Differential diagnosis in patients with ring-like thallium-201 uptake in brain SPECT

Abstract

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 244²⁰¹Tl SPECT images were reviewed. In each study, early (15 min postinjection) and late (3 hr) brain SPECT images were obtained with 111 MBq of²⁰¹Tl. 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, but²⁰¹Tl SPECT has still difficulty in differentiating abscess from brain tumor.