RESUMEN
In 20 primary patients with focal abnormalities on conventional CT we evaluated diagnostic properties of simultaneous double-tracer SPECT. Scintigraphy was performed as a single examination with simultaneous registration of 67Ga and 99mTc-MIBI. Image acquisition was started 48-74 hours after IV injection of 130-175 MBq 67Ga-citrate and immediately after IV injection of 500-740 MBq of 99mTc-MIBI. All images for each agent were classified as positive and negative for primary tumor, N1 and N2 lymph-nodes (LN). According to histology 18 of 20 evaluated patients had non-small cell lung cancer (NSCLC), the other two patients had tuberculosis and nonspecific inflammation. SPECT with 99mTc-MIBI correctly visualized tumor in 18, 67Ga allowed correct visualization in 16 cases. Both tracers were truly negative in a patient with tuberculosis and false positive in a patient with nonspecific inflammation. Double-tracer SPECT was slightly more specific than CT in primary lesions. In 18 patients histological verification of LN status was obtained: NO was revealed in 9 cases, N1 in 4 and N2 in 5 cases. Both tracers correctly discriminated LN-positive and LN-negative cases with 94% specificity. On the contrary, CT was false-positive in 3 and false-negative in another 5 patients. Differentiation between N1 and N2 LN involvement is crucial for therapy planning. 99mTc MIBI and 67Ga revealed N1 in 2 cases and N2 in 4 cases, the diagnosis was later verified by postoperative morphology. In 2 patients SPECT overestimated extent of LN involvement and LN status was changed after surgery from N2 to N1. In 18 patients results of 99mTc-MIBI and 67Ga augmented each other. Accuracy of LN staging by SPECT with 99mTc-MIBI and 67Ga was 83%. CT accurately determined LN stage only in 7 patients, it was overestimated in 7 and underestimated in 4 cases. SPECT with 99mTc-MIBI and 67Ga demonstrated high overall accuracy in diagnostics of regional LN invasion for patients with NSCLC. Diagnostic value of conventional CT was significantly lower. Correct level of LN involvement was determined by SPECT in 83% of cases.
