X射线数字成像系统传递函数模型

Transfer function model on X-ray digital radiography system

基于非晶硅面阵探测器的工业X射线数字成像系统是目前最先进的射线检测技术,其系统传递函数PSF(Point Spread-Function)由非点源形成的系统几何弥散、闪烁体膜层弥散、探测器像元孔径采样3部分组成.通过分析各环节射线透照场强的分布特性,以高斯函数近似各环节相应PSF的数学表达式,建立了整个数字成像系统的PSF及其MTF(Modulation Transfer Function)理论模型,并由系统PSF的半波宽得到系统的近似有效带宽.以PaxScan2520面阵探测器组成的X射线数字成像系统为例,通过实验验证了该模型的合理性,利用此模型可快速估计数字成像系统可分辨被检试件的最小细节,为工业射线检测提供理论基础.

Currently, industry X-ray digital radiography system based on the amorphous silicon X-ray flat-panel detector is the latest test technology. The system transfer function, namely point spread-function （PSF） consists of system geometry dispersion caused by nonpiont-source, scintillator screen dispersion and aperture sampling of detector pixels. The intensity distribution of X-ray penetration field was analyzed at each segment. The mathematical model of system PSF and modulation transfer function （MTF） was established by means of Gassian function which is the mathematic expression to describe the transfer behavior of each compose segment of the system PSF. So the system approximating effective bandwidth was achieved from half-wave width of the system PSF. In the case of the digital radiography system based on PaxScan2520 flat-panel detector; the experiment which validates the mathematical model is simply appropriate to estimate resoluble minimum detail of work-piece tested by the system and provide theoretic foundation for industry X-ray radiography.