In order to be declared brain dead, a person needs to have no activity in either the brain or brain stem, at the base of the brain. Credit: Johan Swanepoel | Shutterstock View full size image.n Jahi's case, three doctors have concluded that she is brain-dead. However, the heart's intrinsic electrical system can keep the organ beating for a short time after a person becomes brain-dead â in fact, the heart can even beat outside the body, Greene-Chandos said.
Noun. 1. anisotropy-the property of being anisotropic; having a different value when measured in different directions. property-a basic or essential attribute shared by all members of a class; a study of the physical properties of atomic particles.
Fractional anisotropy is a method that is used to emphasize and evaluate white matter fiber tracts. This method has been applied to MRI scans in diffusion weighted images. If full tensor data acquisition is applied, the fractional anisotropy (FA) is calculated from the eigenvalues Î» 1, Î» 2, and Î» 3 of the diffusion tensor: where Î» is the mean diffusivity (trace/3). FA takes on values between 0 (perfectly isotropic diffusion) and 1 (the hypothetical case of an infinite cylinder) and is thus directly comparable between subjects. Here FA is multiplied by 1,000.