[Basic principles of ultrasonography and its relevance for internal medicine].

This article gives an overview of the technical possibilities and clinical applications of modern ultrasound. B-mode and Doppler imaging are already essential in daily routine. Advanced technology, such as harmonic imaging, improves image quality. Tissue harmonic imaging provides better resolution by reducing noise, whereas the introduction of contrast agents increases the perceptibility of focal lesions, e.g., liver tumors. Meanwhile the diagnostic accuracy of contrast-enhanced ultrasound imaging is comparable with CT imaging. Other tools, e.g., elastography, ameliorate the detection of liver fibrosis and tumors. Currently, application of three-dimensional and four-dimensional imaging is of low clinical relevance. Panoramic imaging provides images close to CT or MRI.