Density resolution in quantitative computed tomography of foam and lung
Density resolution in quantitative computed tomography of foam and lung
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DOI：
10.1118/1.597757
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发表时间：
1996-10-01
期刊：
影响因子：
3.8
通讯作者：
vanEngelshoven, JMA
中科院分区：
文献类型：
--
作者：
Kemerink, GJ;Kruize, HH;vanEngelshoven, JMA
本研究旨在评估泡沫和肺部定量计算机断层扫描（CT）的密度分辨率。密度分辨率是在CT数直方图中区分不同密度材料的能力的量度，通常由量子噪声确定。在蜂窝状固体中，通过CT采样的体积中的质量的变化通过线性部分体积效应引起密度分辨率的额外退化。样品体积与空间分辨率直接相关，可以通过选择不同的切片厚度和重建滤波器来改变。几种聚乙烯（PE）泡沫，作为肺组织的简单模型，和5名患者进行了研究，使用不同的样本量。对于均匀的PE泡沫，密度分辨率可以直接确定为CT数直方图的半高宽。泡孔尺寸为0.8-1.5 mm的泡沫的密度分辨率主要由有限的样品尺寸引起的效应决定，而不是量子噪声。密度分辨率的相对大小可以用假设的随机胞状固体模型来粗略解释。由于肺部密度不均匀，患者数据的分析更加复杂。结合卷积最小二乘拟合程序，以及在泡沫的研究中获得的信息，被用来确定密度分辨率在肺部研究。泡沫和肺的密度分辨率强烈依赖于样本体积，并且对于薄切片和尖锐过滤器非常差。因此，直方图形状相关的参数是敏感的CT上选择的空间分辨率。不推荐使用带标准或高分辨率滤光片的1 mm切片的薄切片密度测定法，除非用于确定平均密度。当使用较厚的切片时，建议使用与切片厚度相似的平面内空间分辨率。(C)1996年美国医学物理学家协会。
This study was performed to assess density resolution in quantitative computed tomography (CT) of foam and lung. Density resolution, a measure for the ability to discriminate materials of different density in a CT number histogram, is normally determined by quantum noise. In a cellular solid, variations in mass in the volumes sampled by CT cause an additional degradation of density resolution by the linear partial volume effect. The sample volume, which is directly related to spatial resolution, can be varied by choosing different section thicknesses and reconstruction filters. Several polyethene (PE) foams, as simple models of lung tissue, and five patients were investigated using various sample volumes. For the uniform PE foams, density resolution could be directly determined as the full width at half maximum of CT number histograms. Density resolution for foams with cell sizes of 0.8-1.5 mm was dominated by effects caused by the limited sample size, not by quantum noise. The relative magnitudes of density resolution could roughly be explained with a model for a hypothetic random cellular solid. Since lungs are not of uniform density, analysis of patient data was more complicated. A combined convolution least-squares fit procedure, together with information obtained in the studies of foam, were used to determine density resolution in lung studies. Density resolution, both for foams and lung, was strongly dependent on sample volume, and was quite poor for thin sections and sharp filters. Consequently, histogram-shape related parameters are sensitive to the spatial resolution chosen on CT. Thin section densitometry, using a 1-mm section with a standard or high resolution filter, is not recommended except in determining average density. When using thicker sections, an in-plane spatial resolution similar to section thickness is advised. (C) 1996 American Association of Physicists in Medicine.