M Rosenstreich | PubMed Health

PubMed1975

Indium-113m-labeled polyfunctional phosphonates as bone-imaging agents.

Indium-113m complexed with polyfunctional phosphonates EDTMP (an analog of EDTA with carboxylic groups replaced by phosphate groups) and DTPMP (an analog of DTPA) showed preferential skeletal localization in experimental animals. Excellent images of the rabbit skeleton were obtained with both 113mIn and 111In complexes using the scintillation camera. In tissue radioassay using 85Sr as a simultaneous biologic standard, 113mIn-EDTMP compound showed higher concentration in the skeleton than the DTPMP complex and its bone uptake was comparable to that of 85Sr. Renal excretion was greater for the DTPMP complex (70% vs. 50% for EDTMP at 4 hr) and its blood clearance was faster than EDTMP. EDTMP was found to be the superior agent also to two other polyfunctional phosphonates, NTMP and HMDTMP. Because of the excellent skeletal localization with minimal soft-tissue levels, 113mIn-EDTMP may find use in bone scanning in humans wherever 99mTc bone-imaging agents are not available. These compounds may prove useful also in demonstrating acute myocardial infarcts, particularly for repeat studies after 99mTc bone agents have already been administered.

Animals↗

PubMed1975

Technetium-99m-labeled stannous imidodiphosphate, a new radiodiagnostic agent for bone scanning: comparison with other 99mTc complexes.

Imidodiphosphate (IDP) is an analog of pyrophosphate and diphosphonate, with a P-N-P bond instead of P-O-P or P-C-P. We have labeled IDP with 99mTc quantitatively (98%) using stannous ions as the reducing/complexing agent in a freeze-dried kit form. Radiobioassay of this compound was carried out in rabbits and the results were compared with those of eight other Tc-labeled bone-imaging agents, using the performance of simultaneously administered 85Sr as a reference standard. The 99mTc-IDP concentrated 20% higher in the bone, and its soft-tissue and blood levels were lower than with 85Sr. By comparison, the concentrations in the bone of the other 99mTc agents were 20% less than that of 85Sr. Regarding blood levels, Tc-IDP performed worse than the Tc-diphosphonate but better than the pyrophosphate and the other technetium complexes. Scintillation camera images of 99mTc-IDP in both rabbits and dogs showed excellent details of the skeleton. In a preliminary human study, images with 99mTc-IDP were somewhat inferior to those comparably procured with 99Tc-methylene diphosphonate, but count rates with the IDP complex were about twice those with the MDP compound. Because of its better bone uptake, however, it is suggested that 99mTc-IDP may be clinically useful in spite of its relatively slow blood clearance.

Adult↗