Molecular Imaging and Biology

, Volume 18, Issue 5, pp 776–781 | Cite as

Improvements in PET Image Quality in Time of Flight (TOF) Simultaneous PET/MRI

  • Ryogo Minamimoto
  • Craig Levin
  • Mehran Jamali
  • Dawn Holley
  • Amir Barkhodari
  • Greg Zaharchuk
  • Andrei Iagaru
Research Article



An integrated positron emission tomography (PET)/magnetic resonance imaging (MRI) scanner with time of flight (TOF) technology is now available for clinical use. The aim of this study is to evaluate the potential of TOF PET in PET/MRI to reduce artifacts in PET images when compared to non-TOF PET/MRI, TOF PET/X-ray computed tomography (CT), and non-TOF PET/CT.


All patients underwent a single 2-deoxy-2-[18F]fluoro-d-glucose ([18F]FDG) injection, followed first by PET/CT, and subsequently by PET/MRI. PET/CT exams were requested as standard-of-care for oncological indications. Using the PET acquisitions datasets, 4 series of images (TOF PET/CT, non-TOF PET/CT, TOF PET/MRI, and non-TOF PET/MRI) were reconstructed. These image series were visually evaluated for: (1) dental metal artifacts, (2) breathing artifacts, and (3) pelvic artifacts due to scatter correction errors from high bladder [18F]FDG concentration. PET image quality was assessed by a 3-point scale (1—clinically significant artifact, 2—non clinically significant artifact, and 3—no artifact).


Twenty-five patients (mean ± SD age: 56 ± 13 years old; female: 10, male: 15) were enrolled. TOF PET/MRI, non-TOF PET/MRI, TOF PET/CT, and non-TOF PET/CT scores 2.8, 2.5, 2.4, and 2.3, respectively for the presence of dental artifacts, 2.8, 2.5, 2.2, and 1.9, respectively, for the presence of breathing artifacts, and 2.7, 1.7, 2.0, and 1.3, respectively, for the presence of pelvic artifacts TOF PET/MRI images showed the highest image quality scores among the 4 datasets of PET images.


The superior timing resolution and resulting TOF capability of the new PET/MRI scanner improved PET image quality in this cohort by reducing artifacts compared to non-TOF PET/MRI, TOF PET/CT, and non-TOF PET/CT.

Key words

PET/MRI PET/CT Time of flight Artifact Image quality 



We thank Floris Jansen, PhD (GE Healthcare) for valuable technical suggestions and Mehdi Khalighi, PhD (GE Healthcare) for technical support. We also thank Praven Gulaka, PhD, our research coordinators, the radiochemistry staff, and the nuclear medicine technologists. Special thanks to all the patients who agreed to participate in the study and their families.

Compliance with Ethical standards

Financial Support

The authors thank GE Healthcare for supporting the study.

Conflict of Interest

The authors declare that they have no conflict of interest.


