Timing of examination affects reliability of Tc-99m-methoxyisobutylisonitrile SPECT in distinguishing neoplastic from nonneoplastic brain hematomas

99mTc-methoxyisobutylisonitrile (MIBI) SPECT has been reported to be 100% sensitive and specific in the early differential diagnosis between neoplastic and nonneoplastic intraparenchymal cerebral hemorrhage (ICH), because nonneoplastic ICH does not show 99mTc-MIBI accumulation on SPECT examinations performed within 48 h from the onset of clinical symptoms. The aims of this study were to investigate the behavior of nonneoplastic ICH on more delayed 99mTc-MIBI SPECT examinations and to determine how the timing of examination affects the reliability of 99mTc-MIBI SPECT in differentiating neoplastic from nonneoplastic ICH. METHODS: We prospectively enrolled 32 patients with acute neurologic deterioration caused by nontraumatic ICH. Patients were randomly allocated to 4 groups of 8 patients each. Patients in the first, second, third, and fourth groups underwent 99mTc-MIBI SPECT 2, 5, 10, and 30 d, respectively, after the onset of clinical deterioration. Furthermore, patients in the first group underwent a second (99m)Tc-MIBI SPECT examination at 30 d. 99mTc-MIBI SPECT studies were visually and semiquantitatively evaluated. Patients were followed up to confirm the nonneoplastic etiology of the ICH. RESULTS: Two of the 32 studied patients, 1 in the second and 1 in the fourth group, were excluded because the ICH turned out to be related to a neoplastic lesion. Visual analysis showed no 99mTc-MIBI uptake in any patient studied at 2 d, whereas increased radiotracer uptake was found in 1 (14%) of 7, 5 (62.5%) of 8, and 5 (71%) of 7 patients studied 5, 10, and 30 d, respectively, after clinical deterioration. Moreover, with the semiquantitative analysis, a statistically significant difference was found among 99mTc-MIBI indices in the 4 groups (P = 0.0011). All patients in group 1 showed a significant 99mTc-MIBI accumulation when studied at 30 d. CONCLUSION: Nonneoplastic ICH, showing no 99mTc-MIBI uptake within 2 d, can show 99mTc-MIBI accumulation on more delayed imaging. 99mTc-MIBI SPECT can clearly differentiate between neoplastic and nonneoplastic ICH only during the acute phase. Our findings suggest that examination be performed early after the onset of symptoms and certainly within 5 d