Tilted-wire method for measuring resolution properties of CT images under extremely low-contrast and high-noise conditions

Tilted-wire method for measuring resolution properties of CT images under extremely low-contrast... Edge methods are predominantly used for modulation transfer function (MTF) measurements in computed tomography (CT) images reconstructed using iterative methods. However, edge methods employ a relatively large and distinct test object, which is intended to simulate relatively large and distinct clinical organs. If one wants to assess the image quality of a small low-contrast object that is visually indistinct against a noisy background, a small and indistinct test object is desired. Another concern is that information related to the signal amount is discarded during MTF measurements. Choosing a weak impulse as the ultimately small test object, we have developed a tilted-wire method, which is a type of point spread function (PSF) method compatible with extremely low contrast-to-noise ratio (CNR) conditions. The signal amount is measured as the PSF volume. We used two commercial CT systems to evaluate the measurement accuracy of the tilted-wire method. When ensemble-averaged images are used, one can measure the MTF even when the wire is indiscernible from noise. The measurement error under such conditions is a few percent for both the MTF and signal amount. We also applied the tilted-wire method to two hybrid iterative reconstruction methods, namely AIDR-3D and ASiR. The results show that the MTF of ASiR is completely CNR-dependent, but that of AIDR-3D is noise-dependent. The signal amount obtained with ASiR is unchanged from that obtained through filtered back-projection (FBP). The signal amount obtained with AIDR-3D is less than that obtained through FBP, depending on the noise level. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Radiological Physics and Technology Springer Journals

Tilted-wire method for measuring resolution properties of CT images under extremely low-contrast and high-noise conditions

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Publisher
Springer Journals
Copyright
Copyright © 2018 by Japanese Society of Radiological Technology and Japan Society of Medical Physics
Subject
Medicine & Public Health; Imaging / Radiology; Nuclear Medicine; Radiotherapy; Medical and Radiation Physics
ISSN
1865-0333
eISSN
1865-0341
D.O.I.
10.1007/s12194-018-0443-8
Publisher site
See Article on Publisher Site

Abstract

Edge methods are predominantly used for modulation transfer function (MTF) measurements in computed tomography (CT) images reconstructed using iterative methods. However, edge methods employ a relatively large and distinct test object, which is intended to simulate relatively large and distinct clinical organs. If one wants to assess the image quality of a small low-contrast object that is visually indistinct against a noisy background, a small and indistinct test object is desired. Another concern is that information related to the signal amount is discarded during MTF measurements. Choosing a weak impulse as the ultimately small test object, we have developed a tilted-wire method, which is a type of point spread function (PSF) method compatible with extremely low contrast-to-noise ratio (CNR) conditions. The signal amount is measured as the PSF volume. We used two commercial CT systems to evaluate the measurement accuracy of the tilted-wire method. When ensemble-averaged images are used, one can measure the MTF even when the wire is indiscernible from noise. The measurement error under such conditions is a few percent for both the MTF and signal amount. We also applied the tilted-wire method to two hybrid iterative reconstruction methods, namely AIDR-3D and ASiR. The results show that the MTF of ASiR is completely CNR-dependent, but that of AIDR-3D is noise-dependent. The signal amount obtained with ASiR is unchanged from that obtained through filtered back-projection (FBP). The signal amount obtained with AIDR-3D is less than that obtained through FBP, depending on the noise level.

Journal

Radiological Physics and TechnologySpringer Journals

Published: Feb 23, 2018

References

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