[Kinetics and clinical application of 99mTc-technegas].

Biological characteristics and clinical utilization of 99mTc-technegas were evaluated in three normal volunteers and 10 patients with various pulmonary diseases. 99mTc-pertechnetate (296 MBq (8 mCi] was injected in the crusible of 99mTc-technegas generator, and about 37 MBq (1 mCi) of 99mTc-technegas was inhaled in the lung by three times of deep inspiration. Blood activity was appeared immediately after inhalation of 99mTc-technegas and it was 0.2% of the inhaled dose/liter of blood after 2 hours. Urine activity was also increased after inhalation and cumulative dose was 4.96% of the inhaled dose after 24 hours. The tracer dose to distribution to the lung was about 95% of the total dose in whole body. Biological half time of 99mTc-technegas in the lung was 135 hours and pulmonary image was stable even after 24 hours. Radiation dose to the lung was 0.004 Gy/37 MBq (1 mCi). In patients with pulmonary disease, distribution of 99mTc-technegas was similar to that of 81mKr gas, although defect on 99mTc-technegas image was larger in severe obstructive disease. 99mTc-technegas study was superior over 133Xe gas study to identify the areas of ventilation abnormality more clearly, although quantitative evaluation was difficult in 99mTc-technegas study. On comparative study with 99mTc-aerosol, 99mTc-technegas distributed in more peripheral sites and both methods were cooperative for evaluation of ventilatory disturbance. These results suggest that 99mTc-technegas inhalation study is safe and useful method for ventilation study.