Methods for ablating body tissue include providing an ablation device having a single ultrasound transducer； positioning the ultrasound transducer in proximity to a body tissue； controlling the ultrasound transducer to emit an ultrasound beam； and collecting amplitude mode (A-mode) ultrasound information along a sensing pattern traversed by the ultrasound beam. A 3D anatomical reference map of the body tissue is created from the A-mode ultrasound information. A graphical user interface is generated and shown on a display, wherein the graphical user interface comprises the 3D anatomical reference map and a window showing data. The data includes a distance between the ultrasound transducer and a surface of the body tissue. The method also includes identifying a target tissue on the 3D anatomical reference map； ablating the target tissue with the ultrasound transducer to create a lesion； and monitoring a lesion depth in real-time during the ablating, using the A-mode ultrasound information.
