Development of a novel phase retrieval algorithm in phase-contrast X-ray computed tomography

• Main Authors: Wun-Jie Yang, 楊文傑
• Other Authors: Jyh-Cheng Chen
• Format: Others
• Language: zh-TW
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/15767848892986256670

碩士 === 國立陽明大學 === 生物醫學影像暨放射科學系 === 103 === In conventional radiography, it has been given a poor contrast when weakly absorbing objects were imaged such as soft tissues. X-ray phase contrast imaging can improve the visualization of object features utilizes the characteristic of phase shift of x-ray beams. Because both of absorption and phase shift information are involved in phase contrast image, quantitative information cannot be directly obtained. Thus, an algorithm for extracting quantitative information, called phase retrieval method, is needed to restore phase only information. Until now, there is no phase retrieval algorithm been reported that can effectively extract phase information of a multi-material object in one phase contrast image. The purpose of this study is to develop a novel phase retrieval algorithm that can retrieve phase information of the multi-material object effectively in one phase contrast image, utilizes in-line phase contrast imaging at low x-ray energy. According to the results, the novel phase retrieval algorithm shows it can effectively retrieve phase information of multi-material object in one phase contrast image in simulated phantoms. It proves superior to conventional absorption contrast in terms of the signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR). In real phantom experiments, the improvement in the SNR is between 20 and 50 fold, and in the CNR is up to 60 fold. In conclusion, we have developed an effective method to retrieve phase information using the novel phase retrieval algorithm. It also produced good quantitative results in real phantoms.