JP2013244354A - Ultrasonic image processor, ultrasonic image processing program, and ultrasonic image processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultrasonic image processor capable of generating echo images accurately indicating the shape of a measured body.SOLUTION: An image generation part 44 generates echo images in which reception signals that respective vibrators 24 have received reflected waves are connected. A shape detection part 40 detects the shape of the measured body on the basis of the reception signals received by the respective vibrators 24. A deformation function calculation part 47 obtains a deformation function for deforming the echo images so as to make the shape of the measured body detected by the shape detection part 40 be coincident with the shape of the echo image of the measured body included in the echo images. An image deformation part 48 generates a deformed echo image for which the echo image is deformed on the basis of the deformation function.

Description

  The present invention relates to an ultrasonic image processing apparatus that receives a reflected wave from a measured object by a plurality of transducers and processes the reflected wave as an image.

  2. Description of the Related Art There is known an ultrasonic diagnostic imaging apparatus that transmits an ultrasonic signal toward a measurement object, receives a reflected wave (echo) from the measurement object, and visualizes it. As shown in FIG. 2, this type of diagnostic imaging apparatus has a transducer array 22 including a plurality of ultrasonic transducers 24 arranged in a line. By generating ultrasonic waves simultaneously with the transducers 24 of the transducer array 22, a plane wave is transmitted toward the object to be measured (FIG. 2 (a)), and the reflected waves returning from the object to be measured are each oscillated. It is received by the child 24 and an echo image corresponding to the intensity of the received reflected wave is generated.

  On the other hand, in the field of ultrasonic diagnosis, a shape detection device that detects the shape of a bone based on a signal received by a transducer array 22 is known. Such a shape detection apparatus is described in Patent Document 1 to Patent Document 3, for example. Patent Documents 1 to 3 are configurations for deriving the shape of the bone surface based on the arrival direction and propagation time of the reflected wave from the bone surface.

JP 2010-29240 A JP 2010-29241 A JP 2010-246692 A

  Here, an echo image generated by a conventional diagnostic imaging apparatus is illustrated in FIG. In the echo image of FIG. 5, the vertical axis (Y axis) indicates the distance in the direction in which the transducer array 22 transmits a plane wave. The horizontal axis (X axis) indicates the distance in the direction in which the transducers 24 are arranged in the transducer array 22.

  In the echo image of FIG. 5, the luminance of each pixel indicates the intensity of the signal received by each transducer 24. That is, the brighter the color of the pixel, the stronger the reflected wave is received. The echo image of FIG. 5 is obtained by using a human bone as a measurement object. Since the reflected wave reflected from the bone surface is stronger than the reflected signal reflected from blood vessels and fats in soft tissue, the reflected wave reflected from the bone surface is displayed brightly (whiter). Note that the gray dotted line displayed superimposed on the echo image in FIG. 5 is for easy understanding of the bone surface shape indicated by the echo image.

  In addition, a white curve indicating the actual bone shape is superimposed on the echo image of FIG. 5 for comparison. In order to help understanding of FIG. 5, the contents of FIG. 5 are schematically shown in FIG. As shown in FIGS. 5 and 6, the echo image of the bone does not match the actual bone shape and does not correctly represent the shape and size of the bone. That is, an echo image of the bone is displayed at a position where it should not be. Such a phenomenon is called a false image (artifact). When a false image is generated, there is a problem that the shape and size of the bone cannot be accurately recognized on the echo image.

  Such a false image occurs when the surface shape of the bone is curved. This is because when the surface of the bone is curved, a reflected wave oblique to the Y axis is generated (see FIG. 2B). In addition, although a reflected wave in an oblique direction can be generated even in a blood vessel or an organ in a soft tissue, such a reflected wave is not a problem because the intensity is weak. However, since the reflected wave reflected by the bone is strong, the reflected wave in the oblique direction has a considerable intensity, and when this is received by the vibrator 24, a false image is generated. As described above, in the conventional ultrasonic diagnostic imaging apparatus, the shape of the curved bone cannot be accurately displayed as an echo image.

  In this regard, Patent Documents 1 to 3 disclose a configuration that can accurately derive the surface shape of the bone. However, the configurations of Patent Document 1 to Patent Document 3 are not considered for application to an image diagnostic apparatus. That is, in the configurations of Patent Documents 1 to 3, it is only possible to derive an accurate bone surface shape, and it is not possible to confirm an accurate bone shape on an echo image. In image diagnosis using ultrasound, it is important to be able to confirm on the echo image the state around the measured object (for example, the state of soft tissue around the bone). A configuration that can be confirmed is desired.

  The present invention has been made in view of the above circumstances, and a main object thereof is to provide an ultrasonic image processing apparatus capable of generating an echo image accurately representing the shape of a measurement object. .

Means and effects for solving the problems

  The problems to be solved by the present invention are as described above. Next, means for solving the problems and the effects thereof will be described.

  According to the first aspect of the present invention, an ultrasonic image processing apparatus having the following configuration is provided. That is, the ultrasonic image processing apparatus includes a transducer array, an image generation unit, a shape detection unit, a deformation function calculation unit, and an image deformation unit. The transducer array includes a plurality of transducers that transmit ultrasonic transmission waves to the measurement target and receive reflected waves from the measurement target. The image generation unit generates an echo image obtained by connecting reception signals obtained by the transducers receiving the reflected wave. The shape detection unit detects the shape of the measurement object based on the reception signal received by each transducer. The deformation function calculating unit deforms the echo image so that the shape of the measurement object detected by the shape detection unit matches the shape of the echo image of the measurement object included in the echo image. Find a function. The image deforming unit generates a deformed echo image obtained by deforming the echo image based on the deformation function.

