A methodology for image quality evaluation of advanced CT systems
A methodology for image quality evaluation of advanced CT systems
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DOI：
10.1118/1.4791645
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发表时间：
2013-03-01
期刊：
影响因子：
3.8
通讯作者：
Samei, Ehsan
中科院分区：
文献类型：
--
作者：
Wilson, Joshua M.;Christianson, Olav I.;Samei, Ehsan
目的：这项工作涉及到一个基于体模的方法，以量化的性能管电流调制和迭代重建在现代计算机断层扫描（CT）系统的发展。量化包括分辨率，HU的准确性，噪声和噪声纹理占对比度的影响，规定的剂量，重建算法，和身体size.Methods：一个42厘米长，22.5公斤的聚乙烯体模设计模型四个身体尺寸。每个尺寸由用于测量噪声功率谱（SNR）的均匀部分和用于测量HU和基于任务的调制传递函数（T 'TF）的包含各种杆的特征部分表示。使用一系列管电流调制设置（NI水平）和重建方法（FBP和ASIR 30）在临床CT系统（GE，750 HD）上扫描体模。开发了一个图像质量分析程序来处理体模数据，以计算作为对比度，处方剂量和身体尺寸的函数的目标图像质量指标。在管电流调制方面，管电流和产生的图像噪声根据制造商规范的预期作为体模尺寸的函数而变化：从16- 37-cm部分，每个杆的HU对比度与体模尺寸呈负相关，噪声相对恒定（< 5%变化）。通过迭代重建，TTF表现出对比度依赖性，对于较高对比度的对象具有更好的性能。在低噪声水平下，迭代重建的TTF优于FBP，但在高噪声下，这种优势并没有在所有对比度水平下保持。相对于FBP，迭代重建的振幅降低了30%，峰值频率偏移了0.1mm（-1）。结论：创建了体模和图像质量分析软件，用于评估在对比度、剂量和身体尺寸范围内的CT图像质量。该测试平台实现了稳健的SNR、TTF、HU和像素噪声测量，作为能够表征重建算法和管电流调制技术性能的身体尺寸的函数。(C)2013年美国医学物理学家协会。[http：//dx.doi.org/10.1118/1.4791645]
Purpose: This work involved the development of a phantom-based method to quantify the performance of tube current modulation and iterative reconstruction in modern computed tomography (CT) systems. The quantification included resolution, HU accuracy, noise, and noise texture accounting for the impact of contrast, prescribed dose, reconstruction algorithm, and body size.Methods: A 42-cm-long, 22.5-kg polyethylene phantom was designed to model four body sizes. Each size was represented by a uniform section, for the measurement of the noise-power spectrum (NPS), and a feature section containing various rods, for the measurement of HU and the task-based modulation transfer function (T'TF). The phantom was scanned on a clinical CT system (GE, 750HD) using a range of tube current modulation settings (NI levels) and reconstruction methods (FBP and ASIR30). An image quality analysis program was developed to process the phantom data to calculate the targeted image quality metrics as a function of contrast, prescribed dose, and body size.Results: The phantom fabrication closely followed the design specifications. In terms of tube current modulation, the tube current and resulting image noise varied as a function of phantom size as expected based on the manufacturer specification: From the 16- to 37-cm section, the HU contrast for each rod was inversely related to phantom size, and noise was relatively constant (< 5% change). With iterative reconstruction, the TTF exhibited a contrast dependency with better performance for higher contrast objects. At low noise levels, TTFs of iterative reconstruction were better than those of FBP, but at higher noise, that superiority was not maintained at all contrast levels. Relative to FBP, the NPS of iterative reconstruction exhibited an similar to 30% decrease in magnitude and a 0 1 mm(-1) shift in the peak frequency.Conclusions: Phantom and image quality analysis software were created for assessing CT image quality over a range of contrasts, doses, and body sizes. The testing platform enabled robust NPS, TTF, HU, and pixel noise measurements as a function of body size capable of characterizing the performance of reconstruction algorithms and tube current modulation techniques. (C) 2013 American Association of Physicists in Medicine. [http://dx.doi.org/10.1118/1.4791645]