Making solid polymers MR-visible: MR-characterization of micro-sphere modified resins for MR-phantoms and MR-guided radiation therapy

Motivation: Solid polymers could be very useful for MRI Quality-Control using stable-in-time phantoms, however, not being MR-visible due to short T2-relaxation-time. The invisibility represents also a severe problem in MR-guided radiation-therapy dose-planning and attenuation-correction in MR-PET scanners. Goal(s): Can the manufacturing-process be modified, such that polymers can be MR-visualized with adjustable T1/T2/T2*, stable-with-time and 3D-printed? Approach: MR-visibility of resins was obtained with different oil-types adsorbed to micro-spheres before UV-initiated polymerization and MR-characterized for their relaxation-times. Results: Solid polymer-samples, were characterized for relaxation-times (≈200ms<T1<2000ms; 90ms<T2<600ms) Homogeneity, stability-in-time. Molding was successful, but 3D-printing on a simple SLA/LCD-device failed in first exercises due to floating of micro-spheres. Impact: Solid polymers could not be MR-visualized yet. Visibility would be very useful in Quality-Control phantoms, in MR-guided radiation-therapy and MR-PET-scanners. We established an oil-in-micro-sphere modified manufacturing-process for resins and report about MR-characterization (T1/T2/T2*, homogeneity) of the modified MR-visible polymer-material.