  In this way, by detecting the shape of the object to be measured and deforming the echo image according to the detected shape, an echo image (deformed echo image) that accurately represents the actual shape and size of the object to be measured is obtained. be able to.

  The ultrasonic image processing apparatus is preferably configured as follows. That is, the ultrasonic image processing apparatus includes a control point setting unit and a movement target position setting unit. When it is assumed that the reflected wave has arrived from the direction in which the transmission wave is transmitted, the control point setting unit sets the control point at a virtual reflection position where the reflected wave is considered to be reflected by the surface of the measurement object. Set. The movement target position setting unit calculates a propagation path of a reflected wave received by the vibrator from the measured object based on the shape of the measured object detected by the shape detecting unit, and the reflected wave is The movement target position of the control point is set to a reflection position that reflects on the surface of the object to be measured. The deformation function calculation unit calculates a deformation function for deforming the echo image so as to move the control point to the reflection position.

  By setting the control point at the virtual reflection position in this way, the control point can be set on the echo image of the measurement object. The echo image is deformed so that the control point is moved to the position where the reflected wave is actually reflected (reflected position), thereby accurately representing the shape and size of the actual measured object (deformed) Echo image) can be obtained.

  The ultrasonic image processing apparatus is preferably configured as follows. That is, the control point setting unit sets a control point at the position of the vibrator. The deformation function calculation unit calculates a deformation function for deforming the echo image so that a control point at the position of the transducer does not move.

  That is, since the position of each transducer is known, it is preferable that the pixel corresponding to the position of the transducer does not move before and after the deformation of the echo image by the image deformation section. Therefore, by setting a control point at the position of the transducer and deforming the echo image so that the control point does not move, a more accurate transformed echo image can be obtained.

  In the ultrasonic image processing apparatus, the deformation function calculation unit calculates a deformation function for an arbitrary point on the echo image by a least square method weighted by a distance from the point to each control point. It is preferable to do.

  That is, the echo image is smoothly deformed by calculating the deformation function for each point on the echo image so that the influence of the control point at the near position is strong and the influence of the control point at the far position is weak. Can be made.

  According to the second aspect of the present invention, the following ultrasonic image processing program is provided. That is, this ultrasonic image processing program causes a computer to realize a received signal acquisition function, an image generation function, a shape detection function, a deformation function calculation function, and an image deformation function. In the reception signal acquisition function, the transducer array having a plurality of transducers arranged side by side transmits an ultrasonic transmission wave to the object to be measured and receives a reflected wave from the object to be measured to receive the reception signal. get. In the image generation function, each transducer generates an echo image obtained by connecting the reception signals received by the reflected waves. In the shape detection function, the shape of the measurement object is detected based on the reflected signal received by each transducer. In the deformation function calculation function, a deformation that deforms the echo image so that the shape of the measurement object detected by the shape detection function matches the shape of the echo image of the measurement object included in the echo image. Find a function. The image deformation function generates a deformed echo image obtained by deforming the echo image based on the deformation function.

  According to the third aspect of the present invention, the following ultrasonic image processing method is provided. That is, the ultrasonic image processing method includes a reception signal acquisition step, an image generation step, a shape detection step, a deformation function calculation step, and an image deformation step. In the reception signal acquiring step, an ultrasonic wave transmission wave is transmitted to the object to be measured by the vibrator array including a plurality of vibrators arranged, and a reception signal is received by receiving a reflected wave from the object to be measured. get. In the image generation step, an echo image is generated by connecting the reception signals received by the transducers with the reflected waves. In the shape detection step, the shape of the measurement object is detected based on the reception signal received by each transducer. In the deformation function calculation step, a deformation that deforms the echo image so that the shape of the measurement object detected in the shape detection step matches the shape of the echo image of the measurement object included in the echo image. Find a function. In the image deformation step, a deformed echo image is generated by deforming the echo image based on the deformation function.

1 is a block diagram of an ultrasonic diagnostic apparatus according to an embodiment of the present invention. (A) The schematic diagram which shows a mode that a plane wave is transmitted with respect to a bone. (B) The schematic diagram which shows a mode that the reflected wave produced on the surface of the bone. The flowchart of the ultrasonic image processing method which concerns on embodiment of this invention. (A) The graph which illustrates a received signal when a vibrator receives a reflected wave. (B) An envelope signal based on the received signal of (a) above. An echo image with a false image. FIG. 6 is a diagram schematically illustrating the contents of an echo image in FIG. 5. The schematic diagram which shows a mode that the reflected wave reflected on the bone surface was received by the vibrator | oscillator. The figure explaining a mode that an echo image is deformed by moving a control point. The figure explaining the process which detects the shape of a bone surface. 6 is a modified echo image obtained by deforming the echo image of FIG. 5. The figure which illustrates typically the content of the transformed echo image of FIG. The image displayed by superimposing the propagation path of the surface refraction wave on the transformed echo image of FIG. The figure which illustrates typically the content of the transformed echo image of FIG. The figure explaining the modification which sets an interpolation control point.

  Next, embodiments of the invention will be described with reference to the drawings. FIG. 1 is a block diagram of an ultrasonic diagnostic apparatus 1 as an ultrasonic image processing apparatus according to an embodiment of the present invention.

