Evaluation of the effect of scattering uncertainty on photothermal therapy planning

Photothermal therapy (PTT) requires accurate prediction of laser-induced temperature increase to achieve effective tumor treatment outcomes. Such prediction is typically obtained through pretreatment planning based on numerical simulations coupling light transport and heat transfer equations. Simulation accuracy is generally guaranteed by the precise determination of the optical properties characterizing the target tissue. Although absorption is the primary driver of heat generation, scattering governs light propagation through tissue, influencing penetration depth and resulting spatial distribution of temperature. Since tumor malignancy alters tissue microstructure and scattering behavior, understanding the sensitivity of the optical and thermal responses to these variations is fundamental for effective treatment planning and optimized PTT outcomes. In this study, the impact of scattering uncertainty on light fluence and laser-induced temperature was investigated using a numerical phantom with a tumor-mimicking inclusion. The temperature sensitivity analysis comprised multiple cases, including different inclusion geometries, irradiation durations, and illumination source multiplicities. A 780 nm laser source was applied, and the reduced scattering coefficient of the inclusion was varied over a ±20% contrast range relative to the literature-based background value, representing uncertainty arising from the unknown tumor contrast. The results demonstrate minimal sensitivity of the simulated fluence rate and temperature to scattering uncertainty, with a maximum temperature deviation of 0.04℃ at 6 seconds, increasing to approximately 0.1℃ over extended irradiation (24 seconds). These findings indicate that within a physiologically realistic ±20% scattering contrast range, the laser-induced temperature is primarily governed by optical absorption rather than scattering, supporting the use of fixed literature-based scattering values for PTT pretreatment planning.