Model-based PSF and MTF estimation and validation from skeletal clinical CT images
Model-based PSF and MTF estimation and validation from skeletal clinical CT images
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DOI：
10.1118/1.4835515
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发表时间：
2014-01-01
期刊：
影响因子：
3.8
通讯作者：
Whyne, Cari M.
中科院分区：
文献类型：
--
作者：
Pakdel, Amirreza;Mainprize, James G.;Whyne, Cari M.
目的：提出一种利用骨界面估计点扩散函数(PSF)的方法来校正CT图像中由于图像模糊而导致的估计薄骨厚度的系统性误差。方法：从11例身体颅面骨的临床CT扫描图像中，用我们的方法得到具有不同z(扫描)方向和x、y方向幅度的高斯型PSFs。根据扫描参数和重建方法的多种组合对这些PSF进行了估计。在图像切片平面和纵轴内使用倾斜狭缝技术测量每个扫描设置的实际PSF。结果：在xy和z轴上，PSF的实际半高宽(FWHM)分别为0.09+/-0.05和0.14+/-0.11 mm。在75%、50%、25%、10%和5%MTF水平下测量的预测频率在xy和z轴上的总误差分别为0.06+/-0.07和0.06+/-0.04个周期/mm。估计的准确性取决于它们是用标准核(东芝FC68，平均误差0.06+/-0.05 mm，MTF平均误差0.02+/-0.02个周期/mm)还是高分辨率骨核(东芝FC81，PSF FWHM误差0.12+/-0.03 mm，MTF平均误差0.09+/-0.08个周期/mm)重建的。结论：对于使用标准重建核重建的图像，该方法在3D中是准确的，这符合高斯PSF假设，但当使用高分辨率骨核时，精度较低。该方法是一种实用而独立的方法，可以在临床CT图像中估计以皮质骨为特征的PSF，而不需要体模或任何关于扫描仪特定参数的先验知识。(C)2014年美国医学物理学家协会。
Purpose: A method was developed to correct for systematic errors in estimating the thickness of thin bones due to image blurring in CT images using bone interfaces to estimate the point-spread-function (PSF). This study validates the accuracy of the PSFs estimated using said method from various clinical CT images featuring cortical bones.Methods: Gaussian PSFs, characterized by a different extent in the z (scan) direction than in the x and y directions were obtained using our method from 11 clinical CT scans of a cadaveric craniofacial skeleton. These PSFs were estimated for multiple combinations of scanning parameters and reconstruction methods. The actual PSF for each scan setting was measured using the slanted-slit technique within the image slice plane and the longitudinal axis. The Gaussian PSF and the corresponding modulation transfer function (MTF) are compared against the actual PSF and MTF for validation.Results: The differences (errors) between the actual and estimated full-width half-max (FWHM) of the PSFs were 0.09 +/- 0.05 and 0.14 +/- 0.11 mm for the xy and z axes, respectively. The overall errors in the predicted frequencies measured at 75%, 50%, 25%, 10%, and 5% MTF levels were 0.06 +/- 0.07 and 0.06 +/- 0.04 cycles/mm for the xy and z axes, respectively. The accuracy of the estimates was dependent on whether they were reconstructed with a standard kernel (Toshiba's FC68, mean error of 0.06 +/- 0.05 mm, MTF mean error 0.02 +/- 0.02 cycles/mm) or a high resolution bone kernel (Toshiba's FC81, PSF FWHM error 0.12 +/- 0.03 mm, MTF mean error 0.09 +/- 0.08 cycles/mm).Conclusions: The method is accurate in 3D for an image reconstructed using a standard reconstruction kernel, which conforms to the Gaussian PSF assumption but less accurate when using a high resolution bone kernel. The method is a practical and self-contained means of estimating the PSF in clinical CT images featuring cortical bones, without the need phantoms or any prior knowledge about the scanner-specific parameters. (C) 2014 American Association of Physicists in Medicine.