of medical ultrasound. Christoph F. Dietrich.EFSUMB Course Book 2nd Edition, pp.1-23, 2019. DOI:10.37713/ECB01

Quantitative ultrasound (QUS) is a promising technique for bone tissue evaluation. Highly focused transducers used for QUS also have the capability to be applied for tissue-regenerative purposes and can provide spatially limited deposition of acoustic energy. We describe a focused low-intensity pulsed ultrasound (FLIPUS) system, which has been developed for the stimulation of cell monolayers in the defocused far field of the transducer through the bottom of the well plate. Tissue culture well plates, carrying the cells, were incubated in a special chamber, immersed in a temperature-controlled water tank. A stimulation frequency of 3.6 MHz provided an optimal sound transmission through the polystyrene well plate. The ultrasound was pulsed for 20 min daily at 100-Hz repetition frequency with 27.8% duty cycle. The calibrated output intensity corresponded to ${{{I}}_{{\text{SATA}}}} = 44.5 \pm 7.1\;{\text{mW}}/\text{cm}^{2}$ , which is comparable to the most frequently reported nominal output levels in LIPUS studies. No temperature change by the ultrasound exposure was observed in the well plate. The system was used to stimulate rat mesenchymal stem cells (rMSCs). The applied intensity had no apoptotic effect and enhanced the expression of osteogenic markers, i.e., osteopontin (OPN), collagen 1 (Col-1), the osteoblast-specific transcription factor—Runx-2 and E11 protein, an early osteocyte marker, in stimulated cells on day 5. The proposed FLIPUS setup opens new perspectives for the evaluation of the mechanistic effects of LIPUS.

Previous studies showed that using a 1 MHz solid waveguide transducer based on High-Intensity Focused Ultrasound (HIFU)enables 320 μm thick low density polyethylene (LDPE)films heating above the melting temperature within 200 ms. However, the physical mechanisms causing the heating of such thin polymer films are not fully understood. It is not clear in detail, how the waves are transmitted and concentrated. Therefore, in this contribution, the physical principles responsible for polymer films heating are investigated using sound field, vibrometry (sLDV)and infrared measurements. The sound field distribution measured does not look like the typical focused sound field for an unbounded wave propagation. When the gap between waveguide and counterpart is small, the waves cannot propagate to focus and generate an energy concentration in the gap. Depending on the gap size, an irregular superposed wave field occurs. A correlation between the acoustic particle velocity at the waveguide tip and the heating inside the polymer is found. From these findings, it can be concluded that the heating in LDPE-films is caused by waveguide tip hammering on the films leading to intermolecular frictions rather than by the absorption of the focused ultrasonic wave inside the thin films.

The purpose of this study was to assess, if the biomechanical properties of the lower uterine segment (LUS) in women with a previous cesarean section (CS) can be determined by ultrasound (US) elastography. The first aim was to establish an ex-vivo LUS tensile-stress-strain-rupture(break point) analysis with the possibility of simultaneously using US elastography. The second aim was to investigate the relationship between measurement results of LUS stiffness using US elastography in-/ex-vivo with results of tensile-stress-strain-rupture analysis, and to compare different US elastography LUS-stiffness-measurement methods ex-vivo.An explorative experimental, in-/ex-vivo US study of women with previous CS was conducted. LUS elasticity was measured by point Shear Wave Elastography (pSWE) and bidimensional Shear-Wave-Elastography (2D-SWE) first in-vivo during preoperative examination within 24 h before repeat CS (including resection of the thinnest part of the LUS = uterine scar area during CS), second within 1 h after operation during the ex-vivo experiment, followed by tensile-stress-strain-rupture analysis. Pearson's correlation coefficient and scatter plots, Bland-Altman plots and paired T-tests, were used.Thirty three women were included in the study; elastography measurements n = 1412. The feasibility of ex-vivo assessment of LUS by quantitative US elastography using pSWE and 2D-SWE to detect stiffness of LUS was demonstrated. The strongest correlation with tensile-stress-strain analysis was found in the US elastography examination carried out with 2D-SWE (0.78, p 0.001, 95%CI [0.48, 0.92]). The laboratory experiment illustrated that, the break point - as a surrogate marker for the risk of rupture of the LUS after CS - is linearly dependent on the thickness of the LUS in the scar area (Coefficient of correlation: 0.79, p 0.001, 95%CI [0.55, 0.91]). Two extremely stiff LUS-specimens (outlier or extreme values) rupture even at less stroke/strain than would be expected by their thickness.This study confirms that US elastography can help in determining viscoelastic properties of the LUS in women with a previous CS. The data from our small series are promising. However whether individual extreme values of high stiffness and consecutive restricted biomechanical resilience can explain the phenomenon of rupture during TOLAC in cases of LUS with adequate thickness remains a question which prospective trials have to analyze before US elastography can be introduced into clinical practice.

Die medizinischen dopplersonographischen Verfahren lassen sich einteilen in die Spektraldopplerverfahren [“Continuous-wave“ (CW)- und „Pulse-wave“ (PW)-Doppler] und die Verfahren zur farbkodierten Flussdarstellung (Farbdoppler- und Power-Doppler-Verfahren). Alle gemeinsam beruhen sie auf der Tatsache, dass sich das Echo von einem bewegten Reflektor um eine charakteristische Frequenz andert, je nachdem, wie schnell sich der Reflektor von der Schallquelle und zugleich vom Schallempfanger weg- bzw. auf ihn zubewegt. Wahrend der CW-Doppler nur in einem fest vorgegebenen Tiefenbereich Flusse erfasst und dies nicht durch ein zugleich dargestelltes B-Bild gesteuert werden kann, erfolgt beim PW-Doppler unter B-Bild-Fuhrung („Duplexdoppler“) die Platzierung eines Messvolumen unter Sicht. Die gewonnenen Kurven erlauben Aussagen uber die zeitliche Verteilung der Flussgeschwindigkeit und -richtung sowie uber hamodynamische Storungen. Indem intermittierend mit der Erstellung des B-Bilds die Dopplersignale in einem Ausschnitt hiervon rasterformig erfasst werden, kann daraus eine „Farbkarte“ erzeugt werden, die dynamisch bestimmte Parameter des Blutflusses (z. B. mittlere Flussgeschwindigkeit und Flussrichtung) farbkodiert darstellt. Dieser Artikel beschreibt die technischen und physikalischen Grundlagen der Dopplerverfahren.

Aims: The elastic properties of circumscribed tissues (e.g., tendons, lymph nodes, prostates, brain tumors) are of considerable clinical interest. The purpose of this study was thus to compare the Intra-/Inter-observer variation and accuracy in vitro of point shear wave elastography (pSWE) with that of 2D-SWE and to assess 2D-SWE’s precision with variable ROI (vROI) incircumscribed objects.Material and methods: Round targets (Elasticity QA Phantom Model 049) were examined for varying degrees of stiffness (8, 14, 45, and 80 kPa) and diameters (20/10 mm). Three ultrasound systems and four probes were applied (pSWE: Acuson/S3000 9L4/4C1 and Epiq7 C51, 2D-SWE: Aplio/500 PVT375BT). Three different ROIs were used, namely fixed ROI (fROI) and variable ROI: rectangular-best-fitted ROI, and round-best-fitted ROI. Each measurement was performed twice by four observers.Results: A total of 3,604 measurements were conducted. The intra-observer variation of 2D-SWE measurements indicated better agreement (Intraclass Correlation Coefficient (ICC) = 0.971; 95% CI=[0.945; 0.985]), than for the pSWE measurements (ICC = 0.872; 95% CI=[0.794; 0.92]). With both methods, the shear wave elastography applied showed low inter-observer variation: ICC = 0.980; 95% CI=[0.970; 0.987]. However, a significant difference was observed between fROI (pSWE) and vROI (2D-SWE) on circumscribed objects in terms of accuracy. The lowest degree of observationerror was detected in situations where the ROI was not “best fitted”, but placed within the target of 3mm from the border (target diameter: 20mm; mean relative error = 0.15).Conclusions: When estimating the elastic properties of circumscribed tissues, the different measurement techniques performed by commercial shear wave elastography systems reveal a strong susceptibility for observational errors, depending upon the fixed vs. variable ROI of the pSWE vs. 2D-SWE technique.

High-intensity focused ultrasound (HIFU) is increasingly getting in focus of interest for polymer layer joining [1]. It has been found that HIFU is able to heat polymer layers with a temperature rise of over 680 K · s−1 [1]. However the physical mechanisms causing the heating of thin polymer layers using ultrasound with a solid wave guide ultrasonic transducer are still unknown. In this paper, the correlation between sample thickness, particle velocity at the top of the solid wave guide and heating behaviors are investigated by means of scanning Doppler laser vibrometry and infrared thermography. The study showed that the heat generation induced by high-intensity focused ultrasound with a solid wave guide depends on the distribution of the particle velocities at the top of the wave guide for samples thinner than a half wavelength in PMMA. However for the samples thicker than a half wavelength, the heating of the sample depends on the particle velocities distribution at the top of the wave guide, as well as on the sound waves focused by the transducer. The findings are relevant for processes in which solid polymers need to be heated quickly and locally such as in welding or forming.

Ultrasound therapy is a promising, non-invasive application with potential to significantly improve cancer therapies like surgery, viro- or immunotherapy. This therapy needs faster, cheaper and more easy-to-handle quality assurance tools for therapy devices as well as possibilities to verify treatment plans and for dosimetry. This limits comparability and safety of treatments. Accurate spatial and temporal temperature maps could be used to overcome these shortcomings. In this contribution first results of suitability and accuracy investigations of the echo-time-shift method for two-dimensional temperature mapping during and after sonication are presented. The analysis methods used to calculate time-shifts were a discrete frame-to-frame and a discrete frame-to-base-frame algorithm as well as a sigmoid fit for temperature calculation. In the future accuracy could be significantly enhanced by using continuous methods for time-shift calculation. Further improvements can be achieved by improving filtering algo...

Zusammenfassung Die Sonographie als nichtinvasives bildgebendes Verfahren zur Darstellung von Veranderungen der Haut und ihrer Anhangsgebilde, der Subkutis, der subkutanen (regionaren) Lymphknoten sowie der peripheren Gefase gehort fest zum diagnostischen Armamentarium des Dermatologen. Sie besitzt gegenuber anderen Schnittbildverfahren (Rontgen, CT, MRT, PET) eine ganze Reihe von Vorteilen, ist aber mehr als die vorgenannten von der individuellen Erfahrung des Untersuchers abhangig. Eine strukturierte Aus- und Weiterbildung sowie eine standige Fortbildung sind deshalb fur die Ultraschalldiagnostik unerlasslich. Die nachfolgende Ubersicht beschreibt neben den physikalisch-geratetechnischen und administrativen Grundlagen die wichtigsten Indikationen fur die Sonographie in der Dermatologie.

Die Sonographie basiert auf den vielfaltigen Wechselwirkungen zwischen Ultraschallwellen und dem Gewebe wahrend der Ausbreitung. Deswegen enthalten Ultraschallschnittbilder mehr Informationen als eine blose Darstellung der Anatomie. Durch die Beurteilung der unterschiedlichen Echogenitat und Textur von Gewebearealen konnen weiterfuhrende Aussagen zum pathologischen Zustand des Gewebes abgeleitet werden. Zur richtigen Interpretation ist es erforderlich, den gesamten Prozess der Bildentstehung nachvollziehen zu konnen. Das trifft gleichermasen auf die gezielte Anpassung von Gerateparametern zur Optimierung des Bilds zu. In dem Beitrag werden die Phanomene der Ausbreitung von Ultraschall in Gewebe vorgestellt, und das Prinzip zur Erzeugung eines Ultraschallschnittbilds – ausgehend vom Schallkopf bis zur Darstellung auf dem Bildschirm – wird erklart.

