Prototype Phantoms for Characterization of Ultra-Low Field Magnetic Resonance Imaging
Michael A. Boss, John A. Mates, Sarah E. Busch, Paul SanGiorgio, Stephen E. Russek, Kai Buckenmaier, Kent D. Irwin, Hsiao-Mei Cho, Gene C. Hilton, John Clarke
Purpose: Prototype phantoms were designed, constructed, and characterized for the purpose of calibrating ultralow field magnetic resonance imaging (ULF MRI) systems. The phantoms were designed to measure spatial resolution and to quantify sensitivity to systematic variation of proton density and relaxation time, T1. Methods: The phantoms were characterized first with conventional magnetic resonance scanners at 1.5 and 3 T, and subsequently with a prototype ULF MRI scanner between 107 and 128 υT. Results: The ULF system demonstrated a 2-mm spatial resolution and, using T1 measurements, distinguished aqueous solutions of MnCl2 differing by 20 υM [Mn2+]. Conclusion: The prototype phantoms proved well-matched to ULF MRI applications, and allowed direct comparison of the performance of ULF and clinical systems.