利用计算机断层成像方法由观测图像重建等离子体层全球密度分布--投影数据不完备问题

Deduction of the global density of the plasmasphere reconstructed from the observation images using computer tomography technique——Incomplete projection data

在用计算机断层成像方法由EUV观测图像重建等离子体层全球密度分布时,地球的遮挡和有限角度都会导致投影数据不完备,从而无法精确重建出等离子体层的密度分布.本文针对该问题,提出一种基于图像总变差极小化的代数迭代算法.通过重建等离子体层投影数据缺失最为严重的中心子午面,证明该算法能够显著提高重建图像的质量.并且在IMAGE卫星仅能达到90°的有限投影角度下,此算法重建图像的相关系数可达0.760,而代数迭代算法的相关系数仅为0.696.

In deduction of the global density of Earth plasmasphere from its column density by using Computer Tomography（CT） technique,one of the main issues is that the projection data is not theoretically sufficient for exact image reconstruction.We develop an improved iterative reconstruction algorithm based on the minimization of the image total variation.The high quality image is achieved by using this method to reconstruct the meridian plane,which has the most various insufficient data problems.Their reconstruction quality has been analyzed through the correlation coefficient between the Phantom Diagram and the reconstruction results.To match IMAGE satellite,we focus on the limited angular range of 90°.For this angle,the value of this method is 0.760 while iterative reconstruction algorithm method is only 0.696.The result reveals that the method of iterative reconstruction algorithm based on the minimization of the image total variation is more efficient when the Phantom Diagram includes earth′s shelter and limited angular range.