123I-IMP clearance of the lung with diffuse lung disease

N-isopropyl-I-123-p-iodoamphetamine (123I-IMP) is taken up by the capillary endothelial cells during the first pulmonary pass and is released from the lung. To evaluate the effect of the 123I-IMP retention on diffuse lung disease, we studied prolonged 123I-IMP clearance from lung in 5 non-smoking control volunteers and 15 patients with various diffuse lung diseases. The time-activity curve for 60 min after the injection of 111 MBq of 123I-IMP was described as follows: C(t) = A1e-k1t + A2e-k1t (A1, A2: intercepts; K1, K2: slopes of the exponential components). 123I-IMP clearance was delayed in the patient group and K2 was significantly lower. There was a significant correlation between K2 and Ga-computer activity index on the 67Ga scintigraphy in the patient group. K2 was also correlated with %Dlco on the pulmonary function test. Our study suggests that the delayed clearance and retention of 123I-IMP in the diseased lung are influenced by the pathological activity in the lung lesion.