Bone and Joint Institute

Title

Effective magnetic susceptibility of 3D-printed porous metal scaffolds

Document Type

Article

Publication Date

1-25-2022

Journal

Magnetic Resonance in Medicine

PubMed

35076107

URL with Digital Object Identifier

https://doi.org/10.1002/mrm.29136

Abstract

Purpose

3D-printed porous metal scaffolds are a promising emerging technology in orthopedic implant design. Compared to solid metal implants, porous metal implants have lower magnetic susceptibility values, which have a direct impact on imaging time and image quality. The purpose of this study is to determine the relationship between porosity and effective susceptibility through quantitative estimates informed by comparing coregistered scanned and simulated field maps.

Methods

Five porous scaffold cylinders were designed and 3D-printed in titanium alloy (Ti-6Al-4V) with nominal porosities ranging from 60% to 90% using a cellular sheet-based gyroid design. The effective susceptibility of each cylinder was estimated by comparing acquired B0 field maps against simulations of a solid cylinder of varying assigned magnetic susceptibility, where the orientation and volume of interest of the simulations was informed by a custom alignment phantom.

Results

Magnitude images and field maps showed obvious decreases in artifact size and field inhomogeneity with increasing porosity. The effective susceptibility was found to be linearly correlated with porosity (R2 = 0.9993). The extrapolated 100% porous (no metal) magnetic susceptibility was −9.9 ppm, closely matching the expected value of pure water (−9 ppm), indicating a reliable estimation of susceptibility.

Conclusion

Effective susceptibility of porous metal scaffolds is linearly correlated with porosity. Highly porous implants have sufficiently low effective susceptibilities to be more amenable to routine imaging with MRI.

Notes

© 2022 International Society for Magnetic Resonance in Medicine.

Maria Drangova and David W. Holdsworth contributed equally to this study.

Funding information:

The authors acknowledge funding from the Canadian Institutes of Health Research (FDN 148474, PJT 159665), Ontario Research Fund (RE-077-66) and the New Frontiers in Research Fund (NFRFE-2019-00790)

mrm29136-sup-0001-supinfo.pdf (323 kB)
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