A quantitative radiographic framework for longitudinal monitoring of additively manufactured biodegradable scaffolds with graded tantalum reinforcement.

PURPOSE: This study proposes a standardized, quantitative radiographic evaluation framework for assessing the detectability and imaging fidelity of biodegradable scaffolds, enabling longitudinal X-ray-based monitoring through controlled radiopaque microparticle integration.

METHODS

PLA scaffolds with graded tantalum (Ta) microparticle concentrations (0-1.0 wt%) were fabricated by fused deposition modelling and implanted into ex-vivo chicken femoral-defect models. Sagittal and coronal digital radiographs were processed through a semi-automated MATLAB® pipeline for ROI-based segmentation, and a Beer-Lambert-based framework was used to derive scaffold signal intensity, contrast-to-noise ratio, signal-to-noise ratio, attenuation contrast (Δμ), and scaffold-to-bone signal ratio (Rμ). Metrics were analyzed using Kruskal-Wallis H tests across scaffold formulations, excluding the scaffold-free defect as the reference baseline, followed by Dunn post-hoc tests with Holm correction and one-sided Wilcoxon signed-rank tests for detectability.

RESULTS

The proposed framework resolved distinct detectability thresholds across formulations. Scaffolds containing ≤0.1 wt% Ta fell below the detectability thresholds of Δμ ≤ 0 and Rμ < 1.0. Rather than being excluded from the analysis, these samples were retained and classified as radiographically non-detectable. Above the detectability threshold (≥0.25 wt% Ta), signal intensity increased monotonically with Ta content, but higher loadings introduced substantial variability due to artefact formation. The 0.5 wt% formulation achieved the optimal balance, combining high contrast with minimal variability (CV = 0.44%), whereas concentrations ≥0.75 wt% showed increased heterogeneity and reduced imaging reliability despite higher absolute signal.

CONCLUSION

This work establishes a physically grounded and reproducible radiographic evaluation framework for biodegradable scaffolds, enabling standardized comparison of radiopacity and imaging performance across material systems. The results define both minimum-detectability and upper-artefact thresholds, providing design constraints for radiopaque scaffold engineering. The provided framework establishing quantitative radiographic detectability at the initial implantation states and provides a transferable basis for future longitudinal, non-invasive X-ray monitoring, with potential extensibility to CT-based and regulatory imaging workflows.