Department of Radiological Technology, School of Health Sciences, Faculty of Medicine, Niigata University, Niigata 951-8518, Japan.
J Appl Clin Med Phys. 2012 Nov 8;13(6):3868. doi: 10.1120/jacmp.v13i6.3868.
A computed tomography (CT) image simulation technique based on the point spread function (PSF) was applied to analyze the accuracy of CT-based clinical evaluations of lung nodule density. The PSF of the CT system was measured and used to perform the lung nodule image simulation. Then, the simulated image was resampled at intervals equal to the pixel size and the slice interval found in clinical high-resolution CT (HRCT) images. On those images, the nodule density was measured by placing a region of interest (ROI) commonly used for routine clinical practice, and comparing the measured value with the true value (a known density of object function used in the image simulation). It was quantitatively determined that the measured nodule density depended on the nodule diameter and the image reconstruction parameters (kernel and slice thickness). In addition, the measured density fluctuated, depending on the offset between the nodule center and the image voxel center. This fluctuation was reduced by decreasing the slice interval (i.e., with the use of overlapping reconstruction), leading to a stable density evaluation. Our proposed method of PSF-based image simulation accompanied with resampling enables a quantitative analysis of the accuracy of CT-based evaluations of lung nodule density. These results could potentially reveal clinical misreadings in diagnosis, and lead to more accurate and precise density evaluations. They would also be of value for determining the optimum scan and reconstruction parameters, such as image reconstruction kernels and slice thicknesses/intervals.
基于点扩散函数（PSF）的计算机断层扫描（CT）图像模拟技术被应用于分析基于 CT 的肺结节密度临床评估的准确性。测量了 CT 系统的 PSF，并用于进行肺结节图像模拟。然后，以等于临床高分辨率 CT（HRCT）图像中的像素大小和切片间隔的间隔对模拟图像进行重采样。在这些图像上，通过放置通常用于常规临床实践的感兴趣区域（ROI）来测量结节密度，并将测量值与真实值（用于图像模拟的已知物体函数密度）进行比较。定量确定，测量的结节密度取决于结节直径和图像重建参数（内核和切片厚度）。此外，测量的密度取决于结节中心和图像体素中心之间的偏移量而波动。通过减小切片间隔（即使用重叠重建）可以减小这种波动，从而实现稳定的密度评估。我们提出的基于 PSF 的图像模拟与重采样相结合的方法，可以对基于 CT 的肺结节密度评估的准确性进行定量分析。这些结果可能揭示出诊断中的临床误读，并导致更准确和精确的密度评估。它们对于确定最佳扫描和重建参数（例如图像重建内核和切片厚度/间隔）也具有价值。
