Introduction: In thoracic computed tomography (CT) examinations, patients' breasts are exposed to high radiation doses, necessitating the need to reduce the received dose. The aim of this study was to evaluate the efficiency of a new composition of a shielding material with minimal impact on image quality. Materials and methods: Different breast shields were manufactured with varying weight percentages of copper and BaSO4. Thermoluminescent dosimeters (TLD) and thorax phantoms were used to assess the radiation shielding effectiveness. Image quality, in terms of noise and CT number accuracy, was quantitatively evaluated on a CTDI phantom. Additionally, a controlled trial with 60 female participants was conducted to further assess image quality and select the best breast radiation shield. Results: The results indicated that the different shield compositions reduced the surface dose by 14.17-51.69%. The shield with a composition of 90% Cu-10% BaSO4 and 50% Cu-50% BaSO4 had the lowest noise, while the 100% bismuth shield had the highest noise. Importantly, the 50% Cu-50% BaSO4 shield did not cause artifacts in the thoracic CT images. Conclusion: By using the 50% Cu-50% BaSO4 shield, a significant dose reduction was achieved while maintaining appropriate image quality, making it suitable for clinical applications.