Comparative Evaluation of PEEK, 3D-Printed Titanium Mesh and Solid Titanium Implants on HU Distortion and Dose Calculation Accuracy in Radiotherapy

This study investigated the impact of implant materials on Hounsfield Unit (HU) distortion and dose calculation accuracy in radiotherapy planning. Standardized cubic phantoms (1 cm3) of PEEK, titanium mesh, and titanium solid were fabricated and scanned using 120 kV and 140 kV extended CT protocols, with and without iterative metal artifact reduction (iMAR). HU profiles were analyzed to quantify imaging artifacts, and VMAT (Volumetric Modulated Arc Therapy) plans were generated for dosimetric verification. Absolute point dose differences and gamma pass rates (3%/3 mm, global normalization, 10% threshold) were compared between calculated and measured doses. PEEK exhibited HU variations within 3% and gamma pass rates consistently above 96%, confirming its suitability as a radiotherapy-compatible implant material. Titanium mesh demonstrated reduced HU distortion compared with titanium solid, with gamma pass rates of 97–98% meeting the clinical acceptance threshold (≥95%). In contrast, the titanium solid showed severe HU distortion with gamma pass rates as low as 89%, falling below the clinical criterion. The effect of iMAR varied: partial improvement for the titanium solid at 120 kV, deterioration at 140 kV, and negligible influence for PEEK and titanium mesh. Overall, PEEK demonstrated the most stable performance, while titanium mesh was superior to solid titanium.