JP2022161534A - Medical image generation device, medical image generation method, and program - Google Patents

Abstract

To provide a medical image generation device, a medical image generation method, and a program capable of exhibiting a plurality of image effects at the same time.SOLUTION: A medical image generation device includes: first to third signal processing units for outputting first to third processing signals by executing filtering processing for a sample value obtained by sampling internal signals based on an internal structure of a subject with predetermined discrete time respectively; an integration unit for integrating the first to third processing signals and generating an integrated signal; and an image generation unit for generating an image on the basis of the integrated signal. A duration of an impulse response that the first signal processing unit has is shorter than a duration of an impulse response that the second signal processing unit has, and the duration of the impulse response that the second signal processing unit has is equal to or shorter than the duration of the impulse response that the third signal processing unit has.SELECTED DRAWING: Figure 2

Description

An ultrasonic diagnostic apparatus is an example of a medical image generating apparatus that generates medical images. An ultrasonic diagnostic apparatus creates an image of the inside of a subject by transmitting ultrasonic waves to the subject and analyzing information contained in the reflected echoes. A method called color flow mapping (hereinafter sometimes abbreviated as CFM) enables imaging of blood flow in a subject, and is widely used in the medical field to display the state of blood flow. Ultrasound diagnostic equipment is widely used.

The received signal intensity due to the reflected echo obtained from the blood flow is much smaller than the received signal intensity due to the reflected echo obtained from the tissue scatterer and the tissue boundary used for generating the B-mode tomographic image. Therefore, the blood flow velocity and blood flow power (moving blood flow volume) obtained by signal processing in color flow mapping tend to be unstable.

In particular, when the blood flow velocity in the part to be observed is slow, or when the part to be observed is a peripheral blood vessel, the blood flow power becomes small. Information about blood flow velocity or blood flow power is likely to be removed. As a result, a phenomenon occurs in which a portion of the blood flow image that is originally displayed as blood flow is blackened out. As a result, the blood flow portion in the tomographic image suddenly disappears, and the image is not smooth or gives a sense of discomfort.

Moreover, in color flow mapping, it is necessary to repeat transmission and reception of ultrasonic waves many times in order to detect blood flow, and as a result, the time required to construct one frame tends to be long. For this reason, when multiple frames are updated in chronological order to create a moving image, a moving image with high responsiveness to operations, such as a frame rate of less than 10 FPS (FPS: Frame Per Second), and a smooth moving image can be obtained. may be difficult to obtain.

In order to solve this problem, a conventional ultrasonic diagnostic apparatus that performs color flow mapping sometimes performs temporal interpolation processing called persistence processing (afterimage processing) (see, for example, Patent Documents 1 to 3). .

JP-A-8-66396 JP-A-11-276481 Japanese Patent Publication No. 10-511588

According to the persistence processing, by using the signal of the previous frame and the signal of the new frame, an appropriate afterimage effect is given to the image. However, it is possible to prevent the blood flow display from becoming unstable.

However, if the persistence coefficient is simply set so as to increase the afterimage effect, the responsiveness (trackability) of the image to the movement of the ultrasonic probe that transmits ultrasonic waves may deteriorate. This is because increasing the influence of the previous frame in the displayed image makes the influence of the new frame relatively small, so that the persistence effect is high.

Also, if the persistence factor is not set to an appropriate value, noise may increase in the image and the S/N ratio may decrease. In view of these circumstances, in the persistence processing of the color flow mapping method, multiple image effects such as responsiveness to the movement of the ultrasonic probe, improvement of the S/N ratio in the image, and moderate afterimage effect are simultaneously exhibited. is desired.

An object of the present disclosure is to provide a medical image generation apparatus, a medical image generation method, and a program that can simultaneously produce a plurality of image effects.

A medical image generating apparatus according to the present disclosure performs filtering processing on sample values obtained by sampling an internal signal based on the internal structure of a subject at predetermined discrete times, and outputs first to third processed signals. to a third signal processing unit; an integration unit that integrates the first to third processed signals to generate an integrated signal; and an image generation unit that generates an image based on the integrated signal, The duration of the impulse response possessed by the first signal processing unit is shorter than the duration of the impulse response possessed by the second signal processing unit, and the duration of the impulse response possessed by the second signal processing unit is shorter than the duration of the impulse response possessed by the second signal processing unit. 3 is equal to or less than the duration of the impulse response of the signal processing unit No. 3.

The medical image generation method of the present disclosure performs filtering processing on sample values obtained by sampling an internal signal based on the internal structure of a subject at predetermined discrete times, outputs first to third processed signals, An image generation method for generating an integrated signal by integrating first to third processed signals, and generating an image based on the integrated signal, the first signal processing generating the first processed signal The duration of the impulse response of the unit is shorter than the duration of the impulse response of the second signal processing unit that generates the second processed signal, and the duration of the impulse response of the second signal processing unit is , the duration of the impulse response of the third signal processing unit that generates the third processed signal.
program.

The program of the present disclosure causes a computer to perform filtering processing on sample values obtained by sampling internal signals based on the internal structure of a subject at predetermined discrete times, and output first to third processed signals. , a procedure for integrating the first to third processed signals to generate an integrated signal, and a procedure for generating an image based on the integrated signal, wherein the first processed signal is The duration of the impulse response of the first signal processing unit that generates is shorter than the duration of the impulse response of the second signal processing unit that generates the second processed signal, and the second signal processing unit generates The duration of the impulse response possessed is equal to or less than the duration of the impulse response possessed by the third signal processing section that generates the third processed signal.

According to the present disclosure, multiple image effects can be produced simultaneously.

FIG. 1 is a block diagram showing the configuration of an ultrasonic diagnostic apparatus provided with a medical image generating apparatus according to an embodiment of the present disclosure; Block diagram for explaining the configuration of the C-mode image generator FIG. 3 is a diagram for explaining properties of discrete-time filters included in each of the first signal processing unit, the second signal processing unit, and the third signal processing unit; FIG. 4 is a diagram for explaining a method of determining weights to be given to a first processed signal and weights to be given to a second processed signal; FIG. 11 is a diagram showing the configuration of Modified Example 1 of the medical image generating apparatus; FIG. 10 is a diagram for explaining the configuration of the signal processing unit in Modified Example 2 of the medical image generating apparatus; FIG. 10 is a diagram for explaining the configuration of the signal processing unit in Modification 3 of the medical image generating apparatus; A diagram showing how the sampled value suppression unit suppresses sampled values having a value greater than or equal to a predetermined value. FIG. 12 is a diagram for explaining the configuration of the signal processing unit in Modification 4 of the medical image generating apparatus; A diagram showing an example of the influence of a general MTI filter on a complex signal on the complex plane FIG. 10 is a diagram for explaining the configuration of a signal processing unit in Modified Example 5 of the medical image generating apparatus; FIG. 11 is a diagram showing a part of the configuration of Modified Example 6 of the medical image generating apparatus;

Embodiments of the present disclosure will be described below with reference to the drawings. However, the scope of the invention is not limited to the illustrated example. In addition, in the following description, the same reference numerals are given to the components having the same function and configuration, and the description thereof will be omitted.

[Overall configuration]
FIG. 1 is a block diagram showing the configuration of an ultrasonic diagnostic apparatus 100 including a medical image generating apparatus 1 according to an embodiment of the present disclosure. As shown in FIG. 1, the ultrasonic diagnostic apparatus 100 includes a medical image generating apparatus 1, an ultrasonic probe 101, and a display section .

The medical image generation apparatus 1 includes an operation unit 2, a transmission unit 3, a reception unit 4, a B-mode image generation unit 5, an ROI (Region Of Interest) setting unit 6, and a C-mode image generation unit 7. , a display processing unit 8 , a control unit 9 , a frame data storage unit 10 , and a storage unit 11 .

The ultrasonic probe 101 has a plurality of transducers (piezoelectric transducers) 101a, and each transducer 101a converts a drive signal (transmission electric signal) from a transmission unit 3 described later into an ultrasonic wave, Generates a sound beam. Therefore, the user (operator) can irradiate the inside of the object with an ultrasonic beam by placing the ultrasonic probe 101 on the surface of the object, which is the object to be measured. The ultrasonic probe 101 receives reflected ultrasonic waves from the inside of the subject, converts the reflected ultrasonic waves into received electrical signals with a plurality of transducers 101a, and supplies the received electrical signals to the receiving unit 4, which will be described later.

The display unit 102 is a so-called monitor that displays image data output from the medical image generating apparatus 1 (display processing unit 8). Note that the display unit 102 is connected to the ultrasonic diagnostic apparatus 100 in the example shown in FIG. However, for example, a so-called touch panel may be adopted in which the display unit 102 and an operation unit 2 described later are integrally configured and the operation of the operation unit 2 is performed by touching the display unit 102 . In this case, the medical image generating apparatus 1 and the display unit 102 are configured integrally.

The operation unit 2 receives input from the user and outputs commands based on the user's input to the control unit 9 . The operation unit 2 has a mode in which only a B-mode image is displayed (hereinafter referred to as "B mode") or a mode in which a C-mode (color flow mode) image is superimposed on a B-mode image (hereinafter referred to as "C mode"). ”.) can be selected by the user. The operation unit 2 also includes a function for the user to specify the position of the ROI on which the C-mode image is to be displayed on the B-mode image.

The transmission unit 3 generates a drive signal for driving the transducer 101a and performs transmission processing for causing the ultrasound probe 101 to transmit an ultrasound beam. As an example, the transmission unit 3 performs transmission processing to generate a drive signal for transmitting an ultrasonic beam from the ultrasonic probe 101 having the transducer 101a, and transmits the signal to the ultrasonic probe 101 based on this drive signal. On the other hand, the vibrator 101a of the ultrasonic probe 101 is driven by supplying a high-voltage drive electric signal generated at a predetermined timing. As a result, the ultrasound probe 101 can irradiate the subject, which is the object to be measured, with an ultrasound beam by converting the drive electric signal into an ultrasound wave.

In addition to the drive signal, the transmission unit 3 transmits additional information indicating the content of the user's operation to the ultrasound probe 101 in accordance with the operation performed by the user on the operation unit 2 . The additional information includes at least information designating one of the B mode and the C mode, for example.

Under the control of the control unit 9, the receiving unit 4 performs a receiving process of generating a received signal as an electrical RF (Radio Frequency) signal based on reflected ultrasonic waves. The received signal is a signal indicating the intensity of the reflected ultrasonic wave reflected by the internal structure (internal tissue, etc.) of the subject, and is a signal indicating the internal structure of the subject. The received signal corresponds to the "internal signal" of this disclosure. The receiving unit 4, for example, receives the reflected ultrasonic waves with the ultrasonic probe 101, and amplifies the received electric signals converted based on the reflected ultrasonic waves, A/D converts them, and phases them. By performing addition, a received signal (sound ray data) for each frame is generated. In addition, detection may be performed in the processing process of the receiving unit 4 to generate a received signal in the form of a complex number.

Further, the receiving unit 4 acquires the additional information from the transmitting unit 3, and if the B mode is selected in the acquired additional information, the receiving unit 4 supplies the received signal to the B mode image generating unit 5, and the C mode is selected. If so, the received signal is supplied to the C-mode image generator 7 .

The B-mode image generation unit 5 generates B-mode image data from the received signal input from the reception unit 4 and outputs the B-mode image data to the display processing unit 8 under the control of the control unit 9 . The B-mode image generator 5 performs envelope detection processing, logarithmic compression processing, and the like on the received signal, adjusts the dynamic range and gain, and converts the luminance to generate B-mode image data. The B-mode image generator 5 generates and outputs B-mode image data for each frame based on the received signal for each frame.

Under the control of the control unit 9 , the ROI setting unit 6 outputs ROI setting information to the transmission unit 3 and the display processing unit 8 according to the ROI setting information input by the user via the operation unit 2 .

The C-mode image generation unit 7 generates C-mode image data according to the received signal input from the reception unit 4 under the control of the control unit 9 and outputs the C-mode image data to the display processing unit 8 . The C-mode image generator 7 generates and outputs C-mode image data for each frame based on the received signal for each frame. Details of the C-mode image generator 7 will be described later.

The display processing unit 8 constructs display image data to be displayed on the display unit 102 for each frame, and performs processing for causing the display unit 102 to display the display image data. In particular, when the B mode is selected, processing is performed to include a B mode image based on the B mode image data generated by the B mode image generation unit 5 in the display image data as the ultrasonic image. Further, when the C mode is selected, the C mode image generated by the C mode image generation unit 7 is placed at the position of the ROI selected on the B mode image generated by the B mode image generation unit 5 as an ultrasound image. Synthetic image data is generated by superimposing a C-mode image based on image data, and processing is performed to include this in display image data.

The control unit 9 includes, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory). , and controls the operation of each part of the ultrasonic diagnostic apparatus 100 according to the developed program. The RAM forms a work area that temporarily stores various programs executed by the CPU and data related to these programs. The ROM is composed of a non-volatile memory such as a semiconductor, and stores a system program for the ultrasonic diagnostic apparatus 100, various processing programs such as an initial setting program and an ultrasonic diagnostic program that can be executed on the system program, various data, and the like. Remember. These programs are stored in the form of computer-readable program codes, and the CPU sequentially executes operations according to the program codes. In particular, it is assumed that the ROM stores a C-mode image display program.

The storage unit 11 is composed of, for example, a large-capacity recording medium such as a HDD (Hard Disk Drive). synthetic data, etc.). Further, in the storage unit 11, the patient information associated with the patient ID may be stored in association with the ultrasound image data corresponding to the patient.

A part or all of the functions of each functional block of each unit included in the ultrasonic diagnostic apparatus 100 can be realized as a hardware circuit such as an integrated circuit. An integrated circuit is, for example, an LSI (Large Scale Integration), and LSIs are also called ICs (Integrated Circuits), system LSIs, super LSIs, and ultra LSIs depending on the degree of integration. In addition, the method of circuit integration is not limited to LSI, and it may be realized with a dedicated circuit or a general-purpose processor, and it is possible to reconfigure the connection and setting of circuit cells inside FPGA (Field Programmable Gate Array) and LSI. A reconfigurable processor may be used. Also, a part or all of the functions of each functional block may be executed by software. In this case, this software is stored in one or more storage media such as ROMs, optical discs, hard disks, etc., and is executed by the arithmetic processor.

[C mode image generator 7]
FIG. 2 is a block diagram for explaining the configuration of the C-mode image generator 7. As shown in FIG. As shown in FIG. 2 , the C-mode image generation section 7 includes a signal acquisition section 71 , a signal processing section 72 , an integration section 73 and an image generation section 74 .

The signal acquiring unit 71 acquires a received signal as an “internal signal” of the present disclosure from the receiving unit 4 (see FIG. 1).

The signal processing unit 72 performs persistence processing on the received signal. In the present embodiment, the persistence processing is filtering in which the received signal is sampled at a predetermined sampling interval, and the sample value of a specific frame and the previous (past) sample value are averaged. means processing. In the medical image generating apparatus 1 of the present embodiment, the persistence processing of the signal processing unit 72 improves the responsiveness (followability) of the ultrasonic image to the movement of the ultrasonic probe 101 and the S/N ratio in the ultrasonic image. and moderate afterimage effect. Details of the persistence processing of the signal processing unit 72 will be described later.

As shown in FIG. 2 , the signal processing section 72 includes a first signal processing section 721 , a second signal processing section 722 and a third signal processing section 723 . The first signal processing section 721, the second signal processing section 722, and the third signal processing section 723 have discrete time filters with different properties. The first signal processor 721 generates a first processed signal. The second signal processing section 722 generates a second processed signal. The third signal processor 723 generates a third processed signal. Detailed descriptions of the first signal processing unit 721, the second signal processing unit 722, and the third signal processing unit 723 will be given later.

The integration unit 73 weights and integrates the first processed signal, the second processed signal, and the third processed signal to generate an integrated signal. As shown in FIG. 2 , the integrating section 73 has a weight determining section 731 and a weighted integrating section 732 . A detailed description of the weight determination unit 731 and the weighted integration unit 732 will be given later.

The image generator 74 generates C-mode image data based on the integrated signal. The C-mode image data generated by the image generation unit 74 is input to the display processing unit 8 as described above, whereby an ultrasonic image is displayed on the display unit 102 (see FIG. 1).

[Details of the signal processing unit 72]
Details of the signal processing unit 72 will be described. As described above, the signal processing section 72 includes the first signal processing section 721, the second signal processing section 722, and the third signal processing section 723 each having discrete time filters with different properties.

FIG. 3 is a diagram for explaining properties of the discrete-time filters of the first signal processing section 721, the second signal processing section 722, and the third signal processing section 723, respectively. 3A to 3D show sample values of the received signal input to the signal processing unit 72 as impulse inputs having a predetermined time width (sampling interval). This sampling interval corresponds to, for example, one frame.

FIG. 3A is a schematic diagram showing an example of an input signal. 3A to 3D, the horizontal axis indicates the passage of time, and the vertical axis indicates the magnitude of the input value. FIG. 3A is an impulse input, and FIGS. 3B to 3D illustrate its response characteristics. In the following description, the time width (temporal length) of the input signal corresponding to the sampling interval is t.

FIG. 3B is a schematic diagram showing an impulse response signal (first processed signal) output by the first signal processing section 721 with respect to the input signal shown in FIG. 3A. That is, in the example shown in FIG. 3B, the first signal processing section 721 outputs the input signal as it is as the response signal.

In this specification, the temporal length of impulse response signals (first, second, and third processed signals) output by the first, second, and third signal processing units 721, 722, and 723, respectively is described as the duration of each processed signal. In the example shown in FIG. 3B, the duration t1 of the first processed signal output by the first signal processing section 721 is equal to the time width t of the input signal.

FIG. 3C is a schematic diagram showing an impulse response signal (second processed signal) output by the second signal processing section 722 with respect to the input signal shown in FIG. 3A. In the example shown in FIG. 3C, the second signal processing section 722 outputs a response signal whose value is smaller than that of the input signal for an output time four times longer than that of the input signal. That is, in the example shown in FIG. 3C, the duration t2 of the second processed signal output by the second signal processing unit 722 is four times the time width t of the input signal (t2=4t).

Such filtering processing is performed, for example, by using a finite impulse response (FIR) type filter and taking a moving average of signals for several frames that are temporally close to each other. That is, the second discrete time filter included in the second signal processing section 722 is an FIR filter.

FIG. 3D is a schematic diagram showing an impulse response signal (third processed signal) output by the third signal processing section 723 with respect to the input signal shown in FIG. 3A. In the example shown in FIG. 3D, the third signal processing section 723 outputs the response signal for an output time that is 12 times longer than the input signal. That is, in the example shown in FIG. 3D, the duration t3 of the third processed signal output by the third signal processing section 723 is 12 times the time width t of the input signal (t3=12t).

Such filtering processing is performed by weighting and superimposing the signal of the past frame on the signal of the latest frame using, for example, an infinite impulse response (IIR) type filter. That is, the third discrete time filter included in the third signal processing unit 723 is an IIR filter.

In the examples shown in FIGS. 3B to 3D , the duration t1 of the first processed signal, which is the impulse response of the first signal processing unit 721, is the second signal, which is the impulse response of the second signal processing unit 722. shorter than the duration t2 of the processed signal. The duration t2 of the second processed signal, which is the impulse response signal, of the second signal processing section 722 is equal to the duration t3 of the third processed signal, which is the impulse response signal of the third signal processing section 723. shorter. The first, second, and third processed signals having such durations have the following properties.