The reliable description of the ultrasonic fields of high-intensity therapeutic ultrasound (HITU) devices is a prerequisite concerning the safe application of the method in the daily clinical routine. Since ultrasonic sensors used for the characterization of diagnostic fields are at high risk of being damaged in the strong therapeutic fields, the measurements are carried out in burst mode to reduce the acting temporal-average intensities. For the thorough investigation of possible differences between the excitation in continuous wave (cw) and burst mode, the temporal-average total acoustic output powers of two types of HITU transducers with f-numbers of approximately 1 and with working frequencies between 1.1 MHz and 3.3 MHz were investigated by means of a radiation force balance. The maximum cw equivalent power level was 300 W; the duty cycles varied between 1% and 90%. In addition, the possible effect of the transducer–target distance was investigated. It was found that the different turn-on and turn-off behaviour of the transducers caused variations of the effective duty cycle, depending on the power level and the power amplifier used. The temporal-average power declined with increasing distance as expected, and no focal anomaly was detected.

The pressure fields of two different high intensity focused ultrasound (HIFU) transducers operated in burst mode were measured at acoustical power levels of 25 and 50 W (continuous wave equivalent) with three different hydrophones: A fiber-optic displacement sensor, a commercial HIFU needle hydrophone, and a prototype of a membrane hydrophone with a protective coating against cavitation effects. Additionally, the fields were modeled using a freely available simulations software package. The measured waveforms, the peak pressure profiles, as well as the spatial-peak temporal-average intensities from the different devices and from the modeling are compared and possible reasons for differences are discussed. The results clearly show that reliable pressure measurements in HIFU fields remain a difficult task concerning both the reliability of the measured values and the robustness of the sensors used: Only the fiber-optic hydrophone survived all four exposure regimes and the measured spatial-peak temporal-average intensities varied by a factor of up to 1.5 between the measurements and the modeling and between the measurements among themselves.

A fiber-optic sensor is presented that is capable of measuring the particle displacement in high-intensity focused ultrasound (HIFU) fields. For this probe, a secondary calibration was performed, and the resulting complex frequency response is discussed. As a first practical application, the setup was used to measure the pressure in the field of a weakly focusing ultrasound transducer. The result is compared with that of a membrane hydrophone measurement. The feasibility of measurements in HIFU fields is demonstrated by means of measurements of the spatial distribution of the peak particle velocity within the focus of a HIFU transducer and of the dependence of the peak values on the acoustical power level.

Sound field measurements are widely used for the quantitative description of cavitation processes. For practical purposes it is important to know how local a sound field measurement information is, and therefore a technique is presented which allows the determination of the receiving range of such a measurement. The sound field is detected by two calibrated, similar hydrophones, mounted face to face in the cavitation cloud. The distance between the hydrophones is varied and the correlation between the two time-dependent signals is analyzed in the frequency domain defining a local parameter. The dependence of this parameter on the distance between the hydrophones describes the receiving range of a sound field measurement by means of a characteristic distance. The technique was applied to two different cavitation applications, and effective distances in the range 1-3mm were obtained. It is shown that the spatial resolution of a sound field measurement in a cavitation field is determined by the hydrophone size and does not depend on the cavitation conditions if at least a medium cavitation activity is provided.

A fibre-optic technique was applied to measure the sound field in an ultrasonic cleaning vessel under practical conditions. A metal-coated fibre-tip is used as a sensor and a heterodyne interferometer detects the change in the optical path resulting from the movement of the fibre-tip in the sound field. Spectrally resolved sound field parameters such as the fundamental, the subharmonic or cavitation noise are extracted from the measurements and compared with results obtained by a piezo-electric hydrophone. It was found that the fibre sensor provides a signal related to the velocity in the sound field, but the information about cavitation-related parameters is similar to the information for pressure sensing techniques. The fibre-optic sensors have a uniquely high spatial resolution and the sound detection process is strongly influenced by single cavitation events close to the small fibre-tip. This paper shows that fibre-tip sensors are an alternative to common hydrophone techniques. They can open up new possibilities for measurement problems for which so far no solution exists, in particular when a high spatial resolution is required or when the measurement site is small.

