Patent ID: 8333703

Claim:
An ultrasonic diagnostic apparatus comprising: an ultrasonic probe including transducers whose sensitivity can be controlled according to a bias voltage, and configured for transmitting ultrasonic waves to a subject to be examined, and for receiving an echo signal from the subject, wherein the transducers of the ultrasonic probe are Capacitive Micromachined Ultrasonic Transducers (cMUT); a preamplifier for amplifying the echo signal received by the ultrasonic probe; a time gain control (TGC) amplification means for amplifying the signal output from the preamplifier; an A/D conversion means for A/D converting the signal output from the TGC amplification means; an image processing means for constructing an image based on the signal outputted from the A/D conversion means; a display means for displaying the image constructed by the image processing means; and a probe gain control means for changing the bias voltage provided to the transducers according to a depth in the subject, said probe gain control means being configured to increase the bias voltage from a shallow depth to a deeper depth than the shallow depth, wherein the input signal level of the echo signal to the preamplifier is reduced to a voltage which is under or equal to the upper limit of the input range of the preamplifier during a receiving period of the echo at the shallow depth by said probe gain control means, and the input signal level of the echo signal to the preamplifier is increased to the voltage which is under or equal to the upper limit of the input range of the preamplifier during the receiving period of the echo at the deeper depth said probe gain control means.