Twodimensional iterative regionofinterest (ROI) reconstruction from truncated projection data
Abstract
A small detector or limited gantry rotation angles may cause data truncation, in which case the entire object cannot be completely reconstructed. However, a small region of interest (ROI) may be recoverable in certain truncation situations. Two analytical methods have been proposed for exact ROI reconstruction. Here we evaluate the capability of ROI reconstruction using an maximumlikelihood expectationmaximization (MLEM) method, which directly solves the inverse problem of the system equations. ROI reconstruction using the MLEM method is compared with that using the two analytical methods. Comparisons are based on reconstructions of four specifically designed, computersimulated truncation cases. In the simulation, each reconstructed ROI is coupled with its counterpart in the nontruncated case to evaluate the accuracy of the reconstructed ROI. We found that, (a) in two truncation situations the ROI can be reconstructed by both the analytical methods and the twodimensional MLEM method, but the MLEM method may produce a larger ROI; (b) for a truncation case that neither analytical algorithm is applicable, the MLEM method provides a quantitative ROI reconstruction; and (c) for the wellknown 'interior' truncation problem, neither the analytical methods nor the MLEM method can perform an exact ROI reconstruction, but the MLEM method provides informative ROImore »
 Authors:
 Utah Center for Advanced Imaging Research, University of Utah, Salt Lake City, Utah 84108 (United States)
 Publication Date:
 OSTI Identifier:
 20951106
 Resource Type:
 Journal Article
 Resource Relation:
 Journal Name: Medical Physics; Journal Volume: 34; Journal Issue: 3; Other Information: DOI: 10.1118/1.2436969; (c) 2007 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA)
 Country of Publication:
 United States
 Language:
 English
 Subject:
 62 RADIOLOGY AND NUCLEAR MEDICINE; ACCURACY; ALGORITHMS; COMPUTERIZED SIMULATION; IMAGE PROCESSING; IMAGES; ITERATIVE METHODS; MAXIMUMLIKELIHOOD FIT; SINGLE PHOTON EMISSION COMPUTED TOMOGRAPHY
Citation Formats
Zhang, B., and Zeng, G. L.. Twodimensional iterative regionofinterest (ROI) reconstruction from truncated projection data. United States: N. p., 2007.
Web. doi:10.1118/1.2436969.
Zhang, B., & Zeng, G. L.. Twodimensional iterative regionofinterest (ROI) reconstruction from truncated projection data. United States. doi:10.1118/1.2436969.
Zhang, B., and Zeng, G. L.. Thu .
"Twodimensional iterative regionofinterest (ROI) reconstruction from truncated projection data". United States.
doi:10.1118/1.2436969.
@article{osti_20951106,
title = {Twodimensional iterative regionofinterest (ROI) reconstruction from truncated projection data},
author = {Zhang, B. and Zeng, G. L.},
abstractNote = {A small detector or limited gantry rotation angles may cause data truncation, in which case the entire object cannot be completely reconstructed. However, a small region of interest (ROI) may be recoverable in certain truncation situations. Two analytical methods have been proposed for exact ROI reconstruction. Here we evaluate the capability of ROI reconstruction using an maximumlikelihood expectationmaximization (MLEM) method, which directly solves the inverse problem of the system equations. ROI reconstruction using the MLEM method is compared with that using the two analytical methods. Comparisons are based on reconstructions of four specifically designed, computersimulated truncation cases. In the simulation, each reconstructed ROI is coupled with its counterpart in the nontruncated case to evaluate the accuracy of the reconstructed ROI. We found that, (a) in two truncation situations the ROI can be reconstructed by both the analytical methods and the twodimensional MLEM method, but the MLEM method may produce a larger ROI; (b) for a truncation case that neither analytical algorithm is applicable, the MLEM method provides a quantitative ROI reconstruction; and (c) for the wellknown 'interior' truncation problem, neither the analytical methods nor the MLEM method can perform an exact ROI reconstruction, but the MLEM method provides informative ROI images. We also propose an analysis using the truncated projection matrix and its MoorePenrose inverse matrix which can help to determine the recoverable ROI using iterative methods for a given truncation situation.},
doi = {10.1118/1.2436969},
journal = {Medical Physics},
number = 3,
volume = 34,
place = {United States},
year = {Thu Mar 15 00:00:00 EDT 2007},
month = {Thu Mar 15 00:00:00 EDT 2007}
}

Various methods have been proposed for tomographic reconstruction from truncated projection data. In this paper, a reconstructive method is discussed which consists of iterations of filtered backprojection, reprojection and some nonlinear processings. First, the method is so constructed that it converges to a fixed point. Then, to examine its effectiveness, comparisons are made by computer experiments with two existing reconstructive methods for truncated projection data, that is, the method of extrapolation based on the smooth assumption followed by filtered backprojection, and modified additive ART.

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