[Quantitative assessment of the usefulness of MR-fusion Tl-SPECT image in the diagnosis of brain tumor].

201Tl-SPECT (single photon emission computed tomography) had a disadvantage of low spatial resolution with a limited ROI (region of interest) setting. Recently, the diagnosis of brain tumors has been improved by fusion-imaging employing MRI (magnetic resonance imaging) with Tl-SPECT. In order to assess the usefulness of MR-fusion Tl-SPECT quantitatively, we have compared non-fusion (NF) and MR-fusion (MR-F) imaging with Tl-SEPCT in patients with brain tumors. A total of 38 patients (M/F=14/24) hospitalized at our institution during a 5-year period, each with a histologically confirmed brain tumor, were studied. The index of Tl was used for the early ratio (ER), delayed ratio (DR), and retention index (RI), There was no significant difference between NF and MR-F, which were examined using the test-retest method by 2 observers (N&H), but the Pearson's correlation coefficient was higher for MR-F than for NF. The RI value for MR-F was significantly correlated with the WHO histological grading (r=0.605, n=38, p<0.00l). The DR value for MR-F was significantly correlated with MIB-1 index (r=0.464, n=24, p=0.022). We estimated the RI cut-off value for both NF and MR-F in malignancy by ROC analysis. A cut-off value of RI=0.63 and RI=0.70 was good for NF and MR-F, respectively. The likelihood ratio (LR) of RI was higher for MR-F (LR=6.897) than for NF (LR=2.978), suggesting that RI=0.7 for MR-F was suitable for diagnosis of malignant brain tumor. We conclude that MR-fusion Tl-SPECT is better for quantitative analysis of brain tumors than non-fusion Tl-SPECT.