Serial magnetic resonance imaging (MRI) on experimental brain edema in rats

Proton nuclear magnetic resonance imaging was performed in rat brains in vivo with an investigational device. The unit employed a permanent magnet, at a field strength of 0.2 Tesla, and was capable of Spin Echo and Inversion Recovery images with a slice thickness of 2 or 4 mm. The pixel dimensions were 0.3 x 0.3 mm. The images were obtained from the adult male Wistar rats suffering from the cryogenic injury-induced edema from about 30 min, to 14 hours after production of the lesion. The pathological changes in the cortex of rats were depicted 30 min. after injury on a T2-weighted image and reached a maximum in 8 - 12 hours. The pathological changes in white matter temporarily appeared 30 min. after injury on a T2-weighted image. This changes disappeared in 2 hours and re-appeared in 3 hours. This intensity area rapidly spreaded to reach a maximum in 8 - 10 hours. Edematous region on T1-weighted images seems to be smaller than on T2-weighted images in all stages of vasogenic brain edema. T2-weighted images were more sensitive than T1-weighted images on experimental brain edema. MRI does not always demonstrate an increase of the water content of the brain. (author)