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

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 (Ki ) and blood plasma volume (vp ) 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 Ki and vp 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.