Usefulness of dual isotope 123 I-IMP and 201 Tl SPECT for the diagnosis of primary central nervous system lymphoma and glioblastoma

Background Preoperative differential diagnosis between primary central nervous system lymphoma (PCNSL) and glioblastoma (GBM) is important because these tumors require different surgical strategies. This study investigated the usefulness of dual isotope, iodine-123-labeled N -isopropyl- p -iodo-amphetamine ( 123 I-IMP) and thallium-201 chloride single-photon emission computed tomography ( 201 Tl SPECT) for the differential diagnosis. Methods Twenty-five PCNSL patients and 27 GBM patients who underwent dual isotope imaging, 123 I-IMP and 201 Tl SPECT, are included. Tumor-to-normal (T/N) ratio was calculated from the ratio of maximum tracer counts in the lesion to the mean counts in the contralateral cerebral cortex. The mean and minimum apparent diffusion coefficient values (ADC mean and ADC min, respectively) on magnetic resonance imaging were also analyzed. Results Delayed phase 123 I-IMP SPECT was the most useful imaging examination for the differentiation between PCNSL and GBM compared with early phase 123 I-IMP SPECT, early and delayed phase 201 Tl SPECT, ADC mean , and ADC min . However, the median T/N ratios of PCNSL and GBM were 1.32 and 0.83, respectively, in the delayed phase 123 I-IMP SPECT. On the other hand, the median T/N ratios of PCNSL and GBM were 3.10 and 2.34, respectively, in the delayed phase 201 Tl SPECT, with excellent tumor detection. Conclusion Delayed phase 123 I-IMP SPECT could differentiate between PCNSL and GBM with high accuracy, but T/N ratio was low and tumor detection was poor. 201 Tl SPECT was useful for estimation of the malignancy and localization of the tumors with high T/N ratio. Dual isotope 123 I-IMP and 201 Tl SPECT was useful for the preoperative diagnosis of PCNSL and GBM.