The Study Of ROI Based On BPF Of New Window Functions

CT image reconstruction is widely used in many areas, such as medicine. The essence of the image reconstruction is using a mathematical algorithm to process data scanned by the scanner, and then getting valid information of the original image to analysis. The most important part of CT image reconstruction is to design algorithm. The reconstruction algorithms mainly include analytical algorithm and iterative algorithm. Back-projection filtered (BPF) algorithm, which is proposed by Xiaochuan Pan and his colleagues in 2004, belongs to analytical algorithm. Comparing with the filtered back projection (FBP) algorithm, BPF algorithm has advantages obviously of reconstruction of the local region of interest (ROI). This article will to study the reconstruction result of the region of interest of a two-dimensional image using BPF algorithm. However the window has a great influence on reconstruction result of the back-projection filtered algorithm, different windows will lead to the results differently. This paper will further research how to improve the effect of the window, and select a different window with different parameters to reconstruct the same image. According to the numerical comparison of the reconstruction results, we analysis the improvement direction of the window, and find two better new window functions:triangle composite window function and new index window function. Using these two new window functions to complete the reconstruction of entire image and the local region of interest image, besides the results'assessment through three distance measurements. Comparing with the reconstruction results of previous basic window functions (such as sine windows and cosine window), we find the new results changed for better, so that selecting the appropriate window function is essential. Meanwhile, comparing the reconstruction results of the filtered back projection algorithm and the reconstruction results of BPF algorithm which using new windows, we find the results of reconstruction of the latter is better. So BPF algorithm is a better image reconstruction algorithm by far, and what I did is valuable and meaningful.