Which MRI sequence is best suited for this lesion?
Ans. B. Chemical shift Imaging MRI* This is a post contrast axial CT scan of the upper abdomen which shows a mildly enhancing lesion in right adrenal.* This lesion could be an adenoma; however, the other differentials include serious entities like metastases or carcinomas.* Differentiating between them is vital and more emphasis is on imaging as adrenals are small retroperitoneal organs which are surrounded by vascular structure thus obtaining an image guided biopsy becomes difficult.* There are various techniques used to differentiate between them, one of which is in and out phase imaging which is based on the premise that adrenal adenomas are rich in their lipid contents whereas other lesions like carcinoma and metastases are lipid poor.* The characterization of a lesion as an adenoma relies on the ratio of a decreased relative signal intensity from in phase to opposed phase images and the ratio of adrenal mass and various organs on T2-weighted and chemical shift images. Sometimes at the interface of water and fat the adenoma can give rise to dark bands - India ink artefacts.* Other commonly used indices include the relative and absolute washout values of CT scan which used HU values of CT of same area in unenhanced, enhanced and delayed scans.
T2W
Chemical shift imaging MRI
DWI
D STIR
Nervous System