title: Effect of steroids on iopamidol blood-brain transfer constant and plasma volume in brain tumors measured with X-ray computed tomography.
abstract: Tumor blood-brain transfer constant of iopamidol (K) and plasma volume (Vp) were measured in 10 patients with primary brain tumors before and after 7 days of dexamethasone treatment (4 x 4 mg per oral per day) using X-ray computed tomography. Both K and Vp decreased significantly after dexamethasone treatment with p < 0.01 and 0.09 respectively according to one-tail paired t-test. The mean percentage decrease in K and Vp was 32% and 10% respectively. Functional images of the two parameters before and after treatment were generated and showed clearly the effect of steroids on the reduction of K in brain tumors. In contrast, when before and after treatment contrast enhanced CT scans were compared, no difference was observed in the enhancement in 8 out of 10 cases. The result obtained support the conclusion that: (1) corticosteroids reduce the blood-brain permeability to small hydrophilic molecules; (2) the X-ray computed tomography method we have developed can be used to measure the K and Vp response of brain tumors to steroid therapy; and, (3) ordinary contrast enhanced CT scans at one fixed time or multiple times after contrast injection are not sensitive in detecting the reduction of K due to steroids.
authors.affiliation: Department of Diagnostic Radiology, St. Joseph's Health Centre, London, Ontario, Canada.
authors.forename: W T
authors.initials: WT
authors.lastname: Yeung
authors.forename: T Y
authors.initials: TY
authors.lastname: Lee
authors.forename: R F
authors.initials: RF
authors.lastname: Del Maestro
authors.forename: R
authors.initials: R
authors.lastname: Kozak
authors.forename: J
authors.initials: J
authors.lastname: Bennett
authors.forename: T
authors.initials: T
authors.lastname: Brown
mesh_terms: D001812:Blood-Brain Barrier / Q000187:drug effects*; D001932:Brain Neoplasms / Q000098:blood supply* / Q000000981:diagnostic imaging* / Q000473:pathology; D003907:Dexamethasone / Q000494:pharmacology*; D005260:Female; D006801:Humans; D007479:Iopamidol / Q000493:pharmacokinetics*; D008297:Male; D008433:Mathematics; D008577:Meningeal Neoplasms / Q000098:blood supply / Q000000981:diagnostic imaging; D008579:Meningioma / Q000098:blood supply / Q000000981:diagnostic imaging; D008875:Middle Aged; D008954:Models, Biological; D012039:Regional Blood Flow / Q000187:drug effects; D014057:Tomography, X-Ray Computed
chemical_list: D003907:Dexamethasone; D007479:Iopamidol