The diagnostic value of I-123-IMP SPECT in non-Hodgkin's lymphoma of the central nervous system

N-isopropyl-p[I-123]iodoamphetamine (IMP) SPECT is of low diagnostic value in patients with brain tumors, because brain tumors are visualized as uptak e defects. Some reports have described non-Hodgkin's lymphoma of the centra l nervous system (CNS) as showing high uptake on delayed I-123-IMp SPECT im ages, suggesting its usefulness in diagnosing CNS lymphoma. In this study, we investigated the clinical value of I-123-IMP SPECT as a diagnostic tool for CNS lymphoma. Methods: Ninety-six patients with brain tumors, including 12 patients with CNS lymphoma, underwent I-123-IMP SPECT. Eleven patients had primary CNS lymphoma, and 1 had a parenchymal brain metastasis from a b reast lymphoma. The total number of lesions was 18, 14 of which were in the cerebral parenchyma, 3 in the brain stem, and 1 in the ventricle. Early SP ECT images were initiated 15-30 min after intravenous injection of 111 MBq I-123-IMP, and delayed images were collected 4 h later. SPECT images were v isually analyzed with a color-grading scale. Tumor-to-normal activity ratio (T/N) and tumor-to-cerebellum activity ratio (TIC) were calculated for bot h early and delayed images for semiquantitative analysis. Results: By visua l estimation, more than a 3-cm(3) volume of CNS lymphoma was detected as an obvious focus of increased accumulation on delayed images. All other brain tumors tested appeared as decreased accumulation on delayed images. T/Ns a nd T/Cs on delayed images of CNS lymphomas, including tumors less than 3 cm (3) in volume, were 1.48 +/- 0.42 and 1.08 +/- 0.16, respectively. These ra tios in patients with glioma (0.30 +/- 0.05 and 0.31 +/- 0.07 respectively) or meningioma (0.34 +/- 0.10 and 0.41 +/- 0.17, respectively) showed a sig nificant difference from those in patients with CNS lymphoma (P < 0.0005). Conclusion: I-123-IMP SPECT is a helpful tool for diagnosing CNS lymphoma.