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Imaging phantoms are used to calibrate and validate the performance of magneticresonance imaging (MRI) systems. Many new materials have been developed for additivemanufacturing (three-dimensional [3D] printing) processes that may be useful in thedirect printing or casting of dimensionally accurate, anatomically accurate,patient-specific, and/or biomimetic MRI phantoms. The T1, T2, and T2* spin relaxationtimes of polymer samples were tested to discover materials for use as tissue mimics andstructures in MRI phantoms. This study included a cohort of polymer compounds that wastested in cured form. The cohort consisted of 101 standardized polymer samplesfabricated from: two-part silicones and polyurethanes used in commercial castingprocesses; one-part optically cured polyurethanes used in 3D printing; and fuseddeposition thermoplastics used in 3D printing. The testing was performed at 3 T usinginversion recovery, spin echo, and gradient echo sequences for T1, T2, and T2*,respectively. T1, T2, and T2* values were plotted with error bars to allow the reader toassess how well a polymer matches a tissue for a specific application. A correlation wasperformed between T1, T2 , T2* values and material density, elongation, tensilestrength, and hardness. Two silicones, SI_XP-643 and SI_P-45, may be usable mimics forreported liver values; one silicone, SI_XP-643, may be a useful mimic for muscle; onesilicone, SI_XP-738, may be a useful mimic for white matter; and four silicones,SI_P-15, SI_GI-1000, SI_GI-1040, and SI_GI-1110, may be usable mimics for spinal cord.Elongation correlated to T2 (p = 0.0007), tensile strength correlated to T1 (p = 0.002),T2 (p = 0.0003), and T2* (p = 0.003). The 80 samples not providing measurable signalwith T1, T2, T2* relaxation values too short to measure with the standard sequences, maybe useful for MRI-invisible fixturing and medical devices at 3 T.

Characterization of 3-Dimensional Printing and Casting Materials for use in Magnetic Resonance Imaging Phantoms at 3 T