Chair for Computer Aided Medical Procedures & Augmented Reality
Lehrstuhl für Informatikanwendungen in der Medizin & Augmented Reality

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S. Fürst, G. Delso, A. Martinez-Möller, B. Jakoby, F. Schoenahl, C. Ganter, S. Nekolla, S. I. Ziegler, E. Rummeny, M. Schwaiger
Initial performance evaluation of the Biograph mMR
Journal of Nuclear Medicine 2011, 51 (suppl. 1), p320. Proceedings of Annual Meeting of Society of Nuclear Medicine (SNM 2011), San Antonio, TX, USA, June 2011 (bib)

The first fully integrated MR/PET system for clinical use has recently been released (Biograph mMR). The goal was to assess the physical performance in comparison with the PET/CT Biograph TruePoint? TrueV? (BioT?) and to evaluate the impact of simultaneous operation on either modality. Methods: The mMR is based on a 3T magnet and APD-LSO block detectors. A complete set of measurements was conducted following the NEMA NU 2-2007 protocol. For the image quality test, a synthetic attenuation map had to be used due to the resonant response of the standard thoracic phantom to radiofrequency (RF) fields. Sensitivity and spatial resolution tests were also performed with MRI sequences (VIBE, PASL) running. RF noise measurements were performed in three situations: With the PET powered off, on and in presence of activity. Homogeneity of the static B0 and RF fields was compared to that of a Magnetom Verio (3T). Results: As expected, the longer axial FOV (mMR: 25.8cm, BioT?: 21.8cm) and the reduced detector ring diameter (mMR: 65.6cm, BioT?: 84.2cm) lead to higher count rates and an increased sensitivity of >1.25% (BioT?: 0.8%) with and without an MRI scan running simultaneously. The narrower energy window (mMR: 430-610keV, BioT?: 425-650keV) limits the increase of scatter counts, leading to considerably higher noise equivalent count rates and a scatter fraction of 36% (BioT?: 33%). The average spatial resolution of the mMR was measured to be 4.0mm FWHM near the centre of the FOV (BioT?: 4.4mm). The spectrum of the three RF noise measurements matched within 2% and showed no spikes. The B0 field homogeneity was <1ppm in a 22cm sphere. Flip angle differences of <5° were observed independently of PET activity. Both values are comparable to the ones obtained with the Verio. Conclusions: These first results indicate that integration of APD-PET technology and 3T MRI allows simultaneous whole-body imaging without performance limitations in comparison to state-of-the-art MR and PET instrumentation.</TD>
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