What is a requirement for the echo time (TE) in T1 weighted images?

In T1 weighted imaging, the echo time (TE) needs to be kept short to minimize T2 decay effects. T1 weighted images rely on the differences in longitudinal relaxation times of tissues, and a long echo time would allow more time for T2 decay to occur before the echo is read. This decay can blur the contrast between tissues, making it harder to differentiate between them based on their T1 characteristics. By using a short TE, the influence of T2 decay is minimized, allowing for a clearer presentation of the T1 contrast that is essential for accurate diagnosis based on the relative intensities of different tissues on the image.

While echo time indeed interacts with repetition time (TR) in imaging parameters, the primary focus for achieving optimal T1 weighting is to ensure a short TE. In T1 imaging, TE being short does not necessitate that it must be adjusted based on TR; rather, this relationship within T1 weighted imaging serves an ancillary function rather than a primary guideline. Thus, to achieve the desired T1 contrast effectively, a short TE is critical.