High frequency ultrasound for high resolution skin imaging

High frequency and broadband ultrasound in the frequency range above 20 MHz is an efficient modality for the non invasive and high resolution imaging of skin structures and skin diseases like skin tumors and inflammatory proc esses. However, special system designs and signal processing strategies hav e to be applied to account for the strong and frequency dependent attenuati on of high frequency ultrasound in tissue. In this paper the design of an u ltrasound imaging system with a minimum spatial resolution of about 9 mum, utilizing the frequency range from 30 to 150 MHz, is presented. This system enables the high resolution visualization of the uppermost skin layer, whi ch is of great interest in dermatology and cosmetics. To quantify the imagi ng properties of the system reference measurements were performed by imagin g a glass plate and a wire phantom. Furthermore, image processing technique s for the analysis of three dimensional data sets were adapted to investiga te the topology skin structures like skin layers. Results from in vivo meas urements on healthy skin and skin tumors are presented.