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MRI-Simulations

MRI simulations are needed in many cases and deliver many advantages over real systems. The complexity and costs of MRI systems suggest the use of simulations prior to the implementation of new processes on real MRI hardware. Likewise, the work involved in implementing new ideas or optimizing MRI sequence protocols on MRI scanners may require thorough simulations. In favor of general MRI simulations the open source software project jemris, the “Jülich Extensible MRI Simulator”, was developed.

Elements of the jemris user interfaces. Figure 1: Left: interactive MRI sequence design. Right: visualization of multi-channel transmit/receive sensitivities.

jemris provides an MRI sequence development and simulation environment for the MRI community. The development was driven by the desire to achieve generality of simulated 3D MRI experiments reflecting modern MRI systems hardware. The accompanying computational burden is overcome by means of parallel computing. Many aspects are covered which have not hitherto been simultaneously investigated in general MRI simulations such as parallel transmit and receive, important off-resonance effects, non-linear gradients, and arbitrary spatiotemporal parameter variations at different levels. The latter can be used to simulate various types of motion, for instance. The jemris user interface is very simple to use and it presents few limitations (c.f. Fig 1). MRI sequences with arbitrary waveforms and complex inter-dependent modules are modeled in a GUI-based environment requiring no further programming. Example simulations of common MRI artefacts are shown in Figure 2.

Example MRI artefact simulations. Figure 2: The calculation times on a desktop PC are given on the bottom left of each image. In all cases 1.4*10^5 spins were simulated. a) Spatial shift of the fat signal in EPI. b) Image distortions due to a nonlinear spatial encoding field. c) Typical banding artefacts caused by susceptibility-induced field inhomogeneities. d) Spin echo imaging with a refocusing pulse duration in the order of T2.

The official jemris website


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