title: Real-time, near-infrared, fluorescence-guided identification of the ureters using methylene blue.
abstract: BACKGROUND
  The aim of this study was to determine whether the invisible near-infrared (NIR) fluorescence properties of methylene blue (MB), a dye already approved by the U.S. Food and Drug Administration for other indications, could be exploited for real-time, intra-operative identification of the ureters.
  
  
  METHODS
  The optical properties of MB were quantified in vitro. Open surgery and laparoscopic NIR fluorescence imaging systems were employed. Yorkshire pigs were injected intravenously with 0.1-mg/kg MB (n = 8), 10-mg furosemide followed by 0.1-mg/kg MB (n = 6), or 0.5-mg/kg MB (n = 6). The contrast-to-background ratio (CBR) of the kidney and ureters, and the MB concentration in the urine, were quantified.
  
  
  RESULTS
  Peak MB absorbance, emission, and intensity in urine occurred at 668 nm, 688 nm, and 20 mumol/L, respectively. After intravenous injection, doses as low as 0.1-mg/kg MB provided prolonged imaging of the ureters, and a dose of 0.5 mg/kg provided statistically significant improvement of CBR. The preinjection of furosemide increased urine volume but did not improve CBR. Laparoscopic identification of the ureter using MB NIR fluorescence was demonstrated.
  
  
  CONCLUSIONS
  Ureteral imaging using MB NIR fluorescence provides sensitive, real-time, intra-operative identification of the ureters during open and laparoscopic surgeries.
authors.affiliation: Division of Hematology/Oncology, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, MA 02215, USA.
authors.forename: Aya
authors.initials: A
authors.lastname: Matsui
authors.forename: Eiichi
authors.initials: E
authors.lastname: Tanaka
authors.forename: Hak Soo
authors.initials: HS
authors.lastname: Choi
authors.forename: Vida
authors.initials: V
authors.lastname: Kianzad
authors.forename: Sylvain
authors.initials: S
authors.lastname: Gioux
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Lomnes
authors.forename: John V
authors.initials: JV
authors.lastname: Frangioni
mesh_terms: D000818:Animals; D005260:Female; D005453:Fluorescence; D010535:Laparoscopy / Q000379:methods*; D008751:Methylene Blue; D019265:Spectroscopy, Near-Infrared / Q000379:methods*; D013552:Swine; D014513:Ureter / Q000601:surgery*
chemical_list: D008751:Methylene Blue