On MRI, which signal characteristic of a bone lesion on T1-weighted images MOST reliably indicates that the lesion contains fat, consistent with a lipoma or bone infarct?
- A Low T1, high T2 signal
- B Intermediate T1 signal with marked post-contrast enhancement
- C Homogeneous high T1 signal that suppresses on fat-saturation sequences ✓
- D Low T1 signal with chemical shift artefact
Correct answer: C. Homogeneous high T1 signal that suppresses on fat-saturation sequences
Explanation
Fat-containing lesions show characteristic high signal on T1-weighted images (brighter than muscle, similar to subcutaneous fat). The definitive confirmation is signal dropout on fat-saturation (STIR or chemical fat saturation) sequences. Bone lipomas and the fatty zones within bone infarcts follow this pattern. Low T1/high T2 is typical of fluid or oedema. Intermediate T1 with enhancement suggests vascularised tissue. Chemical shift artefact is a separate phenomenon.
Reference: Grainger & Allison's Diagnostic Radiology, 7th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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