Quantification of cerebral arterial blood volume using arterial spin labeling with intravoxel incoherent motion-sensitive gradients

Quantification of cerebral arterial blood volume (CBV_a) is important for understanding vascular regulation. To enable measurement of CBV_a with diffusion-weighted (DW) arterial spin labeling (ASL), a theoretical framework was developed using the effects of intravoxel incoherent motion (IVIM). The pseudo-diffusion coefficient (D*) in the IVIM model was evaluated at 9.4 T in DW-ASL of rat brain under isoflurane anesthesia by variations of both post-labeling delay (w) and magnetization transfer ratio (MTR). D* and its volume fraction decreased at values of w ≥ 0.3 s, and the normalized apparent diffusion coefficient (ADC) increased with MTR, suggesting that D* is closely correlated with CBV_a. Thus, the difference between ASL measurements with and without DW gradients is related to CBV_a. The CBV_a values measured by this approach were compared with values obtained using the modulation of tissue and vessel (MOTIVE) technique with ASL, which varies MT levels without changing spin labeling efficiency. CBV_a values from both methods were highly correlated. The measured CBV_a values were linearly correlated with cerebral blood flow (CBF) for a PaCO₂ range of 25-50 mmHg; ΔCBV_a (ml/100 g) = 0.007 (min^-1) × ΔCBF (ml/100 g/min). The DW-ASL approach is simple and easy to implement for human and animal CBV _a studies.