A computer assisted comparison of 99Tcsup(m)-methylene-diphosphonate and 99Tcsup(m)-pyrophosphate bone imaging

A total of 350 patient studies were carried out using clinical trials' batches of the Technetium (MDP) agent for bone scintigraphy (The Radiochemical Centre), and a commercially available Technetium pyrophosphate agent (CIS). The bone seeking properties of 99Tcsup(m) Sn-methylenediphosphonate (MDP) and 99Tcsup(m) Sn-pyrophosphate (PYP) were evaluated by their comparative uptake in compact bone, cancellous bone and soft tissue using a region-of-interest technique. From these data uptake ratios were computed in order to correlate the values with (a) the amount of 99Tcsup(m)-MDP injected, (b) the time after injection and (c) the age of patient examined. All ratios derived with 99Tcsup(m)-MDP were superior to those using 99Tcsup(m)-PYP and were not dependent on the amount of 99Tcsup(m)-MDP injected. Uptake ratios determined for 99Tcsup(m)-MDP (1.5 h to 2.5 h after injection) were found to be higher than those for 99Tcsup(m)-PYP 2.5 to 3.5 h after injection. Soft tissue accumulation of 99Tcsup(m)-MDP, visible on scintiphotos, occurred only in 26% of cases but with 99Tcsup(m)-PYP, in 75% out of all cases studied. A decrease of cancellous bone/compact bone ratios with increasing age of the patients was found with both radiopharmaceuticals. This is most probably correlated with a diminished mass and/or surface of the cancellous bone in the elderly patient. (author)