Time-efficient measurement of subtle blood-brain barrier leakage using a T1 mapping MRI protocol at 7 T

Abstract

Purpose: Blood-brain barrier (BBB) disruption is commonly measured with DCE-MRI using continuous dynamic scanning. For precise measurement of subtle BBB leakage, a long acquisition time (>20 minutes) is required. As extravasation of the contrast agent is slow, discrete sampling at strategic time points might be beneficial, and gains scan time for additional sequences. Here, we aimed to explore the feasibility of a sparsely sampled MRI protocol at 7 T.

Methods: The scan protocol consisted of a precontrast quantitative T₁ measurement, using an MP2RAGE sequence, and after contrast agent injection, a fast-sampling dynamic gradient-echo perfusion scan and two postcontrast quantitative T₁ measurements were applied. Simulations were conducted to determine the optimal postcontrast sampling time points for measuring subtle BBB leakage. The graphical Patlak approach was used to quantify the leakage rate (K_i ) and blood plasma volume (v_p ) of normal-appearing white and gray matter.

Results: The simulations showed that two postcontrast T₁ maps are sufficient to detect subtle leakage, and most sensitive when the last T₁ map is acquired late, approximately 30 minutes, after contrast agent administration. The in vivo measurements found K_i and v_p values in agreement with other studies, and significantly higher values in gray matter compared with white matter (both p = .04).

Conclusion: The sparsely sampled protocol was demonstrated to be sensitive to quantify subtle BBB leakage, despite using only three T₁ maps. Due to the time-efficiency of this method, it will become more feasible to incorporate BBB leakage measurements in clinical research MRI protocols.

Keywords: 7T; BBB leakage; DCE-MRI; T1 mapping.