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Positron emission tomographic measurement of blood‐to‐brain and blood‐to‐tumor transport of 82 Rb: The effect of dexamethasone and whole‐brain radiation therapy
Author(s) -
Jarden Jens O.,
Dhawan Vijay,
Poltorak Alexander,
Posner Jerome B.,
Rottenberg David A.
Publication year - 1985
Publication title -
annals of neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.764
H-Index - 296
eISSN - 1531-8249
pISSN - 0364-5134
DOI - 10.1002/ana.410180603
Subject(s) - positron emission tomography , brain tumor , dexamethasone , nuclear medicine , medicine , radiation therapy , blood–brain barrier , glioma , brain metastasis , whole blood , pathology , metastasis , central nervous system , cancer , cancer research
Unidirectional blood‐to‐brain and blood‐to‐tumor transport rate constants for rubidium 82 were determined using dynamic positron emission tomography in patients with primary or metastatic brain tumors. Regional influx rate constants ( K 1 ) and plasma water volume ( V p ) were estimated from the time course of blood and brain radioactivity following a bolus injection of tracer. Eight patients were studied before and 24 to 72 hours after treatment using pharmacological doses of dexamethasone, and 6 additional patients with metastatic brain tumors were studied before and within 60 to 90 minutes after 200‐ to 600‐rad whole‐brain radiation therapy. Steroid treatment was associated with a 9 to 48% decrease in tumor K 1 and a 21% mean decrease in tumor V p . No consistent changes in K 1 or V p were observed in control brain regions. Tumor K 1 and V p did not increase in patients undergoing whole‐brain radiation therapy, all of whom were taking dexamethasone at the time of study. These data suggest that corticosteroids decrease the permeability of tumor capillaries to small hydrophilic molecules (including those of some chemotherapeutic agents) and that steroid pretreatment prevents acute, and potentially dangerous, increases in tumor capillary permeability following cranial irradiation.