JP2001198128A - Migration distance estimating method and ultrasonograph - Google Patents

Abstract

PROBLEM TO BE SOLVED: To estimate an exact migration distance of a probe without a complicated constitution and in short calculating time. SOLUTION: This ultrasonograph 100 is provided with an ultrasonic probe 1, an ultrasonic image generating part 2 for generating sound ray data SD (i) and image data P (i) of an ultrasonic image, a speckle noise detecting part 3 for detecting speckle noise, an integrating part 4 for calculating sum of squares, that is, an integrated value D (i) of a difference of speckle noise between ultrasonic images corresponding to adjacent scan surfaces, an integrated value/estimated migration distance table 5 for storing a relation of the integrated value D (i) and an estimated migration distance E (i) of the ultrasonic probe 1, a migration distance estimating part 6 for outputting the estimated migration distance E (i) of the ultrasonic probe 1, a migration start and migration finish detecting part 7 for detecting the migration start and migration finish of the ultrasonic probe 1, a three-dimensional image preparing part 8 for preventing a three-dimensional image based on sound ray data SD (i) and the estimated migration distance E (i) and an indicator 9. The positional relation of cross section of a testee body corresponding to each image can be exactly acquired. In particular, this ultrasonograph useful for preparing a three-dimensional image.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a moving distance estimating method and an ultrasonic diagnostic apparatus, and more particularly, to a moving distance estimating method capable of estimating an accurate moving distance of a probe without a complicated structure and in a short calculation time. The present invention relates to a method and an ultrasonic diagnostic apparatus.

[0002]

2. Description of the Related Art The following techniques (1) to (3) are known as conventional techniques for estimating the position of an ultrasonic probe of an ultrasonic diagnostic apparatus. (1) The distance to be moved from the start of the movement to the end of the movement is input in advance. During the movement of the ultrasonic probe, the frame interval L is calculated assuming that the ultrasonic probe moves at a constant speed, and the position of the ultrasonic probe is estimated. For example, in the case where the cine image is acquired at a period of 30 frames / sec by moving 100 mm in length from the start to the end of the movement in 3.3 seconds and the cine image is acquired at a cycle of 30 frames / sec, the frame interval L is 1/100 / (3.3 × 30). Is calculated. (2) US Pat. No. 5,876,342 discloses a technique for estimating the position of an ultrasonic probe by a speckle correlation method for analyzing a cross-correlation of speckle noise between a plurality of frames. ing. The speckle noise is a fine spot-like noise pattern generated by random interference of ultrasonic waves. (3) A magnetic field generated from a magnetic field source is detected by a magnetic sensor box mounted on the ultrasonic probe, and three-dimensional position coordinates of the ultrasonic probe are estimated based on the detection result.
In connection with a technique for automatically moving an ultrasonic vibrator, there is known a technique for positioning an ultrasonic vibrator using a drive motor and a position detection encoder.

[0003]

However, the above (1)
In the prior art, it takes time and effort to input the distance to be moved in advance. Also, depending on the skill of the operator, the state of the body surface of the scan site, and the like, the ultrasonic probe does not always move at a constant speed, in which case the estimation error increases. Also,
In the above-mentioned prior art (2), since the calculation process for analyzing the cross-correlation of speckle noise is complicated, the calculation time is long. Furthermore, the conventional technique (3) and the conventional technique for automatically moving the ultrasonic vibrator require a complicated configuration, and therefore increase the cost. Therefore, an object of the present invention is to provide a moving distance estimating method and an ultrasonic diagnostic apparatus capable of estimating an accurate moving distance of a probe without a complicated configuration and in a short calculation time.

[0004]

According to a first aspect of the present invention, a plurality of images are generated by scanning the inside of a subject on a scan plane corresponding to the position of a moving probe, and a plurality of images are generated. Alternatively, there is provided a moving distance estimating method characterized by estimating a moving distance of the probe based on a difference in speckle noise between images corresponding to an adjacent scan plane. The moving distance estimation method according to the first aspect focuses on the fact that, when viewed within a relatively narrow range, the difference in speckle noise between the images increases as the distance between the scan planes increases. Is estimated. That is, it is possible to obtain the distance between the scan planes from the difference in speckle noise between images corresponding to scan planes that are adjacent to or close to each other. Thus, even when the probe is manually moved, the moving distance of the probe can be accurately estimated. Further, since the detection of speckle noise and the calculation of the difference between the values are sufficient with a simple calculation process, a complicated configuration is not required and the calculation time is short.

In a second aspect, the present invention provides the moving distance estimating method according to the first aspect, wherein a time point at which the differential value of the change in the moving distance becomes larger than a movement start determination threshold value is determined. A moving distance estimating method is provided, wherein the moving time estimating method is characterized in that it is determined as a starting time, and a point in time when a differential value of the change in the moving distance becomes smaller than a moving end determining threshold is determined as a moving end time of the probe. In the moving distance estimation method according to the second aspect, the differential value of the estimated change in the moving distance is regarded as the moving speed, and when the moving speed becomes larger than the moving start determination threshold, the moving start time is determined. Is smaller than the movement end determination threshold value, the movement end time is determined. This makes it possible to accurately determine the movement start time at which the movement distance needs to be estimated and the movement end time at which the movement distance does not need to be estimated.

[0006] In a third aspect, the present invention provides the moving distance estimating method according to the first aspect or the second aspect,
Estimating the moving distance again assuming that the probe moves at a constant speed, or re-estimating the moving distance assuming that the moving speed of the probe changes smoothly. And a method for estimating a moving distance. The third above
In the moving distance estimation method from the viewpoint of the above, the moving distance is estimated again by assuming that the probe moves at a constant speed, so that only the moving distance corresponding to the moving start time and the moving distance corresponding to the moving end time are obtained. It is possible to estimate all the movement distances at each scan time between both times. In addition, by estimating the moving distance assuming that the moving speed of the probe changes smoothly, even when the variation of the speckle noise for each ultrasonic image becomes relatively large, the estimation error is reduced. Can be reduced.

In a fourth aspect, the present invention provides the moving distance estimating method according to the first to third aspects, wherein the average of the estimated moving distance is estimated for each estimated moving distance block having a fixed time width. A moving distance estimating method for calculating a value, re-estimating the moving distance excluding a moving distance corresponding to an estimated moving distance block having an average value largely deviating from a change characteristic of each average value. I do. In the moving distance estimating method according to the fourth aspect, the moving distance is re-estimated excluding the estimated moving distance block in which the average value of the moving distance is significantly different from the others. Can be reduced.

According to a fifth aspect, the present invention provides the moving distance estimating method according to any one of the first to fourth aspects, wherein speckle noise larger than a threshold for structure discrimination is excluded. Provided is a moving distance estimating method characterized by estimating a moving distance of a probe. In the moving distance estimating method according to the fifth aspect, the moving distance of the probe is estimated by excluding speckle noise that is larger than the threshold value for determining a structure. The estimation error caused by the increase can be reduced.

In a sixth aspect, the present invention provides an ultrasonic probe for transmitting an ultrasonic wave into a subject and receiving an ultrasonic echo from the subject, and an ultrasonic probe based on the ultrasonic echo. Ultrasonic image generating means for generating an acoustic image, speckle noise detecting means for detecting speckle noise based on the ultrasonic image, and a difference between speckle noise differences of ultrasonic images corresponding to scan planes adjacent to each other. A moving distance estimating means for estimating a moving distance of the ultrasonic probe based on an integral value is provided. In the ultrasonic diagnostic apparatus according to the sixth aspect, it is possible to accurately estimate the moving distance of the ultrasonic probe based on the integrated value of the difference in speckle noise between images corresponding to scan planes adjacent to each other. I can do it. Further, since the speckle noise detecting means and the moving distance estimating means have a relatively simple configuration, the cost can be reduced.

In a seventh aspect, the present invention provides the ultrasonic diagnostic apparatus according to the sixth aspect, further comprising a three-dimensional image creating means for creating a three-dimensional image of the subject based on the estimated moving distance. An ultrasonic diagnostic apparatus is provided. In the ultrasonic diagnostic apparatus according to the seventh aspect, a three-dimensional image having high clinical utility value can be created with high accuracy based on the estimated moving distance.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail with reference to the embodiments shown in the drawings. Note that the present invention is not limited by this. FIG. 1 is a configuration diagram illustrating an ultrasonic diagnostic apparatus according to an embodiment of the present invention. The ultrasonic diagnostic apparatus 100 includes an ultrasonic probe 1 that transmits an ultrasonic wave into a subject and receives an ultrasonic echo from the subject, a sound ray data SD (i) and an ultrasonic image. Ultrasound image generation unit 2 for generating image data P (i), speckle noise detection unit 3 for detecting speckle noise σ (i), and speckle noise between ultrasonic images corresponding to adjacent scan planes Sum of squared differences, ie, integral value D
An integration unit 4 for calculating (i), an integrated value / estimated moving distance table 5 for storing a relationship between the integrated value D (i) and the estimated moving distance E (i) of the ultrasonic probe 1, A moving distance estimating unit 6 that outputs an estimated moving distance E (i) of the ultrasonic probe 1 with reference to the integrated value / estimated moving distance table 5.
A movement start / movement end detection unit 7 that outputs a movement start detection signal α when detecting the start of movement of the ultrasonic probe 1 and outputs a movement end detection signal β when detecting the end of movement; A three-dimensional image creating unit 8 that creates a three-dimensional image based on the data SD (i) and the estimated moving distance E (i), and a display 9 that displays the ultrasonic image and the three-dimensional image. It is configured. Note that i is
Scan surface numbers (1, 2, 3,..., N) that change from moment to moment as the ultrasonic probe 1 moves.

FIG. 2 is a view showing an example of the contents of the integrated value / estimated moving distance table 5. As shown in FIG. The integrated value / estimated moving distance table 5 stores a standard estimated moving distance E (i) for each of the integral values D (i). Note that these estimated moving distances are obtained in advance by scanning a standard phantom or the like that imitates a standard subject. For example, an estimated moving distance of 0 corresponds to the integral values “0” and “1”.
[Mm] is stored, and an estimated moving distance of 1 [mm] is stored corresponding to the integral values "2" and "3", and an estimated moving distance of 500 [mm] is corresponding to the integral value "1000".
Is stored.

Next, the operation of the ultrasonic diagnostic apparatus 100 will be described. First, as shown in FIG.
After the ultrasonic probe 1 is applied to the three-dimensional scan start position Qs at one end of the three-dimensional target region R assumed on the subject H, the ultrasonic probe 1 is moved to the three-dimensional target as shown by an arrow. Move along the region R, and move the 3
The ultrasonic probe 1 is stopped at the dimensional scan end position Qe.
During this time, a predetermined period (for example, 1/7 second to 1/160 second)
Each time, a scan plane corresponding to the position of the ultrasonic probe 1 at that time is scanned, a plurality of data on many sound rays constituting the scan plane are acquired, and the ultrasonic image generation unit 2
For example, a B-mode image is generated. In FIG. 4A,
Ultrasonic image data P (i) = P (0), P
(1),. S is speckle noise. U is a tissue image.

The speckle noise detector 3 extracts the speckle noise σ (i) according to σ (i) = | P (i + 1) -P (i) |. FIG. 4B shows the speckle noise σ
(0), σ (1), σ (2),... The tissue image U having no change in the adjacent scan plane is canceled, and only speckle noise remains. From the viewpoint of accurately estimating the moving distance, it is preferable to extract speckle noise only in a pixel region that does not include a body structure such as a blood vessel in an ultrasonic image.

The integrator 4 includes: , The sum of squares of the difference in the speckle noise σ (i) between the scan planes adjacent to each other, that is, the integrated value D (i) is calculated.

The moving distance estimating section 6 reads out the estimated moving distance E (i) corresponding to the integrated value D (i) from the integrated value / estimated moving distance table 5, and detects a moving start / moving end detecting section 7. And sends it to the three-dimensional image creation unit 8. In the example of FIG. 2, for example, when the integral value D (i) is "7", 3 [mm] is sent as the estimated moving distance E (i). FIG.
Is a graph illustrating a change in the estimated moving distance E (i) with respect to time. The black circles indicate the estimated moving distance for each scan plane number. The solid line is a characteristic line of each estimated moving distance E (i).

The moving start / moving end detecting unit 7 calculates an estimated moving speed V by differentiating the change in the estimated moving distance E (i). FIG. 6 is a graph illustrating the estimated moving speed V. When the estimated moving speed V becomes larger than the moving start determination threshold value V1, it is determined that the moving start time is ts, and a moving start detection signal α is sent to the three-dimensional image creating unit 8. When it becomes smaller than the threshold value V2, the movement end time te is determined, and a movement end detection signal β is sent to the three-dimensional image creating unit 8. Although the movement start determination threshold value V1 and the movement end determination threshold value V2 are illustrated as being equal to each other, they may be different.

The three-dimensional image creating unit 8 receives the sound ray data SD (i) and the estimated moving distance E (i) during a moving period from receiving the movement start detection signal α to receiving the movement end detection signal β. , A three-dimensional image is created and displayed on the screen of the display 9. The details of the principle of creating a three-dimensional image are disclosed in, for example, JP-A-9-299364.

According to the ultrasonic diagnostic apparatus 100 described above, the speckle noise σ (i) between the scan planes adjacent to each other is obtained.
The estimated moving distance E of the ultrasonic probe 1 can be accurately calculated based on the sum of the squares of the differences, i.e., the integrated value D (i).

The configuration of the ultrasonic diagnostic apparatus 100 may be changed as follows. (1) As shown by the solid line in FIG. 7, the moving distance may be re-estimated on the assumption that the ultrasonic probe 1 moves at a constant speed from the movement start time ts to the movement end time te. The black circles are the estimated moving distances calculated by the operations described above with reference to FIGS. The white circles indicate the re-estimated moving distance. In this case, by reducing the pixel area for extracting the speckle noise in the ultrasonic image to reduce the amount of calculation, even when the variation of the speckle noise for each ultrasonic image becomes relatively large. , The estimation error can be reduced. (2) The moving distance may be re-estimated on the assumption that the moving speed of the ultrasonic probe 1 changes smoothly. For example, FIG.
When the estimated moving distance E1 on the characteristic line indicated by the dotted line is estimated, the estimated moving distance E2 on the characteristic line indicated by the solid line is re-estimated by applying the estimated moving distance E1 to, for example, a cubic equation. In this case, it is possible to correct the estimated moving distance closer to the actual situation than in the case of the above (1), and it is possible to further reduce the estimation error. (3) The average value of the characteristic line of the estimated moving distance E (i) of the ultrasound probe 1 is calculated for each estimated moving distance block having a certain time width, and the average value greatly deviates from the change characteristic of each average value. The estimated moving distance (i) may be corrected by excluding the moving distance corresponding to the estimated moving distance block having the value. For example, as shown in FIG. 9, the characteristic line of the estimated moving distance E (i) is changed to the estimated moving distance blocks B1, B2, B of the time width Tw.
If the average value when divided into 3,... Is 1, 2, 5,..., The average value “4” corresponding to the estimated moving distance block B6
7 ". The estimated moving distance block B1 before and after the estimated moving distance block B6, as shown in FIG.
To B5 and the estimated moving distance blocks B7 to B1
A characteristic line of the estimated moving distance E (i) of a portion corresponding to the estimated moving distance block B6 is calculated from the average value of 0 by interpolation. In this case, it is possible to reduce an estimation error caused by blurring of speckle noise due to the presence of a body structure or the like. (4) The moving distance of the ultrasonic probe 1 may be estimated by excluding speckle noise that is larger than the threshold value for determining a structure.
In this case, it is possible to reduce an estimation error caused by an extremely large speckle noise due to the presence of a body structure or the like.

