Relaxometry and contrast-free cerebral microvascular quantification using balanced steady-state free precession MR fingerprinting.

Abstract

Purpose: This study proposes a novel, contrast-free Magnetic Resonance Fingerprinting (MRF) method using balanced Steady-State Free Precession (bSSFP) sequences for the quantification of cerebral blood volume (CBV), vessel radius (R), and relaxometry parameters (T ${\hspace{0.17em}}_1$ , T ${\hspace{0.17em}}_2$ , T ${\hspace{0.17em}}_2$ *) in the brain.

Methods: The technique leverages the sensitivity of bSSFP sequences to intra-voxel frequency distributions in both transient and steady-state regimes. A dictionary-matching process is employed, using simulations of realistic mouse microvascular networks to generate the MRF dictionary. The method is validated through in silico and in vivo experiments on six healthy subjects, comparing results with standard MRF methods and literature values.

Results: The proposed method shows strong correlation and agreement with standard MRF methods for T ${\hspace{0.17em}}_1$ and T ${\hspace{0.17em}}_2$ values. High-resolution maps provide detailed visualizations of CBV and microvascular structures, highlighting differences in white matter (WM) and gray matter (GM) regions. The measured GM/WM ratio for CBV is 1.91, consistent with literature values.

Conclusion: This contrast-free bSSFP-based MRF method offers an new approach for quantifying CBV, vessel radius, and relaxometry parameters. Further validation against DSC imaging and clinical studies in pathological conditions is warranted to confirm its clinical utility.