Therefore, {TAIL ~ grid structure} that has a high percentage of {HEAD ~ open area}, but with walls that are highly attenuating for x rays at the appropriate energy is an efficient geometry for this purpose 
Therefore , { TAIL ~ grid structure } that has a high percentage of { HEAD ~ open area } , but with walls that are highly attenuating for x rays at the appropriate energy is an efficient geometry for this purpose
OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH