Position Estimation Method for a Fluorescently Labeled Tumor Based on Beer’s Law: An Analysis Using Monte Carlo Simulations

Estimating the depth of a fluorescently labeled tumor is beneficial in tumor resection. In this study, we proposed a method for the three-dimensional position estimation of fluorescent tumors using Monte Carlo simulations. A limited proof-of-concept experiment was conducted, and the two-dimensional position of a tumor was estimated by calculating the centroid of the fluorescence distribution, which was obtained by using excitation light to scan the surface of the model. The depth of the tumor was estimated by fitting the analytical equation based on Beer’s law to the diffuse fluorescence profile on the surface of the model. In the estimation of the two-dimensional position, the distance between the embedded and estimated tumor coordinates was 0.71 mm. The estimated tumor depths of 2–6 mm closely matched the embedded depths, with an error rate of approximately 20%. In previous studies, depth estimation was limited to 1–5 mm using visible light, whereas for the simulation used in the present study, the use of longer wavelengths enabled estimation at slightly greater depths.