Medical & Biological Engineering & Computing

, Volume 57, Issue 3, pp 643–651 | Cite as

Imaging study of pseudo-CT images of superposed ultrasound deformation fields acquired in radiotherapy based on step-by-step local registration

  • Hongfei Sun
  • Tao Lin
  • Kai Xie
  • Liugang Gao
  • Jianfeng Sui
  • Xinye NiEmail author
Original Article


The purpose of this study is to create a new pseudo-computed tomography (CT) imaging approach under superposed ultrasound (US) deformation fields based on step-by-step local registration. Scanned CT and US 3D image datasets of three patients with postoperative cervical carcinoma were selected, including CT (CTsim) and US images (USsim) acquired during simulated positioning process and cone beam CT (CBCT) and US images for positioning verification (USpv) acquired after treatment for 10 times. Regions of interest such as urinary bladders were segmented out and accepted local registration to obtain different deformation fields. These deformation fields were successively performed according to their order and then applied to localized CT images to obtain pseudo-CT (CTps). After filtering, we obtained the final correct pseudo-CT (CTpsf). The pseudo-CT based on the mask of the whole imaging region of US images (WCTps) were acquired as control. Then, we compared CTpsf, CTps, WCTps, and CBCT in terms of their similarity in anatomical structure and differences in pseudo-CT and CTsim in terms of dosimetry. Structural similarity degree between CTpsf and CBCT was larger compared with that between CTps and WCTps. Target regions and dosages of endangered organs between CTpsf and CTsim were different under the same calculation conditions based on the Monte Carlo algorithm. Compared with the VMAT plan of CTsim, the pass rate of CTpsf in γ analysis under the standards of 2% dosage difference and 2-mm distance difference was 91.8%. The imaging quality of CTpsf was better compared with WCTps and CTps. It exhibited high similarity with CBCT in anatomical structure and had favorable application prospect in adaptive radiotherapy.

Graphical abstract

The local deformation registration is performed between the ultrasound images based on different regions of interest, and then stepwise applied to localized CT images to obtain pseudo-CT. After filtering, the corrected pseudo CT image is obtained.


Image-guided radiotherapy Pseudo-CT Ultrasound 



This work was supported by the Natural Science Foundation of Jiangsu Province Research of China (grant no. BK20151181).

Compliance with ethical standards

Ethics approval and consent to participate

The protocol of this study was approved by the medical ethics committee of Second People’s Hospital of Changzhou, Nanjing Medical University (2017-002-01).

Competing interests

The authors declare that they have no competing interests.

Consent for publication

Not applicable.


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Copyright information

© International Federation for Medical and Biological Engineering 2018

Authors and Affiliations

  • Hongfei Sun
    • 1
    • 2
  • Tao Lin
    • 1
    • 2
  • Kai Xie
    • 1
    • 2
  • Liugang Gao
    • 1
    • 2
  • Jianfeng Sui
    • 1
    • 2
  • Xinye Ni
    • 1
    • 2
    Email author
  1. 1.The Affiliated Changzhou No. 2 People’s Hospital of Nanjing Medical UniversityChangzhouChina
  2. 2.Center of Medical PhysicsNanjing Medical UniversityChangzhouChina

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