This study was performed to investigate lesions with ring-like thallium-201 (201Tl) uptake and to determine whether SPECT provides any information in differential diagnosis.
Methods: A total of 244 201Tl SPECT images were reviewed. In each study, early (15 min postinjection) and late (3 hr) brain SPECT images were obtained with 111 MBq of 201Tl. The early uptake ratio (ER; lesion to normal brain average count ratio) and the late uptake ratio (LR) and the L/E ratio (ratio of LR to ER) were calculated.
Results: Ring-like uptake was observed in pre-therapeutic 26 SPECT images, including ten glioblastoma multiformes (ER, 3.45 +/- 0.64; LR, 2.74 +/- 0.54; L/E ratio 0.80 +/- 0.13), five meningiomas (6.48 +/- 2.34; 4.41 +/- 1.41; 0.72 +/- 0.19), four metastatic lung cancers (3.47 +/- 1.23; 2.40 +/- 0.98; 0.70 +/- 0.14), four brain abscesses (2.48 +/- 1.06; 1.59 +/- 0.30; 0.78 +/- 0.15), one invasive lesion of squamous cell carcinoma from the ethmoid sinus (1.54; 1.52; 0.99), one medulloblastoma (3.53; 3.52; 1.00) and one hematoma (3.32; 2.36; 0.71). The ER of meningioma was significantly higher than those of glioblastoma multiforme (p < 0.0005), metastatic lung cancer (p < 0.005) and brain abscess (p < 0.0005). There were no significant differences among these three entities. The LR of meningioma was significantly higher than those of glioblastoma multiforme (p < 0.005), metastatic lung cancer (p < 0.005) and brain abscess (p < 0.0001). The LR of brain abscess was significantly lower than that of glioblastoma multiforme (p < 0.05). The L/E ratio could not differentiate these four entities.
Conclusion: High ER and high LR in a lesion with ring-like uptake is likely an indicator of meningioma. The LR of brain abscess was significantly lower than that of glioblastoma multiforme, but 201T1 SPECT has still difficulty in differentiating abscess from brain tumor.