Department of Medical Physics, University of Patras, Patras, Greece.
Med Phys. 2012 Apr;39(4):2069-77. doi: 10.1118/1.3694670.
Synchrotron radiation (SR), being the brightest artificial source of x-rays with a very promising geometry, has raised the scientific expectations that it could be used for breast imaging with optimized results. The "in situ" evaluation of this technique is difficult to perform, mostly due to the limited available SR facilities worldwide. In this study, a simulation model for SR breast imaging was developed, based on Monte Carlo simulation techniques, and validated using data acquired in the SYRMEP beamline of the Elettra facility in Trieste, Italy. Furthermore, primary results concerning the performance of SR were derived.
The developed model includes the exact setup of the SR beamline, considering that the x-ray source is located at almost 23 m from the slit, while the photon energy was considered to originate from a very narrow Gaussian spectrum. Breast phantoms, made of Perspex and filled with air cavities, were irradiated with energies in the range of 16-28 keV. The model included a Gd(2)O(2)S detector with the same characteristics as the one available in the SYRMEP beamline. Following the development and validation of the model, experiments were performed in order to evaluate the contrast resolution of SR. A phantom made of adipose tissue and filled with inhomogeneities of several compositions and sizes was designed and utilized to simulate the irradiation under conventional mammography and SR conditions.
The validation results of the model showed an excellent agreement with the experimental data, with the correlation for contrast being 0.996. Significant differences only appeared at the edges of the phantom, where phase effects occur. The initial evaluation experiments revealed that SR shows very good performance in terms of the image quality indices utilized, namely subject contrast and contrast to noise ratio. The response of subject contrast to energy is monotonic; however, this does not stand for contrast to noise ratio, since there is a range of optimal performance for SR (18-21 keV). In comparison to conventional mammography, SR shows improved subject contrast for energies lower than the mean energy of each spectrum.
The comparison of the results of the two models, conventional and SR, proved that SR exhibits better performance in the majority of cases. The proposed simulation model offers the possibility to perform exhaustive search to evaluate the performance of SR in clinical applications such as breast imaging.
同步加速器辐射（SR）是具有极有前途的几何形状的最亮人工 X 射线源，它提高了人们的科学期望，即可以将其用于优化结果的乳房成像。由于全球范围内可用的 SR 设施有限，因此很难对该技术进行“原位”评估。在这项研究中，基于蒙特卡罗模拟技术，开发了一种用于 SR 乳房成像的模拟模型，并使用在意大利的 Trieste 的 Elettra 设施的 SYRMEP 光束线获得的数据进行了验证。此外，还得出了有关 SR 性能的初步结果。
所开发的模型包括 SR 光束线的确切设置，考虑到 X 射线源位于狭缝几乎 23 米处，而光子能量被认为源自非常窄的高斯光谱。使用范围在 16-28keV 的能量照射由 Perspex 制成并充满空气腔的乳房体模。该模型包括与 SYRMEP 光束线中可用的相同特性的 Gd(2)O(2)S 探测器。在开发和验证模型之后，进行了实验以评估 SR 的对比度分辨率。设计并利用了一种由脂肪组织制成并充满多种成分和尺寸的不均匀性的体模，以模拟常规乳房 X 光摄影和 SR 条件下的照射。
模型的验证结果与实验数据非常吻合，对比度的相关性为 0.996。仅在体模的边缘出现明显差异，因为会出现相位效应。初步评估实验表明，SR 在所用的图像质量指标（即主体对比度和对比噪声比）方面表现出非常好的性能。主体对比度对能量的响应是单调的；但是，这不适用于对比噪声比，因为对于 SR 存在最佳性能范围（18-21keV）。与常规乳房 X 光摄影相比，SR 在低于每个光谱的平均能量的能量下显示出改善的主体对比度。
对常规和 SR 两种模型的结果进行比较，证明了 SR 在大多数情况下都具有更好的性能。所提出的模拟模型提供了进行详尽搜索的可能性，以评估 SR 在乳房成像等临床应用中的性能。
