ABSTRACT Purpose To measure magnetic susceptibility ( χ ) with Quantitative Susceptibility Mapping (QSM) and evaluate its repeatability using four phantom doping materials relevant to QSM applications. Methods A cylindrical phantom was constructed containing vials of agarose gel doped with two paramagnetic materials (ferritin, USPIO) and two diamagnetic materials (CaCl 2 , CaCO 3 ) 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. Results 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) (CaCl 2 : 3; 7 T), and 10 −5 × (−9.52 ± 1.44; −9.53 ± 1.18) (CaCO 3 : 3; 7 T). We observed no significant changes in molar susceptibility for ferritin and CaCO 3 over the measured timeframes (24 and 15 months, respectively). Conclusion 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 R 2 */ B 0 to χ .
Hooper et al. (Thu,) studied this question.
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