Which parameter is affected by increasing the TE in a spin echo pulse sequence?

Increasing the echo time (TE) in a spin echo pulse sequence predominantly affects T2 weighting in the acquired images. In magnetic resonance imaging (MRI), T2 relaxation refers to the time it takes for the signal from the excited protons to decay due to interactions with their surroundings, leading to a loss of coherence among spins.

When TE is increased, there is a longer interval between the radiofrequency pulse and the signal acquisition. This extended time allows for more T2 decay to occur before the signal is measured. Consequently, tissues with shorter T2 relaxation times (like fat) will appear relatively brighter, while tissues with longer T2 times (like fluid) will appear darker. Therefore, increasing the TE enhances the differences in image contrast based on T2 characteristics, thus increasing T2 weighting in the images.

In contrast, other parameters remain less affected by changes in TE. For instance, T1 weighting is influenced more by the repetition time (TR) rather than TE. Similarly, an extended TE does not directly improve or worsen the spatial resolution, as that is typically determined by the image acquisition technique parameters such as matrix size and field of view. Signal-to-noise ratio (SNR) may actually decrease with increased TE due to longer acquisition times,