Characterisation and Physically-Based Modelling of Shape Memory Radiopaque Materials for Biomedical Applications

Radiopacity is a critical property in the design of implantable medical devices. However, the quantification of radiopacity remains a significant challenge. Traditional methods often rely on optical density measurements from X-ray film, which are logarithmic in nature and highly sensitive to variables such as exposure settings, film type and processing conditions. These inconsistencies make it difficult to reproduce and compare radiopacity across studies or materials.   This study presents a multi-scale attenuation model that integrates chemical composition, atomic structure and device geometry with spectral attenuation data to predict radiopacity in shape memory alloy (SMA) systems e.g. nickel-titanium alloys. The computational model framework uses literature derived linear attenuation coefficients and MATLAB-based spectral modelling to simulate photon transmission through layered structures, incorporating a physical definition of the crystalline structure and chemical composition. Transmission spectra are generated across a defined energy range, and attenuation is quantified for each constituent element or alloy configuration.  Experimental X-ray imaging is performed on various wire samples. Radiopacity is quantified using a mm-Al equivalent thickness derived from greyscale analysis and calibrated against an aluminium standard. This approach enables direct comparison between modelled attenuation and experimentally derived values to provide a quantitative, robust framework for evaluating and optimising radiopaque materials in clinical device design, thus minimising the requirement to produce and test multiple physical samples.