Which term defines a tissue's dielectric constant?

The term that defines a tissue's dielectric constant is permittivity. Permittivity is a fundamental property of materials that indicates how much electric field (or electrical energy) can be stored in a material when it is placed in an electric field. It essentially quantifies the ability of a material to permit electric field lines to pass through it and is critical in understanding how different tissues respond in the presence of electromagnetic fields, such as those used in MRI.

Understanding permittivity is especially important in magnetic resonance imaging (MRI) as it affects the interaction of radiofrequency (RF) energy with tissue. Different tissues in the body have varying permittivity values, which can influence imaging parameters and the effectiveness of the RF pulse.

In contrast, conductivity relates to how well a material can conduct electric current, permeability is associated with a material's ability to support magnetic field lines, and resistivity is a measure of how strongly a material opposes the flow of electric current. While these properties are important in other contexts, they do not specifically define the dielectric constant, which is what permittivity does.