It works on the principle that most of {TAIL ~ the scattered radiation} enters the image receptor at {HEAD ~ an angle} somewhat different from the original path 
It works on the principle that most of { TAIL ~ the scattered radiation } enters the image receptor at { HEAD ~ an angle } somewhat different from the original path
OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH