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2020-02-26 Per Christian Hansen教授による講演会(その3)

投稿者:  相原 研輔(東京都市大学)
会場: 東京都市大学(世田谷キャンパス) 6号館1階 61A教室
概要: Per Christian Hansen教授(デンマーク工科大学)をお招きし「Algebraic Iterative Reconstruction Methods for X-ray CT and Their Convergence Properties」という題目でご講演頂きます.本件は東京で開催する3つの講演会の3つ目です.

日程 2020年 2月26日(水) 2:30PM-4:30PM
会場 東京都市大学(世田谷キャンパス) 6号館1階 61A教室 (アクセス)
本文 この度,デンマーク工科大学のPer Christian Hansen教授をお招きし,東京都市大学にて下記の講演会を開催することとなりました.
ご興味のある方は是非ご参加ください.

本件は東京で開催する3つの講演会の3つ目です.他2件は2月25日に一橋大学にて開催されます.
This lecture is supported by Invitational Fellowships for Research in Japan (Short-term S).
Speaker Professor Per Christian Hansen
(DTU Compute, Technical University of Denmark) http://www2.compute.dtu.dk/~pcha/
Title Algebraic Iterative Reconstruction Methods for X-ray CT and Their Convergence Properties
Abstract We use algebraic iterative reconstruction methods - such as ART (Kaczmarz), SART, and SIRT - to solve discretized inverse problems in computed tomography. They are very flexible because the underlying system A x = b requires no assumption about the scanning geometry, and it is easy to incorporate convex constraints (e.g., box constraints). Their success in computing regularized solutions is due to a mechanism called semi-convergence. When we implement these methods with a focus on computational efficiency, we often use different discretization schemes for the forward projection and the back projection. This means that there is a mismatch between the back projection matrix B and the transposed of the forward projection matrix A. The use of such an unmatched A,B-pair has two consequences: the accuracy deteriorates (compared to when using a matched pair), and the iteration may fail to converge. In this talk, I will survey some recent results related to the convergence and semi-convergence of the algebraic iterative reconstruction methods. I will also present a novel approach to "fixing" the non-convergence issue with only a small computational overhead. I illustrate the theory with numerical results.
This is joint work with Tommy Elfving, Touraj Nikazad, Yiqiu Dong and Nicolai A. B. Riis.
問い合わせ先 阿部 邦美,相原 研輔
e-mail: abe@gifu.shotoku.ac.jp , aiharakseparatortcu.ac.jp