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