title: The dark lymph node sign on magnetic resonance imaging: a novel finding in patients with sarcoidosis.
abstract: OBJECTIVE
  The purpose of this study was to describe a characteristic magnetic resonance imaging (MRI) appearance of lymphadenopathy in sarcoidosis--the dark lymph node sign (DLNS)--and to determine its prevalence in a retrospective review of cardiopulmonary MRI examinations obtained in patients with sarcoidosis.
  
  
  METHODS
  Fifty-one adult patients with a clinical history of sarcoidosis were evaluated with thoracic MRI during a 15-month span; 29 patients were men, and 22 patients were women. The average age of patients was 53.7±11.2 years. Patients were considered to have the DLNS on MRI if mediastinal or hilar lymph nodes demonstrated internal low intensity with a peripheral circumferential rim of hyperintensity (relative to paraspinal muscle) on post-gadolinium volume-interpolated 3-dimensional gradient echo (3D-GRE/VIBE) and fat-saturated T2-weighted fast spin echo (T2-FSE/BLADE) sequences. Univariate analyses and a logistic regression were used to determine how variables of interest related to the DLNS.
  
  
  RESULTS
  Of the 51 patients with sarcoidosis, 49% (25 patients) demonstrated the DLNS. Nodal calcification was present on computed tomography in 45.7% (16/35) of patients with computed tomography scans obtained within 90 days of MRI. The DLNS sign was not more common in those with nodal calcification. When the DLNS occurred in conjunction with calcified nodes, the extent of hypointensity on MRI was not strictly limited to the calcified portions of the lymph node in 71.4% (5/7) of such cases.
  
  
  CONCLUSIONS
  The DLNS is commonly present on MRI examinations of patients with sarcoidosis, occurring in approximately half of the participants in our study.
authors.affiliation: *Department of Radiology, National Jewish Health, Denver, CO †Department of Diagnostic and Interventional Radiology, Chest Clinics at University Hospital Heidelberg, Heidelberg, Germany.
authors.forename: Jonathan H
authors.initials: JH
authors.lastname: Chung
authors.forename: Christian W
authors.initials: CW
authors.lastname: Cox
authors.forename: Anna V
authors.initials: AV
authors.lastname: Forssen
authors.forename: Juergen
authors.initials: J
authors.lastname: Biederer
authors.forename: Michael
authors.initials: M
authors.lastname: Puderbach
authors.forename: David A
authors.initials: DA
authors.lastname: Lynch
mesh_terms: D003287:Contrast Media; D005260:Female; D005682:Gadolinium; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods; D008198:Lymph Nodes / Q000000981:diagnostic imaging / Q000473:pathology*; D008206:Lymphatic Diseases / Q000000981:diagnostic imaging / Q000473:pathology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012507:Sarcoidosis / Q000000981:diagnostic imaging / Q000473:pathology*; D014057:Tomography, X-Ray Computed / Q000379:methods
chemical_list: D003287:Contrast Media; D005682:Gadolinium