Prolonged lung retention of 123I-IMP in pulmonary fibrosis.

We compared radiographic findings and the retention of N-isopropyl- p[123I]-iodoamphetamine (123I-IMP) in 23 patients with pulmonary fibrosis. During the 30 minutes following a rapid injection of 55.5 MBq of 123I-IMP into the antecubital vein, the image of regional activity was stored. After this, 185 MBq of 99mTc-MAA was injected and its image was stored to determine the region of interest. The half time (T1/2) of 123I-IMP release from the lung was calculated in each pixel between 10 and 25 minutes after the injection. Chest roentgenograms were taken, and the lung field was divided into 6 portions (right upper, middle and lower, and left upper, middle and lower). A quantitative score was assigned to the radiographic finding (X-ray score). The T1/2 values in the above patients were longer than the T1/2 values in normal subjects. Prolonged T1/2 values were observed in the lung fields which had high X-ray scores. The X-ray scores and the T1/2 values in corresponding areas had a positive relation.