CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2014-84967, filed on Apr. 16, 2014, the entire contents of all of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to an ultrasonography apparatus and a control method.

BACKGROUND

Conventionally, a technique called elastography has been known in which the stiffness of a tissue of a living body is measured, and a distribution of measured stiffness is visualized. Elastography is used for diagnosis of diseases in which the stiffness of a tissue varies according to stages of development of a lesion such as cirrhosis, for example. In elastography, as for methods of evaluating the stiffness by causing a displacement in a tissue, there are following two main methods.

The first method is a method of visualizing relative stiffness based on a degree of distortion at each point that is observed in a scanning section when pressure is applied to and released from a tissue through a body surface by an ultrasound probe. The second method is a method in which a displacement based on shear waves is caused in a tissue by applying acoustic radiation force or mechanical vibration to the tissue through a body surface, and a displacement at each point in a scanning section is observed over time, thereby acquiring the propagation speed of shear waves to acquire the elastic modulus. In the former method, the degree of a local displacement is dependent on the scale of manually moving an ultrasound prove, and it is assessed whether a region of interest is relatively hard or soft when compared with a region therearound. On the other hand, in the latter method, the absolute elastic modulus of a region of interest can be acquired.

In the latter method, when a stiffness image showing the stiffness of a tissue is generated, push pulses that are focused ultrasound pulses with a high sound pressure are used as an acoustic radiation force. When shear waves are generated by this push pulse, various transmission conditions are set. Therefore, an operator sets various transmission conditions one by one.

