Pathophysiologic interpretation of time activity curves in dynamic bone imaging.

Reported here is a theoretical model based on a literature review correlating the 60 sec/25 min time activity curves (TAC) of dynamic bone imaging with the histologic components of bone. Information regarding healing versus nonhealing as well as a histophysiologic description of ongoing disease is obtainable from TACs of paired disease and nondiseased limbs. The TACs reflect the movement of Tc-99m MDP complexes across histologic compartments to reach the amorphous calcium phosphate (ACP) regions. These complexes must exit the bone capillaries, pass through the perivascular space, cross the osteoblastic barrier, enter the bone fluid space, and traverse collagen osteoid to reach ACP. The presence of diseases such as osteomyelitis, cellulitis, and degenerative arthritis and septic arthritis variously affect these spaces to cause typical perturbations in the TACs. The distinction of these patterns were observed in 48 patients, 12 per category. The model that explains how 60 sec/25 min TACs can reflect the histologic status of ongoing bone disease was applied to these disorders.