Quantification of water exchange across the blood-brain barrier using non-contrast MR fingerprinting

Abstract

PurposeA method is proposed to quantify cerebral blood volume (vb) and intravascular water residence time (τb) using magnetic resonance fingerprinting (MRF), applied using a spoiled gradient echo sequence, without the need for contrast agent.MethodsAn in silico study optimised an acquisition protocol to maximise the sensitivity of the measurement tovbandτbchanges. Its accuracy in the presence of variations inT1,t,T1,b, andB1was evaluated. The optimised protocol (scan time of 19 minutes) was then tested in a exploratory healthy volunteer study (10 volunteers, mean age 24 ± 3, 6 male) at 3 T with a repeat scan taken after repositioning to allow estimation of repeatability.ResultsSimulations show that assuming literature values forT1,bandT1,t, no variation inB1, while fitting onlyvbandτb, leads to large errors in quantification ofvbandτb, regardless of noise levels. However, simulations also show that matchingandτb, simultaneously is feasible at clinically achievable noise levels. Across the healthy volunteers, all parameter quantifications fell within the expected literature range. In addition, the maps show good agreement between hemispheres suggesting physiologically relevant information is being extracted. Expected differences between white and grey matterT1,t(p<0.0001) andvb(p<0.0001) are observed,T1,bandτbshow no significant differences, p=0.4 and p=0.6 repectively. Good repeatability was seen between repeat scans: mean ICC ofT1,t: 0.91,T1,b: 0.58,vb: 0.90, andvτb: 0.96.ConclusionWe demonstrate that regional simultaneous quantification ofvb,τb,T1,b,T1,t, andB1using MRF is feasible in vivo.