Multiparametric estimation of brain hemodynamics with MR fingerprinting ASL

Abstract

Purpose Assessment of brain hemodynamics without exogenous contrast agents is of increasing importance in clinical applications. This study aims to develop an MR perfusion technique that can provide non-contrast and multi-parametric estimation of hemodynamic markers. Methods We devised an Arterial-Spin-Labeling (ASL) method based on the principle of MR Fingerprinting (MRF), referred to as MRF-ASL. By taking advantage of the rich information contained in MRF sequence, up to seven hemodynamic parameters can be estimated concomitantly. Feasibility demonstration, flip angle optimization, comparison with Look-Locker ASL, reproducibility test, sensitivity to hypercapnia challenge, and initial clinical application in an intracranial steno-occlusive process, Moyamoya disease, were performed to evaluate this technique. Results MRF-ASL provided estimation of up to seven parameters, including B1+, tissue T1, cerebral blood flow (CBF), tissue bolus-arrival-time (BAT), pass-through arterial BAT, pass-through blood volume, and pass-through blood travel time. Coefficients-of-variation (CoV) of the estimated parameters ranged from 0.2% to 9.6%. Hypercapnia resulted in an increase in CBF by 57.7%, and a decrease in BAT by 13.7% and 24.8% in tissue and vessels, respectively. Patients with Moyamoya disease showed diminished CBF and lengthened BAT that could not be detected with regular ASL. Conclusion MRF-ASL is a promising technique for non-contrast, multi-parametric perfusion assessment.

Magnetic resonance fingerprinting – An overview

“…EPI-MRF relaxometry values were in good agreement with gold standard values with a small coefficient of variation (T1: 4 ± 2%, T2*: 4 ± 9%)[8]. On the other hand, Su, et al [9] integrated arterial spin labeling (ASL) concept into MRF framework for estimation of perfusion related tissue properties.…”

“…Each of these steps is discussed in more detail below. While the original MRF description focused on measuring T1, T2, static magnetic field (B 0 ) inhomogeneity or off-resonance frequency and proton density M 0 [2], recent work has shown the feasibility to measure other properties such as radio frequency (RF) transmit field inhomogeneity (B 1 )[6,7], T2*[8], perfusion[9] and microvascular properties[10–12]. …”

“…For data sampling, spiral[2,14–17] or radial[7,18] trajectories are often used because of higher spatial incoherence and sampling efficiency. However, echo-planar imaging (EPI)[8,9] and Cartesian trajectories[6,10,19–21] have also been shown to be useful in MRF framework. Depending on the sequence type, the variation in acquisition parameters and the application, the trajectory re-ordering can be sequential, uniformly rotated or random.…”

“…The extended phase graph formalism[41] has also been utilized in later work on MRF to predict spin behavior. Work on MR vascular fingerprinting (MRvF)[10] and MRF-Arterial Spin labeling (ASL) perfusion [9] have used more complex models to generate database of fingerprints for pattern matching. Pattern matching provides a certain degree of tolerance to errors as long as these errors are spatially and temporally incoherent in such a way that it is possible for the pattern matching algorithm to select the correct match from the dictionary despite the individual errors or noisiness in the timecourse [2].…”

“…Since, the ASL signal is affected by multiple hemodynamic parameters, both Wright et al [KL Wright et al ., Abstract 0417.22 nd Annual Meeting of International Society of Magnetic Resonance in Medicine, Milan, Italy, 2014] and Su, et al [9] recently explored the feasibility of developing an ASL technique based on MRF framework to simultaneously get multiple hemodynamic parameters with one scan. The MRF-ASL acquisition was performed using an EPI readout with whole brain coverage in 3 minutes of scan time and a resolution of 2.8 × 2.8 × 10 mm 3 [9]. Different hemodynamic parameters were extracted depending on the mathematical model used and compared with dictionary values.…”