Evaluation of Phantom Doping Materials in Quantitative Susceptibility Mapping

To measure magnetic susceptibility (χ) with Quantitative Susceptibility Mapping (QSM) and evaluate its repeatability using four phantom doping materials relevant to QSM applications.

A cylindrical phantom was constructed containing vials of agarose gel doped with two paramagnetic materials (ferritin, USPIO) and two diamagnetic materials (CaCl₂, CaCO₃) at five concentrations each. Single orientation QSM measurements (MEDI+0) were carried out on the phantom at 3 and 7 T. We measured molar susceptibility (χ_mol) from QSM and evaluated the precision of QSM measurements using the standard deviation of the ROI measurement (SD_ROI). We evaluated material lifespan by conducting a t-test of χ_mol at various timepoints.

χ_mol (ppm L mmol^-1) were measured as 1.67 ± 0.24 and 0.74 ± 0.09 (USPIO: 3 and 7 T, respectively), 10^-2 × (8.13 ± 1.35; 8.13 ± 1.19) (Ferritin: 3; 7 T), 10^-4 × (-2.68 ± 0.24; -2.71 ± 0.37) (CaCl₂: 3; 7 T), and 10^-5 × (-9.52 ± 1.44; -9.53 ± 1.18) (CaCO₃: 3; 7 T). We observed no significant changes in molar susceptibility for ferritin and CaCO₃ over the measured timeframes (24 and 15 months, respectively).

We recommend using ferritin as a paramagnetic dopant. Further research is required to identify a diamagnetic dopant with a lower electrical conductivity and a lower ratio of R₂*/B₀ to χ.