Choi Chloe J, Barufaldi Bruno, Teixeira João P V, Acciavatti Raymond J, Maidment Andrew D A
Department of Radiology, University of Pennsylvania, Philadelphia, USA.
Federal University of Paraiba, João Pessoa, Brazil.
Proc SPIE Int Soc Opt Eng. 2022 May;12286. doi: 10.1117/12.2626272. Epub 2022 Jul 13.
X-ray imaging results in inhomogeneous irradiation of the detector and distortion of structures in the periphery of the image; yet the spatial dependency of tomosynthesis image-quality metrics has not been extensively investigated. In this study, we use virtual clinical trials to quantify the spatial dependency of lesion detectability in our lab's next-generation tomosynthesis (NGT) system. Two geometries were analyzed: a conventional geometry with mediolateral source motion, and a NGT geometry with T-shaped motion. Breast parenchymal texture was simulated using an open-source library with Perlin noise using 400 random seeds and three breast densities. Spherical mass lesions were inserted in the central slice of the phantoms using the voxel additive method. Image acquisition was simulated using in-house ray-tracing software and simple backprojection was performed using commercial reconstruction software. Lesion detectability with Channelized Hotelling Observers (CHOs) was analyzed using receiver operating characteristic curves to measure the detectability index (d') at 154 unique locations for the lesions. We also divided images into three non-overlapping regions (differing in terms of distance from the chest wall). At the 0.05 level of significance, there was a statistically significant difference between the geometries in terms of d' in one of the three regions, with the T geometry offering superior detectability. Examining all 154 lesion locations, the T geometry was found to offer lower spread (standard deviation) in d' values throughout the image area, and superior d' at 83 of 154 locations (53.9%). In summary, the T geometry enables superior lesion detection and mitigates anisotropies.
X射线成像会导致探测器受到不均匀照射以及图像周边结构的畸变；然而，断层合成图像质量指标的空间依赖性尚未得到广泛研究。在本研究中，我们使用虚拟临床试验来量化我们实验室下一代断层合成（NGT）系统中病变可检测性的空间依赖性。分析了两种几何结构：一种是具有内外侧源运动的传统几何结构，另一种是具有T形运动的NGT几何结构。使用具有柏林噪声的开源库，利用400个随机种子和三种乳腺密度来模拟乳腺实质纹理。使用体素加法方法将球形肿块病变插入到体模的中央切片中。使用内部光线追踪软件模拟图像采集，并使用商业重建软件进行简单的反投影。使用通道化霍特林观察者（CHOs）分析病变可检测性，通过接收者操作特征曲线来测量病变在154个独特位置的检测指数（d'）。我们还将图像分为三个不重叠的区域（根据与胸壁的距离不同）。在0.05的显著性水平下，在三个区域之一中，两种几何结构在d'方面存在统计学上的显著差异，T形几何结构具有更好的可检测性。检查所有154个病变位置，发现T形几何结构在整个图像区域的d'值中具有更低的离散度（标准差），并且在154个位置中的83个（53.9%）具有更高的d'。总之，T形几何结构能够实现更好的病变检测并减轻各向异性。
