Thermal dose as a universal tool to evaluate nanoparticle-induced photothermal therapy

•Thermal isoeffect dose (TID) is applied to evaluate the nanoparticle-induced PTT.•Cell viability can be correlated with TID if the time-temperature data is available.•Cells start to undergo apoptosis if the critical TID of 70 min is reached.•TID can be used for the easy comparison of the PTT studies in different publications.