JPH01166745A - Ultrasonic diagnostic apparatus - Google Patents

Abstract

PURPOSE:To obtain an image having a sharp contour, by a method wherein the average value and dispersion value of the intensities of echo signals are calculated at every sampling points set along the depth direction on one scanning line of ultrasonic beam to calculate the ratio of both values and a sampling point where said ratio becomes max. is explored to set a focus to the depth position of the explored sampling point. CONSTITUTION:The ultrasonic echoes from an examinee are received by a group of vibrators 2 to output the echo signals corresponding to the received ultrasonic echoes. These echo signals are digitalized at every sampling points p1, p2, p3 by A/D converters 22 to be stored in a buffer memory 24. The stored echo signal data at every sampling points are sent to an average and dispersion calculating circuit 26, and the average value (x) and dispersion value sigma thereof at every sampling points are calculated on the basis of the echo signal data. A comparing operation circuit 30 calculates the ratio (sigma/x) of the average value (x) and the dispersion valve sigma at every sampling points and the sampling point where said ratio (sigma/x) becomes max. is explored to apply the data thereof to a delay control circuit 10 which in turn sets the delay time of each of the vibrators 2 so that ultrasonic beam is converged to the sampling point where the calculated ratio sigma/x becomes max.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to an ultrasonic diagnostic apparatus that sequentially and automatically controls the focus of an ultrasonic beam based on received echo signals.

(b) Prior art and its problems Usually, in ultrasonic diagnostic apparatuses, an electronic focusing method is employed to improve the directivity of ultrasonic beams. This electronic focusing method focuses ultrasound waves at a certain depth in a subject by giving a predetermined delay time to each selected transducer group and emitting ultrasound waves.

By the way, conventionally, in ultrasonic diagnostic equipment that uses such an electronic focusing method, the focus setting is done manually, and once the focus is set, it remains fixed unless the focus is reset next time. Yes (see Figure 5). Therefore, when obtaining an image such as a B-mode image, the focus may not necessarily be set at an appropriate location. The clarity of the outline is important when recognizing the shape of a diagnostic part such as an organ based on an image, but as mentioned above, if the focus is not on the outline, the outline will be blurred, making it difficult to make an appropriate diagnosis. This may cause problems such as not being able to do so.

The present invention has been made in view of the above circumstances, and it is possible to obtain a clearer contour image by setting the focus at an effective position for each scanning line of the ultrasound beam. The purpose is to

(c) Means for solving the problem In order to achieve the above object, the present invention provides an ultrasonic beam emitted from a preselected group of transducers by giving a predetermined delay time to the group of transducers selected in advance. An ultrasonic diagnostic apparatus that displays an image based on an echo signal output from the transducer group by electronically focusing the ultrasound echo reflected from the subject and receiving the ultrasound echo reflected by the transducer group, the following configuration Take.

That is, in the ultrasound diagnostic apparatus of the present invention, the average variance calculation means calculates the average value and variance value of the echo signal intensity for each sampling point set along the depth direction on one scanning line of the ultrasound beam. and a search means for calculating the ratio of the mean value and the variance value calculated by this mean variance calculation means and searching for a sampling point where the ratio is maximum, and a search means for searching the sampling point at the depth position searched by this search means. and a focus setting means for setting the focus.

(d) Effect Emit an ultrasound beam corresponding to one scanning line from the selected transducer group, and the ultrasound echo from the subject is received by the same transducer group again, and an echo signal is output from the transducer group. Then, the average variance calculating means calculates the average value X and the variance value σ of the echo signal intensity for each sampling point set along the depth direction on one scanning line of the ultrasound beam. Where there is a contour portion, the echo signal level changes greatly due to the difference in impedance after the contour portion erupts, and the ratio (σ/x) between the average value X and the variance value σ also increases accordingly. In other words, it can be said that the location of the sampling point where the ratio σ/X is the largest corresponds to the contour portion. Therefore, next, the search means calculates the ratio of the average value and the variance value calculated by the mean variance calculation means, and searches for a sampling point where the ratio is maximum. Subsequently, the focus setting means sets the focus at the depth position of the sampling point searched by the search means.

As a result, the focus is set for each scanning line so that the ultrasonic beam is focused on the contour portion.

(e) Embodiment FIG. 1 is a block diagram showing the main parts of an ultrasonic diagnostic apparatus according to an embodiment of the present invention. In the figure, the reference numeral 1 indicates the entire ultrasonic diagnostic apparatus, and 2 indicates each transducer that transmits and receives an ultrasound beam.Actually, a large number of transducers are arranged in an array to constitute a transducer. The figure shows only a group of transducers (six elements in this example) selected to obtain l scanning lines. 4 is a high-frequency pulse oscillator that individually applies excitation drive pulses to each transducer 2; 6 is a high-frequency pulse oscillator that applies a predetermined delay time to a trigger pulse that determines the timing of ultrasonic emission from each transducer 2, and generates an ultrasonic beam by electronic means; A delay circuit 8 for transmitting waves for focusing is a delay circuit 8 for receiving ultrasonic echoes reflected from the object by each transducer 2, and a delay circuit 8 for adjusting the phase of the echo signals output from each transducer. A wave reception delay circuit that gives the same delay time to each vibrator 2; 10 is a delay control circuit that controls the delay time of both the wave transmission and wave reception delay circuits 6.8;
0 is a focus setting means for setting a focus at a depth position of a sampling point based on focus control data in a focus calculation circuit 12, which will be described later. 12 is a focus calculation circuit that calculates the focus position of the ultrasound beam based on the received echo signal.

