エッジ法による presampled MTF の簡便な解析方法の提案と検証

抄録

The edge method adopted by the International Electrotechnical Commission (IEC) for presampled modulation transfer function (presampled MTF) measurement has the advantage that the complexity and limitations of image acquisition are less than those of the slit method. On the other hand, it has the disadvantage that the maintenance of accuracy is difficult because of the noise amplification caused by the differentiation. In order to reduce this disadvantage, we proposed an effective method in which many edge profiles are synthesized and then the synthesized edge profiles are bound into regular interval bins. Furthermore, the influences of some factors in edge profile analysis on measurement accuracy were examined. The appropriate width of one bin was 10-20% of the sampling interval. Measurement error of the inclination angle of the edge should be made up to 0.05°. The range of the angle was allowed to be from 1 to 5 degrees. If these conditions were fulfilled, accurate measurement up to the Nyquist frequency (fn) was possible. Using an actual computed radiography (CR) system, the presampled MTF was obtained by the slit method and our edge method. The two results showed good agreement.