Quantitative Ultrasound (QUS) is a promising technique for bone tissue evaluation. Focused transducers used for QUS also have a capability to be applied for tissue-regenerative purposes and can provide spatially limited deposition of acoustic energy. We describe a focused LIPUS (FLIPUS) system, which has been developed for the stimulation of cell monolayers in the defocused far field of the transducer through the bottom of the well plate. Tissue culture well plates, carrying the cells, were incubated in a special chamber, immersed in a temperature controlled water tank. The ultrasound was introduced at 3.6 MHz, pulsed at 100 Hz repetition frequency with 27.8% duty cycle. The calibrated output intensity corresponded to ISATA = 44.5 ± 7.1 mW/cm2. In this study we evaluated mechanical response of murine C2C12 myoblastic cells to ultrasound. FLIPUS induced 1.5 fold increase (p

Quantitative Ultrasound (QUS) is a promising technique for bone tissue evaluation. Highly focused transducers, used for QUS, have also a capability to be applied for tissue-regenerative purposes and can provide geometrically controlled deposition of an accurate acoustic dose. This allows for overcoming of unwanted artifacts, i.e. standing waves, ring interferences, temperature elevations, cross-stimulation of adjacent wells, which often lead to irreproducible biological results, associated with existing Low-Intensity Pulsed Ultrasound (LIPUS) in-vitro set-ups. Focused LIPUS (FLIPUS) is a novel reliable tool, which is minimizes or avoids the aforementioned artifacts. In this study we evaluated mechanical response of murine C2C12 myoblastic cells, possessing osteogenic-lineage differentiation potential, to the well-controlled FLIPUS dose. The optimized acoustic dose (3.6 MHz, pulsed at 100 Hz with 28% duty cycle, corresponding to I SATA = 29.4 ± 4.8 mW/cm2) induced 1.5 fold increase (p

Ultrasound cleaning baths fitting the full range from micromechanical components up to large machine parts, are regularly used in industry and in the lab. Despite the large number of applications, generally approved principles and objective criteria for parameter settings which allow an efficient operation are non-existent. The empirical selections of the running parameters often impede an optimization in terms of produce and reproducibility. One proposal for an objective description of the processes is the characterization of the sound field in the cleaning bath, which causes cavities, and subsequently, the cleaning process. Sound field measurements in the appropriate frequency range from 20 kHz up to more then 1 MHz incorporate a number of problems, such as large sensors disturbing the sound field, a lack of accuracy and the risk of being destroyed by cavitation bubbles. Measurement systems based on optical fiber tips and piezo-electrical hydrophones will be presented, which fulfil the accuracy requirements and withstand ultrasound fields with high power and cavitation. The spatial distribution of sound field parameters such as positive and negative peak pressure, amplitudes of fundamentals, harmonics and sub-harmonics as well as the energy density and spectral density in several frequency ranges are determined in experiments. Finally, the determined field parameters are related to the cavitation effects by means of photometric analysis of perforated aluminium foil. Perforations as well as intentions are analyzed and quantified from scanner images of the exposed foil samples using special image processing software. The experiments indicate clear differences in the structure of the sound fields and the spectral properties between the several types of cleaning baths, transducer arrangements and excitations.

The spatial and temporal distribution of the temperature elevation caused by high-intensity therapeutic ultrasound (HITU) in a tissue-mimicking material (TMM) has been determined with magnetic resonance (MR) thermometry, infrared (IR) thermometry and a thermal test object with an integrated thin-film thermocouple at three different National Metrological Institutes (PTB/Germany, NPL/UK, INRIM/Italy). Results obtained from the different types of measurement are compared and some general aspects of the methods are discussed, particularly with regard to their suitability for the in vitro characterization of transducers for treatment planning.

Ultrasonography non-invasively visualizes changes within the skin, skin appendages, subcutaneous tissue, subcutaneous (regional) lymph nodes and peripheral vessels. Thus it is an established diagnostic tool in dermatology. Compared to X-ray, MRI and PET, ultrasonography has some advantages; however, it is more dependent on the individual experience of the investigator. Therefore a structured education and continuous training are necessary. This review describes the physical and technical basics, the administrative requirements and the main indications in dermatology.

