Abd Aziz Tajuddin

Development and evaluation of a Perspex anthropomorphic head and neck phantom for three dimensional conformal radiation therapy (3D-CRT)

Purposes To design, construct and evaluate an anthropomorphic head and neck phantom for the dosimetric evaluation of 3D-conformal radiotherapy (3D-CRT) dose planning and delivery, for protocols developed by the Radiation Therapy Oncology Group (RTOG). Materials and methods An anthropomorphic head and neck phantom was designed and fabricated using Perspex material with delineated planning target volumes (PTVs) and organs at risk (OARs) regions. The phantom was imaged, planned and irradiated conformally by a 3D-CRT plan. Dosimetry within the phantom was assessed using thermoluminescent dosimeters (TLDs). The reproducibility of phantoms and TLD readings were checked by three repeated identical irradiations. Subsequent three clinical 3D-CRT plans for nasopharyngeal patients have been verified using the phantom. Measured doses from each dosimeter were compared with those acquired from the treatment planning system (TPS). Results Phantoms measured doses were reproducible with Conclusion The good agreement between predicted and measured dose shows that the phantom is a useful and efficient tool for 3D-CRT technique dosimetric verification.

Evaluation of image quality and radiation dose using gold nanoparticles and other clinical contrast agents in dual-energy Computed Tomography (CT): CT abdomen phantom

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.

Evaluation of efficacy of metal artefact reduction technique using contrast media in Computed Tomography

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.

Image Quality Evaluation in Contrast Agents Computed Tomography Imaging

This main goal of this study was to evaluate image quality in single-energy (SE) and dual-energy (DE) CT imaging with the presence of barium and iodine. A fabricated polymethyl methacrylate abdomen phantom with 32 cm diameter size was used to mimic human abdomen. Two different contrast agents: barium and iodine, were scanned separately. The imaging parameters for SECT were set at tube voltage 80, 120 and 140 kV while the imaging parameters for DECT were set at fixed tube voltage 80/140 kV. Both scan modes were set at the different pitch: 0.6 and 1.0 mm, and the slice thickness was set at 3.0 and 5.0 mm with automatic exposure control for the tube current. The CT images obtained from both scanning were analysed to evaluate the signal-to-noise ratio (SNR). Barium and iodine gave highest SNR of 39.30 and 182.68, respectively, at a tube voltage of 140 kV, a pitch of 1 and a slice thickness of 3 mm for SECT. In DECT mode, the highest SNR for barium and iodine were 36.74 and 112.15 respectively at pitch 1 and slice thickness of 3 mm. There was no significant difference between SNR of barium and iodine obtained with both CT imaging modes with p-values of 0.75 and 0.12, respectively.

Evaluation of Metal Artifacts from Stainless Steel and Titanium Alloy Orthopedic Screw in Computed Tomography Imaging

Artifacts arising from metallic implant had been a concern for Computed Tomography (CT) imaging in obtaining optimal image quality. The main aim of this study was to evaluate the metal artifacts severity from two different types of orthopedics screw and to optimise CT imaging parameters for metallic implants. A water-based abdomen phantom of diameter 32 cm (adult body size) was fabricated using polymethyl methacrylate (PMMA) materials. The fabricated phantom was scanned with dual-energy CT at 80 and 140 kV, and single-energy CT at 120 kV. Two types of orthopedic screws; titanium alloy (grade 5) and stainless steel (grade 316L) was used in this study. A phantom with orthopedics metal screw was scanned at various pitch (0.35, 0.60, 1.20) and slice thickness of 1.0, 3.0, 5.0 mm. The tube current was applied automatically using tube current modulation. In this phantom study, the severity of stainless steel and titanium alloy was analysed. Results showed that the signal-to-noise ratio (SNR) of titanium alloy was higher than the SNR of stainless steel. The optimal image quality of metallic implant was obtained at imaging parameters of pitch at 0.60 and 5.0 mm slice thickness. The use of optimum CT imaging parameters for orthopedic screw resulted in an improved CT image, as the SNR increases. This finding proves that optimum CT imaging parameters are able to reduce the metal artifacts severity on CT images. Therefore, it has potential for improving diagnostic performance in patients with severe metallic artifacts.

Characterization and attenuation study on tannin-added Rhizophora spp. particleboard at high energy photon and electron

The effective atomic number of tannin-added Rhizophora spp. particleboards was determined based on elemental composition using Energy Dispersive X-ray Analysis (EDXA). The value of mass attenuation coefficients were measured using 137Cs and 60Co gamma energies. The attenuation properties of PDD curves and beam profile of tannin-added Rhizophora spp. particleboards were investigated using Gafchromic EBT2 film at 6 MV photon and 6 MeV electrons and compared to the value in water and solid water phantoms. The results showed that tannin-added Rhizophora spp. particleboards having effective atomic number close to the value of water. The mass attenuation coefficients were near to the value of water with χ2 values of 0.018 and 0.357 to 137Cs and 60Co gamma energies respectively. The PDD of tannin-added Rhizophora spp. particleboards at 6 MV photons showed good agreement within 3.21 and 5.91% to that in solid water phantoms and water respectively. The PDD at 6 MeV electrons showed a good agreement within 3.32 and...