Ultrasound diagnostic apparatus and ultrasound image producing method

An ultrasound image producing method, comprising the steps of:

• transmitting ultrasonic beams from an ultrasound probe toward a blood vessel in a subject by a transmission circuit;
• producing sound ray signals by processing reception signals outputted from the ultrasound probe having received ultrasonic echoes from the subject, by a reception circuit;
• producing an ultrasound image by an image producing circuit based on the sound ray signals produced by the reception circuit;
• displaying the ultrasound image produced by the image producing circuit on a monitor;
• distinguishing between a clear first boundary measurement line sound ray where a first boundary between an intima and a vascular lumen in an intima-media complex of a blood vessel extending along a scanning direction can be clearly recognized in the ultrasound image and an unclear first boundary measurement line sound ray where the first boundary cannot be clearly recognized in the ultrasound image based on the sound ray signals produced by the reception circuit, by searching the sound ray signals in a depth direction to specify a sound ray whose sound ray signal has a first local maximum value greater than a predetermined intensity value to be the clear first boundary measurement line sound ray and specify a sound ray whose sound ray signal has a first local maximum value of not greater than the predetermined intensity value to be the unclear first boundary measurement line sound ray;
• distinguishing between a clear second boundary measurement line sound ray where a second boundary between an adventitia and a media in the intima-media complex can be clearly recognized in the ultrasound image and an unclear second boundary measurement line sound ray where the second boundary cannot be clearly recognized in the ultrasound image based on the sound ray signals produced by the reception circuit;
• determining a depth position of the first boundary at the clear first boundary measurement line sound ray based on an intensity distribution of a sound ray signal corresponding to the clear first boundary measurement line sound ray, and ascertaining a depth position of the first boundary at the unclear first boundary measurement line sound ray by performing pattern matching on a sound ray signal corresponding to the unclear first boundary measurement line sound ray by using a sound ray signal corresponding to the clear first boundary measurement line sound ray lying adjacent to the unclear first boundary measurement line sound ray as a reference signal, determining a position where the sound ray signal of the unclear first boundary measurement line sound ray has a maximum correlation coefficient with respect to the reference signal, calculating a deviation amount of the sound ray signal of the unclear first boundary measurement line sound ray from the reference signal, and adding the calculated deviation amount to the determined depth position of the first boundary at the clear first boundary measurement line sound ray to ascertain the depth position of the first boundary at the unclear first boundary measurement line sound ray, thereby determining depth positions of the first boundary at all measurement line sound rays in the ultrasound image;
• and
• determining a depth position of the second boundary at the clear second boundary measurement line sound ray based on an intensity distribution of a sound ray signal corresponding to the clear second boundary measurement line sound ray, and ascertaining a depth position of the second boundary at the unclear second boundary measurement line sound ray by performing pattern matching on a sound ray signal corresponding to the unclear second boundary measurement line sound ray by using a sound ray signal corresponding to a clear second boundary measurement line sound ray lying adjacent to the unclear second boundary measurement line sound ray as a reference signal, determining a position where the sound ray signal of the unclear second boundary measurement line sound ray has a maximum correlation coefficient with respect to the reference signal, calculating a deviation amount of the sound ray signal of the unclear second boundary measurement line sound ray from the reference signal, and adding the calculated deviation amount to the determined depth position of the second boundary at the clear second boundary measurement line sound ray to ascertain the depth position of the second boundary at the unclear second boundary measurement line sound ray, thereby determining depth positions of the second boundary at all measurement line sound rays in the ultrasound image.

An ultrasound diagnostic apparatus, comprising:

• a boundary distinguishing processor adapted to distinguish between a clear first boundary measurement line sound ray where a first boundary between an intima and a vascular lumen in an intima-media complex of a blood vessel extending along a scanning direction can be clearly recognized in the ultrasound image and an unclear first boundary measurement line sound ray where the first boundary cannot be clearly recognized in the ultrasound image and to distinguish between a clear second boundary measurement line sound ray where a second boundary between an adventitia and a media in the intima-media complex can be clearly recognized in the ultrasound image and an unclear second boundary measurement line sound ray where the second boundary cannot be clearly recognized in the ultrasound image based on the sound ray signals produced by the reception circuit, the boundary distinguishing processor distinguishing the clear first boundary measurement line sound ray and the unclear first boundary measurement line sound ray by searching the sound ray signals in a depth direction to specify a sound ray whose sound ray signal has a first local maximum value greater than a predetermined intensity value to be the clear first boundary measurement line sound ray and specify a sound ray whose sound ray signal has a first local maximum value of not greater than the predetermined intensity value to be the unclear first boundary measurement line sound ray;
• and
• a boundary depth position determining processor adapted to:
• determine a depth position of a first boundary of the intima-media complex at the clear first boundary measurement line sound ray based on an intensity distribution of a sound ray signal corresponding to the clear first boundary measurement line sound ray;
• determine a depth position of a second boundary between an adventitia and a media of the intima-media complex at a clear second boundary measurement line sound ray based on an intensity distribution of a sound ray signal corresponding to the clear second boundary measurement line sound ray;
• ascertain a depth position of the first boundary at the unclear first boundary measurement line sound ray based on the depth position of the first boundary at the clear first boundary measurement line sound ray to thereby determine the depth positions of the first boundary at all measurement line sound rays in the ultrasound image;
• ascertain a depth position of the second boundary at an unclear second boundary measurement line sound ray based on the depth position of the second boundary at the clear second boundary measurement line sound ray to thereby determine the depth positions of the second boundary at all measurement line sound rays in the ultrasound image;
• and
• an intima-media complex thickness calculating circuit adapted to calculate an intima-media complex thickness by using the depth position of the first boundary and the second boundary determined by the boundary depth position determining processor,
• wherein the boundary depth position determining processor performs pattern matching on a sound ray signal corresponding to the unclear first boundary measurement line sound ray by using a sound ray signal corresponding to the clear first boundary measurement line sound ray lying adjacent to the unclear first boundary measurement line sound ray as a reference signal, determines a position where the sound ray signal of the unclear first boundary measurement line sound ray has a maximum correlation coefficient with respect to the reference signal, calculates a deviation amount of the sound ray signal of the unclear first boundary measurement line sound ray from the reference signal, and add the calculated deviation amount to the determined depth position of the first boundary at the clear first boundary measurement line sound ray, thereby ascertaining the depth position of the boundary of the intima-media complex at the unclear first boundary measurement line sound ray, and
• wherein the boundary depth position determining processor performs pattern matching on a sound ray signal corresponding to the unclear second boundary measurement line sound ray by using a sound ray signal corresponding to a clear second boundary measurement line sound ray lying adjacent to the unclear second boundary measurement line sound ray as a reference signal, determines a position where the sound ray signal of the unclear second boundary measurement line sound ray has a maximum correlation coefficient with respect to the reference signal, calculates a deviation amount of the sound ray signal of the unclear second boundary measurement line sound ray from the reference signal, and add the calculated deviation amount to the determined depth position of the second boundary at the clear second boundary measurement line sound ray, thereby ascertaining the depth position of the boundary of the intima-media complex at the unclear second boundary measurement line sound ray.