[Safety aspects of ultrasound diagnostics]. / Sicherheitsaspekte der Ultraschalldiagnostik.

Ultrasonography is free of ionizing radiation but during the examination it is accompanied by energy deposition in the tissue. Therefore, users should be familiar with the mechanisms of action and possible risks. Thermal and non-thermal (e.g. cavitation) effects are related to the intensity and sound pressure of ultrasound waves and are therefore also dependent on the ultrasound modality used, e.g., B­mode, color Doppler and/or pulsed wave (pw) Doppler. With B­mode ultrasound no dangerous thermal effects are to be expected. In embryos and foetuses as well as febrile patients caution should be exercised. The pw Doppler mode can cause temperature spikes and the risks increase with the duration of use. Ultrasound contrast media are pathogenic for cavitation and should be avoided during the 24 h prior to shock wave lithotripsy. In ultrasound modalities with high local energy deposition, the values for the thermal index (TI) and mechanical index (MI) displayed on the screen should be observed and as with ionizing radiation, the ALARA (as low as reasonably achievable) principle should be adhered to.

[Quantitative methods in sonography]. / Quantitative Verfahren in der Sonographie.

B­mode 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. B­mode 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.

[Principles of Doppler sonography]. / Verfahren der Dopplersonographie.

The techniques of medical Doppler are spectral Doppler (contiuous-wave (CW) and pulse-wave (PW) Doppler) and color flow imaging (Color Doppler and Power Doppler). All are based on the fact that the frequency of an echo from a moving reflecting particle will be altered by a characteristic frequency shift determined by its velocity in relation to the source/detector. The CW Doppler will only detect flow within a pre-defined depth and will not be guided by an image, whereas the PW Doppler is carried out with B-mode guidance (Duplex doppler). The so derived curves permit to assess the temporal distribution of flow velocities and directions and flow disturbances as well. In the case of color flow imaging, a part of the interrogated tissue section is mapped for Doppler signals and then color-coded, resulting in a dynamic color map of flow, where the colors encode characteristic flow parameters (e. g. mean flow velocity plus direction). This article describes the technical and physical basics of medical Doppler techniques.

[Propagation of ultrasound in tissue and principles of ultrasound imaging]. / Ausbreitung von Ultraschall im Gewebe und Verfahren der Ultraschallbildgebung.

Sonography is based on multiple interactions between ultrasonic waves and the tissue during propagation. Therefore, ultrasound images contain more information than the mere visualization of the anatomic structures. Assessing the different echogenicity and texture of tissue regions yields additional information about the pathologic tissue alterations. Precise interpretation requires knowledge of the whole process of image generation. This also applies for the adjustment of system parameters for image improvement. This article explains the phenomena of ultrasound propagation in tissue and the principles of ultrasound image generation-from the scan head to the image on the screen.

How perfect are you with defective probes? Information on the results of the mini-trial on technical quality assurance during the "Ultraschall 2012" conference in Davos.

This article deals with the technical quality assurance of ultrasound B-systems. As part of a mini-trial during the Dreiländertreffen 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.

[Up to date technologies in ultrasound imaging]. / Aktuelle Technologien in der Ultraschallbildgebung.

The rapid innovation rate of medical ultrasound devices involves continuously new methods in diagnostic sonography. These techniques permit higher resolutions and increased contrast for expressive diagnosis and more reliable results. But the broad spectrum of new techniques and methods also confronts the user with higher requirements in training and application. Knowledge about the mode of operation is helpful for the selection of the right procedure and the proper application of the methods. This article describes a number of new technologies and principles for the design of scan heads, the generation of ultrasound pulses and fast imaging procedures. The ideas behind these techniques are explained along with the connected advantages and drawbacks.

Non-destructive estimation of the intramuscular fat content of the longissimus muscle of pigs by means of spectral analysis of ultrasound echo signals.

The eating quality of porcine meat is supposed to increase with increasing intramuscular fat content (IMF). The aim of this study was to investigate the use of acoustic parameters obtained by spectral analysis of ultrasound echo signals to non-destructively predict intramuscular fat content of porcine longissimus muscle. Ultrasound is regarded as a promising non-destructive technique to characterize tissue. Ultrasound data acquisition was performed at slaughter with a clinical B-mode device equipped with a 3.5 MHz center-frequency transducer on 115 warm carcasses about 45 min postmortem. Acoustic parameters quantifying attenuation, backscattering and cepstral structure were calculated off-line from the recorded primary raw ultrasound echo signals. Their relationship to IMF content was investigated. IMF level significantly influenced powerspectrum amplitudes and backscatter parameters. With partial least-squares regression (PLS), the IMF content could be predicted with root mean standard error of prediction RMSEP of 0.36% IMF. The ultrasound parameters were able to correctly classify nearly 80% of the carcasses into HIGH and LOW level class, respectively. Results indicate the potential use of ultrasound spectral analysis for non-destructive evaluation (NDE) of pig carcasses in order to estimate the IMF content.

