A Simulation Study on the Fat Caused Chemical Shift Effects on the Magnetic Susceptibility Measurement of IONPs With Ultra-Short TEs

To study how the fat affects the quantification of magnetic susceptibility of iron oxide nanoparticles (IONPs) according to the chemical shift effects, especially at ultra-short echo times, simulation experiments were carried out in this paper. Numerical phantom of IONPs solutions with six different concentrations was designed. Magnetic resonance imaging signals with different fat fractions (ffs) were generated according to a multi-peak chemical shift model. Quantitative susceptibility mapping (QSM) was calculated, and the relationship between the QSM value and ff, as well as echo selection, is evaluated. The results show that streaking artifacts become more and more severe when ff increases, which makes QSM value overestimated. Shortened echo spacing time can reduce streaking artifacts with the same ff. These findings will benefit future clinical evaluations for quantification of iron in vivo.