The inversion time (TI) selected to null the signal from a specific tissue should be what percentage of the T1 relaxation time of that tissue?

In magnetic resonance imaging, the inversion time (TI) is crucial when performing inversion recovery sequences, as it serves to null the signal from a specific tissue, enhancing contrast with other tissues. The optimal TI required to achieve this is generally set at approximately 69% of the T1 relaxation time for the target tissue.

This percentage is derived from the understanding of the T1 relaxation process, which dictates how quickly the longitudinal magnetization of the tissue recovers after being inverted. By selecting a TI that is around 69% of T1, the signal from the tissue of interest effectively diminishes to a point that it becomes indistinguishable from the background, allowing for better visualization of adjacent structures or contrasting tissues in the MRI images.

Selecting TI values inaccurately can lead to poor nulling effects, which may compromise image quality and diagnostic accuracy. Therefore, aiming for approximately 69% of T1 for optimal inversion recovery is a key principle in MRI technique, particularly when differentiating tissues based on their T1 characteristics.