Determination of acoustic velocity in bone

A method of determining an acoustic velocity in a segment of a bone covered with a layer of soft tissue having an outer surface, comprising:

• determining a first travel time of a first ultrasonic wave along a first path from said outer surface back to said outer surface which path includes a first bone path in at least a first part of said bone segment and a first soft tissue path in at least part of said soft tissue;
• determining a second travel time of a second ultrasonic wave along a second path from said outer surface back to said outer surface which path includes a second bone path in at least a second part of bone segment and a second soft tissue path in at least part of said soft tissue;
• determining a third travel time of a third ultrasonic wave along a third path from said outer surface back to said outer surface which path includes a third bone path in at least a third part of said bone segment and a third soft tissue path in at least part of said soft tissue;
• and
• defining relationships between the acoustic velocity in bone and the travel times by a set of simultaneous equations, and deriving a value for the acoustic velocity in bone based on a solution of the set of simultaneous equations.