  The ultrasonic diagnostic apparatus 1 of this embodiment uses a human body as a diagnosis target, and particularly uses a bone as a measurement target. The ultrasonic diagnostic apparatus 1 according to the present embodiment has a function as an ultrasonic image processing apparatus that generates an echo image based on an ultrasonic signal returned from a bone and displays the echo image. Thereby, the state of the bones in the body can be confirmed as an image.

  As shown in FIG. 1, the ultrasonic diagnostic apparatus 1 includes an ultrasonic transducer 2 and an apparatus main body 3.

  The ultrasonic transmitter / receiver 2 transmits and receives ultrasonic waves. The ultrasonic transducer 2 includes an abutment surface 2 a that abuts on the surface (skin) of the soft tissue 11 at the measurement site, and a transducer array 22. The transducer array 22 includes a plurality of transducers 24 arranged in a line at equal intervals along the contact surface 2a. In the following description, the direction in which the transducers 24 are arranged in the transducer array 22 is referred to as the X-axis direction.

When an electric signal is given, the vibrator 24 vibrates its surface to generate an ultrasonic wave, and generates and outputs an electric signal when receiving an ultrasonic wave on the surface. That is, each transducer 24 is configured to be able to transmit and receive ultrasonic waves. When it is necessary to distinguish the plurality of transducers 24, with the subscript in the order in which are lined up vibrator, the vibrator 24 _1, vibrator 24 _2, ... vibrator 24 _n, ... Sometimes expressed as a vibrator 24 _N.

  The apparatus main body 3 is connected to the ultrasonic transducer 2 by a cable, and is configured to be able to transmit and receive signals to and from the ultrasonic transducer 2. The apparatus main body 3 includes a transmission circuit 31, a plurality of reception circuits 33, a transmission / reception separation unit 34, a calculation unit 35, and a display unit 32.

  The transmission circuit 31 is configured to generate an electrical pulse signal for generating an ultrasonic wave by vibrating the transducers 24 of the transducer array 22 and to apply the electrical pulse signal to the transducers 24. Yes. The center frequency of the electric pulse signal is, for example, about 1 to 10 MHz. For example, a chirp signal may be used instead of the electric pulse signal.

  The vibrator 24 to which the electric pulse is applied vibrates according to the electric pulse signal and generates an ultrasonic wave. The transmission circuit 31 is configured to apply an electrical pulse signal at an arbitrary timing to each of the plurality of transducers 24 of the transducer array 22. Thereby, it is possible to control to transmit ultrasonic waves from a plurality of transducers 24 all at once or at individual timing.

  The plurality of receiving circuits 33 are respectively connected to the plurality of transducers 24 constituting the transducer array 22. Each receiving circuit 33 receives an electrical signal output by the transducer 24 receiving an ultrasonic wave, and receives the electrical signal subjected to amplification processing, filter processing, digital conversion processing, and the like. A signal is generated and transmitted to the calculation unit 35. The signal directly output from the transducer 24 is an analog waveform signal, and the signal transmitted to the calculation unit 35 is a digital waveform signal subjected to signal processing. However, these are not particularly distinguished in the following description.

  The transmission / reception separation unit 34 is connected between the transducer array 22 and the transmission circuit 31 and the reception circuit 33. The transmission / reception separating unit 34 prevents an electrical signal (electrical pulse signal) sent from the transmission circuit 31 to the transducer array 22 from flowing directly to the reception circuit 33, and also sends electricity sent from the transducer array 22 to the reception circuit 33. This is to prevent a signal from flowing to the transmission circuit 31 side.

  The calculation unit 35 is configured as a computer including hardware such as a CPU, a RAM, and a ROM. The ROM stores software such as an ultrasonic image processing program according to an embodiment of the present invention. The ultrasonic image processing program of the present embodiment is configured to cause the calculation unit 35 to realize a function of generating an echo image based on a reception signal received by the transducer 24.

  The echo image generated by the calculation unit 35 is output to the display unit 32. The display unit 32 is, for example, a liquid crystal display, and is configured to be able to display an echo image. The operator of the ultrasonic diagnostic apparatus 1 can grasp the shape and size of the bone as the measurement target, the state of the soft tissue around the bone, and the like by checking the echo image displayed on the display unit 32.

  Subsequently, the operation of the ultrasonic diagnostic apparatus 1 of the present embodiment will be described with reference to FIGS. 2 and 3.

  When making a diagnosis using the ultrasonic diagnostic apparatus 1, the operator performs a predetermined measurement start operation in a state where the contact surface 2a of the ultrasonic transducer 2 is in contact with the human body surface (skin) to be diagnosed. I do. When the measurement start operation is performed, the transmission circuit 31 applies an electrical pulse signal to each transducer 24 of the transducer array 22 at the same timing. As a result, ultrasonic waves are transmitted from the respective transducers 24 toward the body at the same timing (step S101), so that plane waves traveling in a direction orthogonal to the direction in which the transducers 24 are arranged (X-axis direction) are transmitted. (FIG. 2A). In the following description, the direction in which the plane wave is transmitted from the transducer array 22 is defined as the Y-axis direction.

  The plane wave transmitted from the transducer array 22 travels through the soft tissue 11 and is reflected by the surface of the bone 10 to generate a reflected wave (FIG. 2B). This reflected wave is received by at least some of the plurality of transducers 24 included in the transducer array 22 (step S102, reception signal acquisition step). The reception signal received by each transducer 24 is subjected to appropriate processing such as filtering and sampling by the reception circuit 33 and converted into digital waveform data. The digital reception signal of each transducer 24 generated by the reception circuit 33 is output to the calculation unit 35. The ultrasound image processing program of the present embodiment is configured to cause the calculation unit 35 to realize a reception signal acquisition function for acquiring a digital reception signal output from the reception circuit 33 as described above. As a result, the calculation unit 35 can process the waveform of the received signal received by each transducer 24.

