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Fat suppression: STIR vs spectral vs opposed-phase

A comparison table of three MRI fat techniques across five rows. STIR uses inversion-recovery timing (TI about 0.69 times T1 of fat), is non-specific to fat, is robust to B0 and B1 inhomogeneity, and has lower SNR. Spectral fat saturation uses a narrowband RF pulse at fat's resonance frequency plus a spoiler, is fat-specific, requires a homogeneous B0 field, and has higher SNR. Opposed-phase imaging uses gradient echo at an opposed-phase echo time so fat and water cancel only within mixed voxels; bulk fat stays bright, so it is a detection method rather than a bulk-fat suppressor.

MRI fat-suppression methods compared: STIR, spectral fat saturation, and opposed-phase imaging A comparison table of three MRI fat techniques across five rows. STIR uses inversion-recovery timing (TI about 0.69 times T1 of fat), is non-specific to fat, is robust to B0 and B1 inhomogeneity, and has lower SNR. Spectral fat saturation uses a narrowband RF pulse at fat's resonance frequency plus a spoiler, is fat-specific, requires a homogeneous B0 field, and has higher SNR. Opposed-phase imaging uses gradient echo at an opposed-phase echo time so fat and water cancel only within mixed voxels; bulk fat stays bright, so it is a detection method rather than a bulk-fat suppressor. Comparing MRI fat-suppression methods STIR (inversion recovery) Spectral fat sat (frequency-selective) Opposed-phase (in / out-of-phase) Physical basis Mechanism Fat specificity B0 field homogeneity Relative SNR T1 recovery timing Chemical shift ~3.5 ppm, 220 [email protected] T Chemical-shift phase (in / out of phase) Inversion pulse; TI ≈ 0.69 × T1fat (~150–180 ms @1.5 T) Narrowband RF at fat frequency, + spoiler gradient dephases fat GRE, opposed-phase TE ~2.2 ms (@1.5 T); fat & water cancel Non-specific: nulls any short-T1 tissue (Gd, blood, protein) Fat-specific: targets fat's frequency offset Cancels only mixed fat+water voxels — bulk fat stays bright Robust — tolerates B0 / B1 inhomogeneity Needs homogeneous B0 (good shimming); better at higher field Phase-based GRE Lower — all tissues inverted / saturated Higher — water signal preserved signal drop is the diagnostic cue STIR is usually run as fast spin-echo (STIR-FSE / TSE) — keeps fat-nulling while cutting scan time. Opposed-phase detects microscopic fat: “India ink” edges, adrenal & hepatic lesions. It is a fat–water cancellation / detection method, not a suppressor of bulk adipose tissue.
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