Accuracy of CT-based thickness measurement of thin structures: Modeling of limited spatial resolution in all three dimensions
Accuracy of CT-based thickness measurement of thin structures: Modeling of limited spatial resolution in all three dimensions
复制标题
DOI：
10.1118/1.1521940
复制
发表时间：
2003-01-01
期刊：
影响因子：
3.8
通讯作者：
Genant, HK
中科院分区：
文献类型：
--
作者：
Prevrhal, S;Fox, JC;Genant, HK
用计算机断层扫描（CT）测量薄结构（如椎体或股骨颈的皮质壳）的宽度受到CT系统空间分辨率的限制。有限的空间分辨率存在于CT图像平面内和垂直于它，并且可以分别由平面内点扩散函数（PSF）和跨平面切片灵敏度分布（SSP）来描述。本研究的目的是确认薄结构的厚度测量误差主要取决于对象的空间定位和CT在所有三个维度上的空间分辨率限制，并评估误差本身的大小。我们比较了计算机模型，将这两种影响，以实验评估的欧洲脊柱体模的皮质厚度。分析包括变化。CT切片宽度、测量方向以及纵向扫描仪和体模轴的未对准角度β。在所有配置中，模型与测量值的一致性良好，总体误差为0.17 mm。这表明PSF和SSP是足够的系统特性，可以预测测量值与真实宽度的偏差。测量值和真实皮质厚度值之间的误差Δ（真实）平均为1.5 mm，与切片宽度d和β呈强正相关。当消除跨平面部分容积效应时，有限的平面内分辨率仍然导致Delta（真）高估0.68（137%）、0.27（27%）和0.06 mm（4%）（Delta（真）= 0.5、1.0和1.5 mm）。对于1.0 mm及以上的Delta（真实），表明尽管绝对皮质厚度值可能无法准确测量，但两个值之间的相对差异反映在测量中。皮质厚度测量的含义是脊柱皮质壳太薄，而即使对于较大的错位角度，尤其是当选择较小的CT切片宽度时，也可以使用CT对股骨颈位置进行准确评估，表现出差异和绝对值的较厚皮质壳。(C)2003年美国物理学家协会。在医学方面。
Measurement of the width of thin structures such as the cortical shell of the vertebral body or femoral neck with computed tomography (CT) is limited by the spatial resolution of the CT system. Limited spatial resolution exists both within the CT image plane and perpendicular to it and can be described by the in-plane point spread function (PSF) and the across-plane slice sensitivity profile (SSP), respectively. The goal of this study was to confirm that errors of thickness measurement of thin structures critically depend on the spatial positioning of the object and the spatial resolution limitations of CT in all three dimensions, and to assess the size of the errors themselves. We compared computer models that incorporated both effects to experimentally assessed cortical thicknesses of the European Spine Phantom. Analysis included varying. CT slice width, the orientation of measurement and angle beta of misalignment of longitudinal scanner and phantom axes. Agreement of models with measurements was good in all configurations with an overall error of 0.17 mm. This showed that PSF and SSP are adequate system characteristics to predict deviation of measured values from true widths. Errors between measurements and true cortical thickness values Delta(true) averaged to 1.5 mm were strongly positively correlated with slice width d and beta. When the across-plane partial volume effect was eliminated, limited in-plane resolution still accounted for overestimation of Delta(true) by 0.68 (137%), 0.27 (27%), and 0.06 mm (4%) for Delta(true),=0.5, 1.0, and 1.5 mm, respectively. For Delta(true), of 1.0 mm and above, it was shown that although the absolute cortical thickness values might not be accurately measurable, relative differences between two values are reflected in measurement. Implications for cortical thickness measurement are that the spinal cortical shell is too thin, whereas accurate assessment at locations of the femoral neck exhibiting a thicker cortical shell of both difference and absolute values should be possible with CT even for larger misalignment angles, especially when a smaller CT slice width is chosen. (C) 2003 American Association of Physicists. in Medicine.