IN-VIVO NONINVASIVE DETERMINATION OF ABNORMAL WATER DIFFUSION IN THE RAT-BRAIN STUDIED IN AN ANIMAL-MODEL FOR MULTIPLE-SCLEROSIS BY DIFFUSION-WEIGHTED NMR IMAGING
Mr. Verhoye et al., IN-VIVO NONINVASIVE DETERMINATION OF ABNORMAL WATER DIFFUSION IN THE RAT-BRAIN STUDIED IN AN ANIMAL-MODEL FOR MULTIPLE-SCLEROSIS BY DIFFUSION-WEIGHTED NMR IMAGING, Magnetic resonance imaging, 14(5), 1996, pp. 521-532
In vivo NMR images of the rat brain were obtained using a NMR microsco
pe (7 T) from SMIS (England). Four animals were imaged every 3-4 days
during a pathological cycle (starting after induction and up to 37 day
s) of experimental allergic encephalomyelitis (EAE), an animal model f
or multiple sclerosis. The EAE rats were weighted and clinically score
d daily. We aimed at measuring the apparent diffusion coefficient (ADC
) or the mean diffusivity [D] with a high accuracy, and within a reaso
nable experimental time frame, because of the clinical situation of th
e animals. Therefore, we fitted the ADC value from five diffusion-weig
hted images-with an experimental time of 17 min/image-and chose to app
ly diffusion-sensitizing gradients in a direction intersecting all fib
er directions of the external capsule. With this, we also obtained hig
h b-values. For the control rats, we obtained a statistical mean value
of ADC = (388 +/- 16) 10(-12) m(2)/s for gray matter and a statistica
l mean value of [D] of (750 +/- 30) 10(-12) m(2)/s for white matter, m
easured in the external capsule. For the EAE rats, no alterations in A
DC values of gray matter with increasing clinical scores were observed
. Concerning white matter, as determined in the external capsule, ther
e were no significant differences in [D] values between controls and E
AE rats before clinical signs occurred. However, when clinical signs w
ere observed, we could demonstrate a significant positive correlation
between the clinical score and the [D] values in the external capsule.
As the clinical signs became more severe, we measured a rise in water
diffusion (increase in [D]) in the external capsule, which was accomp
anied by the occurrence of interstitial edema as revealed by a complem
entary histological study.