Imaging Research, Sunnybrook Health Sciences Centre, S-657, 2075 Bayview Avenue, Toronto, Ontario M4N 3M5, Canada.
Med Phys. 2009 Oct;36(10):4425-32. doi: 10.1118/1.3215926.
Digital breast tomosynthesis uses a limited number (typically 10-20) of low-dose x-ray projections to produce a pseudo-three-dimensional volume tomographic reconstruction of the breast. The purpose of this investigation was to characterize and evaluate the effect of scattered radiation on the image quality for breast tomosynthesis. In a simulation, scatter point spread functions generated by a Monte Carlo simulation method were convolved over the breast projection to estimate the distribution of scatter for each angle of tomosynthesis projection. The results demonstrate that in the absence of scatter reduction techniques, images will be affected by cupping artifacts, and there will be reduced accuracy of attenuation values inferred from the reconstructed images. The effect of x-ray scatter on the contrast, noise, and lesion signal-difference-to-noise ratio (SDNR) in tomosynthesis reconstruction was measured as a function of the tumor size. When a with-scatter reconstruction was compared to one without scatter for a 5 cm compressed breast, the following results were observed. The contrast in the reconstructed central slice image of a tumorlike mass (14 mm in diameter) was reduced by 30%, the voxel value (inferred attenuation coefficient) was reduced by 28%, and the SDNR fell by 60%. The authors have quantified the degree to which scatter degrades the image quality over a wide range of parameters relevant to breast tomosynthesis, including x-ray beam energy, breast thickness, breast diameter, and breast composition. They also demonstrate, though, that even without a scatter rejection device, the contrast and SDNR in the reconstructed tomosynthesis slice are higher than those of conventional mammographic projection images acquired with a grid at an equivalent total exposure.
数字乳腺断层合成技术使用有限数量（通常为 10-20 个）的低剂量 X 射线投影来产生乳房的伪三维体积断层重建。本研究的目的是描述和评估散射辐射对乳腺断层合成图像质量的影响。在模拟中，使用蒙特卡罗模拟方法生成的散射点扩散函数在乳房投影上进行卷积，以估计每个断层合成投影角度的散射分布。结果表明，在没有散射减少技术的情况下，图像将受到杯状伪影的影响，并且从重建图像推断出的衰减值的准确性将会降低。测量了 X 射线散射对断层合成重建中的对比度、噪声和病变信号-噪声比（SDNR）的影响，作为肿瘤大小的函数。当将有散射的重建与无散射的重建进行比较时，对于压缩后的 5 厘米乳房，观察到以下结果。类瘤肿块（直径 14 毫米）的重建中央切片图像中的对比度降低了 30%，体素值（推断的衰减系数）降低了 28%，SDNR 降低了 60%。作者已经量化了散射在很大范围内降低图像质量的程度，这些范围与乳腺断层合成术相关，包括 X 射线束能量、乳房厚度、乳房直径和乳房组成。然而，他们还表明，即使没有散射排斥装置，重建断层合成切片中的对比度和 SDNR 也高于在等效总曝光下使用网格获得的常规乳腺摄影投影图像。
