skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Reliable automatic alignment of tomographic projection data by passive auto-focus

Abstract

Purpose: The authors present a robust algorithm that removes the blurring and double-edge artifacts in high-resolution computed tomography (CT) images that are caused by misaligned scanner components. This alleviates the time-consuming process of physically aligning hardware, which is of particular benefit if components are moved or swapped frequently. Methods: The proposed method uses the experimental data itself for calibration. A parameterized model of the scanner geometry is constructed and the parameters are varied until the sharpest 3D reconstruction is found. The concept is similar to passive auto-focus algorithms of digital optical instruments. The parameters are used to remap the projection data from the physical detector to a virtual aligned detector. This is followed by a standard reconstruction algorithm, namely the Feldkamp algorithm. Feldkamp et al.[J. Opt. Soc. Am. A 1, 612-619 (1984)]. Results: An example implementation is given for a rabbit liver specimen that was collected with a circular trajectory. The optimal parameters were determined in less computation time than that for a full reconstruction. The example serves to demonstrate that (a) sharpness is an appropriate measure for projection alignment, (b) our parameterization is sufficient to characterize misalignments for cone-beam CT, and (c) the procedure determines parameter values with sufficientmore » precision to remove the associated artifacts. Conclusions: The algorithm is fully tested and implemented for regular use at The Australian National University micro-CT facility for both circular and helical trajectories. It can in principle be applied to more general imaging geometries and modalities. It is as robust as manual alignment but more precise since we have quantified the effect of misalignment.« less

Authors:
; ; ; ;  [1]
  1. Department of Applied Mathematics, Research School of Physics and Engineering, The Australian National University, Canberra, ACT 0200 (Australia)
Publication Date:
OSTI Identifier:
22098607
Resource Type:
Journal Article
Journal Name:
Medical Physics
Additional Journal Information:
Journal Volume: 38; Journal Issue: 9; Other Information: (c) 2011 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0094-2405
Country of Publication:
United States
Language:
English
Subject:
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; 62 RADIOLOGY AND NUCLEAR MEDICINE; ACCURACY; ALGORITHMS; ALIGNMENT; BEAMS; CALCULATION METHODS; CALIBRATION; CAT SCANNING; COMPUTERIZED TOMOGRAPHY; IMAGE PROCESSING; LIVER; MANUALS; RABBITS; RESOLUTION; TRAJECTORIES

Citation Formats

Kingston, A., Sakellariou, A., Varslot, T., Myers, G., and Sheppard, A. Reliable automatic alignment of tomographic projection data by passive auto-focus. United States: N. p., 2011. Web. doi:10.1118/1.3609096.
Kingston, A., Sakellariou, A., Varslot, T., Myers, G., & Sheppard, A. Reliable automatic alignment of tomographic projection data by passive auto-focus. United States. doi:10.1118/1.3609096.
Kingston, A., Sakellariou, A., Varslot, T., Myers, G., and Sheppard, A. Thu . "Reliable automatic alignment of tomographic projection data by passive auto-focus". United States. doi:10.1118/1.3609096.
@article{osti_22098607,
title = {Reliable automatic alignment of tomographic projection data by passive auto-focus},
author = {Kingston, A. and Sakellariou, A. and Varslot, T. and Myers, G. and Sheppard, A.},
abstractNote = {Purpose: The authors present a robust algorithm that removes the blurring and double-edge artifacts in high-resolution computed tomography (CT) images that are caused by misaligned scanner components. This alleviates the time-consuming process of physically aligning hardware, which is of particular benefit if components are moved or swapped frequently. Methods: The proposed method uses the experimental data itself for calibration. A parameterized model of the scanner geometry is constructed and the parameters are varied until the sharpest 3D reconstruction is found. The concept is similar to passive auto-focus algorithms of digital optical instruments. The parameters are used to remap the projection data from the physical detector to a virtual aligned detector. This is followed by a standard reconstruction algorithm, namely the Feldkamp algorithm. Feldkamp et al.[J. Opt. Soc. Am. A 1, 612-619 (1984)]. Results: An example implementation is given for a rabbit liver specimen that was collected with a circular trajectory. The optimal parameters were determined in less computation time than that for a full reconstruction. The example serves to demonstrate that (a) sharpness is an appropriate measure for projection alignment, (b) our parameterization is sufficient to characterize misalignments for cone-beam CT, and (c) the procedure determines parameter values with sufficient precision to remove the associated artifacts. Conclusions: The algorithm is fully tested and implemented for regular use at The Australian National University micro-CT facility for both circular and helical trajectories. It can in principle be applied to more general imaging geometries and modalities. It is as robust as manual alignment but more precise since we have quantified the effect of misalignment.},
doi = {10.1118/1.3609096},
journal = {Medical Physics},
issn = {0094-2405},
number = 9,
volume = 38,
place = {United States},
year = {2011},
month = {9}
}