The lead provides for efficient attenuation of x rays, and {HEAD ~ the high percentage} of open area provides for {TAIL ~ unrestricted passage} of the desired imaging x rays 
provides for
The lead provides for efficient attenuation of x rays , and { HEAD ~ the high percentage } of open area provides for { TAIL ~ unrestricted passage } of the desired imaging x rays
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH