Proton Acquisition with Variable Flip Angle to Simulate and Optimized Hyperpolarized He MRI with Parallel Acquisition

Introduction: MRI using hyperpolarized He is an effective and powerful tool to study morphological, functional, and mechanical and other properties of lungs. The price of the He and technical difficulties of polarization and logistic, prompt to employ computer simulation to optimise the acquisition parameters and optimal usage of available gas. However, in such simulations, the whole influence of MRI environment on image acquisition cannot be taken into account. Additionally, due to intellectual property protection, the sophisticated commercial reconstruction algorithms for parallel imaging (e.g. SENSE, GRAPPA) are not exportable to the simulation workstation. To employ the scanner’s software computational capabilities and to simulate the complete measurement process without using expensive hyperpolarized gas we developed the dedicated H MRI acquisition protocol with using variable flip angle pulse sequence. In the current work this protocol was investigate the effect of different k-space sampling ordering on images acquired with integrated parallel acquisition techniques (iPAT). Methods: The phantom used for the MRI acquisition was filled with copper sulfate solution to obtain a respectively T1 and T2* time of 50 ms and 50 ms. The MR-images were acquired on a 1.5T MR-scanner (SIEMENS Sonata, Erlangen, Germany) using a modified GRE sequence. In all the experiment, the repetition time was set to 120 ms to recover all the longitudinal magnetization between two consecutive excitations. To simulate the 3He experiment the flip angle used for the n-th excitation was set to: