JP6809950B2 - Ultrasonic image processing equipment - Google Patents

Description

The present invention relates to an ultrasonic image processing apparatus.

An ultrasonic diagnostic apparatus is a typical example of an ultrasonic image processing apparatus that forms an ultrasonic image based on data obtained by transmitting and receiving ultrasonic waves. As the ultrasonic image, a two-dimensional image such as a B-mode image or a color Doppler image is well known. Further, there is also known a device for forming an ultrasonic image (three-dimensional ultrasonic image) that three-dimensionally projects a tissue or a foetation in a living body. For example, based on the volume data obtained three-dimensionally by transmitting and receiving ultrasonic waves, a rendering process is executed for each line of sight (ray) of a plurality of lines of sight to create an ultrasonic image that three-dimensionally projects the diagnosis target. The technique of forming is known.

For example, Patent Document 1 describes a technique for forming a three-dimensional image by performing volume rendering on voxel data on each line of sight (ray). In particular, Patent Document 1 discloses a technique for performing smoothing processing on voxel data on each line of sight (ray), and as a specific example of the smoothing processing, voxel data on each line of sight (light). A specific example of applying a finite impulse response filter (FIR filter) to the above is described (see paragraph 0048 of Patent Document 1).

Japanese Unexamined Patent Publication No. 2006-51202

According to the technique described in Patent Document 1, image noise centered on high-frequency components can be reduced. However, if the degree of smoothing processing is too strong, the image will be blurred as a whole, and for example, the diagnosis target may be enlarged to be larger than it should be and imaged.

Further, for example, when the diagnosis target is a foetation, the image of the foetation may be obstructed by the influence of a shield such as a floating substance in the placenta or amniotic fluid. It is expected to realize a smoothing treatment that works well on shields such as placenta and suspended matter.

An object of the present invention is to provide an improved technique for smoothing processing suitable for ultrasonic rendering processing.

An ultrasonic image processing apparatus suitable as an aspect of the present invention includes a rendering processing means that executes rendering processing for each line of sight of a plurality of lines of sight based on ultrasonic volume data, and an infinite number of data on each line of sight. By applying the impulse response filter, a smoothing processing means that executes a smoothing process for each line of sight of the plurality of lines of sight, and a smoothing processing means obtained by the rendering process and the smoothing process for each line of sight of the plurality of lines of sight. It is characterized by having an image forming means for forming an ultrasonic image based on a pixel value.

According to the above configuration, as a smoothing process suitable for ultrasonic rendering processing, a smoothing process in which an infinite impulse response (IIR) filter is applied to data on each line of sight is realized.

For example, the smoothing processing means initializes the data input at the start of the filter processing to the initial value corresponding to the minimum brightness in the filter processing in which the data arranged on each line of sight is input to the infinite impulse response filter one after another. It is desirable to do. For example, if the minimum brightness is the brightness value 0 (zero), the brightness value 0 is set as the initial value. The initial value may be a low luminance value that can be regarded as substantially 0 (zero). In an infinite impulse response filter, the influence of the initial value lasts for a long time (theoretically, it continues infinitely), so the initialization is performed by initializing the data input at the start of the filtering process to the initial value corresponding to the minimum brightness. The impact can be reflected in the filtering of subsequent data. Thereby, for example, the shield on the front side (viewpoint side) of the diagnosis target on each line of sight can be reduced by the smoothing process, and preferably the shield can be substantially removed.

For example, it is desirable that the rendering processing means execute the rendering process for each line of sight using the data after the smoothing process and the opacity corresponding to the data after the smoothing process. With this configuration, a rendering process that reflects the result of the smoothing process in both the data (for example, voxel data on each line of sight) and the opacity (opacity) is realized.

For example, it is desirable that the rendering processing means execute the rendering process for each line of sight using the data before the smoothing process and the opacity corresponding to the data after the smoothing process. With this configuration, the rendering process using the data before and after the smoothing process is realized.

Further, the functions corresponding to each part of the above-mentioned suitable ultrasonic image processing apparatus (including desirable specific examples) may be realized by a computer (including a tablet type terminal). For example, the computer functions as the above-mentioned suitable ultrasonic image processing apparatus by a program that realizes the function as the rendering processing means, the function as the smoothing processing means, and the function as the image forming means on the computer. be able to. The program may be stored in a computer-readable storage medium such as a disk or memory and provided to the computer via the storage medium, or may be provided to the computer via a telecommunication line such as the Internet. May be provided.

The present invention provides an improved technique for smoothing processing suitable for ultrasonic rendering processing. For example, according to a preferred embodiment of the present invention, as a smoothing process suitable for ultrasonic rendering processing, a smoothing process in which an infinite impulse response filter is applied to data on each line of sight is realized.

It is an overall block diagram of the ultrasonic diagnostic apparatus which is a preferable specific example of this invention. It is a figure which shows the specific example of a rendering process. It is explanatory drawing of the rendering process on each line of sight. It is a figure which shows the specific example of the rendering process and the smoothing process on each line of sight. It is a figure which shows the specific example of the data which was smoothed by the IIR filter. It is a figure which shows the specific example of the initialization in the smoothing process by an IIR filter.

FIG. 1 is an overall configuration diagram of an ultrasonic diagnostic apparatus which is a preferable specific example of the ultrasonic image processing apparatus according to the present invention. The probe 10 is an ultrasonic probe for a three-dimensional image, and transmits and receives ultrasonic waves in a three-dimensional space including a diagnostic object such as a foetation. For example, a two-dimensional array probe (matrix array probe) having a plurality of two-dimensionally arranged vibrating elements, a mechanical probe for mechanically moving a plurality of one-dimensionally arranged vibrating elements, and the like are suitable for the probe 10. This is a concrete example.

The transmission / reception unit 12 has functions as a transmission beam former and a reception beam former. That is, the transmission / reception unit 12 forms a transmission beam by outputting a transmission signal to each of the plurality of vibration elements included in the probe 10, and further, for a plurality of received signals obtained from the plurality of vibration elements. The received beam is formed by performing phasing addition processing or the like.

Further, the transmission / reception unit 12 three-dimensionally scans an ultrasonic beam (transmission beam and reception beam) in, for example, a three-dimensional space including a diagnosis target. As a result, the received ultrasonic wave data is collected from within the three-dimensional space including the diagnosis target.

The volume configuration unit 20 forms volume data corresponding to the three-dimensional space by performing reconstruction processing on the received data obtained from the three-dimensional space. The volume configuration unit 20 performs reconstruction processing such as coordinate conversion processing and interpolation processing on the received data obtained in the scanning coordinate system (for example, rθφ coordinate system), and corresponds to the orthogonal coordinate system (for example, xyz coordinate system). Form the volume data. Volume data is composed of a plurality of voxel data arranged three-dimensionally in, for example, a data space of a Cartesian coordinate system.

The rendering processing unit 30 executes a rendering process (voxel calculation) based on a plurality of voxel data constituting the volume data.

FIG. 2 is a diagram showing a specific example of the rendering process. In the rendering process (rendering operation), a virtual viewpoint in calculation is set outside the volume data 32 corresponding to the three-dimensional space, and a plurality of lines of sight (rays) 34 are provided to the volume data 32 from the viewpoint side. Set. Further, an arithmetic screen 36 that functions as an image plane is set. Although the screen 36 is shown on the opposite side of the viewpoint with the volume data 32 in between in FIG. 2, the screen 36 may be arranged on the viewpoint side of the volume data 32.

In the rendering process, for each line of sight 34 of the plurality of line of sight (rays) 34 set for the volume data 32, a plurality of voxel data corresponding to the line of sight 34 is processed. For example, from a plurality of voxel data constituting the volume data 32, a plurality of voxel data corresponding to each line of sight 34 (arranged on each line of sight) can be obtained by interpolation processing or the like. Then, the rendering process is executed on each line of sight 34.

