Abstract
Cerebral blood volume (CBV) plays an important role for quantitative assessment of the brain physiology and pathophysiology state, which can be obtained with vascular-space-occupancy (VASO) MRI. One approach to determine absolute cerebral blood volume (aCBV) in humans is VASO MRI, which has been reported previously by Lu et al. The VASO MRI technique uses an inversion recovery pulse to null blood signal. Then, the signal difference before and after injection of T1 shortening Gd contrast agent can be used to calculate absolute CBV values with a reference signal. The aCBV was estimated by EPI sequence in previous reports, which may cause image distortion and partial volume effect. In order to overcome these problems, the RARE sequence was utilized in this study. Aiming to optimize the imaging parameters and evaluating the accuracy of VASO MRI, three experiments were preformed. First, we conducted computer simulations to estimate optimal imaging parameters. Second, phantom experiments were performed to assess the accuracy of aCBV with different parameters. Finally, the in vivo experiments were performed on a normal rat model. The results of the phantom experiments showed that the accuracy of aCBV value was higher for RARE sequence with IR preparation than without it. It is speculated that the interference of tissue signal is suppressed by the IR preparation. Compared with longer TR (4000ms), the aCBV estimated with shorter TR (1600 ms) was more accurate for IR-RARE sequence in phantom studies. In animal experiments, using the optimized parameters, the aCBV estimated with shorter TR is in good agreement with values reported in the literatures. Therefore, it is believed that our modified VASO MRI method will be beneficial for assessing aCBV.