  The ultrasound image processing program of the present embodiment is configured to cause the computing unit 35 to realize an image generation function for generating an echo image based on the received signal acquired as described above. Therefore, it can be said that the calculation unit 35 is the image generation unit 44.

  First, the image generation unit 44 calculates an envelope (envelope) of a reception signal received by each transducer 24, and generates an envelope signal indicating a temporal change of the envelope (step S103). For example, when a received signal received by a certain transducer 24 is represented by a graph as shown in FIG. 4A, an envelope signal based on this received signal is as shown in FIG. 4B. Here, the amplitude of the envelope signal indicates the intensity of the received signal received by the transducer 24 at a certain time. The larger the amplitude of the envelope signal, the stronger the signal received.

  When it is assumed that the reflected wave received by each transducer 24 is returned from the Y-axis direction (the direction in which the plane wave is transmitted), the envelope signal of each transducer 24 is Y-axis viewed from the transducer 24. It can be considered as a one-dimensional echo image in the direction. For example, when the amplitude of the envelope signal is considered as the luminance of the pixel, the envelope signal can be regarded as a one-dimensional image expressed by a bright pixel at a position where the signal strength is strong and a dark pixel at a weak position.

  On the other hand, since the transducers 24 are arranged in a line in the X-axis direction perpendicular to the Y-axis, a two-dimensional echo image can be obtained by arranging the envelope signals of the transducers 24 in the X-axis direction. . Therefore, the image generation unit 44 connects the envelope signals (one-dimensional image data in the Y-axis direction) of each transducer 24 in the order in which the transducers 24 are arranged in the X-axis direction (step S104). As a result, two-dimensional echo image data expressed in XY orthogonal coordinates can be generated.

  Subsequently, the image generation unit 44 performs various types of image processing on the image data generated as described above. Various image processing can be performed at this time. For example, data decimation or interpolation between pixels can be performed.

  For example, the resolution in the Y direction of the image data generated in step S104 is determined by the sampling frequency of the envelope signal. However, there are cases where such a resolution is not necessary for an image. Therefore, the image generation unit 44 decimates the image data in the Y-axis direction (time-axis direction), thereby reducing the resolution in the Y-axis direction and reducing the data capacity of the image data (Step S1). S105).

  Further, the resolution in the X-axis direction of the image data generated in step S104 depends on the distance between the transducers 24. When the distance between the transducers 24 is long, the resolution in the X-axis direction is low, so that the image may be difficult to see. In such a case, the image generation unit 44 performs a pixel interpolation process in the X direction and the like to increase the resolution in the X axis direction (step S106).

  The echo image based on the reflected wave received by the transducer 24 can be generated by the image generation process of steps S103 to S106 described above. The echo image generated in this way is exemplified in FIG.

  As described above, when an echo image is generated by the image generation unit 44, it is assumed that the reflected wave returns from the Y-axis direction. However, when the surface of the bone 10 is curved, the reflected wave reflected by the surface can arrive at the vibrator 24 from a direction other than the Y-axis direction. When a reflected wave from a direction other than the Y-axis direction is received, the above assumption is not correct, so the generated echo image does not correctly represent the shape of the bone surface (that is, Fake image).

Here, the case where the bone surface is curved will be described with reference to FIG. In FIG. 7, after a plane wave is transmitted from the transducer array 22, the reflected wave generated at the reflection position Q ₁ on the bone surface arrives at the transducer 24 ₁ from an oblique direction with respect to the Y-axis direction. Show. Thus, when a reflected wave arrives from an oblique direction, a false image is generated in the echo image. The position where the false image appears on the echo image is referred to as a virtual reflection position (false image appearance position) P ₁ .

The echo image (false image) that appears at the virtual reflection position P ₁ in the echo image should be displayed at the reflection position Q ₁ (position on the bone surface) where the reflected wave is actually generated. It can be said that. Therefore, it is considered that the echo image can be corrected so as to accurately represent the shape of the bone 10 by moving the echo image that appears at the virtual reflection position P ₁ of the echo image to the reflection position Q ₁ .

  The ultrasonic diagnostic apparatus 1 of the present embodiment is configured to move a false image that appears in an echo image to a correct position based on the above viewpoint.

First, as shown in FIG. 8A, the ultrasonic diagnostic apparatus 1 sets a plurality of control points at positions (virtual reflection positions) P ₁ , P ₂ ... Where false images are generated in the echo image. Subsequently, the echo image is deformed, and each control point is moved to the corresponding reflection position Q ₁ , Q ₂ ... (FIG. 8B). Thereby, the echo image in which the false image is generated can be corrected to match the actual shape of the bone 10. The virtual reflection position P _n and the reflection position Q _n can be set for each transducer 24 _n that has received the reflected wave from the bone 10.

Since the reflection positions Q ₁ , Q ₂ ... Are points on the surface of the actual bone 10, information on the correct surface shape of the bone 10 is necessary to set the reflection positions Q ₁ , Q ₂ . Therefore, the ultrasonic image processing program of the present embodiment is configured to cause the calculation unit 35 to realize a shape detection function for detecting the surface shape of the bone 10 based on the reception signal received by each transducer 24. Accordingly, it can be said that the calculation unit 35 is the shape detection unit 40.

