An integrated system capable of performing high frame-rate two-dimensional (2D) temperature imaging in realtime is has been developed. The system consists of a SonixRP ultrasound scanner and a custom built data processing unit connected with Gigabit Ethernet (GbE). The SonixRP scanner which serves as the frontend of the integrated system allows us to have flexibilities of controlling the beam sequence and accessing the radio frequency (RF) data in realtime through its research interface. The RF data is then streamlined to the backend of the system through GbE, where the data is processed using a 2D temperature estimation algorithm running in a general purpose graphics processing unit (GPU). Using this system, we have developed a 2D high frame-rate imaging mode, M2D, for imaging the mechanical and thermal tissue response to subtherapeutic HIFU beams. In this paper, we present results from imaging subtherapetic HIFU beams in vitro porcine heart before and after lesion formation. The results demonstrate the feasibility of tissue parameter changes due to HIFU-induced lesions.