Seeing the light: Improving the usability of fluorescence-guided surgery by adding an optimized secondary light source

Background: Tumors that take up and metabolize 5-aminolevulinic acid (5-AlA) emit bright pink fluorescence when illuminated with blue light, aiding surgeons in identifying the margin of resection. The adoption of this method is hindered by the blue light illumination, which is too dim to safely operate under, and therefore, necessitates switching back and forth from white-light mode. This paper examines the addition of an optimized secondary illuminant adapter (SIA) to improve usability of blue-light mode without degrading tumor contrast. Methods: We used color science methods to evaluate the color of the secondary illuminant and its impact on color rendering index (CRI) as well as the tumor-to-background color contrast (TBCC). A secondary illuminant adapter was built to provide 475-600 nm light the intensity of which can be controlled by the surgeon and was evaluated in two patients. Results: Secondary illuminant color had opposing effects on color rendering index (CRI) and tumor to background color contrast (TBCC); providing surgeon control of intensity allows this trade-off to be balanced in real-time. Experience in two cases suggests additional visibility adds value. Conclusion: The addition of a secondary illuminant may mitigate surgeon complaints that the operative field is too dark under the blue light illumination required for 5-ALA fluorescence guidance by providing improved CRI without completely sacrificing TBCC.