Frequency is swept in acoustic radiation force impulse (ARFI) scanning. Different frequencies are used at different times during the ARFI. For example, different frequencies are focused to different depths in the ARFI transmit beam. Since the frequency sweep is used for the ARFI pushing pulse rather than a transmit pulse for which echoes are received, the rate of change of the frequency is not dictated by the speed of sound. The rate of change of the frequency may be adjustable or set based on other factors, such as the type of tissue. In combination with a time varying focal position, the frequency sweep may better compensate for loss as compared to a focus sweep alone. The frequency sweep may better compensate for loss as compared to a single point focus ARFI.