FIG. 3 is an explanatory diagram of the rendering process on each line of sight. In FIG. 3, one line of sight 34, which is a typical example of the plurality of line of sight 34, is shown, and a plurality of voxels arranged on the line of sight 34 are shown.

In the rendering process, for each line of sight 34, voxel operations based on the rendering method using opacity (opacity) are sequentially performed on a plurality of voxel data (voxel brightness information) corresponding to the line of sight 34 from the viewpoint side. Is executed. Then, as a result of the final voxel calculation for each line of sight 34, the luminance information corresponding to the line of sight 34 is determined.

Further, a plurality of data (voxel data) arranged on each line of sight 34 are subjected to smoothing processing. In the smoothing process, an Infinite Impulse Response (IIR) filter is applied.

Returning to FIG. 1, the smoothing processing unit 40 executes smoothing processing for each line of sight of a plurality of lines of sight by applying an infinite impulse response filter to the data on each line of sight. Then, by the rendering process executed by the rendering processing unit 30 and the smoothing process executed by the smoothing processing unit 40, the brightness information obtained for each line of sight from a plurality of lines of sight is used as the pixel value of each pixel to obtain a screen. Pixel values of a plurality of pixels in (image surface) can be obtained. As a result, projected image data of luminance information with the screen as the projection surface is formed.

FIG. 4 is a flowchart showing a specific example of the rendering process and the smoothing process on each line of sight. First, data is sampled on each line of sight (S1). For example, a plurality of voxel data arranged on each line of sight are sampled in order from the viewpoint side. All voxel data on each line of sight may be sampled, or voxel data may be sampled discretely at a data interval defined by, for example, a sampling interval (rendering pitch).

Next, the smoothing process is executed by applying an infinite impulse response filter (IIR filter) to the sampled data (S2). An arithmetic expression that is a preferable specific example of the infinite impulse response filter is the equation (1).

[Number 1] V _n ′ = α × V _n + (1-α) V _n-1 ′

In the equation 1, V _n is the nth (n is a natural number) sampling data (boxel data sampled in S1), and V _n ′ is after the smoothing process of the nth sampling data (after applying the IIR filter). V _n-1 ′ is the data after the smoothing process of the (n-1) th sampling data. And α is the time constant of the infinite impulse response filter (IIR filter). The data V _n ′ after the smoothing process is temporarily held in, for example, a memory (S3).

Next, the opacity O [V _n ′] corresponding to the data V _n ′ after the smoothing process is acquired (S4). For example, from the capacity curve (function of opacity) that defines the correspondence between the boxel data (luminance value) and the opacity (opacity), the capacity O [V _n ′] corresponding to the data V _n ′ after the smoothing process. Is derived.

Then, the rendering process is executed using the data V _n ′ after the smoothing process and the opacity O [V _n ′] (S5). As the rendering process, a known specific example (any of various arithmetic expressions) is used.

The rendering process on each line of sight is sequentially executed until the end condition is satisfied (S6). When the end condition is satisfied, for example, when "the opacity integrated value is saturated" or "the final voxel ends", the processing on the line of sight ends. Then, the rendering processing result (luminance information of each line of sight) at the end time is set as the pixel value of each pixel in the screen (image plane).

The process shown in the flowchart of FIG. 4 is a specific example of the rendering process and the smoothing process on each line of sight, and the rendering process and the smoothing process shown in FIG. 4 are executed for each line of sight of the plurality of lines of sight.

Although FIG. 4 shows a specific example of performing the rendering process and the smoothing process in parallel on each line of sight, the rendering process on the line of sight is executed after the smoothing process of all the sampling data on each line of sight. You may.

Further, in the embodiment of FIG. 4, and perform the rendering processing using _'and its smoothing data V _{n after'} data V _n after smoothing processing opacity O corresponding to [V n _'] (See S5 in FIG. 4). As a modification of this specific example, for example, even if the rendering process is executed using the data V _n before the smoothing process and the opacity O [V _n ′] corresponding to the data V _n ′ after the smoothing process. Good.

FIG. 5 is a diagram showing a specific example of data smoothed by an IIR filter (infinite impulse response filter). FIG. 5 (1) shows voxel data on each line of sight before the smoothing process, and FIG. 5 (2) shows voxel data on each line of sight after the smoothing process by the IIR filter. In FIG. 5, the horizontal axis represents the line-of-sight direction of each line of sight (the viewpoint is on the left side), and the vertical axis represents the voxel data value (voxel value).

FIG. 5 shows a specific example when a foetation is used as a diagnosis target, and FIG. 5 shows a mass of voxel data corresponding to the foetation and a mass of voxel data corresponding to a floating substance on the viewpoint side of the foetation. Has been done.

Before the smoothing process of FIG. 5 (1), the voxel data corresponding to the floating matter has a relatively large voxel value, and if the rendering process is executed as it is, the voxel data corresponding to the floating matter has a strong influence on the rendering process. For example, in the three-dimensional ultrasonic image obtained as a result of the rendering process, floating matter may block the fetus.

On the other hand, after the smoothing process of FIG. 5 (2), the voxel data corresponding to the suspended matter is smoothed to a relatively small voxel value. As a result, the influence of the voxel data corresponding to the floating matter on the rendering process is reduced. For example, the imaging of the floating matter is suppressed in the three-dimensional ultrasonic image obtained as a result of the rendering process, and the image of the foetation becomes clear. It is projected on.

Further, comparing before and after the smoothing treatment, the steep rise of the fetal image is suppressed after the smoothing treatment. In addition, a steep fall is also suppressed. As a result, for example, even if the data on the fetal surface is rough (there is a sharp change) before the smoothing treatment, the smoothing treatment applying the IIR filter can obtain a continuous and visually natural image of the fetal surface. it can.

In the filter processing in which the data lined up on each line of sight is input to the IIR filter (infinite impulse response filter) one after another, the smoothing processing unit 40 of FIG. 1 initially inputs the data input at the start of the filter processing to correspond to the minimum brightness. It is desirable to initialize it to a value.

FIG. 6 is a diagram showing a specific example of initialization in the smoothing process by the IIR filter. FIG. 6 (1) shows voxel data on each line of sight before the smoothing process. 6 (2) and (3) show voxel data on each line of sight after smoothing by the IIR filter, FIG. 6 (2) shows the case without initialization, and FIG. 6 (3) shows with initialization. It corresponds to the case of. In FIG. 6, the horizontal axis represents the line-of-sight direction of each line of sight (the viewpoint is on the left side), and the vertical axis represents the voxel data value (voxel value).

FIG. 6 is a specific example when a foetation is used as a diagnosis target. FIG. 6 shows a mass of voxel data corresponding to the foetation in contact with the placenta, and the foetation is in contact with the placenta located on the viewpoint side. In the specific example of FIG. 6, the data portion corresponding to the placenta is excluded from the processing, and the rendering processing and smoothing are performed on the voxel data corresponding to the foetation from the calculation start position S corresponding to the boundary between the placenta and the foetation. The conversion process is started.

Before the smoothing process of FIG. 6 (1), the voxel data corresponding to the foetation has a relatively large voxel value immediately after the calculation start position S. Then, the voxel data corresponding to the foets lined up on each line of sight from the calculation start position S are input to the IIR filter one after another, and the IIR filter is applied. The result obtained by applying the voxel data of FIG. 6 (1) to the IIR filter without performing initialization is the voxel data after the smoothing process shown in FIG. 6 (2).

On the other hand, the voxel data shown in FIG. 6 (3) is a specific example of the case where the data input at the start of the filter processing is initialized to the initial value corresponding to the minimum luminance. In FIG. 6 (3), in the filter processing in which the box cell data corresponding to the fetuses lined up on each line of sight from the calculation start position S are input to the IIR filter one after another, the box cell data first input to the IIR filter (for example, FIG. 4). initially sampled data) is initialized to the lowest luminance (e.g. voxel value 0) in S1. That is, the value of the first voxel data is changed to the lowest luminance value.

