Thanakrit Chanchayanon, MSc¹ , Suttharat Suwanmanee, BSc¹ , Seri Sakjirapapong, MSc¹ , Natee Ina, MSc¹ , Suthinee Teerajaruwat, MD¹ , Jongwat Cheewakul, MSc¹

Background: Reliable quantitative computed tomography (CT) imaging requires rigorous quality control. Scan parameters such as tube voltage (kVp), tube current (mA), and slice thickness can affect CT number accuracy, image uniformity, and image noise.

Objective: To investigate the effects of tube voltage, tube current, and slice thickness on CT number accuracy, image uniformity, and noise in comparison with the International Atomic Energy Agency (IAEA) standards.

Materials and Methods: CT number uniformity and image noise were assessed using a water phantom, while CT number accuracy was evaluated using a TOS phantom containing six materials of different densities: air, water, Delrin, acrylic, nylon, and polypropylene. The linear relationship between CT numbers and material density was analyzed using regression analysis (R²), and the results were compared with IAEA tolerances.

Results: No significant differences (p>0.05) were observed between reference and measured CT numbers across the tested materials. Increasing tube current did not significantly affect CT numbers or image uniformity, although higher tube current reduced image noise. CT number linearity remained strong across all tube current settings, with R² values consistently above 0.9. Image noise for all settings remained within the IAEA tolerance range. However, at 80 kVp, image uniformity exceeded the ±10 HU limit, whereas 100-135 kVp complied with the standard.

Conclusion: CT number linearity and accuracy were highly stable across variations in tube current and slice thickness, whereas image uniformity was affected at low tube voltage. These findings emphasize the importance of selecting an appropriate kVp, particularly 120 kVp, to preserve image quality and maintain compliance with IAEA quality control standards. The results provide evidence-based support for optimizing CT imaging protocols.

Received 10 November 2025 | Revised 29 April 2026 | Accepted 8 May 2026

J Med Assoc Thai 2026;109(10):828-34

DOI: 10.35755/jmedassocthai.2026.10.03932