HISTORY OF HIGH-FREQUENCY SONOGRAPHY

The development of high frequency sonography (<20MHz) has gained increasing importance since the last decade. In this field A-mode-scanner were used firstly in the measurement of skin thickness. 1987 the first commercial available 20 MHz B-scanning system was introduced. These systems provided the possibility of correlating the ultrasound images with the micromorphological findings in histology. With these correlations we were able to interpret ultrasound phenomena and in conclusion we were able to measure tumour thicknesses with direct impact on the therapeutic regimen. In inflammatory skin diseases the role of high frequency ultrasound in follow up investigations of morphea and systemic sclerosis must be underlined. We believe that in this field the technique is the ''golden standard''. In other inflammatory diseases (e.g. psoriasis) or wound healing ultrasound is mainly used for scientific purposes. The investigation of intraepidermal structures and differential diagnosis is only possible with higher frequencies than 20 MHz. Therefore we developed 50 and 100 MHz in vivo scanning systems. With resolution up to 11 mu m (100 MHz) we hope to answer open questions in the future. Ultrasound microscopy is widely used for scientific evaluation of tissue morphology in vitro (resolution < 1 mu m). Computer-based three-dimensional reconstructions provide additional information (e.g. tumour volume or tumour surface). These parameters are well suited to follow up the effect of systemic or local therapies on skin metastases of different cancers. However, also the tumour volume of the primary tumour (in vivo) might be of great interest as a prognostic parameter in future. Image analysis is important for the quantification (and differential diagnosis) of ultrasound images; however this is at present in a very early stage and should not be overrated.