[0021]

According to the moving distance estimating method and the ultrasonic diagnostic apparatus of the present invention, the moving distance of the probe is estimated based on the difference in speckle noise between images. The positional relationship of the cross section can be accurately obtained. In particular, it is useful for creating a three-dimensional image.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an ultrasonic diagnostic apparatus according to one embodiment of the present invention.

FIG. 2 is an exemplary diagram showing an integrated value / estimated moving distance table in the ultrasonic diagnostic apparatus of FIG. 1;

FIG. 3 is an explanatory diagram illustrating a state in which an ultrasonic probe is applied to a three-dimensional target area and scanning is performed.

FIG. 4 is an explanatory diagram showing a principle of calculating an integrated value of speckle noise.

FIG. 5 is a graph illustrating a characteristic line of an estimated moving distance.

FIG. 6 is a graph illustrating an estimated moving speed.

FIG. 7 is a graph showing a characteristic line of a moving distance re-estimated assuming that the ultrasonic probe moves at a constant speed.

FIG. 8 is a graph showing a characteristic line of the moving distance re-estimated assuming that the moving speed of the ultrasonic probe changes smoothly.

FIG. 9 is an explanatory diagram illustrating a principle of calculating an estimated moving distance average value for each estimated moving distance block.

FIG. 10 is an explanatory diagram showing a principle of correcting an estimated moving distance by an interpolation calculation.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 ultrasonic diagnostic apparatus 1 ultrasonic probe 2 ultrasonic image generating unit 3 speckle noise detecting unit 4 integrating unit 5 integrated value / estimated moving distance table 6 moving distance estimating unit 7 moving start / moving end detecting unit 8 three-dimensional Image creation unit 9 Display D (i) Integral value E (i) Estimated moving distance P (i) Image data SD (i) Sound ray data α Move start detection signal β Move end detection signal σ (i) Speckle noise

Claims (7)

[Claims] 1. A scan plane corresponding to a position of a moving probe scans the inside of a subject to generate a plurality of images, and speckle noise between images corresponding to scan planes that are adjacent to or close to each other. A moving distance of the probe based on a difference between the two. 2. The moving distance estimating method according to claim 1, wherein a time point at which the differential value of the change in the moving distance becomes larger than a movement start determination threshold value is determined as a movement start time of the probe, and A moving distance estimating method, wherein a time point at which a differential value of a change in distance becomes smaller than a moving end determination threshold value is determined as a movement end time of the probe. 3. The moving distance estimating method according to claim 1, wherein the moving distance is re-estimated on the assumption that the probe moves at a constant speed, or the probe is moved. And estimating the moving distance again on the assumption that the moving speed of the moving distance changes smoothly. 4. The moving distance estimating method according to claim 1, wherein an average value of the estimated moving distance is calculated for each estimated moving distance block having a certain time width, and the average value is calculated. A moving distance estimating method comprising re-estimating the moving distance excluding a moving distance corresponding to an estimated moving distance block having an average value greatly deviating from a value change characteristic. 5. The moving distance estimating method according to claim 1, wherein the moving distance of the probe is estimated by excluding speckle noise that is larger than a structure discrimination threshold. Characteristic moving distance estimation method. 6. An ultrasonic probe for transmitting an ultrasonic wave into a subject and receiving an ultrasonic echo from the subject,
An ultrasonic image generating means for generating an ultrasonic image based on the ultrasonic echo, a speckle noise detecting means for detecting speckle noise based on the ultrasonic image, and an ultrasonic wave corresponding to a scan plane adjacent to each other An ultrasonic diagnostic apparatus comprising: moving distance estimating means for estimating a moving distance of the ultrasonic probe based on an integrated value of a difference between speckle noises of images. 7. The ultrasonic diagnostic apparatus according to claim 6, further comprising a three-dimensional image creating means for creating a three-dimensional image of the subject based on the estimated moving distance. apparatus.