title: Indocyanine green as a near-infrared fluorescent agent for identifying parathyroid glands during thyroid surgery in dogs.
abstract: BACKGROUND
  Surgical procedures involving the thyroid gland require identification of the parathyroid glands. Indocyanine green (ICG) is a near-infrared (NIR) fluorescent contrast agent used for a variety of procedures such as intraoperative angiography, extrahepatic cholangiography, and lymph node mapping. In this study, we used a canine model to evaluate ICG for NIR fluorescent imaging of the parathyroid gland.
  
  
  METHODS
  Three dogs were used for the study. The dogs were administered general anesthesia, and after surgical dissection, each dog received a series of intravenous ICG doses ranging from 12.5 to 100 µg/kg ICG. The excitation light source used to illuminate the operating field was a NIR laser (λ = 785 nm). Intravascular ICG fluorescence (λ = 835/45 nm) was recorded using a charge-coupled device that employed optical filtering to block ambient and laser light. Fluorescent imaging was assessed after injection of each dose of ICG.
  
  
  RESULTS
  NIR fluorescent imaging visualized the parathyroid glands. The intensity curves showing the peak and plateau of fluorescence are similar regardless of the concentration of ICG. The time to peak fluorescent intensity was 50.2 ± 2.0 s after injection of ICG. Taking into consideration background fluorescent intensity, the estimated optimal dose of ICG was 18.75 µg/kg. At 106.7 ± 5.8 s, the parathyroid glands lost much of their fluorescence, although they remained sufficiently fluorescent to be distinguishable. There was a positive correlation of fluorescent intensity with ICG dose escalation up to 25 µg/kg.
  
  
  CONCLUSIONS
  ICG NIR fluorescent imaging was useful in detecting the parathyroid glands of dogs. By allowing detection of parathyroid glands, the current technique shows promise for use by endocrine surgeons performing thyroidectomies.
authors.affiliation: Department of Surgery, Seoul National University Hospital and College of Medicine, 101 Daehak-Ro, Jongno-Gu, Seoul, 110-744, Korea, nicizm@gmail.com.
authors.forename: Yong Joon
authors.initials: YJ
authors.lastname: Suh
authors.forename: June Young
authors.initials: JY
authors.lastname: Choi
authors.forename: Young Jun
authors.initials: YJ
authors.lastname: Chai
authors.forename: Hyungju
authors.initials: H
authors.lastname: Kwon
authors.forename: Jung-Woo
authors.initials: JW
authors.lastname: Woo
authors.forename: Su-Jin
authors.initials: SJ
authors.lastname: Kim
authors.forename: Kyu Hyung
authors.initials: KH
authors.lastname: Kim
authors.forename: Kyu Eun
authors.initials: KE
authors.lastname: Lee
authors.forename: Yong Taik
authors.initials: YT
authors.lastname: Lim
authors.forename: Yeo-Kyu
authors.initials: YK
authors.lastname: Youn
mesh_terms: D000818:Animals; D004285:Dogs; D005456:Fluorescent Dyes / Q000008:administration & dosage; D007208:Indocyanine Green / Q000008:administration & dosage; D008297:Male; D010280:Parathyroid Glands; D019265:Spectroscopy, Near-Infrared / Q000379:methods*; D013965:Thyroidectomy
chemical_list: D005456:Fluorescent Dyes; D007208:Indocyanine Green