Systems and methods for treating tissue are disclosed.The target tissue is ablated. A real-time image of the targettissue is generated during the ablation. The real-time blood perfusionlevel of the target tissue is determined from the real-timeimage and compared to an initial blood perfusion level of the targettissue. The comparison provides a metric for the progress ofthe ablation, and ablation is halted when the real-time blood perfusiondrops below a threshold level relative to the initial bloodperfusion level.