Thermal therapy ablation detection uses medical diagnostic ultrasound. Since acoustically measured information becomes unreliable for temperature estimation at a temperature close the time at which treatment is complete, the information is instead or additionally used to detect a tissue condition indicating sufficient treatment, such as detecting cell death. Using multiple different types of parameters as input and/or a machine-learnt classifier, the completion of treatment from a tissue alteration perspective is detected using the transition that makes temperature estimation less reliable.