ADRENAL ADENOMAS - RELATIONSHIP BETWEEN HISTOLOGIC LIPID AND CT AND MR FINDINGS

PURPOSE: To assess the relationship between the quantity of lipid in r esected adrenal adenomas and the unenhanced computed tomographic (CT) attenuation number and the relative change in signal intensity on chem ical shift magnetic resonance (MR) images. MATERIALS AND METHODS: The percentage of lipid-rich cortical cells in histologic sections from 20 resected adrenal adenomas was assessed. The results were correlated w ith the corresponding unenhanced CT attenuation number or the relative change in signal intensity on chemical shift MR images, or both. RESU LTS: There was an inverse linear relationship between the percentage o f lipid-rich cortical cells in the adrenal adenomas and the unenhanced CT attenuation number (R(2) = .68, P = .0005). There was a similar in verse linear relationship to the relative change in MR signal intensit y on chemical shift images by using both quantitative (R(2) = .83, P = .004) and qualitative (R(2) = .70, P = .019) assessment. CONCLUSION: The presence and amount of histologic lipid in many adrenal adenomas a ccounts for their low attenuation on unenhanced CT scans and their los s in relative signal intensity on chemical shift MR images.