For GRE coherent T2* weighted scans, what is the suggested long TE value?

The suggested long echo time (TE) value for GRE (Gradient Echo) coherent T2*-weighted scans is typically set at 15 ms or longer. This is important because T2* weighting is sensitive to magnetic susceptibility differences in tissues, which affects the decay of the signal.

Using a longer TE allows for greater differentiation of tissues based on their T2* relaxation properties, enhancing contrast for structures with varying iron content or in the presence of flow effects, which are often important in imaging applications like brain, liver, and vascular assessments. A TE of 15 ms or more helps to capture the full decay of the signal, maximizing the T2* contrast in the final images.

Although shorter TE values can still provide images, they may not fully utilize the T2* effects that are critical for certain diagnostic interpretations. Therefore, employing a TE value of at least 15 ms is optimal for achieving the desired contrast and diagnostic utility in GRE coherent T2*-weighted imaging.