Technical performance evaluation of a human brain PET/MRI system
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Technical performance evaluation of a human brain PET/MRI system.
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.
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.
PET and MRI phantom tests and first patient data exhibit the device’s potential for simultaneous multiparametric imaging.
• 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.
KeywordsPET/MRI MR-PET Brain PET/MRI Multimodality imaging Multiparametric imaging
T1w flash sequence for attenuation correction
main magnetic field
blood oxygen level-dependent
constant fraction discriminator
chemical shift imaging sequence
echo planar imaging
EPI BOLD sequence
difference between echo times
Function Biomedical Informatics Research Network
fast low angle shot
full width at half maximum
full width at tenth maximum
Geiger mode avalanche photodiode
gradient echo map
magnetic resonance spectroscopy
National Electrical Manufacturers Association
noise equivalent count rate
normal spin echo
ordinary Poisson ordered subset expectation maximisation
phase map with echo time of 10 ms
phase map with echo time of 20 ms
radius of decorrelation
B 1 mapping service sequence
manufacturer service sequence
root mean square
spin echo sequence
maximal signal intensity
minimal signal intensity
signal to fluctuation noise ratio
signal to noise ratio
single voxel press spectroscopy sequence
T1w flash sequence
T2w turbo spin echo sequence
time of flight
ultra short echo time sequence
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.
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