A digital image acquisition device is for acquiring digital images including one or more preview images. Particles may, for example, include different targeting agents on their surfaces, and the aptamer or aptamers may be evolved to provide better targeting of the particles. A comparator compares a signal received by the antenna with threshold values to obtain a reception signal, which is supplied to a processing unit. Session parameters are determined according to the varying channel conditions and the device capacities of the client devices to create intended sessions.