The salt and pepper sign is used to refer to a speckled appearance of tissue. It is used in many instances, but most commonly on MRI. Please note that pathologists also use the term.
Used to describe some highly vascular tumours which contain foci of haemorrhage, typically a paraganglioma. The appearance is on T1 weighted sequences, and is made up of:
- punctate regions of hyperintensity = salt
- small flow voids = pepper
Typical tumours with this appearance include:
Similar appearance may be seen on T2 sequences or post contrast T1 sequences in patients with juvenile nasopharyngeal angiofibromas 6.
This appearance can also be seen in other hypervascular tumours such as metastatic hypernephroma or metastatic thyroid carcinoma 7.
A less common usage for the term is for vertebral haemangiomas which have a courser black and white dotted appearance especially on axial T2 and T1 images (salt = fat, pepper = coarsened trabeculae).
MRI noise artefact
A related use of the term is to describe the noise sometimes seen in MRI images.
When you think about it, you can probably find folk who have used the term for all sorts of lesions; any lesion that has a fine granular imaging texture will do the trick.
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- 6. Seo CS, Han MH, Chang KH et-al. Angiofibroma confined to the pterygoid muscle region: CT and MR demonstration. AJNR Am J Neuroradiol. 1996;17 (2): 374-6. AJNR Am J Neuroradiol (abstract) [pubmed citation]
- 7. Chavhan GB, Shroff MM. Twenty classic signs in neuroradiology: A pictorial essay. Indian J Radiol Imaging. 19 (2): 135-45. doi:10.4103/0971-3026.50835 - Free text at pubmed - Pubmed citation