Clinical evaluation of TOF versus non-TOF on PET artifacts in simultaneous PET/MR: a dual centre experience

  • Edwin E. G. W. ter Voert
  • Patrick Veit-Haibach
  • Sangtae Ahn
  • Florian Wiesinger
  • M. Mehdi Khalighi
  • Craig S. Levin
  • Andrei H. Iagaru
  • Greg Zaharchuk
  • Martin Huellner
  • Gaspar Delso
Original Article



Our objective was to determine clinically the value of time-of-flight (TOF) information in reducing PET artifacts and improving PET image quality and accuracy in simultaneous TOF PET/MR scanning.


A total 65 patients who underwent a comparative scan in a simultaneous TOF PET/MR scanner were included. TOF and non-TOF PET images were reconstructed, clinically examined, compared and scored. PET imaging artifacts were categorized as large or small implant-related artifacts, as dental implant-related artifacts, and as implant-unrelated artifacts. Differences in image quality, especially those related to (implant) artifacts, were assessed using a scale ranging from 0 (no artifact) to 4 (severe artifact).


A total of 87 image artifacts were found and evaluated. Four patients had large and eight patients small implant-related artifacts, 27 patients had dental implants/fillings, and 48 patients had implant-unrelated artifacts. The average score was 1.14 ± 0.82 for non-TOF PET images and 0.53 ± 0.66 for TOF images (p < 0.01) indicating that artifacts were less noticeable when TOF information was included.


Our study indicates that PET image artifacts are significantly mitigated with integration of TOF information in simultaneous PET/MR. The impact is predominantly seen in patients with significant artifacts due to metal implants.


Time-of-flight Artifacts Positron emission tomography Magnetic resonance imaging Clinical research 


Compliance with ethical standards


This study received funding from GE. Part of the study was carried out in the context of a GE-sponsored clinical trial to obtain CE marking and FDA approval of the TOF-PET/MR prototype.

Conflicts of Interest

The authors declare relationships with the following companies: P.V.-H. received IIS grants from Bayer Healthcare, Siemens Healthcare and Roche Pharmaceuticals, and speaker’s fees from GE Healthcare; G.Z. received research support and speaker’s fees from GE Healthcare; A.H.I. received research support and speaker’s fees from GE Healthcare; C.S.L. received research sponsorship from Siemens Healthcare, Philips Healthcare, and GE Healthcare; S.A. and F.W. are employees of GE Global Research; M.M.K. and G.D. are employees of GE Healthcare.

Ethical approval

All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the principles of the 1964 Declaration of Helsinki and its later amendments or comparable ethical standards.

Supplementary material

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Copyright information

© Springer-Verlag Berlin Heidelberg 2017

Authors and Affiliations

  • Edwin E. G. W. ter Voert
    • 1
    • 2
  • Patrick Veit-Haibach
    • 1
    • 2
    • 3
  • Sangtae Ahn
    • 4
  • Florian Wiesinger
    • 5
  • M. Mehdi Khalighi
    • 6
  • Craig S. Levin
    • 7
  • Andrei H. Iagaru
    • 8
  • Greg Zaharchuk
    • 9
  • Martin Huellner
    • 1
    • 2
    • 10
  • Gaspar Delso
    • 6
  1. 1.Department of Nuclear MedicineUniversity Hospital ZurichZurichSwitzerland
  2. 2.University of ZurichZurichSwitzerland
  3. 3.Department of Diagnostic and Interventional RadiologyUniversity Hospital ZurichZurichSwitzerland
  4. 4.GE Global ResearchNiskayunaUSA
  5. 5.GE Global ResearchMünchenGermany
  6. 6.GE HealthcareWaukeshaUSA
  7. 7.Department of Radiology, Molecular Imaging Program at StanfordStanford UniversityStanfordUSA
  8. 8.Department of Radiology, Division of Nuclear Medicine and Molecular ImagingStanford UniversityStanfordUSA
  9. 9.Department of Radiology, NeuroradiologyStanford UniversityStanfordUSA
  10. 10.Department of NeuroradiologyUniversity Hospital ZurichZurichSwitzerland

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