Single photon emission computed tomography usingTl chloride in pulmonary nodules: Comparison withGa citrate andTc-labeled hexamethyl-propyleneamine-oxime

A single photon emission computed tomography (SPECT) withTl chloride (Tl-201) was carried out prospectively in 50 patients with pulmonary nodules and its diagnostic value was compared with those ofGa citrate (Ga-67) andTc-labeled hexamethyl-propyleneamineoxime (Tc-99m-HMPAO). Tl-201 SPECT provided 88% (early)--91% (delayed) sensitivity, 85% (early and delayed) specificity and 87% (early)--89% (delayed) accuracy. The sensitivity of the Tl-201 planar image was 56 (early)--62% (delayed), which was significantly lower than that of SPECT. Delayed SPECT images at 2 hour postinjection were more preferable to disclose the malignant pulmonary nodule than early SPECT images at 15 minutes postinjection. The application of SPECT with Ga-67 failed to improve the sensitivity of planar imaging for malignant pulmonary nodules. Tc-99m-HMPAO was concentrated in 62% of 13 patients with malignant pulmonary nodules, which was slightly higher than Ga-67 in 54% of 28 patients. In an analysis of the histologic types of lung cancer, the sensitivity of Tl-201 was not significantly different in all types. On the other hand, Ga-67 was positive only in 25% of 12 patients with adenocarcinoma.