Magnetic resonance Spectrum simulator (MARSS), a novel software package for fast and computationally efficient basis set simulation

The aim of this study was to develop a novel software platform for the simulation of magnetic resonance spin systems, capable of simulating a large number of spatial points (1283) for large in vivo spin systems (up to seven coupled spins) in a time frame of the order of a few minutes. The quantum mechanical density‐matrix formalism is applied, a coherence pathway filter is utilized for handling unwanted coherence pathways, and the 1D projection method, which provides a substantial reduction in computation time for a large number of spatial points, is extended to include sequences of an arbitrary number of RF pulses. The novel software package, written in MATLAB, computes a basis set of 23 different metabolites (including the two anomers of glucose, seven coupled spins) with 1283 spatial points in 26 min for a three‐pulse experiment on a personal desktop computer. The simulated spectra are experimentally verified with data from both phantom and in vivo MEGA‐sLASER experiments. Recommendations are provided regarding the various assumptions made when computing a basis set for in vivo MRS with respect to the number of spatial points simulated and the consideration of relaxation. A novel software package, Magnetic Resonance Spectrum Simulator (MARSS), which is able to compute basis sets for any arbitrary MRS experiment, is developed. MARSS is able to compute a basis set for a three‐pulse experiment (including both glucose anomers, seven coupled spins) with 1283 spatial points in 26 min. It is shown that experimental details (exact pulse shapes, timings) for the same sequence can generate markedly different spectral shapes. Recommendations for obtaining accurate basis sets are provided.