Ultrasound diagnostic apparatus and signal processing method thereof

Abstract

The presently disclosed subject matter is intended to correctly determine an ambient sound velocity at each level of pixels or line images constituting an ultrasound image, and construct a high-precision ultrasound image. A region-of-interest setting unit sets a region of interest on an ultrasound image. A transmission focus control unit gives a transmission focus instruction, so that a transmitting circuit performs transmission focusing on the region of interest. A set sound velocity specification unit specifies a set sound velocity used to perform reception focusing on RF data. A focus index calculation unit performs reception focusing on the RF data for each of a plurality of set sound velocities to calculate the focus index of the RF data. An ambient sound velocity determination unit determines the ambient sound velocity of the region of interest on the basis of the focus index for each of the plurality of set sound velocities.

1 . An ultrasound diagnostic apparatus comprising:
 an ultrasound probe including a plurality of ultrasound transducers for transmitting ultrasound waves to an object and receiving ultrasound waves reflected by the object to output an ultrasound detection signal;   a region-of-interest setting device which sets a region of interest within the object;   a transmission focus instruction device which causes the ultrasound probe to bring the ultrasound waves into transmission focus on the region of interest;   a set sound velocity specification device which specifies a plurality of set sound velocities used to perform reception focusing on the ultrasound detection signal from the region of interest;   a focus index calculation device which calculates the focus index of the ultrasound detection signal for each of the plurality of set sound velocities by performing the reception focusing; and   an ambient sound velocity determination device which determines the ambient sound velocity of the region of interest on the basis of the focus index for each of the plurality of set sound velocities.   
     
     
         2 . The ultrasound diagnostic apparatus according to  claim 1 , wherein the focus index is at least one of an integration value, a square integration value, a peak value, a contrast value, a half bandwidth, a frequency-spectral integration value or square integration value, a square sum normalized by a mean value, a frequency-spectral half bandwidth, a frequency-spectral integration value or square integration value normalized by a maximum value or a direct current component, and an autocorrelation value of the ultrasound detection signal. 
     
     
         3 . The ultrasound diagnostic apparatus according to  claim 1 , wherein the focus index is an index which does not include the intensity information of the ultrasound detection signal but is based only on the frequency spectrum information. 
     
     
         4 . The ultrasound diagnostic apparatus according to  claim 1 , wherein the index based only on the frequency spectrum information is at least one of a square sum normalized by a mean value, a frequency-spectral integration value or square integration value normalized by a maximum value or a direct current component, an autocorrelation value, and a frequency-spectral half bandwidth. 
     
     
         5 . The ultrasound diagnostic apparatus according to  claim 1 , wherein the focus index is an index multiplied by such a coefficient as to become smaller in value toward the peripheral portions of an image generated by performing reception focusing on the ultrasound detection signal. 
     
     
         6 . The ultrasound diagnostic apparatus according to  claim 1 , wherein a determination is made as to whether or not any structural object is included in the region of interest, so that the ambient sound velocity is determined using a focus index according to the result of the determination. 
     
     
         7 . The ultrasound diagnostic apparatus according to  claim 6 , wherein the focus index utilizes a line image when a determination is made as to whether or not any structural object is included in the region of interest and if a structural object is not included therein, and is based only on the frequency spectrum information of the ultrasound detection signal without including the intensity information thereof. 
     
     
         8 . The ultrasound diagnostic apparatus according to  claim 6 , wherein the focus index utilizes a line-by-line common image when a determination is made as to whether or not any structural object is included in the region of interest and if a structural object is included therein, and is based only on the intensity information of the line-by-line common image without including the frequency spectrum information. 
     
     
         9 . The ultrasound diagnostic apparatus according to  claim 8 , wherein the index based only on the intensity information is at least one of an integration value, a square integration value, a peak value, and a frequency-spectral integration value or square integration value. 
     
     
         10 . The ultrasound diagnostic apparatus according to  claim 1 , further comprising an ultrasound image construction device which constructs an ultrasound image of the region of interest on the basis of the ambient sound velocity. 
     
     
         11 . The ultrasound diagnostic apparatus according to  claim 1 , wherein the region of interest set by the region-of-interest setting device is a point reflection region on a sound ray region within the object. 
     
     
         12 . The ultrasound diagnostic apparatus according to  claim 1 , wherein the region of interest set by the region-of-interest setting device is a one-sound ray region within the object. 
     
     
         13 . The ultrasound diagnostic apparatus according to  claim 12 , wherein the region of interest set by the region-of-interest setting device is a two-dimensional region including a plurality of the one-sound ray regions. 
     
     
         14 . A signal processing method of an ultrasound diagnostic apparatus, comprising:
 a region-of-interest setting step of setting a region of interest within an object;   a transmission focus instruction step of causing an ultrasound probe to bring ultrasound waves into transmission focus on the region of interest;   a set sound velocity specification step of specifying a plurality of set sound velocities used to perform reception focusing on an ultrasound detection signal from the region of interest;   a focus index calculation step of calculating the focus index of the ultrasound detection signal for each of the plurality of set sound velocities by performing the reception focusing; and   an ambient sound velocity determination step of determining the ambient sound velocity of the region of interest on the basis of the focus index for each of the plurality of set sound velocities.   
     
     
         15 . The signal processing method of an ultrasound diagnostic apparatus according to  claim 14 , wherein the focus index is at least one of an integration value, a square integration value, a peak value, a contrast value, a half bandwidth, a frequency-spectral integration value or square integration value, a square sum normalized by a mean value, a frequency-spectral half bandwidth, a frequency-spectral integration value or square integration value normalized by a maximum value or a direct current component, and an autocorrelation value of the ultrasound detection signal. 
     
     
         16 . The signal processing method of an ultrasound diagnostic apparatus according to  claim 14 , further comprising an ultrasound image construction step of constructing an ultrasound image of the region of interest on the basis of the ambient sound velocity.