Microstructural characterization and validation of a 3D printed phantom for diffusion MRI

PurposeTo introduce and characterize inexpensive and easily produced 3D-printed axon-mimetic (3AM) diffusion MRI (dMRI) phantoms in terms of pore geometry and diffusion kurtosis imaging (DKI) metrics. MethodsPhantoms were 3D-printed with a composite printing material that exhibits microscopic fibrous pores. Confocal microscopy and synchrotron phase contrast micro-CT imaging were performed to visualize and assess the pore sizes. dMRI scans of four identical phantoms and phantoms with varying print parameters were performed at 9.4T. DKI was fit to both datasets and used to assess the reproducibility between phantoms and effects of print parameters on DKI metrics. Identical scans were performed 25 and 76 days later to test their stability. ResultsPore segmentation showed 33.6% of pores with diameters of 1.5-8m with mean, median, and standard deviation of 20m, 13m, and 20m, respectively. Phantoms with identical parameters showed a low coefficient of variation ([~]10%) in DKI metrics. Printing temperature and speed had a small effect on DKI metrics ( 16%). The stability analysis showed small changes over 2.5 months (<7%). Conclusion3AM phantoms can mimic the fibrous structure of axon bundles on a microscopic scale, serving as complex, anisotropic dMRI phantoms.