title: Dual-energy CT for characterization of adrenal nodules: initial experience.
abstract: OBJECTIVE
  The purpose of this study was to determine whether use of dual-energy technique can improve the diagnostic performance of CT in the differential diagnosis of adrenal adenomas and metastatic lesions.
  
  
  METHODS
  Thirty-one adrenal nodules were prospectively identified in 17 patients who underwent dual-energy CT at 140 and 80 kVp. Attenuation measurements were performed for each nodule at both tube voltages. The mean attenuation change (increase or decrease) between 140 kVp and 80 kVp was determined for each adrenal nodule.
  
  
  RESULTS
  Twenty-six adrenal nodules were benign adenomas (attenuation less than +10 HU or stability for at least 1 year). Five adrenal nodules were classified as metastatic (rapid growth in 1 year and history of extraadrenal malignancy). The mean attenuation change between 140 kVp and 80 kVp was 0.4 +/- 7.1 HU for adenomas and 9.2 +/- 4.3 HU for metastatic lesions (p < 0.003). Fifty percent of adenomas had an attenuation decrease at 80 kVp. All metastatic lesions had an attenuation increase at 80 kVp. With a decrease in attenuation at 80 kVp as an indicator of intracellular lipid within an adenoma, dual-energy CT has 50% sensitivity, 100% specificity, 100% positive predictive value, and 28% negative predictive value in the diagnosis of adenoma.
  
  
  CONCLUSIONS
  A decrease in attenuation of an adrenal lesion between 140 kVp and 80 kVp is a highly specific sign of adrenal adenoma. However, because an increase in attenuation at 80 kVp is seen with metastatic lesions and some adenomas, the sensitivity of this test is low. These data suggest that dual-energy CT can be used to help differentiate some lipid-poor adrenal adenomas from metastatic lesions.
authors.affiliation: Department of Radiology, Duke University Medical Center, Durham, NC 27710, USA. rajan.gupta@duke.edu
authors.forename: Rajan T
authors.initials: RT
authors.lastname: Gupta
authors.forename: Lisa M
authors.initials: LM
authors.lastname: Ho
authors.forename: Daniele
authors.initials: D
authors.lastname: Marin
authors.forename: Daniel T
authors.initials: DT
authors.lastname: Boll
authors.forename: Huiman X
authors.initials: HX
authors.lastname: Barnhart
authors.forename: Rendon C
authors.initials: RC
authors.lastname: Nelson
mesh_terms: D000310:Adrenal Gland Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology; D018246:Adrenocortical Adenoma / Q000000981:diagnostic imaging* / Q000473:pathology; D000368:Aged; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D008297:Male; D009362:Neoplasm Metastasis; D011237:Predictive Value of Tests; D011446:Prospective Studies; D011857:Radiographic Image Interpretation, Computer-Assisted; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*