Quantitative measurements of regional cerebral blood volume using MRI in rats: Effects of arterial carbon dioxide tension and mannitol

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Abstract
A three‐dimensional (3D) T1‐weighted sequence was used to acquire high spatial resolution whole brain images in rats before and after the injection of an intravascular contrast agent. These T1‐weighted images were used to estimate regional cerebral blood volume (rCBV) as a percentage of blood volume in each voxel. Ventilation was manipulated to investigate the effects of altered arterial carbon dioxide tension (PaCO2) on rCBV. In addition, different doses of a hypertonic mannitol solution were used to investigate the sensitivity of the proposed method in a serial monitoring paradigm. An rCBV of 2.40% ± 0.34% was obtained before any physiological manipulation, in good agreement with literature values using alternative techniques. Using this method, it was found that there exists a linear relationship between PaCO2 and rCBV (R2 = 0.77) and that rCBV increased in a dose and time dependent fashion in mannitol‐treated rats. High signal‐to‐noise was available due to the substantial increase in blood signal from the intravascular contrast agent.