{HEAD ~ An effective amount} of a photosensitive agent for PDT is administered to {TAIL ~ a patient} 
is administered to
{ HEAD ~ An effective amount } of a photosensitive agent for PDT is administered to { TAIL ~ a patient }
HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL