Nonspecificity of short inversion time inversion recovery (STIR) as a technique of fat suppression: Pitfalls in image interpretation

Short inversion time inversion recovery (STIR) and the rapid acquisition with relaxation enhancement (RARE) version of STIR are commonly used pulse sequences that are sensitive enough to detect a broad range of pathologic conditions. In addition to suppressing the signal from fat, the STIR sequence achieves additive T1-weighted, T2-weighted, and proton density-weighted contrast to facilitate lesion conspicuity. Fat suppression with STIR sequences is based on short T1 relaxation rates and therefore is not tissue specific. The signal from any tissue with a short T1, similar to that of fat, may be nulled as well. The signal from tissues that accumulate paramagnetic contrast agents also may be suppressed with STIR sequences when an appropriate degree of T1 shortening results.