Abstract: Acoustic output power is adaptively regulated in medical diagnostic ultrasound imaging. Given transmit settings, the acoustic power and/or another setting may be altered to avoid violating a limit set by regulation. The limit is based, at least in part, on an assumed attenuation. By measuring the attenuation, such as by identifying a type of tissue, the power and/or limit may be altered or adapt. By accounting for the attenuation in the region to be scanned, a greater output power may be possible while still providing the same level of safety.