{HEAD ~ Various derivatives} of DTPA , including those disclosed herein, are {TAIL ~ preferred chelators} for such ions in compounds according to the present invention 
are
{ HEAD ~ Various derivatives } of DTPA , including those disclosed herein , are { TAIL ~ preferred chelators } for such ions in compounds according to the present invention
HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH