The intensity of {TAIL ~ the reflective ultrasonic signals} is used to determine {HEAD ~ the location} of a preselected body structure 
The intensity of { TAIL ~ the reflective ultrasonic signals } is used to determine { HEAD ~ the location } of a preselected body structure
OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH