Disappearance of soft tissue 99mTc diphosphonate activity following radiation therapy.

The appearance of soft tissue concentrations of technitium labeled phosphate compounds has been observed in a variety of pathological conditions. The mechanism and pathophysiology of this phenomenon remain unclear.Seven new patients diagnosed with lung cancer received (99m)Tc diphosphonate bone scans during the period of January 1975 to November 1975. Three of the seven subjects showed a significant accumulation of isotope in the region of the chest infiltrate at the time of diagnosis. Upon repeat technitium bone scans six months post radiation, two patients showed a sharp reduction in the soft tissue activity previously observed.The material is presented and a possible explanation of this phenomenon is offered.