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Technical performance evaluation of a human brain PET/MRI system

  • Molecular Imaging
  • Published:
European Radiology Aims and scope Submit manuscript

Abstract

Objectives

Technical performance evaluation of a human brain PET/MRI system.

Methods

The magnetic field compatible positron emission tomography (PET) insert is based on avalanche photodiode (APD) arrays coupled with lutetium oxyorthosilicate (LSO) crystals and slip-fits into a slightly modified clinical 3-T MRI system. The mutual interference between the two imaging techniques was minimised by the careful design of the hardware to maintain the quality of the B 0 and B 1 field homogeneity.

Results

The signal-to-noise ratio (SNR) and the homogeneity of the MR images were minimally influenced by the presence of the PET. Measurements according to the Function Biomedical Informatics Research Network (FBIRN) protocol proved the combined system’s ability to perform functional MRI (fMRI). The performance of the PET insert was evaluated according to the National Electrical Manufacturers Association (NEMA) standard. The noise equivalent count rate (NEC) peaked at 30.7 × 103 counts/s at 7.3 kBq/mL. The point source sensitivity was greater than 7 %. The spatial resolution in the centre field of view was less than 3 mm. Patient data sets clearly revealed a noticeably good PET and MR image quality.

Conclusion

PET and MRI phantom tests and first patient data exhibit the device’s potential for simultaneous multiparametric imaging.

Key Points

• Combination of PET and MRI is a new emerging imaging technology.

• Evaluated brain PET/MRI enables uncompromised imaging performance.

• PET/MRI aims to provide multiparametric imaging allowing acquisition of morphology and metabolism.

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Abbreviations

AC:

attenuation correction

AC_T1_FLASH3D:

T1w flash sequence for attenuation correction

APD:

avalanche photodiode

B 0 :

main magnetic field

B 1 :

radiofrequency field

BOLD:

blood oxygen level-dependent

CFD:

constant fraction discriminator

CSI:

chemical shift imaging sequence

CP:

circular polarised

EPI:

echo planar imaging

EPI_BOLD:

EPI BOLD sequence

ΔTE:

difference between echo times

FBIRN:

Function Biomedical Informatics Research Network

FLASH:

fast low angle shot

FWHM:

full width at half maximum

FWTM:

full width at tenth maximum

G-APD:

Geiger mode avalanche photodiode

γ:

gyromagnetic ratio

GE_MAP:

gradient echo map

LSO:

lutetium oxyorthosilicate

MRS:

magnetic resonance spectroscopy

NEMA:

National Electrical Manufacturers Association

NEC:

noise equivalent count rate

NSE:

normal spin echo

OP-OSEM3D:

ordinary Poisson ordered subset expectation maximisation

P(TE10):

phase map with echo time of 10 ms

P(TE20):

phase map with echo time of 20 ms

r_dc:

radius of decorrelation

RF_FIELD:

B 1 mapping service sequence

RF_NOISE:

manufacturer service sequence

rms:

root mean square

SE:

spin echo sequence

σ :

noise signal

s max :

maximal signal intensity

s min :

minimal signal intensity

SFNR:

signal to fluctuation noise ratio

SNR:

signal to noise ratio

STE:

stimulated echo

SVS_SE:

single voxel press spectroscopy sequence

T1_FL2d:

T1w flash sequence

T2_TSE:

T2w turbo spin echo sequence

TOF:

time of flight

TX/RX:

transmit/receive

UTE:

ultra short echo time sequence

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Acknowledgments

The authors thank Andreas Schmid and Johannes Breuer for their helpful advice on programming the software for the data analysis. We thank the Radiopharmacy of the University Hospital Tübingen for providing the radiotracers as well as Andreas Boss for helpful discussions.

The authors also appreciate the discussions within the Brain PET insert partners at MGH, Boston Massachusetts, USA, the Research Center Jülich, Germany, and Emory University, Atlanta, Georgia, USA.

Financial support from the German Research Association (DFG) was provided through grants PI771/1-1, PI771/3-1, PI771/5-1.

Author information

Authors and Affiliations

  1. Department of Preclinical Imaging and Radiopharmacy, Eberhard Karls University, Roentgenweg 13, 72076, Tübingen, Germany

    Armin Kolb, Hans F. Wehrl, Matthias Hofmann, Martin S. Judenhofer & Bernd J. Pichler

  2. Max Planck Institute for Biological Cybernetics, Tübingen, Germany

    Matthias Hofmann

  3. Department of Diagnostic and Interventional Radiology, Department of Radiology, Eberhard Karls University, Tübingen, Germany

    Matthias P. Lichy, Heinz-Peter Schlemmer & Claus D. Claussen

  4. Siemens Healthcare, Knoxville, TN, USA

    Lars Eriksson, Ralf Ladebeck, Larry Byars, Christian Michel & Matthias Schmand

  5. Siemens Healthcare, Erlangen, Germany

    Matthias P. Lichy

  6. University of British Columbia, Vancouver, Canada

    Vesna Sossi

Authors
  1. Armin Kolb
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  2. Hans F. Wehrl
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  3. Matthias Hofmann
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  4. Martin S. Judenhofer
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  9. Christian Michel
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  10. Heinz-Peter Schlemmer
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  11. Matthias Schmand
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  12. Claus D. Claussen
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  13. Vesna Sossi
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  14. Bernd J. Pichler
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Corresponding author

Correspondence to Bernd J. Pichler.

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Kolb, A., Wehrl, H.F., Hofmann, M. et al. Technical performance evaluation of a human brain PET/MRI system. Eur Radiol 22, 1776–1788 (2012). https://doi.org/10.1007/s00330-012-2415-4

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  • DOI: https://doi.org/10.1007/s00330-012-2415-4

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