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“School of Cognitive Sciences”

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Paper   IPM / Cognitive Sciences / 13732
School of Cognitive Sciences
  Title:   Torque and Translational force Considerations for ferromagnetic shells in MR Imaging
1.  V. Ghodrati
2.  A. Nasiraei Moghaddam
  Status:   In Proceedings
  Proceeding: ISMRM_2014
  Year:  2014
  Supported by:  IPM
MRI is a powerful system in the Medical Imaging that provides the highest contrast between soft tissues with no known adverse effect in the absence of ferromagnetic objects. However, in some injuries, such as those happen in the battle field, part of shells or foreign objects that may include magnetic materials remain in victim’s body. This is considered a serious contraindication for MRI scan since the shell may move or rotate in the strong static magnetic field. In particular, if the shell is in the head region, the effect of this motion or torque may cause an irreversible defect. In general torque makes a greater health risk compared to the translational force [1]. Since the shape and material of these objects are unknown, a shape classification that covers the most problematic situations is helpful. For calculation of the translational force we may only focus on spherical geometry, however, for approximation of torque a more general shape like an ellipsoid is required. “Ellipsoid of revolution” has an axis of symmetry and two equivalent principle axes. Here we present the force and torque estimation for a ferromagnetic object using these general shapes and discuss the worst case scenario that may occur for these patients.

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