Blood flow extraction image forming device, method of forming blood flow extraction image, and blood flow extraction image forming program

A blood flow extraction image forming device comprising one or more processors configured to perform a method for forming a blood flow extraction image, the method comprising:

• acquiring a plurality of pieces of frame data for a plurality of frames, the plurality of pieces of the frame data being generated on the basis of a plurality of reception signals obtained by causing an ultrasonic probe that transmits and receives ultrasonic waves to and from a subject, to transmit ultrasonic waves to a same scanning plane a plurality of times and receive reflected waves of the ultrasonic waves from the subject and having signal values indicating signal intensity of the reflected waves;
• calculating a correlation matrix indicating a correlation between the signal values in the plurality of pieces of the frame data for each data element of the frame data corresponding to each pixel of an ultrasonic image formed based on the frame data;
• performing singular value decomposition on the correlation matrix to calculate a plurality of singular values whose ranks are defined in order of magnitude and a plurality of singular vectors corresponding to the singular values;
• forming a blood flow luminance image by applying, to the frame data, a blood flow extraction filter formed based on the singular value of a rank equal to or lower than a preset first threshold rank and the singular vector corresponding to the singular value;
• forming a tissue image on the basis of the signal value of each data element forming the plurality of pieces of the frame data;
• forming a blood flow extraction image by subtracting the tissue image from the blood flow luminance image;
• specifying a calculation target region including the data element corresponding to tissue in the frame data, the correlation matrix being calculated in the method only for the calculation target region;
• acquiring high-rank extraction data including signal components of a rank higher than a second threshold rank by performing singular value decomposition on the plurality of pieces of the frame data;
• and
• setting, as the calculation target region, a set of the data elements having the signal values equal to or larger than a threshold signal value among the plurality of data elements forming the high-rank extraction data.

A blood flow extraction image forming device comprising one or more processors configured to perform a method for forming a blood flow extraction image, the method performed by the one or more processors comprising:

• acquiring a plurality of pieces of frame data for a plurality of frames, the plurality of pieces of the frame data being generated on the basis of a plurality of reception signals obtained by causing an ultrasonic probe that transmits and receives ultrasonic waves to and from a subject, to transmit ultrasonic waves to a same scanning plane a plurality of times and receive reflected waves of the ultrasonic waves from the subject and having signal values indicating signal intensity of the reflected waves;
• specifying, in the frame data, a calculation target region including a data element of the frame data corresponding to each pixel of an ultrasonic image formed based on the frame data, the data element corresponding to tissue;
• calculating a correlation matrix indicating a correlation between the signal values in the plurality of pieces of the frame data for each data element forming the frame data, the correlation matrix being calculated only for the calculation target region;
• performing singular value decomposition on the correlation matrix to calculate a plurality of singular values whose ranks are defined in order of magnitude and a plurality of singular vectors corresponding to the singular values;
• forming a blood flow luminance image by applying, to the frame data, a blood flow extraction filter formed based on the singular value of a rank equal to or lower than a preset first threshold rank and the singular vector corresponding to the singular value;
• forming a tissue image by applying, to the frame data, a tissue extraction filter formed based on the singular value of a rank higher than the first threshold rank and the singular vector corresponding to the singular value;
• and
• forming a blood flow extraction image by subtracting the tissue image from the blood flow luminance image;
• acquiring high-rank extraction data including signal components of a rank higher than a second threshold rank, by performing singular value decomposition on the plurality of pieces of the frame data;
• thinning out some of data elements forming the high-rank extraction data;
• and
• setting thinned frame data as the calculation target region.

A method of forming a blood flow extraction image, the method comprising:

• a frame data acquisition step of acquiring a plurality of pieces of frame data for a plurality of frames, the plurality of pieces of the frame data being generated on the basis of a plurality of reception signals obtained by causing an ultrasonic probe that transmits and receives ultrasonic waves to and from a subject, to transmit ultrasonic waves to a same scanning plane a plurality of times and receive reflected waves of the ultrasonic waves from the subject and having signal values indicating signal intensity of the reflected waves;
• a correlation matrix calculation step of calculating a correlation matrix indicating a correlation between the signal values in the plurality of pieces of the frame data for each data element of the frame data corresponding to each pixel of an ultrasonic image formed based on the frame data;
• a singular value decomposition calculation step of performing singular value decomposition on the correlation matrix to calculate a plurality of singular values whose ranks are defined in order of magnitude and a plurality of singular vectors corresponding to the singular values;
• a blood flow luminance image forming step of forming a blood flow luminance image by applying, to the frame data, a blood flow extraction filter formed based on the singular value of a rank equal to or lower than a preset first threshold rank and the singular vector corresponding to the singular value;
• a tissue image forming step of forming a tissue image on the basis of the signal value of each data element forming the plurality of pieces of the frame data;
• a blood flow extraction image forming step of forming a blood flow extraction image by subtracting the tissue image from the blood flow luminance image;
• specifying a calculation target region including one or more data elements corresponding to tissue in the frame data, the correlation matrix being calculated in the correlation matrix calculation step only for the calculation target region;
• acquiring high-rank extraction data including signal components of a rank higher than a second threshold rank, by performing singular value decomposition on the plurality of pieces of the frame data;
• thinning out some of data elements forming the high-rank extraction data;
• and
• setting thinned frame data as the calculation target region.