  The shape detection unit 40 detects the surface shape of the bone 10 based on the received signal of each transducer 24 acquired in step S102 (step S107, shape detection step). Methods for detecting the shape of the bone 10 are described in Patent Documents 1 to 3, but will be briefly described below.

First, the shape detection unit 40 identifies two adjacent transducers among the plurality of transducers 24 as the transducer pair 25. Here, as shown in FIG. 9, it is assumed that the reflected wave has arrived from the direction having an angle of θ _{a with} respect to the Y axis with respect to the vibrator pair 25 including the vibrator 24 _n and the vibrator 24 _{n + 1.} To do. Assuming that the interval (distance in the X-axis direction) between the two transducers 24 _n and 24 _{n + 1} is W, as will be apparent from FIG. 9B, it arrives at one transducer 24 _n of the transducer pair 25. reflected wave will be received propagates only long distance Wsinshita _a than the other of the vibrator 24 n _{+ 1.} For this reason, the two vibrators have
Δt = Wsinθ _a / SOS _soft
The reflected wave is received with a time difference only. Note that SOS _soft is the speed of sound in the soft tissue 11.

Based on the time difference Δt at which the two transducers 24 _n and 24 _{n + 1} of the transducer pair 25 receive the reflected wave, the shape detection unit 40 obtains the arrival angle θ _a of the reflected wave with respect to the transducer pair 25. That is, the arrival angle θ _a is
θ _a = arc sin (SOS _soft Δt / W)
Can be obtained. In the present embodiment, an empirical value is used for the sound speed SOS _soft in the soft tissue 11. However, the present invention is not limited to this, and an actual measurement value of sound velocity in the soft tissue 11 may be used.

Based on the arrival angle θ _a of the reflected wave received by the transducer pair 25 and the arrival time T _a required for the reflected wave to reach the transducer pair 25 after the plane wave is transmitted, the shape detection unit 40 detecting the reflection point R _a of the reflected wave arriving at each transducer pair 25. Incidentally, the arrival time T _a from being transmitting the plane wave by the transducer array 22, two constituting the vibrator pair 25 of the vibrator 24 _n, 24 _n + ₁ time to the reflected waves in each reach The average value may be used. The distance in the X-axis direction from the vibrator pair 25 to the reflection point R _a put L _x, the distance in the Y-axis direction L _Y. As is clear from FIG. 9A, the propagation distance L of the reflected wave is
L = L _Y + L _Y / cosθ _a
It becomes. On the other hand, the use of sound velocity SOS _soft in arrival time T _a and the soft tissue 11,
L = SOS _soft × T _a
Therefore, the position of the reflection point Ra is
L _Y = SOS _soft × T _a × cos θ _a / (1 + cos θ _a )
L _X = L _Y × tan θ _a = SOS _soft × T _a × sin θ _a / (1 + cos θ _a )
Can be obtained. As described above, the shape detection unit 40 can calculate the position of the reflection point R _a based on the plane wave arrival angle θ _a and the arrival time T _a .

Shape detecting unit 40, for all of the transducers 24 constituting the transducer array 22, constitute a vibrator pair, obtaining the same reflecting point R _a for each transducer pair. And the shape detection part 40 detects a bone surface line by connecting the reflection point calculated | required as mentioned above with a straight line or a curve. As described above, the surface shape (bone surface line) of the bone 10 can be obtained by the shape detection unit 40.

  Next, an operation for setting a control point on an echo image will be described. The ultrasound image processing program of the present embodiment is configured to cause the calculation unit 35 to realize a control point setting function for setting a control point at the virtual reflection position. Therefore, it can be said that the calculation unit 35 is a control point setting unit 45.

The control point setting unit 45 is a position (virtual reflection position P) where each of the transducers 24 ₁ , 24 ₂ ... Receives a reflected wave from the bone 10 and a false image is generated on the echo image. ₁ , P ₂ ... The X coordinate of the position where the false image is generated in the echo image (virtual reflection position P _n ) can be obtained for each transducer 24 as follows.
(X coordinate of point P _n ) = (X coordinate of transducer 24 _n )
Since the position of each transducer is known, the X coordinate of the point P _n can be obtained immediately.

The position in the Y-axis direction of the position where the false image is generated on the echo image (virtual reflection position P _n ) is that a reflected wave is received by a certain transducer 24 _n after a plane wave is transmitted from the transducer array 22. It can be calculated on the basis of the time t _n required to complete.

First, the control point setting unit 45 detects the time t _n based on the waveform of the received signal received by each transducer 24 _n . In addition, since the reflected wave from the surface of the bone 10 is received with a certain time width, there is a problem as to when the reflected wave is received. In the present embodiment, the control point setting unit 45 assumes that the reflected wave is received by the transducer 24 _n when the envelope of the received signal received by the transducer 24 _n reaches the maximum. That is, as shown in FIG. 4A, the control point setting unit 45 detects a point where the envelope of the received signal of the transducer 24 _n is maximized. Then, the control point setting unit 45 detects the time taken from when the plane wave is transmitted until the envelope of the received signal becomes maximum as t _n .

Subsequently, the control point setting unit 45 calculates the Y coordinate of the virtual reflection position P _n based on t _n obtained as described above. That is, the distance that the ultrasonic wave propagates through the soft tissue 11 during the time t _n is t _n × SOS _soft . Assuming that the reflected wave arrives from the Y-axis direction, it is assumed that the distance that the plane wave travels from the transducer array 22 to the bone surface is the same as the distance that the reflected wave returns from the bone surface to the transducer 24 _n. Therefore, the distance between the virtual reflection position P _{n of the} ultrasonic signal and the transducer 24 _n in this case can be expressed as follows.
(Distance between vibrator 24 _n and point P _{n in} the Y-axis direction) = t _n × SOS _soft ÷ 2

Then, the control point setting unit sets a control point at each of the virtual reflection positions P ₁ , P ₂ ... (Position where the false image is generated) on the echo image (step S108, control point setting step). Thereby, a plurality of control points are set on the echo image (false image) of the surface of the bone 10 appearing in the echo image.

  Further, the ultrasound image processing program of the present embodiment is configured to cause the calculation unit 35 to realize a movement target position setting function for setting a movement target position of each control point. Therefore, it can be said that the calculation unit 35 is the movement target position setting unit 46.

The movement target position setting unit 46 obtains the true reflection positions Q ₁ , Q ₂ ... Of the reflected waves arriving at the transducers 24 ₁ , 24 ₂ .

First, the movement target position setting unit 46 calculates the propagation path of the reflected wave arriving at each transducer 24 ₁ , 24 ₂ ... Based on the bone surface line detected by the shape detection unit 40. Since the position of each transducer is known, the propagation path can be easily calculated based on the inclination of the bone surface line. Subsequently, the movement target position setting unit 46 obtains the true reflection positions Q ₁ , Q ₂ ... Of the reflected waves arriving at the transducers 24 ₁ , 24 ₂ . Then, the movement target position setting unit 46 sets the movement target position of the control point at the reflection positions Q ₁ , Q ₂ ... On the echo image (step S109, movement target position setting step).

In the present embodiment, the control point setting unit 45 is configured to set control points at the positions of the transducers 24 ₁ , 24 ₂ . The control points set at the positions of the vibrators 24 ₁ , 24 ₂ ... Are C ₁ , C ₂ . Since the positions of the vibrators 24 ₁ , 24 ₂ ... Are fixed, it is preferable not to move the control points C ₁ , C ₂ . Therefore, the movement target position setting unit 46 sets the movement target position of the control points C ₁ , C ₂ ... To the position of the control point itself. As a result, the control points C ₁ , C ₂ ... Set at the positions of the vibrators 24 ₁ , 24 ₂ .

  The ultrasound image processing program of the present embodiment is configured to cause the computing unit 35 to realize a deformation function calculation function for obtaining a deformation function for deforming an echo image. Therefore, it can be said that the calculation unit 35 is a deformation function calculation unit 47.

This deformation function is a function that, when given the XY coordinates of an arbitrary point v on the echo image, outputs the XY coordinates of the point v ′ after the image deformation. That is, when the deformation function is f, the position v ′ after deformation of the point v is
v ′ = f (v)
Can be obtained. The deformation function f may be any function, but is preferably a function that can smoothly deform an image. For example, the deformation function f can be a known affine transformation. In this case, the deformation function f is
f (v) = Mv + T
Can be expressed as Note that M is a linear deformation matrix and T is a translation vector.

Here, the plurality of control points set by the control point setting unit 45 will be referred to as control points p ₁ , p ₂ . Further, the movement target position corresponding to each control point p _1, p ₂ ..., denoted again q _1, q ₂ ... and. The deformation function calculation unit 47 of the present embodiment uses a least square method to generate a deformation function f that deforms an image so that the control points p ₁ , p ₂ ... Are moved to corresponding target positions q ₁ , q ₂ . Ask. For example, when the deformation function f is affine transformation, the deformation function calculation unit 47 obtains the linear deformation matrix M and the translation vector T by the least square method. More specifically, the deformation function calculation unit 47 obtains a deformation function f that minimizes the value of Equation 1 below.

Here, w _i is a weighting coefficient and is defined by the following Equation 2. Α is a parameter for adjusting the effectiveness of the weighting coefficient.

As can be seen from Equation 2, the weighting coefficient w _i is defined so that the weight increases as the distance between the point v and the control point p _i decreases. In other words, the deformation function f is determined so as to be easily influenced by the control points at the close positions and not so much affected by the control points at the distant positions. Thereby, the whole echo image can be smoothly deformed using a small number of control points p ₁ , p ₂ .

Since the definition of the weighting coefficient w _i includes the distance between the point v and the control point p _i , the deformation function f needs to be obtained for each point v. Therefore, the deformation function calculation unit 47 calculates the deformation function f for each point on the echo image (step S110, deformation function calculation step).

  The ultrasonic image processing program of the present embodiment is configured to cause the computing unit 35 to realize an image deformation function for deforming an echo image based on the deformation function. Therefore, it can be said that the calculation unit 35 is the image deformation unit 48.

  The image deformation unit 48 applies the deformation function calculated by the deformation function calculation unit 47 to the echo image generated by the image generation unit 44 to generate a deformed echo image (step S111, image deformation process). Thereby, the echo image can be deformed so as to move the set control point to the movement target position. Therefore, an echo image (deformed echo image) obtained by deforming the echo image (false image) of the bone 10 that appeared in the original echo image so as to match the actual bone surface line can be obtained.

Note that the method for obtaining the image deformation function by the least square method as described above is described in detail in, for example, the following non-patent documents.
Scott Schaefer, Travis McPhail, Joe Warren. 2006. 'Image Deformation Using Moving Least Squares'. [Online]. [Retrieved on 2011-10-30]. Internet: <URL: http: //faculty.cs.tamu.edu /schaefer/research/mls.pdf>.

  The deformed echo image generated by the image deformation unit 48 is output to the display unit 32. As a result, an echo image accurately representing the shape and size of the bone 10 can be displayed on the display unit 32.

