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European Radiology

, Volume 22, Issue 8, pp 1776–1788 | Cite as

Technical performance evaluation of a human brain PET/MRI system

  • Armin Kolb
  • Hans F. Wehrl
  • Matthias Hofmann
  • Martin S. Judenhofer
  • Lars Eriksson
  • Ralf Ladebeck
  • Matthias P. Lichy
  • Larry Byars
  • Christian Michel
  • Heinz-Peter Schlemmer
  • Matthias Schmand
  • Claus D. Claussen
  • Vesna Sossi
  • Bernd J. Pichler
Molecular Imaging

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.

Keywords

PET/MRI MR-PET Brain PET/MRI Multimodality imaging Multiparametric imaging 

Abbreviations

AC

attenuation correction

AC_T1_FLASH3D

T1w flash sequence for attenuation correction

APD

avalanche photodiode

B0

main magnetic field

B1

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

smax

maximal signal intensity

smin

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

Notes

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.

Supplementary material

330_2012_2415_MOESM1_ESM.doc (440 kb)
ESM 1 Electronic supplementary material. (DOC 440 kb)

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Copyright information

© European Society of Radiology 2012

Authors and Affiliations

  • Armin Kolb
    • 1
  • Hans F. Wehrl
    • 1
  • Matthias Hofmann
    • 1
    • 2
  • Martin S. Judenhofer
    • 1
  • Lars Eriksson
    • 4
  • Ralf Ladebeck
    • 4
  • Matthias P. Lichy
    • 3
    • 5
  • Larry Byars
    • 4
  • Christian Michel
    • 4
  • Heinz-Peter Schlemmer
    • 3
  • Matthias Schmand
    • 4
  • Claus D. Claussen
    • 3
  • Vesna Sossi
    • 6
  • Bernd J. Pichler
    • 1
  1. 1.Department of Preclinical Imaging and RadiopharmacyEberhard Karls UniversityTübingenGermany
  2. 2.Max Planck Institute for Biological CyberneticsTübingenGermany
  3. 3.Department of Diagnostic and Interventional Radiology, Department of RadiologyEberhard Karls UniversityTübingenGermany
  4. 4.Siemens HealthcareKnoxvilleUSA
  5. 5.Siemens HealthcareErlangenGermany
  6. 6.University of British ColumbiaVancouverCanada

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