Badano Aldo, Kyprianou Iacovos S, Freed Melanie, Jennings Robert J, Sempau Josep
NIBIB/CDRH Laboratory for the Assessment of Medical Imaging Systems, Division of Imaging and Applied Mathematics, Office of Science and Engineering Laboratories, US FDA, Silver Spring, MD 20993 USA.
IEEE Trans Med Imaging. 2009 May;28(5):696-702. doi: 10.1109/TMI.2008.2010443. Epub 2008 Dec 9.
We quantify the variation in resolution due to anisotropy caused by oblique X-ray incidence in indirect flat-panel detectors for computed tomography breast imaging systems. We consider a geometry and detector type utilized in breast computed tomography (CT) systems currently being developed. Our methods rely on mantis, a combined X-ray, electron, and optical Monte Carlo transport open source code. The physics models are the most accurate available in general-purpose Monte Carlo packages in the diagnostic energy range. We consider maximum-obliquity angles of 10 ( degrees ) and 13 ( degrees ) at the centers of the 30 and 40 cm detector edges, respectively, and 16 ( degrees ) at the corner of the detector. Our results indicate that blur is asymmetric and that the resolution properties vary significantly with the angle (or location) of incidence. Our results suggest that the asymmetry can be as high as a factor of 2.6 between orthogonal directions. Anisotropy maps predicted by mantis provide an understanding of the effect that such variations have on the imaging system and allow more accurate modeling and optimization of breast CT systems. These maps of anisotropy across the detector could lead to improved reconstruction and help motivate physics-based strategies for computer detection of breast lesions.
我们对用于乳腺计算机断层扫描成像系统的间接平板探测器中因倾斜X射线入射导致的各向异性所引起的分辨率变化进行了量化。我们考虑了当前正在开发的乳腺计算机断层扫描（CT）系统中所使用的一种几何结构和探测器类型。我们的方法依赖于螳螂（Mantis），这是一个结合了X射线、电子和光学的蒙特卡罗传输开源代码。这些物理模型是诊断能量范围内通用蒙特卡罗软件包中可用的最精确模型。我们分别考虑了在30厘米和40厘米探测器边缘中心处最大倾斜角为10度和13度，以及在探测器角落处为16度的情况。我们的结果表明模糊是不对称的，并且分辨率特性会随着入射角度（或位置）的变化而显著不同。我们的结果表明，正交方向之间的不对称性可能高达2.6倍。由螳螂预测的各向异性图有助于理解此类变化对成像系统的影响，并允许对乳腺CT系统进行更精确的建模和优化。这些探测器上的各向异性图可能会带来改进的重建效果，并有助于推动基于物理的乳腺病变计算机检测策略的发展。
