title: Intraoperative near infrared fluorescence guided identification of the ureters using low dose methylene blue: a first in human experience.
abstract: OBJECTIVE
  Near infrared fluorescence imaging is a promising technique that offers real-time visual information during surgery. In this study we report the first clinical results to our knowledge of ureteral imaging using near infrared fluorescence after a simple peripheral infusion of methylene blue. Furthermore, we assessed the optimal timing and dose of methylene blue.
  
  
  METHODS
  A total of 12 patients who underwent lower abdominal surgery were included in this prospective feasibility study. Near infrared fluorescence imaging was performed using the Mini-FLARE™ imaging system. To determine optimal timing and dose, methylene blue was injected intravenously at doses of 0.25, 0.5 or 1 mg/kg after exposure of the ureters. Imaging was performed for up to 60 minutes after injection.
  
  
  RESULTS
  In all patients both ureters could be clearly visualized within 10 minutes after infusion of methylene blue. The signal lasted at least up to 60 minutes after injection. The mean signal-to-background ratio of the ureter was 2.27 ± 1.22 (4), 2.61 ± 1.88 (4) and 3.58 ± 3.36 (4) for the 0.25, 0.5 and 1 mg/kg groups, respectively. A mixed model analysis was used to compare signal-to-background ratios among dose groups and times, and to assess the relationship between dose and time. A significant difference among time points (p <0.001) was found. However, no difference was observed among dose groups (p = 0.811).
  
  
  CONCLUSIONS
  This study demonstrates the first successful use of near infrared fluorescence using low dose methylene blue for the identification of the ureters during lower abdominal surgery.
authors: Department of Surgery, Leiden University Medical Center, Leiden, The Netherlands.
authors: Floris P R
authors: FP
authors: Verbeek
authors: Joost R
authors: JR
authors: van der Vorst
authors: Boudewijn E
authors: BE
authors: Schaafsma
authors: Rutger-Jan
authors: RJ
authors: Swijnenburg
authors: Katja N
authors: KN
authors: Gaarenstroom
authors: Henk W
authors: HW
authors: Elzevier
authors: Cornelis J H
authors: CJ
authors: van de Velde
authors: John V
authors: JV
authors: Frangioni
authors: Alexander L
authors: AL
authors: Vahrmeijer
mesh_terms: D000005:Abdomen / Q000601:surgery; D005240:Feasibility Studies; D005260:Female; D005453:Fluorescence; D006801:Humans; D007430:Intraoperative Care; D008297:Male; D008751:Methylene Blue / Q000008:administration & dosage*; D011446:Prospective Studies; D019265:Spectroscopy, Near-Infrared / Q000379:methods*; D014513:Ureter / Q000033:anatomy & histology*
chemical_list: D008751:Methylene Blue
keywords: BMI; MB; NIR; SBR; body mass index; fluorescence; methylene blue; molecular imaging; near infrared; signal-to-background ratio; ureter; urology