Schiabel H, Frére A F, Marques P M
Escola De Engenharia De São Carlos, Universidade De São Paulo, Department of Electrical Engineering, Brazil.
Med Phys. 1993 Jul-Aug;20(4):999-1005. doi: 10.1118/1.597146.
In this paper, it is demonstrated that obtaining OTF's for only two directions, parallel and perpendicular to the x-ray tube axis, is insufficient to completely describe the performance of nonisotropic radiographic systems. By performing experiments with three radiological systems in which slit images were obtained for ten different directions, we confirmed that OTF's vary in a nonlinear fashion for directions that are intermediate to the parallel and perpendicular ones. Moreover, we have also identified for each system a range of field orientations--referred to as "Optimum Region"--where sharper images can be obtained. These experimental results can be accounted for by the transfer functions theory.
本文表明，仅获取平行于和垂直于X射线管轴的两个方向的光学传递函数（OTF）不足以完全描述非各向同性射线照相系统的性能。通过对三个放射系统进行实验，在十个不同方向上获取狭缝图像，我们证实，对于介于平行和垂直方向之间的中间方向，OTF呈非线性变化。此外，我们还为每个系统确定了一系列视野方向——称为“最佳区域”——在该区域可获得更清晰的图像。这些实验结果可用传递函数理论来解释。