  An example of the deformed echo image generated by the image deforming unit 48 is shown in FIG. The deformed echo image of FIG. 10 is generated by deforming the echo image of FIG. For comparison, a white curve indicating the actual bone shape is displayed by superimposing the deformed echo image of FIG. Further, in order to help understanding of FIG. 10, the contents of FIG. 10 are schematically shown in FIG. As can be seen from FIG. 10, the echo image of the bone 10 can be made to match the actual shape of the bone surface by deforming the echo image by the image deforming unit 48. Thereby, the operator of the ultrasonic diagnostic apparatus 1 can correctly recognize the shape and size of the bone 10 on the deformed echo image.

  In addition, since the above-described method is to obtain a deformed echo image by deforming the echo image itself, if an echo image of a blood vessel or an organ in the soft tissue 11 is included in the original echo image, these soft tissue 11 can also be confirmed by the transformed echo image. Thereby, since the echo image of the blood vessel and organ in the soft tissue 11 can be displayed together with the accurate echo image of the bone 10, the state of the soft tissue 11 around the bone 10 can be accurately determined.

  As described above, the ultrasonic diagnostic apparatus 1 according to the present embodiment includes the transducer array 22, the image generation unit 44, the shape detection unit 40, the deformation function calculation unit 47, and the image deformation unit 48. I have. The transducer array 22 includes a plurality of transducers 24 that transmit ultrasonic transmission waves to the bone 10 and receive reflected waves from the bone 10. The image generation unit 44 generates an echo image obtained by connecting the reception signals received by the transducers 24. The shape detection unit 40 detects the shape of the bone 10 based on the reception signal received by each transducer 24. The deformation function calculation unit 47 obtains a deformation function f that deforms the echo image so that the shape of the bone 10 detected by the shape detection unit 40 matches the shape of the echo image of the bone 10 included in the echo image. . The image deformation unit 48 generates a deformed echo image obtained by deforming the echo image based on the deformation function f.

  Thus, by detecting the shape of the bone 10 and deforming the echo image according to the detected shape, an echo image (deformed echo image) that accurately represents the actual shape and size of the bone 10 can be obtained. it can.

  Next, a modification of the above embodiment will be described.

  As described above, the ultrasonic diagnostic apparatus 1 of the present invention can generate a deformed echo image that accurately indicates the shape and size of the echo image of the bone 10. Therefore, when the deformed echo image is displayed on the display unit 32, various information related to the shape of the bone 10 may be added and displayed. This makes it possible to display the information accurately.

  For example, when measuring the bone sound speed, information regarding the propagation path of the surface refracted wave may be displayed superimposed on the transformed echo image. The surface refracted wave is an ultrasonic signal that travels through the inside of the bone and then is emitted again into the soft tissue and received by the vibrator 24. Based on this surface refracted wave, the speed of sound (bone speed of sound) in the bone 10 can be obtained. In addition, since the structure which calculates | requires the sound speed in the bone 10 based on a surface refraction wave is described in patent documents 1 to 3, for example, detailed description is abbreviate | omitted here.

  For example, in the example shown in FIG. 12, the propagation path of the surface refracted wave is displayed with a dotted line superimposed on the transformed echo image. To help understanding of FIG. 12, the contents of FIG. 12 are schematically shown in FIG.

  As shown in FIG. 12, the propagation path of the surface refracted wave is superimposed on the echo image of the bone so that the echo speed of the bone sonic wave derived using the surface refracted wave following the propagation path is echoed. It can be confirmed on the image. Since the deformed echo image obtained by the configuration of the present invention accurately represents the shape of the bone, the surface refraction wave propagation path is displayed by superimposing the surface refraction wave propagation path on the deformed echo image. Can be evaluated accurately.

  Since the deformed echo image obtained by the configuration of the present invention includes echo images of blood vessels around the bone, for example, whether a blood vessel or the like exists in the middle of the propagation path of the surface refracted wave. I can judge. When a blood vessel or the like exists in the propagation path of the surface refracted wave, the operator adjusts the position of the ultrasonic transducer 2 so as to avoid the blood vessel or the like while checking the deformed echo image of FIG. Thus, the bone sound velocity can be measured again. Thereby, a bone sound speed can be measured appropriately.

  The preferred embodiment of the present invention has been described above, but the above configuration can be modified as follows, for example.

  The configuration of the present invention is not limited to an ultrasonic diagnostic apparatus for displaying an echo image of a bone. For example, an ultrasonic geological survey apparatus that surveys a geological formation or an underground structure using ultrasonic waves is used for other than bones. The present invention can be widely used in devices that are measured objects.

  In the above-described embodiment, when the control point setting unit 45 calculates the virtual reflection position, the time when the envelope of the reception signal is maximized is the reception time of the reflected wave. However, the present invention is not limited to this. For example, the time when the envelope of the received signal starts to rise can be handled as the time when the reflected wave is received by the transducer 24.

In the above embodiment, the control points are set corresponding to the respective transducers 24 ₁ , 24 ₂ ..., But unless the control points are set corresponding to all the transducers included in the transducer array 22. It does not mean that a plurality of control points can be set on the echo image of the bone 10.

In the above embodiment, the control points C ₁ , C ₂ ... Are set at the positions of the vibrators 24 ₁ , 24 ₂ ... So that the control points C ₁ , C ₂ . Instead of this, or in addition to this, a control point that does not move can be set at another location. The control point that does not move may be set at a position on the echo image where it is known in advance that no false image appears. According to this, it is possible to prevent the originally correct echo image from being distorted by the deformation function. For example, when the inclination of a blood vessel in a soft tissue (a target other than the bone surface) is zero (when the blood vessel is orthogonal to the plane wave transmission direction), the echo generated in the blood vessel is not a false image. . Therefore, it is preferable to detect a position where the inclination of the echo image of a target (such as a blood vessel) other than the bone surface is zero and set a control point that does not move to that position.

