Which factor does NOT influence the characteristics of gradient echo sequences?

Gradient echo sequences are primarily influenced by factors that affect the way the magnetic field interacts with spins in the tissue being imaged. The characteristics of gradient echo sequences, such as image contrast, resolution, and artifacts, can be significantly affected by chemical shift, magnetic susceptibility, and inhomogeneity of the magnetic field.

Chemical shift is a phenomenon where different tissues resonate at slightly different frequencies due to varying chemical environments. This difference can lead to variations in signal intensity between fat and water, thereby influencing the resulting image.

Inhomogeneity refers to variations in the magnetic field, whether due to imperfections in the magnet or external factors. These variations can cause distortions and other artifacts in the images, affecting the quality and clarity of gradient echo sequences.

Susceptibility artifacts occur when there are differences in magnetic susceptibility between adjacent tissues, such as air and soft tissue. These differences can lead to distortions and signal loss in certain areas of the image, impacting the overall characteristics of gradient echo images.

Inversion time, on the other hand, specifically relates to inversion recovery sequences, which utilize the principle of inversion-recovery to suppress specific tissue signals, such as fat or fluid. It is not a factor that influences gradient echo sequences directly, making this the correct answer to the