Department of Nuclear Science, Faculty of Science, University of Colombo, Sri Lanka.
Department of Statistics, Faculty of Science, University of Colombo, Sri Lanka.
Biomed Phys Eng Express. 2024 Oct 18;10(6). doi: 10.1088/2057-1976/ad857a.
The introduction of automatic tube current modulation (ATCM) has resulted in complex relationships between scanner parameters, patient body habitus, radiation dose, and image quality. ATCM adjusts tube current based on x-ray attenuation variations in the scan region, and overall patient dose depends on a combination of factors. This work aims to develop mathematical models that predict CT radiation dose and image noise in terms of attenuating diameter and all relevant scanner parameters.A homogenous phantom, equipped with the features to conduct discrete and continuous adaption tests, was developed to model ATCM in a Philips CT scanner. Scanner parameters were varied based on theoretical dose relationships, and a MATLAB script was developed to extract data from DICOM images. R statistical software was employed for data analysis, plotting, and regression modelling.Phantom data provided the following insights: Median tube current decreased by 81% as tube potential varied from 80 kVp to 140 kVp. Doubling the DoseRight Index (DRI) from 12 to 24, at 24 cm diameter, produced a 294% increase in mA and a 46% decrease in noise. Mean mA increased by 53% whilst mean noise increased by 5.7% as helical pitch increased from 0.6 to 0.925. Changing rotation time from 0.33s to 0.75s gave a 56% reduction in mean mA and no change in image noise. Increasing detector collimation () resulted in higher tube currents and lower output image noise values, asandwere varied independently. Interpreting these results to apply transformations relevant to each independent variable produced models for tube current and noise with adjusted R-squared values of 0.965 and 0.912, respectively.The models developed more accurately predict radiation dose and image quality for specific patients and scanner settings. They provide imaging professionals with a practical tool to optimize scan protocols according to patient diameters and clinical objectives.
自动管电流调制（ATCM）的引入导致了扫描参数、患者体型、辐射剂量和图像质量之间的复杂关系。ATCM 根据扫描区域的 X 射线衰减变化来调整管电流，而患者的总剂量取决于多种因素的组合。本研究旨在开发数学模型，以衰减直径和所有相关扫描参数来预测 CT 辐射剂量和图像噪声。
我们开发了一个配备有离散和连续自适应测试功能的均质体模，以在飞利浦 CT 扫描仪中模拟 ATCM。根据理论剂量关系来改变扫描仪参数，并开发了一个 MATLAB 脚本从 DICOM 图像中提取数据。采用 R 统计软件进行数据分析、绘图和回归建模。
当管电压从 80kVp 变化到 140kVp 时，管电流中位数降低了 81%。在 24cm 直径处，将 DoseRight Index（DRI）从 12 倍增加到 24 倍，会使 mA 增加 294%，噪声降低 46%。当螺旋桨从 0.6 增加到 0.925 时，平均 mA 增加 53%，平均噪声增加 5.7%。将旋转时间从 0.33s 改变到 0.75s 会使平均 mA 降低 56%，而图像噪声没有变化。增加探测器准直（）会产生更高的管电流和更低的输出图像噪声值，当和独立变化时。
解释这些结果以应用于每个独立变量的变换，分别为管电流和噪声生成了调整后的 R 平方值为 0.965 和 0.912 的模型。
所开发的模型能够更准确地预测特定患者和扫描仪设置的辐射剂量和图像质量。它们为影像专业人员提供了一种实用工具，可以根据患者直径和临床目标来优化扫描协议。
