99mTc complex of hexamethylpropylene amine oxime (99mTc-HMPAO), which has been used as a tracer for regional
cerebral blood flow (rCBF), has been shown to localize in primary brain tumors with wide spectrum of its
uptake. The causes of the wide spectrum of tumor uptake, however, has not been understood in detail. We
performed autoradiographic study with this agent to get further knowledge about HMPAO distribution in 10
cases of transplanted rat gliomas. Eight cases of rat gliomas without tumor necrosis, showed decreased
uptake of 99mTc-HMPAO in the autoradiography (average tumor/normal (T/N) uptake ratio: 0.75, range:
0.40-0.90). On the other hand, two cases with tumor necrosis revealed increased uptakes of this agent
in central necrotic area. T/N uptake ratios of these two cases were 1.23 and 1.42, respectively. In
addition, three patients with histologically proven glioblastoma with tumor necrosis were studied after
administration of 20mCi 99mTc-HMPAO. Two out of three patients showed higher uptake of 99mTc-HMPAO in
tumor necrotic area than the contralateral area. Our findings suggest that the necrotic area of brain
tumor may retain 99mTc-HMPAO and causes an increased uptake.
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