DOI: 10.1007/s00259-017-3619-2Pages: 1223-1233

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

1. University Hospital Zurich, Department of Nuclear Medicine

2. University of Zurich

3. University Hospital Zurich, Department of Diagnostic and Interventional Radiology

4. GE Global Research

5. GE Global Research

6. GE Healthcare

7. Stanford University, Department of Radiology, Molecular Imaging Program at Stanford

8. Stanford University, Department of Radiology, Division of Nuclear Medicine and Molecular Imaging

9. Stanford University, Department of Radiology, Neuroradiology

10. University Hospital Zurich, Department of Neuroradiology

Correspondence to:
Edwin E. G. W. Voert
Tel: +41 44 556 30 88




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.

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  • Accepted: Jan 4, 2017
  • Online: Jan 26, 2017

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