PULMONARY UPTAKE IN INDIUM-111-ANTIMYOSIN FAB FRAGMENT IMAGING FOLLOWING HUMAN CARDIAC TRANSPLANTATION

Recent studies suggest that cardiac uptake of In-111-labeled antimyosi n monoclonal antibody may be estimated semiquantitatively by calculati ng a heart-to-lung activity ratio, with pulmonary uptake serving as a reference region. Methods: We obtained 96 In-111-antimyosin scintigrap hs to monitor rejection occurrence after heart transplantation in 26 p atients. Results: 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 activit y in the heart was essentially unchanged. Four of these scintigraphs c oincided with ongoing pulmonary infection and the fifth with an occurr ence of a high anti-CMV titer. Conclusion: The mechanism of apparent n onspecific antimyosin accumulation in the lungs is uncertain, although increased capillary permeability may be one possibility. Attention sh ould be given to activity in the lungs if this activity is used as a r eference in studies of In-111-antimyosin uptake in the heart.