Development of a method for the Bloch image simulation of biological tissues

The purpose of this study is to develop a method for the Bloch image simulation of biological tissues including various chemical components and T2* distribution. The nuclear spins in the object material were modeled as a spectral intensity function Sr→ω defined by superposition of Lorentz functions with various central precession frequencies and the half width of 1/(πT2′), where 1/T2′ is a relaxation rate attributable to microscopic field inhomogeneity in a voxel. Four-dimensional numerical phantoms were created to simulate Sr→ω and used for MRI simulations of the phantoms containing water and fat protons. Single slice multiple (16) gradient-echo sequences (ΔTE = 2.2 and 1.384 ms) were used for experiments at 1.5 T and 3 T and MRI simulations to evaluate the validity of the approach. Experimentally measured image intensities of the multiple gradient-echo imaging sequences were well reproduced by the MRI simulations. The correlation coefficients between the experimentally measured image intensities and those numerically simulated were 0.9895 to 0.9992 for the 4-component phantom at 1.5 T and 0.9580 to 0.9996 for the 7-component phantom at 3 T. T2* and chemical shift effects were successfully implemented in the MRI simulator (BlochSolver). Because this approach can be applied to other MRI simulators, the method developed in this study is useful for MRI simulation of biological tissues containing water and fat protons. •A method for Bloch image simulation for chemical shift and T2* was developed.•4D numerical phantoms were developed to describe chemical shift and T2*.•Phantom experiments at 1.5 T and 3 T were performed and compared to simulations.•Simulations for multiple gradient echo images reproduced the experiments very well.•Our method holds promise for Bloch image simulations of tissues with water and fat.