What characteristic of tissue defines its dielectric constant?

The characteristic of tissue that defines its dielectric constant is permittivity. Permittivity is a measure of a material's ability to store electrical energy in an electric field. In the context of tissues, this property reflects how the tissue interacts with electromagnetic fields, particularly those used in magnetic resonance imaging (MRI).

Tissues with higher permittivity can store more energy when exposed to an electric field, which is a crucial aspect when considering how various types of tissues respond to the radiofrequency (RF) fields employed in MRI. The dielectric constant itself is defined as the ratio of the permittivity of a material to the permittivity of free space. It provides insight into how well a material can insulate against electric fields, which is vital for understanding the behavior of RF energy in biological tissues during imaging procedures.

In summary, permittivity is the key factor that defines the dielectric constant of tissues, impacting their interaction with magnetic and electric fields in medical imaging applications.