Guidelines for QSM phantom production and evaluation of candidate phantom materials

Abstract Purpose Quantitative susceptibility mapping (QSM) is an MR technique that depicts and precisely quantifies spatial biodistributions from MR phase images. Recently, QSM has gained much uptake as method for mapping iron and identifying calcium. However, QSM as a quantitative method needs an objective reference to assess its accuracy. Here we present guidelines for reproducible workflows for QSM phantom design and production to help standardization efforts and provide characterizations and recommendations for iron- and calcium-based materials given the repeatability and reproducibility. Methods 5 concentrations of 4 materials (USPIO, ferritin, calcium chloride, calcium carbonate) were imaged with a multi-echo gradient-echo acquisition at 3 and 7 Tesla. Magnetic susceptibility and R2* relaxivity as well as intra-session, inter-session repeatability, inter-scanner reproducibility and molar susceptibility by QSM were quantified. Results The QSM measurements of USPIO had a moderate to good inter-session repeatability. The molar susceptibility was approximately 2.45 times larger at 3 T compared to 7 T. The QSM measurements of ferritin had excellent inter-session repeatability. The molar susceptibility was approximately 4 % larger at 3 T compared to 7 T. The QSM measurements of calcium chloride had excellent inter-session repeatability and excellent inter-scanner reproducibility. The QSM measurements of calcium carbonate had a good to excellent inter-session repeatability and an excellent inter-scanner reproducibility. Conclusion This work reveals ferritin and calcium chloride to be the most repeatable and reproducible iron-and calcium-based materials for QSM, respectively. A detailed methodology for phantom production, concentration ranges, visual analysis and statistical analysis are provided.