A polyurethane composition containing solid beads dispersed therein, is formed of a microcellular polyurethane foam, and the composition has a storage modulus of elasticity at 40\xb0 C. Along one or more lateral walls of the bedstead, side ducts are provided with lateral escape ports for the out-flow of air from the air-conduction unit. Another system is configured to image one or more materials in an imaging volume of a measurement device.