3D MR Fingerprinting for Dynamic Contrast-Enhanced Imaging of Whole Mouse Brain.

Purpose: Quantitative MRI enables direct quantification of contrast agent concentrations in contrast-enhanced scans. However, the lengthy scan times required by conventional methods are inadequate for tracking contrast agent transport dynamically in mouse brain. We developed a 3D MR fingerprinting (MRF) method for simultaneous T₁ and T₂ mapping across the whole mouse brain with 4.3-min temporal resolution.

Method: We designed a 3D MRF sequence with variable acquisition segment lengths and magnetization preparations on a 9.4T preclinical MRI scanner. Model-based reconstruction approaches were employed to improve the accuracy and speed of MRF acquisition. The method's accuracy for T₁ and T₂ measurements was validated in vitro, while its repeatability of T₁ and T₂ measurements was evaluated in vivo (n=3). The utility of the 3D MRF sequence for dynamic tracking of intracisternally infused Gd-DTPA in the whole mouse brain was demonstrated (n=5).

Results: Phantom studies confirmed accurate T₁ and T₂ measurements by 3D MRF with an undersampling factor up to 48. Dynamic contrast-enhanced (DCE) MRF scans achieved a spatial resolution of 192 ✕ 192 ✕ 500 μm³ and a temporal resolution of 4.3 min, allowing for the analysis and comparison of dynamic changes in concentration and transport kinetics of intracisternally infused Gd-DTPA across brain regions. The sequence also enabled highly repeatable, high-resolution T₁ and T₂ mapping of the whole mouse brain (192 ✕ 192 ✕ 250 μm³) in 30 min.

Conclusion: We present the first dynamic and multi-parametric approach for quantitatively tracking contrast agent transport in the mouse brain using 3D MRF.