Development of fluorescent x-ray detection technique in FXCT

点击翻译按钮获取中文摘要

Fluorescent x-ray technique is used to evaluate very low contents of specific elements in the order of picograms, however the measurement must be performed in the surfade of object. Then for in biological sample, the specimen is required to be cut into thin slices and scanned with a beam perpendicular to its surface. Fluorescent x-ray computed tomography (FXCT) have being developed to reveal the distribution of specific element in living state. By positioning the x-ray detector at 90° to the beam, the linear polarization of synchrotron x-rays helps to significantly reduce the Compton scattering overlapping the K_α line of specific elements. However, Compton scattering has increased markedly in large object, and highly purified germanium detector cannot measure the huge amounts of photon. To improve this problem, three experiments such as filter method, parallel collimator method and Laue-mirror method, were done to examine the reduction of Compton scattering from object.Filter method, which is firstly thought most easy and highly effective method to reduce Compton scattering, is not useful because secondary fluorescent x-ray was generated by filter itself and this fluorescent x-ray overlaps on the iodine K_α line. Intense parallel collimator method, which reduces the efficacy of fluorescent x-ray detection, is most effective to reduce Compton scattering and to detect small amounts of fluorescent x-ray. Most ideal Laue-mirror method is difficult to set up the mirror system, so further improvement of x-ray mirror and its dedicate control is needed.For in vivo FXCT imaging, collimator or Laue-mirror method appear to be an useful technique to reduce the huge amounts of Compton scattering from large object.