To compare diagnostic ability of thallium-201 SPECT for brain tumor between quantitative evaluation, semi- quantitative evaluation and ADC values upon MRI.

Aim: Thallium-201 single-photon emission computed tomography (SPECT) and diffusion-weighted imaging (DWI) of magnetic resonance imaging (MRI) are reliable imaging modalities for differential diagnosis of brain tumors. Here we compare thallium scintigraphy with quantitative evaluation for the diagnosis of brain tumor between standardized uptake values (SUV), semi- quantitative evaluation [early uptake ratio (ER), delayed uptake ratio (DR), and retention index (RI)], and ADC values were measured by MRI.Methods: We included 26 cases (male 14, female 12) who underwent thallium-201 brain SPECT with pathologically proven histology and had not received any therapy before the examination. SPECT images were obtained during the early (15 min) and delayed (3 h) phases after intravenous injection. The mean count of the region of interest in the tumor and background in both early and delayed images was measured. ER and DR (lesions/background) and RI were calculated. For early and delayed phases, maximum SUV (SUVmax) was calculated with vendor-provided quantitative software (G.I. Bone Mediphysics, Japan). Furthermore, early and delayed SUVratio(lesion/background) and RI-SUV (delayed SUVratio/early SUVratio) were calculated. The minimum apparent diffusion coefficient (ADCmin) and average apparent diffusion coefficient (ADCave) as measured by DWI of MRI were also evaluated.Results: There were significant differences between tumor malignancy groups (WHO grade I-II vs. WHO grade III-IV) in ER, DR, RI, and SUVmax (p = 0.037). Moreover, in the differential diagnosis of brain tumor, delay SUVmax ratio performed differently for glioblastoma and malignant lymphoma (p = 0.017). No significant difference was observed for semi-quantitative assessment (ER, DR, and RI) or ADC value.Conclusion: Quantitative assessment of thallium-201 brain scintigraphy is useful for predicting grade according to the WHO brain tumor classification. The results presented here show that thallium-201 brain scintigraphy is more effective than existing methods for differentiating brain tumors according to the pathological type.