RADIOACTIVE isotopes are being used with increasing frequency to localize brain tumors. Either the locally increased permeability of the blood-brain barrier or the active metabolism of the tumors—it is not at present clear which— causes a higher concentration of some isotopes in the tissue of the neoplasm than in the normal brain. The investigations of Hevesy and Hahn1 showed that only a small fraction of radioactive phosphorus (P32), approximately 0.02% of the total amount, given parenterally, is deposited in the brain. This finding was considered evidence of a slow phosphorus turnover in the central nervous system. Lindberg and I,2 working on the theory that the blood-brain barrier plays a decisive role in this phenomenon, injected P32 directly into the cerebrospinal fluid, bypassing the barrier, and found that this isotope would indeed accumulate rapidly in the brain. After such an injection into the cisterna magna (cisterna cerebellomedullaris)
BAKAY L. STUDIES ON THE BLOOD-BRAIN BARRIER WITH RADIOACTIVE PHOSPHORUS. AMA Arch NeurPsych. 1951;66(4):419–426. doi:10.1001/archneurpsyc.1951.02320100019003
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