DIAGNOSIS OF LUNG-CANCER USING 2-PHASE TL-201 SPECT AND MODIFIED RETENTION IMAGE TO VIEW TUMOR IN THE COLLAPSED LUNG - COMPARISON WITH BOLUS CT

In this report the usefulness of Tl-201 SPECT and modified retention i mages in the differentiation of lung cancer and postobstructive collap se was studied. Two-phase Tl-201 SPECT was performed in 20 lung cancer lesions in which postobstructive collapse was suspected on CT. Retent ion imaging was done afterward. Three types of Tl-201 images were comp ared with the bolus CT images. Bolus CT differentiated lung cancer fro m postobstructive collapse in 7 of the 20 lesions (35%). Tl-201 SPECT differentiated the two conditions in 9 of 20 lesions (45%) on early Tl -201 SPECT and in 13 of 20 lesions (65%) on delayed imaging. With modi fied retention images, differentiation was possible in 13 of 20 lesion s (65%). By combining delayed Tl-201 SPECT and modified retention imag es, lung cancer alone could be demonstrated in 18 of 20 lesions (90%). Combined delayed Tl-201 SPECT and modified retention images were more effective than bolus CT in delineating the extent of lung cancer in t he presence of postobstructive collapse.