FIG. 2 is a block diagram showing a specific configuration of the focus calculation circuit 12 described above. In the figure, 20 is an STC circuit that temporally changes the gain of the echo signal output from each transducer 2 in order to remove the influence of absorption and attenuation along the depth direction, and 22 is a CPU (not shown). Each sampling point p set along the depth direction on one scanning line of the ultrasound beam based on the input sampling clock
This is an A/D converter that digitizes echo signals obtained corresponding to I, p2, pl, . 24 is the echo signal data (6 elements) obtained from the − group of transducers 2 (6 elements in this example) at each sampling point 1) l, pt, ...
A buffer memory 26 stores the echo signal data stored in the buffer memory 24, and calculates the average value and variance value for each sampling point 1) 1SI) t, . . . based on the stored echo signal data. This is an average variance calculation circuit. Further, 28 indicates data of the average value and variance value at each sampling point P+, pz, . . . calculated by the average variance calculation circuit 26 in the depth direction of the scanning line of the ultrasound beam as shown in Line buffer memory 28 is a line buffer memory that is sequentially arranged and stored along the line buffer memory 28, and 30 is a sampling that calculates the ratio of the average value and variance value from data of the average value and variance value at each sampling point stored in the line buffer memory 28, and that maximizes the ratio. This is a comparison calculation circuit as a search means for searching for points.

Next, a focus control operation of the ultrasonic diagnostic apparatus 1 having the above configuration will be explained. When ultrasonic echoes from the subject are received by one layer of transducers 2, each transducer 2 outputs an echo signal corresponding to the received ultrasonic echo. After the echo attenuation due to distance is corrected in the STC circuit 20, each of these echo signals is processed by the A/D converter 22 at each sampling point pHpt set along the depth direction on one scanning line of the ultrasound beam. , p5, . . , are digitized and then stored in the buffer memory 24 at the next stage.

The echo signal data (six points) for each sampling point stored in the buffer memory 24 is sent to the average variance calculation circuit 26 at the next stage. The average variance calculation circuit 26 calculates the average value X and variance value σ based on the manually input echo signal data. The calculation result is stored in the line buffer memory 28. Therefore, the line buffer memory 28 stores each sampling point p as shown in FIG.
The data of the average value X and the variance value σ in rs pt, . . . are sequentially arranged and stored along the depth direction of the scanning line.

In this way, when the line buffer memory 28 has data for each sampling point 1) I, I) *, . Find the ratio (σ/x) between the average value X and the variance value σ in .... The level of the echo signal intensity obtained near the contour changes greatly due to the difference in impedance before and after the contour, so the ratio of the average value X to the variance value σ (σ).

/x) also increases. In other words, the location of the sampling point where the ratio σ/X is the largest corresponds to the contour portion. Therefore, the comparison calculation circuit 30 further calculates the ratio (σ/
Search for the sampling point where X) is maximum. and,
The data at the sampling point is given to the delay control circuit IO.

The delay control circuit IO focuses the ultrasonic beam on the sampling point where the obtained ratio σ/X is maximum in the scanning line with the same line number when scanning the next adjacent scanning line or the next field. Set the delay time of each vibrator 2. As a result, as shown in FIG. 3, the focus is set for each scanning line so that the ultrasonic beam is focused on the contour portion.

Note that when setting the focus of the next scanning line to the sampling point determined by the focus calculation circuit 12,
The focus position will shift by the amount of the scanning line, but
Since the distance between adjacent scanning lines is small, the effect of a shift in focus position by one scanning line can be almost ignored with the naked eye.

(f) Effects As described above, according to the present invention, since the focus position is set at an effective position for each scanning line of the ultrasound beam, an image with a clearer outline can be obtained. Excellent effects such as being able to perform more appropriate diagnosis based on images are exhibited.

[Brief explanation of the drawing]

Figures 1 to 4 show embodiments of the present invention, with Figure 1 being a block diagram showing the main parts of an ultrasonic diagnostic device, and Figure 2 being a block diagram showing the specific configuration of a focus calculation circuit. 3 are explanatory diagrams showing the relationship between the focus position and the outline, and FIG. 4 is an explanatory diagram showing the storage state of data in the line buffer memory. Further, FIG. 5 is an explanatory diagram showing a conventional method of setting focus. l... Ultrasonic diagnostic device, 2... Vibrator, 10...
Focus setting means (delay control circuit), 26...average variance calculation means (average variance calculation circuit), 30... search means (comparison calculation circuit).

Claims (1)

[Claims] (1) A pre-selected transducer group is given a predetermined delay time, the ultrasound beam emitted from the transducer group is electronically focused, and the ultrasound echo reflected by the subject is received by the transducer group. In an ultrasonic diagnostic apparatus that displays an image based on echo signals output from the transducer group by Mean variance calculation means for calculating the average value and variance value of signal intensity; and search means for determining the ratio of the average value and variance value calculated by this average variance calculation means and searching for a sampling point at which the ratio is maximum. An ultrasonic diagnostic apparatus comprising: and a focus setting means for setting a focus at a depth position of a sampling point searched by the search means.