In the filter processing using the IIR filter, the influence of the initial value lasts for a relatively long time. Therefore, by initializing the data input at the start of the filtering process to the initial value corresponding to the minimum brightness, the initial value becomes the subsequent data. It also affects filtering. As a result, for example, as in the specific example shown in FIG. 6 (3), the steep rise of the image of the foetation immediately after the calculation start position S is suppressed. As a result, for example, even when the foetation and the placenta are in contact with each other, the boundary of the image of the foetation in contact with the placenta becomes natural and smooth, and the discomfort of the image of the foetation due to separation from the placenta is reduced.

Returning to FIG. 1, the image forming unit 60 forms an ultrasonic image based on the pixel values obtained for each line of sight of the plurality of lines of sight by the rendering process and the smoothing process. The image forming unit 60 forms an ultrasonic image in which a diagnosis target such as a foetation is three-dimensionally projected based on the projected image data of the luminance information obtained from the rendering processing unit 30. The ultrasonic image formed in the image forming unit 60 is displayed on the display unit 62.

The control unit 100 controls the inside of the ultrasonic diagnostic apparatus of FIG. 1 as a whole. The overall control by the control unit 100 also reflects instructions received from users such as doctors and laboratory technicians via the operation device 70.

Of the configurations shown in FIG. 1, each unit of the transmission / reception unit 12, the volume configuration unit 20, the rendering processing unit 30, the smoothing processing unit 40, and the image forming unit 60 uses hardware such as an electric / electronic circuit or a processor, for example. It can be realized, and a device such as a memory may be used in the realization as needed. Further, at least a part of the functions corresponding to each of the above parts may be realized by a computer. That is, at least a part of the functions corresponding to each of the above parts may be realized by the cooperation of hardware such as a CPU, a processor, and a memory, and software (program) that defines the operation of the CPU and the processor.

Preferable specific examples of the display unit 62 are a liquid crystal display, an organic EL (electroluminescence) display, and the like. The operation device 70 can be realized by at least one of, for example, a mouse, a keyboard, a trackball, a touch panel, and other switches. The control unit 100 can be realized, for example, by cooperating with hardware such as a CPU, a processor, and a memory, and software (program) that defines the operation of the CPU and the processor.

Further, among the configurations shown in FIG. 1, for example, the functions of the rendering processing unit 30, the smoothing processing unit 40, and the image forming unit 60 may be realized by a computer, and the computer may function as an ultrasonic image processing device.

Although preferred embodiments of the present invention have been described above, the above-described embodiments are merely examples in all respects, and do not limit the scope of the present invention. The present invention includes various modified forms without departing from its essence.

10 probe, 12 transmission / reception unit, 20 volume configuration unit, 30 rendering processing unit, 40 smoothing processing unit, 60 image forming unit, 62 display unit, 70 operation device, 100 control unit.

Claims (2)

Rendering processing means that executes rendering processing for each line of sight of a plurality of lines of sight set for volume data obtained by transmitting and receiving ultrasonic waves, and
A smoothing processing means for executing a smoothing process for each voxel data string on each line of sight by applying an infinite impulse response filter to the voxel data strings sampled on each line of sight prior to the rendering process. When,
An image forming means for forming an ultrasonic image based on a pixel value obtained for each voxel data string on each line of sight by the smoothing process and the rendering process.
Have,
The smoothing processing means, said executes the smoothing process by the respective voxel data constituting the voxel data string on each line of sight to enter one after another into the infinite impulse response filter,
The smoothing processing unit performs the initialization for changing the values of voxel data which is first input to the infinite impulse response filter in the voxel data string on each line of sight, to the initial value corresponding to the lowest luminance,
The rendering processing means executes the rendering process based on the data string after the smoothing process for each line of sight.
An ultrasonic image processing device characterized by this. In the ultrasonic image processing apparatus according to claim 1,
The rendering processing means executes the rendering process for each line of sight by using the data string after the smoothing process and the opacity sequence corresponding to the data string after the smoothing process.
An ultrasonic image processing device characterized by this.