A simple test method, feasible for remote or online testing of multi-element ultrasound transducer arrays, is presented. The test requires only a conventional ultrasonic B-mode image visualizing the transducer under investigation emitting into air. In preparation of the test a gray value profile is computed from the image data. Defective trans-ducer elements cause deviations in the profile, which are analyzed by means of a statistical procedure. The perform-ance of the test was investigated using an ultrasonic imaging system (SonixTOUCH, Ultrasonix Medical Corporation, Richmond, Canada) in research mode and masking single elements or element groups to simulate damaged piezoelec-tric elements. The test method allows to detect 2 adjacent defective elements out of a total of 128 transducer elements. Keywords: ultrasound diagnostic, multi-element trans-ducer arrays, quality assessment, statistic evaluation Introduction The quality and reliability of a diagnosis drawn on the basis of a ultrasonic investigation depends to a great ex-tend on the technical quality of the imaging system. Over the last years a number of test methods has been estab-lished which are able to detect different failure types at specific points in the signal chain and at different levels [1]. The ultrasound probe - a high sensitive, mechatronic device - is considered to be the most failure-prone part of the system [2]. Consequently a simple, user independent and reliable test of the transducer elements is a prerequi-site for a broader acceptance of technical quality assur-ance (TQA) in the user community. The analysis of B-mode images acquired when the ultrasound waves are emitted into air could provide such a test modality.

This article deals with the technical quality assurance of ultrasound B-systems. As part of a mini-trial during the Dreilandertreffen in Davos "Ultrasound 2012", we addressed the question as to whether physicians can detect faulty probes spontaneously during live scanning B-mode. For this purpose a special diagnostic device had been prepared so that groups of piezoelectric elements in the array were without function. Then the images had to be characterized by test persons without knowledge of the faulty elements. The results show that a deterioration of the image could be detected starting at five disabled elements. Due to the small number of test persons, our statements are only preliminary.

This paper describes a statistical procedure working on ultrasound B-mode images that were recorded with the transducer array radiating in air. From the digital image data, a gray value profile was generated using a computer program. A statistical procedure was developed to examine if there are significant deviations from the mean. They occur, for example, when single piezoelements are severely damaged or completely out of function. The entire technique was tested using an ultrasonic imaging system (SonixTouch, Ultrasonix Medical Corporation, Richmond, Canada) in which individual elements or groups of elements can be turned off via firmware. A failure of as large as two out of 128 elements was detectable.

Time harmonic elastography (THE) has recently been introduced for measurement of the periodic alteration in myocardial shear modulus based on externally induced low-frequency acoustic vibrations produced by a loudspeaker. In this study, we propose further developments of cardiac THE toward a clinical modality including integration of the vibration source into the patient bed and automated parameter extraction from harmonic shear wave amplitudes, wall motion profiles and synchronized electrocardiographic records. This method has enabled us to evaluate the delay between wall motion and wave amplitude alteration for the measurement of isovolumetric times of elasticity alteration during contraction (τ(C)) and relaxation (τ(R)) in a group of 32 healthy volunteers. On average, the wave amplitudes changed between systole and diastole by a factor of 1.7 ± 0.3, with a τ(C) of 137 ± 61 ms and a τ(R) of 68 ± 73 ms, which agrees with results obtained with the more time-consuming and expensive cardiac magnetic resonance elastography. Furthermore, because of the high sampling rate, elasto-morphometric parameters such as transition times and the area of wave amplitude-cardiac motion cycles can be processed in an automated way for the future clinical detection of myocardial relaxation abnormalities.

