[Comparative ultrasound visualization of clinically relevant structures for evaluating the infant hip joint utilizing trapezoidal vs. parallel transducers]. / Vergleichende Darstellung beurteilungsrelevanter Strukturen der kindlichen Hüfte mittels paralleler und trapezförmiger Ultraschallabbildung.

PURPOSE: Sonographic evaluation of the infant hip joint according to the method of Graf has proven to be an important pediatric investigative instrument. Our goal was to investigate quantitatively whether (and in what ways) the clinically relevant infant hip joint structures visualize differently when utilizing trapezoidal as opposed to linear transducers. Our approach was both theoretical via a mathematical model and practical with in-vivo measurements in neonates. MATERIALS AND METHODS: In a prospective study: 1. theoretical and computed analyses were performed for both linear and trapezoidal transducers regarding their respective accuracy for demonstrating the anatomic geometry of the infant hip, assuming not only correctly centered transducer positioning but also cases with off-centered displacement in the cranial or caudal direction; 2. both hip joints in 97 infants were examined by experienced investigators with comparison of the results for parallel vs. trapezoidal transducers. RESULTS: Theoretical mathematical error analysis reveals no intrinsic systemic deviations between trapezoidal vs. parallel transducers in US scanning of the infant hip and furthermore no inherent disadvantages in the trapezoidal technique. Even when off-center transducer alignments of 1.5 cm are employed in the mathematical models, there is no significant relative distortion of the required anatomic structures when comparing the characteristics of both transducers. The practical in-vivo data from our 97 neonates confirmed the theoretical considerations. CONCLUSION: No loss of accuracy or other negative factors are evident when trapezoidal transducers are used to visualize the infant hip joint in comparison with the customary parallel technique. There are no significantly measurable differences between the two approaches.

[Prospective comparison of different ultrasound modalities to measure thicknesses less than 1 mm]. / Prospektiver Vergleich verschiedener Ultraschallverfahren zur Dickenmessung im Grenzbereich von Dicken unter 1 Millimeter.

PURPOSE: New ultrasound techniques with improved visualization and better transducers constantly expand the methods of measurement. In the border area in the case of thickness measurements of less than 1 millimeter, e. g. the measurement of the "Intima-Media Thickness" (IMT), it is not clear if better visualization comes at the price of incorrect measurement values. We checked different modalities for accuracy and visualization quality. MATERIALS AND METHODS: We prospectively examined the IMT of obese children using different ultrasound modalities. The image quality was evaluated by two independent pediatric radiologists. A phantom with an exact thickness of 0.3 mm (value of the thinnest measured IMT thickness) was subsequently created by precision engineers. Measurements were carried out and analyzed using fundamental ultrasound, tissue harmonic imaging, speckle reduction imaging and cross beam (real-time compound) imaging. RESULTS: The best image quality was reached using speckle reduction imaging. This technique and fundamental ultrasound produced the most exact data. However, the recognizability was worse in fundamental ultrasound than in speckle reduction imaging. CONCLUSION: Speckle reduction imaging appears to be the best technique for measuring thicknesses less than 1 mm.

[Sonographic artifacts of round reflectors]. / Sonographische Artefakte an rundlichen Reflektoren.

The appearance of the proximal curved edge artifact using linear-array systems is demonstrated in five cases. Furthermore simulation of this artifact was achieved in a waterbath. A physical explanation of this phenomenon is discussed.

[Methods for discriminating flow direction with continuous wave Doppler equipment]. / Methoden der Richtungstrennung bei Dauerschall-Dopplergeräten.

The application of ultrasound Doppler units for the localization of incompetent venous valves, the examination of extracranial vessels, and the evaluation of the hemodynamic effect of certain cardiac dysfunctions requires directional models with the possibility of recording Doppler wave forms. Various techniques are used to determine flow direction all of them presenting specific advantages and disadvantages in practical use. After briefly explaining the basic Doppler technique, the three most commonly used methods, the two-channel filter technique, the McLeod system, and the outphaser system, are described. The characteristics of the various signal processing techniques are discussed, particularly in the case of complex hemodynamic conditions.