Therapeutic ultrasound generator with radiation dose control

Abstract

A therapeutic ultrasound generator controlling an ultrasonic transducer based on actually sensing the amount of power radiated by the transducer to the patient. A controllable ultrasound generator, supplies a controllable amount of electric power to a transducer. A sensing circuit, coupled to the transducer, senses an amount of power radiated by the transducer. A control loop, which is responsive to the amount of power radiated, and a preset radiation power, controls the controllable amount of electric power delivered to the transducer. The radiation power is sensed by detecting an instantaneous current through the transducer, and an instantaneous voltage across the transducer. The instantaneous current and voltage are then used to compute an impedance. The computed impedance, and known characteristics of the transducer, are used to determine the actual amount of power radiated by the transducer to the patient. The generator can also be programmed to provide a preset dosage of energy over coupling conditions varying beyond the range within which the power control loop can supply constant radiated power. The applicators each include an indicator of an applicator type. A circuit is provided for reading the indicator, and supplying characteristics of the transducer for use in determining the amount of power radiated. The control circuit automatically self calibrates by measuring the resonant frequency, and transducer loss resistance for each applicator coupled to the device.