Sphere phantom approach to measure mtf of computed tomography system using convolutional autoencoder network

Changwoo Lee, Jongduk Baek

Research output: Chapter in Book/Report/Conference proceedingConference contribution


Image quality assessment is important task to maintain and improve the imaging system performance, and modulation transfer function (MTF) is widely used as a quantitative metric describing the spatial resolution of an image for fan beam computed tomography (CT) system. In MTF measurement, although fine wire and edge objects are generally used, there are difficulties in precise phantom alignment. To overcome this limitation, a sphere object was considered as an alternative phantom due to spherically symmetric property. However, the sphere phantom is more suitable for measuring 1D MTF along the particular direction than 2D MTF for fan beam CT system. In this work, we proposed a sphere phantom approach to measure whole 2D MTF of fan beam CT system using convolutional autoencoder network. We generated projection data of point and sphere objects, and reconstructed using filtered back-projection (FBP). The reconstructed point image was regarded as an ideal 2D point spread function (PSF). The ideal 2D modulation transfer function (MTF) was calculated by taking Fourier transform of the ideal 2D PSF. To measure 2D MTF, we divided the Fourier transform of reconstructed sphere phantom by that of ideal sphere object. The estimation errors caused by the inverse filtering were corrected using proposed convolutional autoencoder network. After applying the network, the estimated 2D MTF shows a good agreement with the ideal 2D MTF, indicating that the convolutional autoencoder network is effective for measuring 2D MTF of fan beam CT system.

Original languageEnglish
Title of host publicationMedical Imaging 2021
Subtitle of host publicationPhysics of Medical Imaging
EditorsHilde Bosmans, Wei Zhao, Lifeng Yu
ISBN (Electronic)9781510640191
Publication statusPublished - 2021
EventMedical Imaging 2021: Physics of Medical Imaging - Virtual, Online, United States
Duration: 2021 Feb 152021 Feb 19

Publication series

NameProgress in Biomedical Optics and Imaging - Proceedings of SPIE
ISSN (Print)1605-7422


ConferenceMedical Imaging 2021: Physics of Medical Imaging
Country/TerritoryUnited States
CityVirtual, Online

Bibliographical note

Funding Information:
Bio & Medical Technology Development Program of the National Research Foundation (NRF) funded by the Ministry of Science and ICT (2018M3A9H6081482, 2018M3A9H6081483).

Publisher Copyright:
© COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only.

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Biomaterials
  • Atomic and Molecular Physics, and Optics
  • Radiology Nuclear Medicine and imaging


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