Exploring the optimal fluorescein dose in probe-based confocal laser endomicroscopy for colonic imaging

BACKGROUND: Probe-based confocal laser endomicroscopy (pCLE) is an emerging method for in-vivo imaging of the gastrointestinal tract and requires a contrast agent. Fluorescein is the most commonly used agent. The optimal dose of fluorescein for pCLE in colon is unknown. OBJECTIVE: Exploration of optimal dose of fluorescein for pCLE in colon. DESIGN: Comparative, prospective pilot trail. SETTING: Tertiary-care center. PATIENTS: 18 participants underwent colonoscopy without complications. INTERVENTIONS: pCLE videos were recorded in normal cecum, using 10% fluorescein intravenously. MAIN OUTCOME MEASUREMENTS: For subjective analysis, pCLE videos were scored for quality, by 2 observers, independently and blinded to fluorescein dose. For objective analysis, signal-to-noise ratios (SNR) were calculated for each video by an expert. RESULTS: 6 fluorescein doses were used, including 0.5 mL, 1 mL, 2.5 mL, 5 mL, 7.5 mL and 10 mL and each dose was used in three patients. For each dose, median image quality score was 2.5, 2.0, 3.25, 4.0, 4.0 and 3.5 by first observer and 2.0, 3.0, 4.0, 5.0, 4.0 and 4.0 by second observer, respectively. The subjective quality scores increased from 0.5 mL to 5.0 mL, with no evidence of further improved quality at 7.5 mL and 10 mL doses. SNR were not significantly different between doses but trended higher for higher doses. LIMITATIONS: Small sample size. The results can not be applied to other parts of gastrointestinal tract i.e. duodenum, esophagus with different blood supply. CONCLUSION: This preliminary study suggests that the optimal dose of fluorescein for high quality pCLE imaging in colon is approximately 5.0 mL.