For example, as shown in FIG. 14, the control point C ₁ which is set to the position of the transducer 24 _1, the control point P ₁ set on the echo image corresponding to the transducers 24 _1, between The control point setting unit may automatically set the interpolation control points D ₁ , D ₂ . Movement target position of the interpolation control point, for example, can be set as the movement target position to Q ₁ control point P _1, on a straight line connecting the control points C _1, a. This interpolation control point can be set similarly for the other transducers 24. Thus, by setting the interpolation control points for interpolating between the control points, the echo image can be deformed with higher accuracy.

  In the flowchart of FIG. 3, the image generation process (steps S <b> 103 to S <b> 106) by the image generation unit and the processing from the detection of the bone shape to the calculation of the deformation function (steps S <b> 107 to S <b> 110) are performed in parallel. Although shown, it is not limited to this, and may be performed sequentially. In short, it is sufficient that the calculation of the deformation function and the generation of the echo image are completed before the deformation of the echo image is performed in the image deformation process of step S111.

  The number of vibrators 24 shown in the figure can be changed as appropriate.

  In the above embodiment, each function of the ultrasonic image processing apparatus is realized by executing the ultrasonic image processing program by the calculation unit 35. However, the present invention is not limited to this, and a part or all of the functions of the ultrasonic image processing apparatus may be realized by dedicated hardware.

  The process shown in the flowchart of FIG. 3 may be automatically and repeatedly executed. In this case, the deformed echo image displayed on the display unit 32 is updated as needed, so that the operator can confirm an accurate echo image of the bone 10 in real time.

1 Ultrasonic diagnostic equipment (ultrasonic image processing equipment)
2 transducer 22 transducer array 24 transducer 35 arithmetic unit (computer)
40 shape detection unit 44 image generation unit 45 control point setting unit 46 movement target position setting unit 47 deformation function calculation unit 48 image deformation unit

Claims (6)

A transducer array including a plurality of transducers arranged to transmit a transmission wave of an ultrasonic wave to the measurement target and receive a reflected wave from the measurement target;
An image generation unit that generates an echo image obtained by connecting the reception signals received by the transducers and the reflected wave;
Based on the received signal received by each transducer, a shape detection unit for detecting the shape of the measurement object, the shape of the measurement object detected by the shape detection unit, and the measurement object included in the echo image A deformation function calculation unit for obtaining a deformation function for deforming the echo image so as to match the shape of the echo image of
An image deformation unit that generates a deformed echo image obtained by deforming the echo image based on the deformation function;
An ultrasonic image processing apparatus comprising: The ultrasonic image processing apparatus according to claim 1,
When it is assumed that the reflected wave has arrived from the direction in which the transmitted wave is transmitted, a control point setting unit that sets a control point at a virtual reflection position where the reflected wave is considered to be reflected by the surface of the measurement object; ,
A propagation path of a reflected wave received by the vibrator from the measured object is calculated based on a shape of the measured object detected by the shape detecting unit, and the reflected wave is reflected on a surface of the measured object. A movement target position setting unit for setting a movement target position of the control point at a reflection position;
With
The ultrasonic image processing apparatus, wherein the deformation function calculation unit calculates a deformation function for deforming the echo image so as to move the control point to the movement target position. The ultrasonic image processing apparatus according to claim 2,
The control point setting unit sets a control point at the position of the vibrator,
The ultrasonic image processing apparatus, wherein the deformation function calculation unit calculates a deformation function for deforming the echo image so that a control point at the position of the transducer does not move. The ultrasonic image processing apparatus according to claim 2, wherein
The ultrasonic image processing apparatus, wherein the deformation function calculation unit calculates a deformation function for an arbitrary point on the echo image by a least square method weighted by a distance from the point to each control point. . A reception signal acquisition function for transmitting a transmission wave of an ultrasonic wave to a measurement object and receiving a reflected wave from the measurement object and acquiring a reception signal by a transducer array including a plurality of transducers arranged side by side; ,
An image generation function for generating an echo image obtained by connecting the reception signals received by the transducers with the reflected wave;
Based on the received signal received by each transducer, a shape detection function for detecting the shape of the measurement object, a shape of the measurement object detected by the shape detection function, and the measurement object included in the echo image A deformation function calculation function for obtaining a deformation function for deforming the echo image so as to match the shape of the echo image of
An image deformation function for generating a deformed echo image obtained by deforming the echo image based on the deformation function;
An ultrasonic image processing program characterized in that a computer is realized. A reception signal acquisition step of transmitting an ultrasonic transmission wave to the object to be measured and receiving a reflected wave from the object to be measured and acquiring a reception signal by the vibrator array including a plurality of vibrators arranged side by side; ,
An image generation step of generating an echo image obtained by connecting the reception signals received by the respective reflected waves by the transducers;
Based on the received signal received by each transducer, a shape detecting step for detecting the shape of the measured object, the shape of the measured object detected in the shape detecting step, and the measured object included in the echo image A deformation function calculating step for obtaining a deformation function for deforming the echo image so as to match the shape of the echo image of
An image deformation step of generating a deformed echo image obtained by deforming the echo image based on the deformation function;
An ultrasonic image processing method comprising: