The Minimum Percentage of Triolein Emulsion for Studying Cerebral Vascular Permeability with Least Brain Edema

BACKGROUND Triolein emulsion infusion into the brain produces transiently increased vascular permeability. OBJECTIVES The purpose of this study was to find the minimum percentage of triolein emulsion required for studying vascular permeability with minimal brain edema. MATERIALS AND METHODS Sixty healthy cats were divided into six groups according to the concentration of emulsified triolein infused into the carotid artery: group 1, 0.125% (n = 10); group 2, 0.25% (n = 10); group 3, 0.5% (n = 10); group 4, 1% (n = 10); group 5, 2% (n = 10); and group 6, saline infusion (control group, n = 10). T2-, T1- and contrast enhanced T1-weighted MR images were obtained 2 hours after infusing triolein emulsion. Contrast enhancement ratios (CERs) and signal intensity ratios (SIRs) versus contralateral hemispheres were calculated. Statistical analysis was performed by analysis of variance followed by Tukey's test. P values of ≤ 0.05 were considered significant. RESULTS The lesion hemispheres showed mild hyperintensity due to edema on T2-weighted images, and contrast enhancement on post-contrast T1-weighted images in cats of group 1-5. CERs showed statistically significant differences between the control group and group 3 (P = 0.006), group 4 (P = 0.003), and group 5 (P < 0.001). However, SIRs were significantly different between the control group and group 5 only (P < 0.001). CONCLUSION The minimum concentration of triolein emulsion required to increase vascular permeability adequately with minimal brain edema in a cat model was 0.5%.