[High uptake of N-isopropyl-p-[123I]-iodoamphetamine (123I-IMP) demonstrated by dynamic SPECT in some cases of glioma].

Selective high uptake of N-isopropyl-p-[123I]-iodoamphetamine (123I-IMP) in the brain tumors is not common, the mechanism of uptake in the brain tumor is not yet clearly understood. Among 26 cases of gliomas investigated by dynamic SPECT, 4 cases including 2 cases of anaplastic astrocytoma and 2 cases of oligodendroglioma, showed high uptake of 123I-IMP. New three detector type camera which enables us to investigate rapid successive scanning, was used in our study. In dynamic SPECT, 15 successive scans of 2 minutes interval were made for 30 minutes after administration of 123I-IMP. In addition, quick dynamic SPECT was tried in 2 cases, in which 10 quick successive scans of 24 seconds interval were investigated for initial 4 minutes immediately after administration of 123I-IMP. Radioactivity in the region of interest inside the tumor (T) and radioactivity of the corresponding site in the contralateral hemisphere (C) was measured respectively, and T/C ratio was calculated. Time course change of radioactivity (time activity curve: TAC) was analyzed in all cases. Radioactivity was always higher in the tumor and the average T/C ratio was 1.40. TAC showed rapid increase of 123I-IMP in the tumor during initial 2 minutes after administration and keeping its high plateau level for 30 minutes. Angiography in these cases revealed a remarkable tumor stain. On the other hand, these gliomas showed no or slight enhancement effect in CT or MRI. These findings are interpretable as that early high uptake of 123I-IMP in some gliomas is attributable to an increased vascular bed and blood flow with no or minimal derangement of blood brain barrier in these tumors.