Significance: The fluorescence-guided imaging for surgical intervention community recognizes the need for performance standards for these imaging devices. Tissue phantoms are used to track an imager’s performance as a fluorescence detector, but imager-specific units are of limited utility.

Aim: Tissue phantoms can be calibrated to be traceable to the international system of units (SI) and in turn be used to calibrate imagers such that fluorescence measurements can be reported in universally accepted units.

Approach: The radiometry to convert imager-specific arbitrary digital counts to SI-traceable unit of watts is described in this paper.

Results: An example of an imager calibration is included.

Conclusions: Calibrated tissue phantoms become a tool for metrological traceability.