EFFECT OF STEROIDS ON IOPAMIDOL BLOOD-BRAIN TRANSFER CONSTANT AND PLASMA-VOLUME IN BRAIN-TUMORS MEASURED WITH X-RAY COMPUTED-TOMOGRAPHY

Tumor blood-brain transfer constant of iopamidol (K) and plasma volume (V-p) were measured in 10 patients with primary brain tumors before a nd after 7 days of dexamethasone treatment (4 x 4 mg per oral per day) using X-ray computed tomography. Both K and V-p decreased significant ly after dexamethasone treatment with p < 0.01 and 0.09 respectively a ccording to one-tail paired t-test. The mean percentage decrease in K and V-p was 32% and 10% respectively. Functional images of the two par ameters before and after treatment were generated and showed clearly t he effect of steroids on the reduction of K in brain tumors. In contra st, when before and after treatment contrast enhanced CT scans were co mpared, no difference was observed in the enhancement in 8 out of 10 c ases. The result obtained support the conclusion that: (1) corticoster oids reduce the blood-brain permeability to small hydrophillic molecul es; (2) the X-ray computed tomography method we have developed can be used to measure the K and V-p response of brain tumors to steroid ther apy; and, (3) ordinary contrast enhanced CT scans at one fixed time or multiple times after contrast injection are not sensitive in detectin g the reduction of K due to steroids.