Pulmonary uptake in indium-111-antimyosin fab fragment imaging following human cardia transplantation

Recent studies suggest that cardiac uptake of {sup 111}In-labeled antimyosin monoclonal antibody may be estimated semiquantitatively by calculating a heart-to-lung activity ratio, with pulmonary uptake serving as a reference region. The authors obtained 96 {sup 111}In-antimyosin scintigraphs to monitor rejection occurrence after heart transplantation in 26 patients. On five scintigraphs, the count rate density in ROIs over the lungs was markedly higher (mean 53% higher) than that in the immediately preceding and following scintigraphs, whereas the activity in the heart was essentially unchanged. Four of these scintigraphs coincided with ongoing pulmonary infection and the fifth with an occurrence of a high anti-CMV titer. The mechanism of apparent nonspecific antimyosin accumulation in the lungs is uncertain, although increased capillary permeability may be one possibility. Attention should be given to activity in the lungs if this activity is used as a reference in studies of {sup 111}In-antimyosin uptake in the heart. 15 refs., 3 figs., 1 tab.