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Even though a TE value of 25 ms does not seem "long" by spin-echo imaging standards, it is relatively long compared to the T2* values of tissues, which are much shorter than tissue T2's. Increasing TE much beyond 30 ms also impairs signal-to-noise of the sequence and results in too much susceptibility artifact near the skull base.
Chavhan GB, Babyn PS, Thomas B, Shroff MM, Haacke EM. Principles, techniques, and applications of T2*-based MR imaging and its special applications. Radiographics 2009; 29:1433-1449. (good review of traditional GRE T2*-weighted imaging with a lead-in to SWI)
Mittal S, Wu Z, Neelavalli J, Haacke EM. Susceptibility-weighted imaging: technical aspects and clinical applications, part 2. AJNR Am J Neuroradiol 2009; 30:232-252. (clinical applications)
Tong KA, Ashwal S, Obenaus A, et al. Susceptibility-weighted MR imaging" a review of clinical applications in children. AJNR Am J Neuroradiol 2008; 29:9-17. (Good review showing superiority of SWI over GRE for detecting small hemorrhagic lesions).
What is susceptibility?