Usefulness of dual isotope I-IMP and 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 (I-IMP) and thallium-201 chloride single-photon emission computed tomography (Tl SPECT) for the differential diagnosis.

METHODS

Twenty-five PCNSL patients and 27 GBM patients who underwent dual isotope imaging, I-IMP and 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 and ADC respectively) on magnetic resonance imaging were also analyzed.

RESULTS

Delayed phase I-IMP SPECT was the most useful imaging examination for the differentiation between PCNSL and GBM compared with early phase I-IMP SPECT, early and delayed phase Tl SPECT, ADC, and ADC. However, the median T/N ratios of PCNSL and GBM were 1.32 and 0.83, respectively, in the delayed phase 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 Tl SPECT, with excellent tumor detection.

CONCLUSION

Delayed phase I-IMP SPECT could differentiate between PCNSL and GBM with high accuracy, but T/N ratio was low and tumor detection was poor. Tl SPECT was useful for estimation of the malignancy and localization of the tumors with high T/N ratio. Dual isotope I-IMP and Tl SPECT was useful for the preoperative diagnosis of PCNSL and GBM.