title: Near infrared fluorescence imaging of rabbit thyroid and parathyroid glands.
abstract: BACKGROUND
  Near infrared fluorescence imaging using intravenous methylene blue (MB) is a novel technique that has potential to aid the parathyroid gland (PG) localization during thyroid and parathyroid surgery. The aim of this study was to examine MB fluorescence in the rabbit neck and determine the influence of MB dose and time following administration on fluorescence from thyroid and PGs.
  
  
  METHODS
  Thyroid and external PGs were exposed in six New Zealand white rabbits under anesthesia. Varying doses of MB (0.025-3 mg/kg) were injected through the marginal ear vein. Near infrared fluorescence from exposed tissues was recorded at different time intervals (10-74 min) using Fluobeam 700. Specimens of identified glands were then resected for histologic assessment.
  
  
  RESULTS
  Histology confirmed accurate identification of all excised thyroid and PGs; these were the only neck structures to demonstrate significant fluorescence. The parathyroid demonstrated lower fluorescence intensities and reduced washout times at all MB doses compared with the thyroid gland. A dose of 0.1 mg/kg MB was adequate to identify fluorescence; this also delineated the blood supply of the external PGs.
  
  
  CONCLUSIONS
  The study demonstrates that near infrared fluorescence with intravenous MB helps differentiate between thyroid and PGs in the rabbit. This has potential to improve outcomes in thyroid and parathyroid surgery by increasing the accuracy of parathyroid identification; however, the findings require replication in human surgery. The use of low doses of MB may also avoid the side effects associated with currently used doses in humans (3-7 mg/kg).
authors: Department of Oncology, University of Sheffield, Sheffield, UK. Electronic address: r.antakia@sheffield.ac.uk.
authors: Ramez
authors: R
authors: Antakia
authors: Fluoptics, Grenoble, France.
authors: Pascal
authors: P
authors: Gayet
authors: Fluoptics, Grenoble, France.
authors: Stephanie
authors: S
authors: Guillermet
authors: Department of Histopathology, Sheffield Teaching Hospitals, Sheffield, UK.
authors: Tim J
authors: TJ
authors: Stephenson
authors: Department of Oncology, University of Sheffield, Sheffield, UK.
authors: Nicola J
authors: NJ
authors: Brown
authors: Department of General Surgery, Sheffield Teaching Hospitals, Sheffield, UK.
authors: Barney J
authors: BJ
authors: Harrison
authors: Department of Oncology, University of Sheffield, Sheffield, UK.
authors: Saba P
authors: SP
authors: Balasubramanian
mesh_terms: D000818:Animals; D004210:Dissection / Q000379:methods; D004791:Enzyme Inhibitors / Q000493:pharmacokinetics; D005260:Female; D007275:Injections, Intravenous; D007432:Intraoperative Period; D008297:Male; D008751:Methylene Blue / Q000493:pharmacokinetics; D009333:Neck / Q000601:surgery; D010280:Parathyroid Glands / Q000033:anatomy & histology* / Q000378:metabolism / Q000601:surgery; D011817:Rabbits; D013050:Spectrometry, Fluorescence / Q000379:methods*; D019265:Spectroscopy, Near-Infrared / Q000379:methods*; D013961:Thyroid Gland / Q000033:anatomy & histology* / Q000378:metabolism / Q000601:surgery
chemical_list: D004791:Enzyme Inhibitors; D008751:Methylene Blue
keywords: Methylene blue; Near-infrared fluorescence; Parathyroid; Thyroid