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Open Access

Compatibility of metal additive manufactured tungsten collimator for SPECT/MRI integration

  • Amine M Samudi1,
  • Karen Van Audenhaege2,
  • Gunter Vermeeren1,
  • Luc Martens1,
  • Roel Van Holen2 and
  • Wout Joseph1
EJNMMI Physics20152(Suppl 1):A52

Published: 18 May 2015

The Erratum to this article has been published in EJNMMI Physics 2015 2:27


Supporting StructureAdditive ManufacturingEddy CurrentGradient StrengthGlobal Reduction

We optimized the MR-compatibility of a novel tungsten collimator, produced with metal additive manufacturing that is part of a microSPECT insert for a preclinical SPECT/MRI scanner. We characterized the current density due to the gradient field and adapted the collimators by smart design to reduce the induced eddy currents. The z-gradient coil and the collimator were modeled with SEMCAD. The gradient strength was 510 mT/m, the gradient efficiency was about 3.4 mT/m/A. The setup was simulated with a working frequency of 10 kHz. The system consists of 7 identical collimators and digital silicon photomultipliers assembled in a ring. We evaluated the global reduction in current density J (reduction) based on the sum of all current densities in the collimator. We applied the following optimizations on the collimator: 1. We reduced the excessive material in the flanges. 2. We applied horizontal slits of 2 mm in the collimator surface. 3. We reduced material in the core; the photons are attenuated before they reach the core. The collimator will need a supporting structure. 4. The supporting structure can be avoided by using two vertical slits in the middle of the collimator. 5. We used a Z-shaped slit instead of the vertical slit. Results of simulations show that smaller flanges reduce the current density with 23%. The horizontal slits reduce the eddy currents with 6%. Using less material in the core or applying vertical slits results in the same reduction of current density. However, the vertical slits are cheaper because a hollow collimator requires supporting structures during production. Both can be combined if z-shaped slits are used to prevent attenuation problems. The reduction is then 27%. Finally, when all previous adaptations are combined, the reduction in eddy currents is about 56.3%.


Authors’ Affiliations

INTEC, Ghent University/iMinds, Ghent, Belgium
ELIS, Ghent University/iMinds, Gent, Belgium


© Samudi et al; licensee Springer. 2015

This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.