Ultrasonograph

1. An ultrasonic diagnostic apparatus comprising:

a transmitting section configured to drive an ultrasonic probe to transmit an ultrasonic wave toward a measuring region of a subject including an arterial vascular wall;

a receiving section configured to receive a reflected wave, produced by getting the ultrasonic wave reflected by the subject, at the ultrasonic probe to generate a received signal;

a movement information deriving section configured to derive movement information about at least an axial movement of the arterial vascular wall based on the received signal, wherein the axial movement is movement in the direction in which the artery runs; and

a boundary locating section configured to locate at least one of the blood flow-intima boundary, the media-adventitia boundary and the adventitia-body's connective tissue boundary of the arterial vascular wall in the measuring region based on the movement information,

wherein the movement information comprises a radial distribution of the axial movement information at a plurality of radial positions along the radial direction of the arterial vascular wall.

2. The ultrasonic diagnostic apparatus of claim 1 , further comprising a tomographic image processing section for generating a signal representing a tomographic image of the measuring region based on the received signal,

wherein the at least one boundary is superimposed on the tomographic image.

3. The ultrasonic diagnostic apparatus of claim 2 , further comprising a modulus of elasticity calculating section for calculating, based on the received signal, a modulus of elasticity between measuring points within the measuring region,

wherein a two-dimensional map image of the moduli of elasticity calculated is further presented.

4. The ultrasonic diagnostic apparatus of claim 1 , wherein the movement information comprises a displacement distribution curve representing the radial distribution, and the axial movement information comprises magnitudes of axial displacements that have been measured at the plurality of radial positions along the radial direction of the arterial vascular wall.

5. The ultrasonic diagnostic apparatus of claim 4 , wherein the transmitting section and the receiving section scan the measuring region with the ultrasonic wave, thereby getting the received signals, each corresponding to one frame, a number of times, and

wherein the movement information deriving section compares the respective amplitudes of the received signals between two different frames, thereby calculating the magnitude of axial displacement of each measuring point within the measuring region.

6. The ultrasonic diagnostic apparatus of claim 5 , wherein the movement information deriving section calculates the degree of correlation between information about the amplitude of the received signal representing a first frame and information about the amplitude of the received signal representing a second frame, thereby calculating the magnitude of axial displacement of each measuring point between the two frames within the measuring region.

7. The ultrasonic diagnostic apparatus of claim 4 , wherein the boundary locating section locates the blood flow-intima boundary by finding a steep rise on the displacement distribution curve that is closest to a vascular lumen.

8. The ultrasonic diagnostic apparatus of claim 4 , wherein the boundary locating section locates the media-adventitia boundary by finding a local minimum value on the displacement distribution curve that is closest to the body's connective tissue.

9. The ultrasonic diagnostic apparatus of claim 4 , wherein the boundary locating section locates the adventitia-body's connective tissue boundary by finding a steep fall on the displacement distribution curve that is closest to the body's connective tissue