Purpose
Near-infrared (NIR) fluorescence imaging is a promising technique that offers, real-time, visual information during surgery. The current study reports the first clinical results of ureter imaging using NIR fluorescence after a simple peripheral infusion of methylene blue (MB). Furthermore, optimal timing and dose of MB were assessed.
Materials and Methods
A total of 12 patients that underwent lower abdominal surgery were included in this prospective feasibility study. NIR fluorescence imaging was performed using the Mini-FLARE™ imaging system. To determine optimal timing and dose, MB was injected intravenously at doses of 0.25, 0.5 or 1 mg/kg, after exposure of the ureters. Subsequently imaging was performed for up to 60 min following injection.
Results
In all patients both ureters could be clearly visualized within 10 minutes after infusion of MB. Signal lasted at least up to 60 minutes after injection. The mean signal-to-background ratio (SBR) of the ureter was 2.27 ± 1.22 (N = 4), 2.61 ± 1.88 (N = 4) and 3.58 ± 3.36 (N = 4) for the 0.25, 0.5 and 1 mg/kg groups, respectively. A mixed model analysis was used to compare SBRs between dose groups and time points and to assess the relation between dose and time. A significant difference between time points (P < 0.001) was found. However no difference between dose groups was observed (P = 0.811).
Conclusions
This study demonstrates the first successful use of NIR fluorescence using low-dose MB for the identification of the ureters during lower abdominal surgery.