A therapy system includes a therapy module, e.g., a high-intensity-focused ultrasound transmitter, to perform successive deposits of energy in a target zone. The successive deposits being separated by a cool down period. The therapy system further includes a thermometry module, e.g. by a magnetic resonance examination system, configured for thermometry to measure temperature in a measurement field. A control module regulates the cool down period in dependence of the measured off-focus maximum temperature during the energy deposit preceding the cool down period.