title: Adrenal Incidentaloma triage with single-source (fast-kilovoltage switch) dual-energy CT.
abstract: OBJECTIVE
  The purpose of this article is to evaluate single-source dual-energy CT (DECT) for distinguishing benign and indeterminate adrenal nodules, with attention to the effects of phase of IV contrast enhancement.
  
  
  METHODS
  A retrospective review revealed 273 contrast-enhanced abdominal DECT examinations from November 2009 through March 2012. Fifty adrenal nodules 0.8 cm or larger were identified in 41 patients (22 women and 19 men; average age, 66 years; age range, 36-88 years). CT postprocessing and measurements were independently performed by two radiologists (readers 1 and 2) for each nodule, as follows: attenuation (in Hounsfield units) on true unenhanced images; contrast-enhanced attenuation (in Hounsfield units) on monochromatic spectral images at 40, 75, and 140 keV; and contrast-enhanced material density (in milligrams per milliliter) on virtual unenhanced images. Nodules were classified as benign (< 10 HU) and indeterminate (≥ 10 HU) according to true unenhanced images.
  
  
  RESULTS
  Interreader agreement regarding benign and indeterminate nodules was high (κ = 0.92; 95% CI, 0.8-1.0). At 140 keV, the attenuation of benign nodules was significantly lower (reader 1, 7.0 ± 12.5 HU; reader 2, 7.8 ± 9.2 HU) than that of indeterminate nodules (reader 1, 15.7 ± 20.5 HU [p = 0.004]; reader 2, 17.5 ± 13.4 HU [p < 0.0001]). On virtual unenhanced images, benign nodules had significantly lower material density (reader 1, 992.4 ± 9.9 mg/mL; reader 2, 992.7 ± 9.6 mg/mL) than did indeterminate nodules (reader 1, 1001.1 ± 20.5 mg/mL [p = 0.038]; reader 2, 1007.6 ± 13.4 mg/mL [p < 0.0001]).
  
  
  CONCLUSIONS
  DECT tools can mathematically subtract iodine or minimize its effects in high-energy reconstructions, approximating unenhanced imaging and potentially reducing the need for additional studies to triage adrenal nodules detected on contrast-enhanced DECT examinations.
authors: 1 Department of Radiology, University of Michigan, UH B1D502, 1500 E Medical Center Dr, Ann Arbor, MI 48109.
authors: Daniel I
authors: DI
authors: Glazer
authors: Katherine E
authors: KE
authors: Maturen
authors: Ravi K
authors: RK
authors: Kaza
authors: Isaac R
authors: IR
authors: Francis
authors: Nahid R
authors: NR
authors: Keshavarzi
authors: Robert A
authors: RA
authors: Parker
authors: Joel F
authors: JF
authors: Platt
mesh_terms: D000310:Adrenal Gland Neoplasms / Q000000981:diagnostic imaging*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003287:Contrast Media; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011857:Radiographic Image Interpretation, Computer-Assisted; D012189:Retrospective Studies; D013382:Subtraction Technique; D014057:Tomography, X-Ray Computed / Q000379:methods*; D014218:Triage
chemical_list: D003287:Contrast Media
keywords: adrenal adenoma; adrenal glands; dual-energy CT; incidentaloma; low-kilovoltage CT