Bone-to-bone, joint-to-bone and joint-to-joint ratios in normal and diseased skeletal states using region-of-interest technique and bone-seeking radiopharmaceuticals.

Bone-to-bone, iliosacral joint-to-os sacrum and joint-to-joint ratios were computed using the region-of-interest technique 2 to 3 hrs. after injection of 99mTc Sn-methylene-diphosphonate or 99mTc Sn-pyrophosphate in 139 patients with skeletal diseases (bone tumours, degenerative changes of the spine and joints, inflammatory changes of joints) as well as in 123 patients with normal skeletal states. In the latter group, iliosacral joint-to-os sacrum ratios decreased with increasing age of the patients. In patients with osseous metastases of the spine ratios of 0.80 to 4.0 occurred ( reference area second vertebra below or above the affected vertebra). In degenerative changes of the spine values of 0.80 to 1.69 were computed. These results show, that 74% of the spine metastases could not be differentiated from benign changes of the spine by determining their relative amounts of bone uptake. In bone tumours of the extremities and in rheumatoid or gouty arthritis of the small joints (hands and feet) the highest ratios, i.e. contrasts, occurred referring to a contralateral reference area. Osteoarthritic and inflammatory alterations of the big joints could not be differentiated because of percentual distribution of the increased joint-to-joint ratios turned out to be nearly identical.