Accuracy of conventional x-ray CT and 67Ga-emission CT (Ga-ECT) in diagnosing primary lung cancer

We evaluated the ability of X-ray CT and Ga-ECT to assess primary lung cancer on 100 operated cases. (I) T factor: X-ray CT was of great value in assessing the extension of the tumor to the surrounding organ such as heart, great vessels and thoracic wall. But, because of its poor ability to recognize the tumor itself in surrounding atelectasis or pneumonia and to identify interlobar fissures or diaphragm, overall accuracy of the X-ray CT to assess the T factors remained to be the low value of 67%. (II) N factor (concerning the mediastinal nodes): X-ray CT shown the high sensitivity to detect the lymphonodes swollen over 11 mm of diameters irrespective of the region, but in terms of the malignant involvements of the nodes, X-ray CT revealed overall accuracy of 70% (sensitivity 71%, specificity 70%) mainly because of non malignant lymphonodes swellings. For this reason, we performed Ga-ECT on the recent 27 cases in addition to the conventional X-ray CT. By combining the informations of the two methodes, our ability to diagnose the malignant involvements of the mediastinal nodes improved to be 85% of overall accuracy (Sensitivity 71%, Specificity 89%). That is, abnormal accumulation of Ga to the normal mediastinum on Ga-ECT images and non malignant lymphonodes swellings on X-ray CT images could be diagnosed as metastasis free by adding the informations of the another method each other. (author)