[New techniques in uro-sonography]. / Neue Techniken der Urosonographie.

New sonographic techniques in urology, together with their principles of operation, will be presented. Together with the utilization of broadband ultrasound scanners and digital beam formers, leading to better spatial resolution and increased line density in ultrasound imaging, panorama sonography enables the outline of wide lateral regions independent of the width of the scanner. Spatial compound sonography achieves a comparatively better visualization of details in the b-mode image than has yet been available. The continuously improved 3-D, now leading to 4-D, techniques, which means real time capabilities, make the visualization of unrestricted imaging planes, which are not seen in conventional 2-D techniques, possible. The second harmonic imaging technique, including the special applications tissue harmonic imaging (THI) and contrast harmonic imaging (CHI), uses special ultrasound signal processing procedures for capturing and evaluating tissue hemoperfusion-here in combination with ultrasound contrast agents (UCA). Furthermore, microvascular imaging (MVI) enables the visualization of perfusion in tissues reaching the microcirculation regions. This leads to new possibilities for the assessment of pathological perfusion patterns, e.g. in andrology (perfusion of testicles) and uro-oncology (hyperperfusion of malignant regions).

[Determination of acoustic parameters from ultrasound raw and HF data--a comparison]. / Bestimmung von akustischen Parametern aus Ultraschall roh- und HF-Daten--ein Vergleich.

Different methods for determination of acoustical tissue parameters based on rf data acquisition as well as the analysis of B-mode image data are well established. Because of limitations of the dynamic range and the restricted control of the tgc and focus settings the analysis of image data is not achievable in clinical practice. On the other side rf data are not available in most of the clinical scanners. So the analysis of raw data can be used as an compromise. Raw- and rf-data of complete B-mode scans obtained form a set of test phantoms by a clinical ultrasound device (HDI 5000, Philips) in connection with the applied gain settings were analyzed. For different system settings the estimated parameters showed a good agreement with the acoustical properties of the phantoms.

[Transrectal ultrasound of the prostate. Current status and prospects]. / Transrektale Sonographie der Prostata. Aktueller Stand und Perspektiven.

In recent years the role of ultrasound in the diagnosis of prostate carcinoma has increased in importance. In view of the increasing incidence of prostate cancer, which is the most frequent malignant neoplasm in men, TRUS (transrectal ultrasound) is an important imaging method in the diagnosis of various prostate diseases. This paper provides a basic overview of physical and technical bases of TRUS investigation of the prostate. It concerns technical developments and modern techniques designed to improve its value in diagnosis. Impressive innovations in ultrasound equipment, particularly in the area of colour-coded Doppler sonography in association with microbubble-enhanced colour Doppler ultrasound, have given rise to justifiable hope of improvements in the early diagnosis of prostate cancer.

[Equipment-independent ultrasound tissue characterization of testis and prostate]. / Geräteunabhängige Ultraschall-Gewebecharakterisierung von Hoden und Prostata.

The result of a B-scan ultrasound examination is strongly dependent on the type of the used B-system, the chosen system parameters and the experience and critical analysis of the clinical investigator. The estimation of quantitative acoustic parameters, independent of the type of the used B-system, is one way to overcome the subjective nature and the problems of the interpretation of B-scan images. A procedure was developed to determine acoustical tissue specific parameters (ultrasound attenuation, relative backscatter coefficient) in terms of the ultrasound spectroscopy and to correct the system effects. A requirement for the calculation of acoustical parameters is the availability of primary rf echo signals without any preprocessing. Up to now measurements of phantom materials and in-vivo investigations on human testis and prostate have been carried out. The effects of pathological changes in the tissue state on the acoustical parameters are demonstrated in some examples.

[Difficulty in determining ultrasonic attenuation values from selective echograms]. / Zur Problematik der Bestimmung von Ultraschall-Schwächungswerten aus selektiven Echogrammen.

The value of tomography is beyond all doubt. Custom systems allow the quantitative assessment of topographic and kinetic parameters of various organs and the blood. The assessment of tissue, however, is still qualitative and experimental methods for quantitative tissue characteristics are still expensive. We propose a method, that allows the determination of attenuation coefficients with little technical expense.