Evaluation of parallactic unsharpness caused by flat panel detector in digital radiography / 中华放射学杂志

ABSTRACT

Objective To evaluate the parallactic unsharpness caused by flat panel detector in digital radiography using different incident angle of central ray. Methods R-1 square-wave phantom was exposed by Kodak DR3000 system with X-ray tube angled 0°, 10°, 20°, 30°, and 40° respectively. Then,presampled modulation transfer function (MTF) was calculated for each case above. Subsequently,experimental data were processed and Wilcoxon signed ranks test were performed by statistic software SPSS 10. 0, in which P ＜ 0. 05 was considered as statistically significant difference. Results The presampled MTF curves of incident angle of 0°-40° degree, were presented orderly from top to bottom, especially the incident angle of 40° was obviously the lowest. The incident angle of 0° was considered as a control group and other groups were compared against it. There was no statistically significant difference for MTF of incident angle of 10°( Z = - 1. 893 ,P = 0. 058 ), while there were significant difference for MTF of incident angle of 20°, 30°, and 40° ( Z = - 2. 547, - 2. 666, - 2. 666, P ＜ 0. 05 ). Conclusions For flat panel detector in digital radiography, the bigger the incident angle of central ray, the larger the parallactic unsharpness. In addition, this effect has less influence on structures of low spatial frequency than those of high spatial frequency.