Interpretation of dielectric shadow artifact - occurring due to the dielectric phenomenon and one of the disadvantages of imaging in high field magnetic resonance imaging systems (≥ 3.0 Tesla). The term dielectric effect refers to the interaction of matter - and in this case of biological tissues and materials - with the coexisting electric field (E1) of an electromagnetic field.

Magnetic and Electrical Fields in MRI In the MRI, together with the B1 of the RF coexists an electric field (E1). As described by the Maxwell equations, the fields B1 and E1 oscillate vertically with each other in the direction of wave propagation. When electromagnetic waves meet the human body, various phenomena occur The main ones are the following: (i) wavelength reduction (ii) electrical current generation and (iii) somewhat reflection / refraction of wave during the transition between different tissues. In all of the images...

The degree to which matter interacts with electric and magnetic fields can be described by three parameters:i) Magnetic permeability (μ).(ii) Electrical permeability (e).iii) Electrical conductivity (σ).For weakly conductive dielectric materials such as those of the human body, the internal RF field is disturbed by a jump current (JC) and displacement current flux (JD) that can be described by Ampère's law with the Maxwell correction∇ X B = μJC + μJD = μσE + iεεEIn human tissues, the RF frequencies used in JC and JD are...

Dielectric phenomena and associated pseudo-images are progressively more important and morecomplex as the field strength increases. With MultiTransmit technology, the power, range, phase and waveform of all RF sources are automatically adjusted for optimal homogeneity in each patient's unique anatomy. In this way, MultiTransmit technology provides optimal signal homogeneity and stability

V.G.SyrgiamiotisRT,BSc,MSc,PhD(c) ,EFRS Treasurer,Lab assistantATEI of Athens, General Childrens hospital of Athens Agia Sophia CT-MRI Department Thomas Theofanis RT,BSc,MSc (c),University hospital of Ioannina Maliakas Vasileios RT,BSc,MSc,PhD(c) ,University hopsital of Ioannina Loukas Astrakas Assistant Professor Medical Physists ,University hospital of Ioannina Argyropoulou Maria Professor Radiology ,University hospital of Ioannina Ploussi Agapi Medical Physist ,BSc,MSc,PhD(c) University hospital of Athens , Attiko

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