Abstract. The aim of this study was to evaluate the image quality and radiation dose using commercial gold nanoparticles and clinical contrast agents in dual-energy Computed Tomography (CT). Five polymethyl methacrylate (PMMA) tubes were used in this study, where four tubes were filled with different contrast agents (barium, iodine, gadolinium, and gold nanoparticles). The fifth tube was filled with water. Two optically stimulated luminescence dosimeters (OSLD) were placed in each tube to measure the radiation dose. The tubes were placed in a fabricated adult abdominal phantom of 32 cm in diameter using PMMA. The phantom was scanned using a DECT at low energy (80 kV) and high energy (140 kV) with different pitches (0.6 mm and 1.0 mm) and different slice thickness (3.0 mm and 5.0 mm). The tube current was applied automatically using automatic exposure control (AEC) and tube current modulation recommended by the manufacturer (CARE Dose 4D, Siemens, Germany). The contrast-to-noise ratio (CNR) of each contrast agent was analyzed using Weasis software. Gold nanoparticles has highest atomic number (Z = 79) than barium (Z = 56), iodine (Z = 53) and gadolinium (Z = 64). The CNR value of each contrast agent increases when the slice thickness increases. The radiation dose obtained from this study decreases when the pitch increases. The optimal imaging parameters for gold nanoparticles and other clinical contrast agents is obtained at pitch value of 1.0 mm and slice thickness of 5.0 mm. Low noise and low radiation dose obtained at these imaging parameters. The optimal imaging parameters obtained in this study can be applied in multiple contrast agents imaging. IntroductionComputed tomography (CT) is one of diagnostic tool that is applied in clinical and preclinical applications. This is because CT has high diagnostic efficiency which provides anatomical information of tumor and good accessibility. Conventional CT uses a wide energy spectrum and digital integrating sensor 1,2 . However, conventional CT cannot distinguish the tissues because the attenuation of x-ray is not at a specific energy but it is over the broad energy for all tissues within the voxel. The contrast resolution for soft tissues do not adequate for conventional CT 1,3 . Thus, innovation in CT imaging technology has overcome this limitation with the use of an advanced imaging technique known as a dual-energy CT (DECT) imaging.

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Abstract. The aim of this study was to evaluate the efficacy of metal artefact reduction using contrasts media in Computed Tomography (CT) imaging. A water-based abdomen phantom of diameter 32 cm (adult body size) was fabricated using polymethyl methacrylate (PMMA) material. Three different contrast agents (iodine, barium and gadolinium) were filled in small PMMA tubes and placed inside a water-based PMMA adult abdomen phantom. The orthopedic metal screw was placed in each small PMMA tube separately. These two types of orthopedic metal screw (stainless steel and titanium alloy) were scanned separately. The orthopedic metal crews were scanned with single-energy CT at 120 kV and dual-energy CT at fast kV-switching between 80 kV and 140 kV. The scan modes were set automatically using the current modulation care4Dose setting and the scans were set at different pitch and slice thickness. The use of the contrast media technique on orthopedic metal screws were optimised by using pitch = 0.60 mm, and slice thickness = 5.0 mm. The use contrast media can reduce the metal streaking artefacts on CT image, enhance the CT images surrounding the implants, and it has potential use in improving diagnostic performance in patients with severe metallic artefacts. These results are valuable for imaging protocol optimisation in clinical applications.