Correction Method of Nonlinearity Due to Logarithm Operation for X-Ray CT Projection Data with Noise in Photon-Starved State

Shin-ichiro IWAMOTO; Akira SHIOZAKI

doi:10.1093/ietisy/e90-d.10.1697

Correction Method of Nonlinearity Due to Logarithm Operation for X-Ray CT Projection Data with Noise in Photon-Starved State

Shin-ichiro IWAMOTO, Akira SHIOZAKI

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In the acquisition of projection data of X-ray CT, logarithm operation is indispensable. But noise distribution is nonlinearly projected by the logarithm operation, and this deteriorates the precision of CT number. This influence becomes particularly remarkable when only a few photons are caught with a detector. It generates a strong streak artifact (SA) in a reconstructed image. Previously we have clarified the influence of the nonlinearity by statistical analysis and proposed a correction method for such nonlinearity. However, there is a problem that the compensation for clamp processing cannot be performed and that the suppression of SA is not enough in photon shortage state. In this paper, we propose a new technique for correcting the nonlinearity due to logarithm operation for noisy data by combining the previously presented method and an adaptive filtering method. The technique performs an adaptive filtering only when the number of captured photons is very few. Moreover we quantitatively evaluate the influence of noise on the reconstructed image in the proposed method by the experiment using numerical phantoms. The experimental results show that there is less influence on spatial resolution despite suppressing SA effectively and that CT number are hardly dependent on the number of the incident photons.

Publication: IEICE TRANSACTIONS on Information Vol.E90-D No.10 pp.1697-1705

Publication Date: 2007/10/01

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Online ISSN: 1745-1361

DOI: 10.1093/ietisy/e90-d.10.1697

Type of Manuscript: PAPER

Category: Biological Engineering

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Shin-ichiro IWAMOTO, Akira SHIOZAKI, "Correction Method of Nonlinearity Due to Logarithm Operation for X-Ray CT Projection Data with Noise in Photon-Starved State" in IEICE TRANSACTIONS on Information, vol. E90-D, no. 10, pp. 1697-1705, October 2007, doi: 10.1093/ietisy/e90-d.10.1697.
Abstract: In the acquisition of projection data of X-ray CT, logarithm operation is indispensable. But noise distribution is nonlinearly projected by the logarithm operation, and this deteriorates the precision of CT number. This influence becomes particularly remarkable when only a few photons are caught with a detector. It generates a strong streak artifact (SA) in a reconstructed image. Previously we have clarified the influence of the nonlinearity by statistical analysis and proposed a correction method for such nonlinearity. However, there is a problem that the compensation for clamp processing cannot be performed and that the suppression of SA is not enough in photon shortage state. In this paper, we propose a new technique for correcting the nonlinearity due to logarithm operation for noisy data by combining the previously presented method and an adaptive filtering method. The technique performs an adaptive filtering only when the number of captured photons is very few. Moreover we quantitatively evaluate the influence of noise on the reconstructed image in the proposed method by the experiment using numerical phantoms. The experimental results show that there is less influence on spatial resolution despite suppressing SA effectively and that CT number are hardly dependent on the number of the incident photons.
URL: https://global.ieice.org/en_transactions/information/10.1093/ietisy/e90-d.10.1697/_p

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@ARTICLE{e90-d_10_1697,
author={Shin-ichiro IWAMOTO, Akira SHIOZAKI, },
journal={IEICE TRANSACTIONS on Information},
title={Correction Method of Nonlinearity Due to Logarithm Operation for X-Ray CT Projection Data with Noise in Photon-Starved State},
year={2007},
volume={E90-D},
number={10},
pages={1697-1705},
abstract={In the acquisition of projection data of X-ray CT, logarithm operation is indispensable. But noise distribution is nonlinearly projected by the logarithm operation, and this deteriorates the precision of CT number. This influence becomes particularly remarkable when only a few photons are caught with a detector. It generates a strong streak artifact (SA) in a reconstructed image. Previously we have clarified the influence of the nonlinearity by statistical analysis and proposed a correction method for such nonlinearity. However, there is a problem that the compensation for clamp processing cannot be performed and that the suppression of SA is not enough in photon shortage state. In this paper, we propose a new technique for correcting the nonlinearity due to logarithm operation for noisy data by combining the previously presented method and an adaptive filtering method. The technique performs an adaptive filtering only when the number of captured photons is very few. Moreover we quantitatively evaluate the influence of noise on the reconstructed image in the proposed method by the experiment using numerical phantoms. The experimental results show that there is less influence on spatial resolution despite suppressing SA effectively and that CT number are hardly dependent on the number of the incident photons.},
keywords={},
doi={10.1093/ietisy/e90-d.10.1697},
ISSN={1745-1361},
month={October},}

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TY - JOUR
TI - Correction Method of Nonlinearity Due to Logarithm Operation for X-Ray CT Projection Data with Noise in Photon-Starved State
T2 - IEICE TRANSACTIONS on Information
SP - 1697
EP - 1705
AU - Shin-ichiro IWAMOTO
AU - Akira SHIOZAKI
PY - 2007
DO - 10.1093/ietisy/e90-d.10.1697
JO - IEICE TRANSACTIONS on Information
SN - 1745-1361
VL - E90-D
IS - 10
JA - IEICE TRANSACTIONS on Information
Y1 - October 2007
AB - In the acquisition of projection data of X-ray CT, logarithm operation is indispensable. But noise distribution is nonlinearly projected by the logarithm operation, and this deteriorates the precision of CT number. This influence becomes particularly remarkable when only a few photons are caught with a detector. It generates a strong streak artifact (SA) in a reconstructed image. Previously we have clarified the influence of the nonlinearity by statistical analysis and proposed a correction method for such nonlinearity. However, there is a problem that the compensation for clamp processing cannot be performed and that the suppression of SA is not enough in photon shortage state. In this paper, we propose a new technique for correcting the nonlinearity due to logarithm operation for noisy data by combining the previously presented method and an adaptive filtering method. The technique performs an adaptive filtering only when the number of captured photons is very few. Moreover we quantitatively evaluate the influence of noise on the reconstructed image in the proposed method by the experiment using numerical phantoms. The experimental results show that there is less influence on spatial resolution despite suppressing SA effectively and that CT number are hardly dependent on the number of the incident photons.
ER -