Simulations of Perfusion Signals of Pulsed Arterial Spin Labeling MRI

Abstract

2 Purpose : A pulsed arterial spin labeling (PASL) signal usually depends on several parameters. The objective of this study was to determine the optimal parameters using simulation for perfusion signals of PASL magnetic resonance imaging (MRI). Materials and Methods : Perfusion signals, ΔM/M0b, derived from the Bloch equation were evaluated in regard to the four most important parameters in PASL MRI: the tissue-to-blood coefficient (λ ), the longitudinal relaxation time of blood (T1b), the arterial transit delay from the application of tag (δ t), and the magnetic field strength (B0). The simulation was conducted with Mathematica software. Results : First, perfusion signals differed depending on the value of λin brain tissue. The maximum signal, ΔM/M0b = 0.390, was obtained at an inversion time (TI) = 1.53 sec for gray matter on 3T MRI. Second, perfusion signals were reduced with increasing δ t. The maximum signal, ΔM/M0b = 0.526, was obtained at TI = 2.1 sec for δ t = 0.5 sec. Finally, perfusion signals increased with increasing B0. The maximum signal, ΔM = 1.15, was obtained at TI = 1.52 sec for 3T MRI. Conclusion : We reported that the optimized TI values were obtained to provide the highest PASL signals. It is very important that optimized TI values be used to obtain high-quality perfusion signals using PASL MRI.