Zusammenfassung Wahrend Ischamie unterliegen Organe fortschreitenden Veranderungen, die zu einem Zustand fuhren, der eine Wiederbelebung unmoglich macht. Die Beobachtung dieser Veranderungen ist von grosem praktischen Interesse fur die Einschatzung der Moglichkeit einer erfolgreichen Wiederbelebung des Organs. Die Schadigung des Gewebes andert dessen elektrische Eigenschaften, welche mit der Impedanzspektroskopie in einem geeigneten Frequenzbereich gemessen werden. Die Impedanz von Custodial ® -protektionierten Hundelebern wurde wahrend Ischamie in einem Frequenzbereich von 10 Hz bis 10 MHz untersucht. Die charakteristischen Veranderungen der Spektren haben ihre Ursache im wesentlichen in zwei Prozessen: der Entwicklung von Zellodemen und dem Schliesen von gap junctions (interzellularen Verbindungen). Anderungen der elasto-mechanischen Eigenschaften des Gewebes konnen mit der Ultraschallspektroskopie untersucht werden. Die Ruckstreu- und Durchschallsignale einer Gewebeprobe wurden digitalisiert und in Abstanden von 5 min gespeichert. Mit Hilfe von Fensterfunktionen wurden Signalanteile innerhalb der Probe fur die Bestimmung der akustischen Parameter ausgewahlt. Es konnte die Abhangigkeit des relativen Ruckstreukoeffizienten von dem Zustand des Gewebes gezeigt werden.

The thermo acoustic sensor measures ultrasound field intensities by evaluating the warming of an absorber material. In the range of medical used ultrasound intensity there is a linear dependency between intensity and absorber warming. By using different absorber materials the sensitivity of the sensors can be influenced. Several materials were tested to make the absorber most sensitive. In addition to sensitivity measurements, measurements of linearity, response time and spatial resolution were performed for all sensors. Transfer functions between temperature differences and intensities were evaluated. Furthermore investigations on sensors with nonmetal housings show an increase in sensitivity. Combining materials and housings enables sensors for several intensities. A new sensor concept containing a half-bridge measurement circuit improves the evaluation and leads to handy and user- friendly intensity measurement applications in future.

In this work, a calibration phantom based on an electrical resistor heating rod is presented, which creates a temperature distribution similar to those in typical HIFU fields (diameter ∼2 mm, heating rate ∼10 K/s). The temperature distribution is measured first with a calibrated reference device and then with MR thermometry. Equal conditions for both measurements can be ensured by monitoring the voltage and current across the resistor during the heating. From the comparison of both measurements, the accuracy of the MR measurement can be assessed. The calibration phantom is MR compatible, and it has high reproducibility and low production costs. A wide variety of possible heating sequences can be employed and the phantom has a compact and easy setup. Thus, it can be used to quickly verify the results from newly developed MR thermometry sequences as well as to evaluate the uncertainties of existing sequences.

Der Ultraschall fand zunachst in den technischen Disziplinen Anwendung, bevor er zu medizinischen Zwecken genutzt wurde. Er diente bereits zu Beginn des 20. Jahrhunderts zur Echolotung in der Schifffahrt und findet bis in die Gegenwart z. B. in der Materialprufung Anwendung.

Within the framework of a European project several techniques for measurements in high-intensity therapeutic ultrasound (HITU) fields were improved in a collaboration of four national metrology institutes (NPL, UK; PTB, Germany; INRIM, Italy; UME, Turkey). This contribution focuses on measurement techniques for the characterization of HITU sources, in particular on measurements of the acoustic output power of HITU transducers and on the characterization of their pressure field.

The characterization and quantification of High Intensity Therapeutic Ultrasound (HITU) fields is a difficult challenge, as appropriate sensors need to withstand very high local intensities in small focal regions and to measure them with a high reliability. Due to their high robustness and their small dimensions, fiber‐optic probes have proven to be a promising approach for this purpose. In this paper, a fiber‐optic displacement sensor and an interferometric optical set‐up are presented and the potential as well as the limitations of this set‐up are discussed.

To ensure the success of high-intensity focused ultrasound (HIFU) treatment, lesion formation and focus dislocation has to be monitored online. For an automatic and immediate stop of HIFU exposure in case of irregularities of the lesion formation a monitoring technique allowing real time feedback is needed. For this purpose, we propose the analysis of shear waves which are radiated from treated tissue when the exposure with HIFU is intermitted. By A-scans close to the focal region the changes in time-of-flight and magnitude of shear waves are investigated. It is shown that dislocation of the focus can be detected by a decrease of shear wave magnitude in regions below the original focus. Deformation of lesion comes along with considerable changes in magnitude and time-of-flight of the shear wave.