We describe a finite-element-based algorithm for the reconstruction of absolute temperature distribution in tissue using photoacoustic measurements. Assuming a linear temperature dependence of the Grueneisen parameter in tissue, the algorithm aims to recover the temperature-dependent acoustic speed while a heating mechanism is used. The absolute temperature over time is then calculated using the recovered temperature-dependent acoustic speed. To validate our method, photoacoustic measurements were conducted using a graphene nanosheet-containing target embedded in a 20-mm-diameter tissue-like phantom with varied heating power. The results obtained suggest that quantitatively accurate temperature images can be produced, suggesting that our method may serve as a tool to guide and monitor the temperature distribution in tissue in real time noninvasively and to improve the safety and efficacy of thermotherapy.
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