Type:
Educational Exhibit
Keywords:
Not applicable, Education and training, Technical aspects, Imaging sequences, MR, Image manipulation / Reconstruction, Radiographers, MR physics, Extremities, MRI
Authors:
C. Rasagna1, F. Abubacker Sulaiman2, A. RAJENDRAN3, A. Asokan4; 1Chennai/IN, 2Chennai, TN/IN, 3Chennai, TA/IN, 4Kelambakkam/Chennai, Ta/IN
DOI:
10.26044/ecr2020/C-13075
Background
The presence of metal can result in severe variations in the static magnetic field because of susceptibility variations between metal and surrounding tissue.
Magnetic susceptibility is the property which is determined by the way the object behaves in the presence of an external magnetic field. The magnetic field and metal-tissue interactions , based on the objects ,are classified as follows :
- Diamagnetic materials
- Paramagnet materials
- Ferromagnet materials
1. Diamagnet Materials
These materials when placed in the magnetic field are mildly magnetized in a direction opposite to that of the field (Fig.1(a)). Thus the susceptibilty of the material is small and negative. Ex: Tissue, Water, Copper, nitrogen etc
2.Paramagnetic Materials
These materials also get mildly magnetized when placed in the external magnetic fields but in the direction of the field (Fig.1(b)) . Thus , they have a small positive susceptibilty. Ex: Oxygen, Magneium, Gadolinium etc
3.Ferromagnetic Materials
These materials , when placed in an external magnetic field , are strongly magnetized in the direction of the field (Fig.1(c)) . Therefore , they have a very large positive susceptibility value. Ex: Iron, Cobalt, Nickel.
This is the primer driver of metal artifact in MR Imaging.