Angelika Hoffmann1, Xavier Helluy1, Tassilo Dege1, Reiner Kunze2, Hugo Marti2, Sabine Heiland1, Martin Bendszus1, and Mirko Pham1
1Neuroradiology, University of Heidelberg, Heidelberg, Germany, 2Physiology and Pathophysiology, University of Heidelberg, Heidelberg, Germany
Synopsis
Very
early post ischemic blood-brain barrier disruption has been difficult to detect
in vivo. In this study we show that the experimental contrast agent
Gadofluorine M visualizes very early blood-brain barrier disruption in a mouse
model of ischemic stroke at 9.4T. Contrast agent leakage occurs multifocally along cortical and subcortical microvessels. The degree of leakage predicts final infarct
severity and could therefore serve as a new predictive marker in ischemic
stroke. Purpose
Early
blood-brain barrier disruption has not yet been visualized in experimental
murine ischemia. As the experimental contrast agent GadofluorineM (GfM), which binds to serum albumin, has previously detected blood-brain barrier disturbances with
a higher sensitivity than conventional Gd-DTPA (1, 2), we
tested whether it also depicts early ischemic blood-brain barrier
disruption.
Methods
Adult mice
were subjected to a transient (60 min) filament occlusion of the right middle
cerebral artery followed by GfM injection (0.2mmol/kg) 30 minutes after
reperfusion. In a subgroup fluorescent GfM was used to correlate MR findings with histology. MRI was performed on a 9.4T small animal
scanner (BioSpec 94/20 USR, Bruker, Ettlingen, Germany) using a volume
resonator for RF transmission and a 4-channel-phased-array surface receiver
coil. Mice were imaged three times. The first scan assessed contrast
agent dynamics from 2 hours to 4 hours after reperfusion using
serial T1 –weighted
imaging (TR/TE=5ms/1.9ms, FA=8.5, isotropic resolution 0.156µm) and T2 relaxometry (TR/TE=
3100ms/
incremented from 8ms to
136ms, 8ms interecho time, in plane resolution 0.116 x 0.116µm). Characterization of infarct and vasculature was
performed with diffusion- (3400ms/20ms,
b
value =1500s/mm2, 30 directions, in plane resolution 0.117 x 0.117µm) and T2*-weighted (TR/TE=50ms/18ms, FA=12, isotropic resolution 80µm) sequences. A 6 hour and 24h follow-up scan included the same sequences, but no serial measurements.
Results
85% of mice showed an early multifocal leakage
pattern of GfM with a total volume of
0.72
± 0.26 mm3 at 2 hours after reperfusion. At 4h after reperfusion the total volume significantly increased to 1.2
± 0.4 mm3 (p=0.026). The location of early contrast agent extravasation was closely associated with cortical and subcortical perforator vessels and was confirmed on histological sections. The multifocal
pattern turned confluent at 6 hours until filling the infarct area 24 hours
after reperfusion (Fig 1A). Early GfM leakage volume correlated strongly with final infarct size at 24 hours after reperfusion (R=0.78) (Fig 1B).
Discussion
GfM detects early ischemic blood-brain barrier disruption and could serve as novel predictor for infarct severity.
Acknowledgements
The expert
technical assistance of Manuel Fischer, Maria Harlacher and Inge Keller is gratefully
acknowledged. AH is supported by a postdoctoral fellowship of the University of
Heidelberg, MP by a memorial
stipend of the Else Kröner-Fresenius-Stiftung.References
1, Bendszus M, Ladewig G, Jestaedt L, Misselwitz B, Solymosi L,
Toyka K, et al. Gadofluorine M enhancement allows more sensitive detection of
inflammatory CNS lesions than T2-w imaging: a quantitative MRI study. Brain. 2008;131(9):2341-52.
2,
Jestaedt L,
Lemke D, Weiler M, Pfenning PN, Heiland S, Wick W, et al. Gadofluorine M
enhanced MRI in experimental glioma: superior and persistent intracellular
tumor enhancement compared with conventional MRI. Journal of magnetic resonance
imaging : JMRI. 2012;35(3):551-60.