Analysis of the Relationship Between Tube Current-Time (Mas) and Exposure Index in Digital Chest Radiography

Chest radiography is one of the most frequently performed radiological examinations, requiring optimization of exposure parameters to achieve adequate image quality while minimizing unnecessary radiation exposure. Milliampere-second (mAs) is an important exposure parameter that affects the quantity of X-ray photons reaching the detector and consequently influences image noise and Exposure Index (EI). This study aimed to analyze the effect of mAs variations on image noise and EI in digital chest radiography and to determine an appropriate mAs setting based on the relationship between these parameters. This quantitative experimental study used an anthropomorphic chest phantom and a digital radiography system. Seven mAs variations of 4, 8, 10, 12, 16, 20, and 25 mAs were applied while maintaining a constant tube voltage of 80 kVp. Image noise was measured as the standard deviation (SD) of pixel values, while EI was recorded from the digital radiography system. Data were analyzed using descriptive statistics, normality testing, and simple linear regression with IBM SPSS Statistics version 27. The results showed that EI increased consistently with increasing mAs, from 285.44 at 4 mAs to 1,709.81 at 25 mAs. Regression analysis demonstrated a statistically significant positive effect of mAs on EI (F = 1009.928; p < 0.001), with a regression coefficient of 68.609, indicating an increase of 68.609 EI units for every 1 mAs increase. In contrast, noise values fluctuated across the mAs variations, ranging from 456.882 at 4 mAs to 170.658 at 16 mAs and increasing to 331.297 at 25 mAs. The effect of mAs variation on noise was not statistically significant (F = 2.782; p = 0.156).