[Clinical evaluation of lung scintigraphy with 99mTc-technegas]

The aim of this study is to evaluate the safety and clinical usefulness of lung scintigraphy using 99mTc-technegas produced by the evaporation of pertechnetate elution at 2500 degrees C. Lung images were recorded by the gamma camera-computer system after a few deep inspirations of 99mTc-technegas. One healthy volunteer and 32 patients including 10 with lung cancer, 8 with chronic obstructive lung disease, 5 with pulmonary embolism, 2 with interstitial pneumonia, 2 with bronchiectasis and 12 with other various disease were studied. Delayed images were taken at more than 1 hour later in one healthy and 13 patients to investigate the interval changes of the intrapulmonary distribution of 99mTc-technegas. Obvious differences of radioactive distribution between early and delayed image were observed in only 2/14 cases. Penetration index (P.I.) averaged 0.81 +/- 0.11 for early images and 0.85 +/- 0.12 for delayed image. There was no significant difference between P.I. for early and delayed images. More than 97 MBq of 99mTc-macroaggregated albumin (99mTc-MAA) were required to obtain the adequate perfusion images after the acquisition of lung images with about 37 MBq of 99mTc-technegas. Bronchial deposits of 99mTc-technegas were shown in 12/33 cases and pathological defects in 26/32 patients (81.3%). Twenty three of 33 cases also had a perfusion scintigraphy with 99mTc-MAA. Ventilation perfusion mismatches were presented in 5/5 patients with pulmonary embolism and 1/10 patients with lung cancer. The safety was confirmed in all cases and clinical usefulness in 30/32 patients (94%). In conclusion, the safety and clinical usefulness of lung scintigraphy with 99mTc-technegas were proven in this study.