[Evaluation of brain tumors by simultaneous dual isotope SPECT with 201Tl-chloride and 99mTc-MIBI]

Single photon emission computed tomography (SPECT) is useful for detecting brain tumors. In this study, we evaluated the utility of simultaneous dual SPECT with 201Tl-Chloride (Tl) and 99mTc-MIBI (MIBI) for diagnosis of brain tumors. We evaluated 20 cases, including 2 glioblastomas, 7 anaplastic astrocytomas, 2 oligodendrogliomas, 2 anaplastic ependymomas, 2 medulloblastomas, 2 meningiomas, 1 malignant meningioma, 1 pituitary adenoma, and 1 craniopharyngioma. We analyzed the uptake ratio (T/N ratio) of tracers in both Tl and MIBI at max counts/pixels ratio in the region of interest. The T/N ratios in early and delayed images were described as early ratios (ER) and delay ratios (DR), respectively. The retention index (RI) was calculated as the DR/ER ratio. Significant correlations were found between ER and DR for both Tl (DR = 0.797 * ER + 0.359, r = 0.871), and MIBI (DR = 0.961 * ER - 0.191, r = 0.784). Next, we analyzed the correlations between Tl and MIBI SPECT, for ER, DR, and RI. ER values for the two were strongly correlated (r = 0.791), DR values were weakly correlated (r = 0.556), and RI exhibited no correlation between them (r = 0.328). There were no correlations between tumor volume and T/N ratio for the two (ER-Tl; r = 0.0095, DR-TI; r = 0.0050, ER-MIBI; r = 0.036, DR-MIBI; r = 0.254). Lastly no correlation was found between RI-Tl and RI-MIBI (r = 0.328). We discuss the difference in the mechanism of accumulation of two tracers and the significance of simultaneous dual SPECT using them for the differential diagnosis of pituitary tumors, regrowth of oligodendrogliomas, and multidrug resistance of chemotherapy. Dual SPECT with Tl and MIBI appears to be useful for the diagnosis of brain tumor.