Antonio Matos MD, Presenter: Nothing to Disclose

Jorge Miguel Ramalho DO, Abstract Co-Author: Nothing to Disclose

Vasco Heredia, Abstract Co-Author: Nothing to Disclose

Joao Manuel Palas DO, Abstract Co-Author: Nothing to Disclose

Filipe Veloso Gomes MBBCh, Abstract Co-Author: Nothing to Disclose

Richard Charles Semelka MD, Abstract Co-Author: Nothing to Disclose

To describe a novel approach for the evaluation of adrenal nodules using a standard abdominal MRI protocol.

A consecutive search was performed between January 2008 and December 2012. The final sample comprised 149 subjects with 132 adenomas and 40 non-adenomas. Adrenal signal intensity indices (AI) were calculated. Lesions were clustered in 3 groups according to the wash-in time to peak (arterial-Type1EP, portal-venous-Type2EP or interstitial-Type3EP). The relative and absolute washouts were calculated. Independent-samples Student-t test was used to test for mean differences between adenomas and non-adenomas concerning quantitative parameters and ratios. ROC curve analysis was performed. An optimal threshold value was calculated. The probability for lipid-poor adenomas occurring with Type1EP, Type2EP and Type3EP was calculated by means of multiple event probability.

The mean AI of adrenal adenomas was significantly higher than that of nonadenomas (p<0.0001). CSI had a sensitivity and specificity of 94.4% and 100% for differentiate adenomas from non-adenomas. For all the enhancement patterns, significant differences for mean wash-in percentages were found. 47.6% adenomas exhibited a Type1EP, 48.5% a Type2EP and 3.9% a Type3EP. The majority of non-adenomas fitted in Type2EP (38.5%) and Type3EP (48.7%). There was a trend toward better lesion differentiation using the absolute washout calculation for lesions presenting with Type1EP and the relative washout for lesions presenting with Type2EP with sensitivity and specificity of of 71.4% and 80%, and 68% and 100%, respectively. The probability of a lipid-poor lesion exhibiting Type3EP being a non-adenoma is greater than 99%.

The presence of intracytoplasmatic lipid calculated by means of CSI continues to be the strongest indicator of benignity. In the absence of intracytoplasmatic lipid, a lesion presenting with Type1EP is very likely to be an adenoma and, conversely, a non-adenoma when presenting with Type3EP. There is considerable overlap for lesions presenting with Type2EP and in our approach we suggest the choice of the relative washout calculation, as an additional tool to separate lipid-poor adenomas from non-adenomas.

Late washout periods are not usually performed on MRI for the diagnose of adrenal nodules. A combination of CSI with categorization of dynamic enhancing patterns yields high diagnostic accuracy.

Matos, A, Ramalho, J, Heredia, V, Palas, J, Veloso Gomes, F, Semelka, R, Novel Approach on the Characterization of Adrenal Nodules Using Standard Abdominal MRI Protocol.  Radiological Society of North America 2013 Scientific Assembly and Annual Meeting, December 1 - December 6, 2013 ,Chicago IL. http://archive.rsna.org/2013/13044159.html