The present invention communication network system and method facilitates authentication and registration in a communication network as mobile nodes move from one geographical region to another. The system of the invention conducts a therapy exercise by displaying a picture; generating a speech prompt asking the patient for information about the picture; receiving the patient’s speech response and processing it to determine its semantic content; determining whether the patient’s response was correct; and outputting feedback to the patient. A cell is selected from one or more cells in a given collection of standardized cells. Frequently co-occurred adjacent segments become candidates for markers of landmarks. The flat solid state detector can be adjusted in such a way that a longitudinal edge can be positioned parallel to a chest wall of a female patient in a first position, and a transverse edge can be positioned parallel to the chest wall of the female patient in a second position.