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Lubis, L. E.
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Energy Physics

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Weighted CTDI Equation for 3D Rotational Angiography: A Monte Carlo Study Azzi, A.; Hidayat, R.; Rosa, A.; Lubis, L. E.
Atom Indonesia VOL 50, NO 1 (2024): APRIL 2024
Publisher : National Research and Innovation Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.55981/aij.2024.1307

Abstract

This study aims to verify the weighted Computed Tomography Dose Index (CTDIw) coefficients of 3D rotational angiography (3DRA) procedure using Monte Carlo simulation. The Monte Carlo simulation EGSnrc usercode was employed for 3D dose simulations of the rotational angiography procedure. A virtual phantom resembles the head CTDI phantom was constructed, with a diameter of 16 cm and a density resembling polymethyl methacrylate (1.13 g/cm3). A series of virtual phantoms consisting of 5 images with ionization chamber detectors at the center position, 12 o'clock, 9 o'clock, 6 o'clock, and 3 o'clock were acquired. Simulations were performed with photon sources of 70 and 109 kVp for 200-degree x-ray tube rotation. The field of view was divided into narrow, wide, and full beam with diameters of 1.7 cm; 4.9 cm; and 8.6 cm, respectively. The simulated doses at the ionization chamber were processed into weighting factor for weighted CTDI and compared with direct measurements. The dose ratio between peripheral and center positions for 360° CBCT and 200° 3DRA was 1:1 and 1:3 in this study. The weighting factors for 3DRA were determined as CTDIcenter = ¼ and CTDIperiphery = ¾. The measured average percentage difference of CTDIw between our weighted factor and conventional CTDIw was 1.75 % (-3.99 % to 6.08 %). The x-ray tube position of 3DRA impacted the accuracy of weighting factor of CTDIw, with implications for the proposed weighting factor (Wcenter = ¼ and Wperiphery = ¾) when using a 3DRA machine.
Comparison of Lung Cancer Lesion Detection Capability on Standard Dose and Low Dose Computed Tomography Capabilities: An In-House Phantom Study Hutami, A. K.; Raharja, H. D. R.; Lubis, L. E.; Soejoko, D. S.
Atom Indonesia Vol 51, No 3 (2025): DECEMBER 2025
Publisher : National Research and Innovation Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.55981/aij.2025.1587

Abstract

The use of Low-Dose Computed Tomography (LDCT) protocols has garnered significant attention, particularly in detecting cancerous lesions in high-risk populations. However, the drawback of low-dose CT protocols results in image noise. Solutions introduced, such as the use of reconstruction techniques, tend to be time-inefficient, complex, and costly. This paper aims to explain the design and construction of an approach for evaluating the quality of lung cancer lesion imaging that is adequate and easily implementable. In this study, a custom-designed in-house phantom is required to simulate lung cancer lesions. The in-house phantom was constructed from organ or tissue-equivalent materials and equipped with various Hounsfield Unit values and lesion diameter sizes, which were determined based on data from 73 patients, consisting of both males and females, using contrast. Scans were performed on the phantom using standard-dose and low-dose protocol parameters. The results demonstrated that the low-dose protocol was able to detect small lesions at lower radiation levels. The contrast difference is quite good with a Signal Difference to Noise Ratio (SDNR) value ≥ 5. The image was optimum with a relatively high Figure of Merit (FOM). Additionally, Noise Power Spectrum (NPS) measurements provided accurate results within a specific range of spatial frequencies.
Co-Authors Azzi, A. Hutami, A. K. R. Hidayat Raharja, H. D. R. Rosa, A. Soejoko, D. S.