title: Use of contrast-enhanced ultrasound imaging to detect the first draining lymph node (FDLN) in a swine model: correlation of imaging findings with the distance from the injection site to the FDLN.
abstract: OBJECTIVE
  The purpose of this study was to investigate the use of contrast-enhanced ultrasound imaging (CEUS) to detect the first draining lymph node (FDLN) in a swine model and to determine whether the distance from the contrast agent injection site to the FDLN has any affect on the ability to detect contrast-enhanced FDLNs.
  
  
  METHODS
  Thirteen swine (25-32 kg) were anesthetized during examinations and euthanized afterward. In every swine, 1 mL of a sulfur hexafluoride microbubble ultrasound contrast agent was bilaterally injected subcutaneously below a mammilla. The examined distances varied from 6 to 36 cm. The contrast-enhanced lymphatic channels were visualized with low-mechanical index CEUS and mapped from the injection site to the FDLN. After CEUS was performed, blue dye was injected in the same locations as the contrast agent, and dye-guided surgery was used to localize the FDLNs. To ensure the lymph node detected with the blue dye technique was the same found with CEUS, it was scanned again to confirm contrast enhancement.
  
  
  RESULTS
  After 26 injections, 22 inguinal FDLNs were detected with CEUS and the blue dye technique. After 4 injections in 2 swine, contrast-filled lymphatic channels were identified with a course running toward the neck. In all cases but 1, the FDLNs received the contrast agent within 5 minutes.
  
  
  CONCLUSIONS
  In this swine model, it was possible to use CEUS to locate the FDLNs. In these preliminary experiments, the distances from the contrast agent injection site to the FDLN did not affect the ability to detect the contrast-enhanced FDLNs.
authors.affiliation: Department of Radiology, Section of Ultrasound X4123, Copenhagen University Hospital-Rigshospitalet, DK-2100 Copenhagen, Denmark.
authors.forename: Kristina R
authors.initials: KR
authors.lastname: Nielsen
authors.forename: Hanne S
authors.initials: HS
authors.lastname: Grossjohann
authors.forename: Carsten P
authors.initials: CP
authors.lastname: Hansen
authors.forename: Michael B
authors.initials: MB
authors.lastname: Nielsen
mesh_terms: D000818:Animals; D003287:Contrast Media / Q000008:administration & dosage; D007089:Image Enhancement / Q000379:methods*; D007267:Injections / Q000379:methods; D008198:Lymph Nodes / Q000000981:diagnostic imaging* / Q000187:drug effects; D010743:Phospholipids / Q000008:administration & dosage*; D021701:Sentinel Lymph Node Biopsy / Q000379:methods; D013459:Sulfur Hexafluoride / Q000008:administration & dosage*; D013552:Swine; D014463:Ultrasonography / Q000379:methods*
chemical_list: D003287:Contrast Media; D010743:Phospholipids; C420843:contrast agent BR1; D013459:Sulfur Hexafluoride