Imaging characteristics of x-ray capillary optics in digital mammography.
Imaging characteristics of x-ray capillary optics in digital mammography.
复制标题
数字乳腺X线摄影中X射线毛细管光学器件的成像特性。
DOI：
10.1118/1.597703
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发表时间：
1996
期刊：
影响因子：
3.8
通讯作者：
C. MacDonald
中科院分区：
文献类型：
--
作者：
D. Kruger;C. Abreu;E. Hendee;A. Kocharian;W. Peppler;C. Mistretta;C. MacDonald
计算机放射成像 (CR) 因其良好的低空间频率 MTF 和相对较宽的曝光宽容度而在数字乳腺 X 线摄影筛查中显示出前景。 CR 图像格式尚未获得临床认可，因为与胶片屏幕图像相比，其高空间频率分辨率较低。 X 射线毛细管光学器件在乳房和 CR 磷光体成像板之间对齐，几乎完全捕获初级 X 射线光子。由于接受角度非常小，与主轨迹成角度超过约 1.6 x 10(-3) 弧度的散射光子将不会在毛细管光学入口处被接受。检测到的散射的虚拟消除意味着几乎 100% 的可能的主要对比度应该在图像中可见。此外，图像可以放大，而焦点不会模糊。 CR 图像的有效分辨率可以提高等于该放大倍数的倍数。未来毛细管光学器件的临床实施预计将采用大型、固定、患者术后光学器件的形式，该光学器件接受来自整个乳房的原发性光学器件，或者采用扫描整个乳房的扇形光学器件。测试毛细管光学器件的测量显示散射分数降低至 0.018。与防散射网格和无网格方法相比，有机玻璃对比度细节模型的图像显示图像对比度相应增加。使用高纯度锗探测器进行的光谱透射测量显示，在乳腺 X 光检查能量范围内具有良好的初级透射率 (45%-50%)。固定和扫描毛细管光学器件的 MTF 测量结果显示，扫描光学器件的 MTF 水平在 5% 时提高到 8.4 mm-1，固定光学器件的 MTF 提高到 9.2 mm-1，与没有放大或毛细管光学器件的 CR MTF 相比分别提高了 68% 和 84%。
Computed radiography (CR) has shown promise in digital mammographic screening due to its good low spatial frequency MTF and its relatively wide exposure latitude. The CR image format has not gained acceptance clinically because of reduced high spatial frequency resolution as compared to film-screen images. X-ray capillary optics, aligned between the breast and CR phosphor imaging plate, will capture primary x-ray photons almost exclusively. Due to the very small angle of acceptance, scattered photons angled more than about 1.6 x 10(-3) radians from primary trajectory will not be accepted at the capillary optic entrance. The virtual elimination of detected scatter means almost 100% of the possible primary contrast should be visible in the image. In addition, the image can be magnified without focal spot blurring. Effective resolution of CR images can be increased by a factor equal to that magnification. Clinical implementation of future capillary optics are expected to be either in the form of a large, stationary, post-patient optic that accepts primary from the entire breast or a fan-shaped optic that is scanned across the breast. Measurements of a test capillary optic showed a reduction of scatter fraction to 0.018. Images of a lucite contrast detail phantom revealed a corresponding increase in image contrast when compared to anti-scatter grid and no grid methods. Spectral transmission measurements using a high-purity germanium detector showed good primary transmission (45%-50%) in the mammographic energy range. The MTF measurements of both stationary and scanned capillary optics showed improvement at the 5% MTF level to 8.4 mm-1 for scanned optics and 9.2 mm-1 for stationary optics representing a 68% and 84% respective increase over the CR MTF without magnification or capillary optics.