Because of the common etiologic factor, such as smoking, lung cancer and chronic obstructive Pulmonary disease are often present in the same patient. The preoperative prediction of remaining pulmonary function after the resectional surgery is very important to prevent serious complication and postoperative respiratory failure. ^99mTc-MAA perfusion scan has been used for the prediction of postoperative pulmonary function, but it may be inaccurate in case of large V/Q mismatching. We compared ^99mTc-DTPA radioaerosol inhalation scan with ^99mTc-MAA perfusion scan in predicting postoperative lung function.

Preoperative inhalation scan and/or perfusion scan were performed and pulmonary function test were performed preoperatively and 2 month after operation. We predicted the postoperative pulmonary functions using the following equations. Postpneumonectomy FEV₁=Preop FEV₁x% of total function of lung to remain

1) The inhalation scan showed good correlations between measured and predicted FEV₁, FVC and FEF_25-75%. (correlation coefficiency; 0.94, 0.91, 0.87 respectively). 2) The perfusion scan also showed good correlations between measured and predicted FEV₁, FVC and FEF_25-75%. (correlation coefficiency; 0.86, 0.72, 0.97 respectively). 3) Among three parameters, FEV₁ showed the best correlations in the prediction by lung scans. 4) Comparison between inhalation scan and perfusion scan in predicting pulmonary function did not show any significant differneces except FVC.

The inhalation scan and perfusion scan are very useful in the prediction of postoperative lung function and don't make a difference in the prediction of pulmonary function although the former showed a better correlation in FVC.