Echographic Measurement of Skin Thickness in Children

To optimize a medical device for intradermal injection, knowledge concerning the thickness of epidermis and dermis at the proximal forearm is required. Since scientific knowledge is lacking, the investigators will examine the skin thickness (epidermis and dermis) of children (aged 8 weeks to 18 years) using imaging technology (High Frequency Ultrasound). The investigators hypothesize that they are able to correlate the thickness of the (epi)dermis to a specific combination of parameters age, gender, and BMI. Based on these results, the investigators can define which needle type and length is needed to correctly perform injections into the dermal layer