Medical Metrology Team, Safety Measurement Institute, Korea Research Institute of Standards and Science (KRISS), Daejeon, South Korea.
School of Integrated Technology, Yonsei University, Incheon, South Korea.
PLoS One. 2022 May 19;17(5):e0267850. doi: 10.1371/journal.pone.0267850. eCollection 2022.
We investigated the effect of the optical blurring of X-ray source on digital breast tomosynthesis (DBT) image quality using well-designed DBT simulator and table-top experimental systems. To measure the in-plane modulation transfer function (MTF), we used simulated sphere phantom and Teflon sphere phantom and generated their projection data using two acquisition modes (i.e., step-and-shoot mode and continuous mode). After reconstruction, we measured the in-plane MTF using reconstructed sphere phantom images. In addition, we measured the anatomical noise power spectrum (aNPS) and signal detectability. We constructed simulated breast phantoms with a 50% volume glandular fraction (VGF) of breast anatomy using the power law spectrum and inserted spherical objects with 1 mm, 2 mm, and 5 mm diameters as breast masses. Projection data were acquired using two acquisition modes, and in-plane breast images were reconstructed using the Feldkamp-Davis-Kress (FDK) algorithm. For the experimental study, we used BR3D breast phantom with 50% VGF and obtained projection data using a table-top experimental system. To compare the detection performance of the two acquisition modes, we calculated the signal detectability using the channelized Hotelling observer (CHO) with Laguerre-Gauss (LG) channels. Our results show that spatial resolution of in-plane image in continuous mode was degraded due to the optical blurring of X-ray source. This blurring effect was reflected in aNPS, resulting in large β values. From a signal detectability perspective, the signal detectability in step-and-shoot mode is higher than that in continuous mode for small spherical signals but not large spherical signals. Although the step-and-shoot mode has disadvantage in terms of scan time compared to the continuous mode, scanning in step-and-shoot mode is better for detecting small signals, indicating that there is a tradeoff between scan time and image quality.
我们使用精心设计的数字乳腺断层合成（DBT）模拟器和台式实验系统研究了 X 射线源光学模糊对 DBT 图像质量的影响。为了测量平面调制传递函数（MTF），我们使用模拟球体和聚四氟乙烯球体，并使用两种采集模式（即步进式和连续式）生成它们的投影数据。重建后，我们使用重建球体的图像来测量平面 MTF。此外，我们还测量了解剖噪声功率谱（aNPS）和信号检测能力。我们使用幂律谱构建了具有 50%乳腺解剖体积腺体分数（VGF）的模拟乳腺体模，并插入了直径为 1 毫米、2 毫米和 5 毫米的球形物体作为乳腺肿块。使用两种采集模式获取投影数据，并使用 Feldkamp-Davis-Kress（FDK）算法重建平面乳腺图像。在实验研究中，我们使用具有 50%VGF 的 BR3D 乳腺体模，并使用台式实验系统获得投影数据。为了比较两种采集模式的检测性能，我们使用具有拉盖尔-高斯（LG）通道的信道化霍特林观测器（CHO）计算信号检测能力。我们的结果表明，由于 X 射线源的光学模糊，连续模式下的平面图像空间分辨率降低。这种模糊效应反映在 aNPS 中，导致较大的β值。从信号检测能力的角度来看，对于小球形信号，步进式模式的信号检测能力高于连续式模式，但对于大球形信号则不然。尽管与连续模式相比，步进式模式在扫描时间方面存在劣势，但在检测小信号方面，步进式扫描更好，这表明在扫描时间和图像质量之间存在权衡。
