Adrenal Nodule Calculator MRI

Adrenal Signal intensity index (ASII): (lesion IP – lesion OP)/lesion IP
ASII >16.5% at 1.5 Tesla or >1.7% at 3 Tesla indicates a lipid-rich adenoma

Adrenal-to-spleen ratio (ASR): [((lesion IP/spleen OP)/(lesion IP/spleen IP)) – 1] *100
ASR ≤ -35.9% at 1.5 Tesla or ≤ 17.2% at 3 Tesla indicates a lipid-rich-adenoma

Adrenal-to-liver ratio (ALR): [((lesion IP/liver OP)/(lesion IP/liver IP)) – 1] *100
ALR ≤ -32.6% at 1.5 Tesla or ≤ 24.5% at 3 Tesla indicates a lipid-rich-adenoma

Adrenal-to-muscle ratio (AMR): [((lesion IP/muscle OP)/(lesion IP/muscle IP)) – 1] *100
AMR ≤ -29.3% at 1.5 Tesla or ≤ 39.6 % at 3 Tesla indicates a lipid-rich-adenoma

The spleen is the most commonly used reference tissue because the liver and muscles may be unreliable in patients with fatty infiltration.

The spleen may be sometimes also unreliable because of iron deposition, in which case the kidney can be used as a reference.

References:

Adam, Sharon Z., et al. “Chemical shift MR imaging of the adrenal gland: principles, pitfalls, and applications.” Radiographics 36.2 (2016): 414-432.

Schieda, Nicola, and Evan S. Siegelman. “Update on CT and MRI of Adrenal Nodules.” American Journal of Roentgenology 208.6 (2017): 1206-1217.

Suggested Reading:

MRI of Adrenal Glands – Articl.net

The information provided is not a substitute for clinical judgment. Confirm the calculations before use. The author makes no claims of the accuracy of information.