  1. 1.
    Pichler BJ, Kolb A, Nägele T, Schlemmer H-P (2010) PET/MRI: paving the way for the next generation of clinical multimodality imaging applications. J Nucl Med 51:333–336CrossRefPubMedGoogle Scholar
  2. 2.
    Drzezga A, Souvatzoglou M, Eiber M et al (2012) First clinical experience with integrated whole-body PET/MR: comparison to PET/CT in patients with oncologic diagnoses. J Nucl Med 53:845–855CrossRefPubMedGoogle Scholar
  3. 3.
    Quick HH, von Gall C, Zeilinger M et al (2013) Integrated whole-body PET/MR hybrid imaging: clinical experience. Invest Radiol 48:280–289CrossRefPubMedGoogle Scholar
  4. 4.
    Al-Nabhani KZ, Syed R, Michopoulou S et al (2014) Qualitative and quantitative comparison of PET/CT and PET/MR imaging in clinical practice. J Nucl Med 55:88–94CrossRefPubMedGoogle Scholar
  5. 5.
    Iagaru A, Mittra E, Minamimoto R et al (2015) Simultaneous whole-body time-of-flight 18F-FDG PET/MRI: a pilot study comparing SUVmax with PET/CT and assessment of MR image quality. Clin Nucl Med 40:1–8CrossRefPubMedGoogle Scholar
  6. 6.
    Levin C, Deller T, Peterson W et al (2014) Initial results of simultaneous whole-body ToF PET/MR. J Nucl Med Suppl 55:660Google Scholar
  7. 7.
    Kinahan PE, Hasegawa BH, Beyer T (2003) X-ray-based attenuation correction for positron emission tomography/computed tomography scanners. Semin Nucl Med 33:166–179CrossRefPubMedGoogle Scholar
  8. 8.
    Goerres G, Hany T, Kamel E et al (2002) Head and neck imaging with PET and PET/CT: artefacts from dental metallic implants. Eur J Nucl Med 29:367–370CrossRefGoogle Scholar
  9. 9.
    Kamel E, Burger C, Buck A et al (2003) Impact of metallic dental implants on CT-based attenuation correction in a combined PET/CT scanner. Eur Radiol 13:724–728CrossRefPubMedGoogle Scholar
  10. 10.
    Nehmeh SA, Erdi YE (2008) Respiratory motion in positron emission tomography/computed tomography: a review. Semin Nucl Med 38:167–176CrossRefPubMedGoogle Scholar
  11. 11.
    Osman M, Cohade C, Nakamoto Y, Wahl R (2003) Respiratory motion artifacts on PET emission images obtained using CT attenuation correction on PET-CT. Eur J Nucl Med 30:603–606CrossRefGoogle Scholar
  12. 12.
    Hargreaves BA, Worters PW, Pauly KB et al (2011) Metal-induced artifacts in MRI. Am J Roentgenol 197:547–555CrossRefGoogle Scholar
  13. 13.
    Hofmann M, Bezrukov I, Mantlik F et al (2011) MRI-based attenuation correction for whole-body PET/MRI: quantitative evaluation of segmentation- and atlas-based methods. J Nucl Med 52:1392–1399CrossRefPubMedGoogle Scholar
  14. 14.
    Hofmann M, Steinke F, Scheel V et al (2008) MRI-based attenuation correction for PET/MRI: a novel approach combining pattern recognition and atlas registration. J Nucl Med 49:1875–1883CrossRefPubMedGoogle Scholar
  15. 15.
    Malone IB, Ansorge RE, Williams GB et al (2011) Attenuation correction methods suitable for brain imaging with a PET/MRI scanner: a comparison of tissue atlas and template attenuation map approaches. J Nucl Med 52:1142–1149CrossRefPubMedGoogle Scholar
  16. 16.
    Fraum T, Fowler K, McConathy J et al (2015) PET/MRI for the body imager: abdominal and pelvic oncologic applications. Abdom Imaging 40:1387–1404CrossRefGoogle Scholar
  17. 17.
    Boellaard R, Hofman MBM, Hoekstra OS, Lammertsma AA (2014) Accurate PET/MR quantification using time of flight MLAA image reconstruction. Mol Imaging Biol 16:469–477CrossRefPubMedGoogle Scholar
  18. 18.
    Kitajima K, Suzuki K, Nakamoto Y et al (2010) Low-dose non-enhanced CT versus full-dose contrast-enhanced CT in integrated PET/CT studies for the diagnosis of uterine cancer recurrence. Eur J Nucl Med Mol Imaging 37:1490–1498CrossRefPubMedGoogle Scholar
  19. 19.
    Surti S (2015) Update on time-of-flight PET imaging. J Nucl Med 56:98–105CrossRefPubMedGoogle Scholar
  20. 20.
    Mehranian A, Zaidi H (2015) Impact of time-of-flight PET on quantification errors in MR imaging–based attenuation correction. J Nucl Med 56:635–641CrossRefPubMedGoogle Scholar
  21. 21.
    Burger IA, Wurnig MC, Becker AS et al (2015) Hybrid PET/MR imaging: an algorithm to reduce metal artifacts from dental implants in Dixon-based attenuation Map generation using a multiacquisition variable-resonance image combination sequence. J Nucl Med 56:93–97CrossRefGoogle Scholar
  22. 22.
    Nehmeh SA, Erdi YE, Ling CC et al (2002) Effect of respiratory gating on reducing lung motion artifacts in PET imaging of lung cancer. Med Phys 29:366–371CrossRefPubMedGoogle Scholar
  23. 23.
    Meirelles GSP, Erdi YE, Nehmeh SA et al (2007) Deep-inspiration breath-hold PET/CT: clinical findings with a New technique for detection and characterization of thoracic lesions. J Nucl Med 48:712–719CrossRefPubMedGoogle Scholar
  24. 24.
    Würslin C, Schmidt H, Martirosian P et al (2013) Respiratory motion correction in oncologic PET using T1-weighted MR imaging on a simultaneous whole-body PET/MR system. J Nucl Med 54:464–471CrossRefPubMedGoogle Scholar
  25. 25.
    Rakheja R, DeMello L, Chandarana H et al (2013) Comparison of the accuracy of PET/CT and PET/MRI spatial registration of multiple metastatic lesions. Am J Roentgenol 201:1120–1123CrossRefGoogle Scholar
  26. 26.
    Maurizio C (2011) Why is TOF PET reconstruction a more robust method in the presence of inconsistent data? Phys Med Biol 56:155CrossRefGoogle Scholar

Copyright information

© World Molecular Imaging Society 2016

Authors and Affiliations

  • Ryogo Minamimoto
    • 1
    • 2
  • Craig Levin
    • 2
  • Mehran Jamali
    • 1
    • 2
  • Dawn Holley
    • 3
  • Amir Barkhodari
    • 1
  • Greg Zaharchuk
    • 3
  • Andrei Iagaru
    • 1
  1. 1.Department of Radiology, Division of Nuclear Medicine and Molecular ImagingStanford UniversityStanfordUSA
  2. 2.Department of Radiology, Molecular Imaging Program at StanfordStanford UniversityStanfordUSA
  3. 3.Department of RadiologyStanford UniversityStanfordUSA

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