The first processed signal is a signal that the first signal processing unit 721 outputs the input latest received signal as it is. Therefore, the first processed signal is a response signal that is not affected by past frames and immediately reflects changes in the value of the input signal. Therefore, the first processed signal is a signal with high responsiveness (followability) to the input signal.

The second processed signal is a signal obtained by the second signal processing unit 722 outputting a moving average of several frames including the latest frame as a second processed signal using a second FIR discrete time filter. be. In this way, since the signal is the moving average of several frames including the latest frame, the second processed signal is a signal from which the noise component of each frame has been removed. Therefore, it can be said that the second processed signal is a signal with a high S/N ratio.

The third processed signal is a signal generated by the third signal processing unit 723 while feeding back the past output signal using the IIR type third discrete time filter. Therefore, the third processed signal becomes a signal containing information of past frames appropriately, and the image generated using the third processed signal becomes an image having a natural afterimage effect.

Thus, according to the first, second and third signal processing units 721, 722 and 723, the first, second and third processed signals having different properties are generated and output.

Note that in the examples shown in FIGS. 3B to 3D, the duration t1 of the first processed signal is equal to the temporal length t of the input signal, the duration t2 of the second processed signal is four times t, and The case where the duration t3 of the third processed signal is twelve times t has been described. However, the durations of the first, second, and third processed signals output by the first, second, and third signal processing units 721, 722, and 723 are not limited to the examples shown in FIGS. 3B to 3D. . In order for the first, second, and third processed signals output by the first, second, and third signal processing units 721, 722, and 723 to have the properties described above, the following equation (1) condition is required.

t1<t2≦t3 (1)

According to the condition of equation (1), the duration t1 of the first processed signal is the shortest in order to obtain responsiveness, and the duration t2 of the second processed signal is several neighboring frames in order to remove noise. Since the average of minutes is output, it is longer than t1. The duration t3 of the third processed signal is longer than t2 in order to obtain an appropriate afterimage effect. Note that equation (1) includes the case where t2 and t3 have the same duration. This is because the attenuation signal may be included over a plurality of frames even after the average value of , in which case the duration t2 of the second processed signal may be equal to the duration t3 of the third processed signal. .

The first, second, and third signal processing units 721 , 722 , and 723 generate the first, second, and third processed signals for each sampling interval and output them to the integration unit 73 .

[Details of Integration Unit 73]
Next, details of the integration unit 73 will be described.

(1) Weight determination unit 731
The first, second, and third processed signals output from the first, second, and third signal processing units 721, 722, and 723 are input to the weight determination unit 731. FIG. The weight determination unit 731 generates weight information regarding the magnitude of the weight to be assigned to each processed signal based on the first, second, and third processed signals at each sampling interval.

As mentioned above, the first, second and third processed signals have different properties. The weight determination unit 731 determines the magnitude of weights to be given to the first, second, and third processed signals, for example, based on the magnitude of the sample value of the received signal.

In the following, for simplicity, a method of determining the magnitude of the weight to be assigned to the first processed signal and the second processed signal based on the sample values of the received signal will be described. FIG. 4 is a diagram for explaining a method of determining weights to be given to the first processed signal and weights to be given to the second processed signal.

The horizontal axis in FIG. 4 indicates the magnitude of the sample value, and the vertical axis indicates the magnitude of the weight. The noise level upper limit value shown in FIG. 4 is a preset value. The noise level upper limit value may be input from the outside of the medical image generating apparatus, or may be stored in advance in a storage unit (not shown) of the medical image generating apparatus 1, for example. FIG. 4 shows how the magnitude of the weight given to the first processed signal and the second processed signal changes depending on whether or not the magnitude of the sample value is greater than the noise level upper limit.

When the magnitude of the sample value is smaller than the noise level upper limit, the weight is determined such that the weight given to the second processed signal is greater than the weight given to the first processed signal. Thus, when the magnitude of the sample value is small, in other words, when the signal strength of the received signal is small, the contribution of the noise component in the received signal is relatively large. Therefore, by setting the weight given to the second processed signal, which is a signal with a high S/N ratio, to be greater than that of the first processed signal, the S/N ratio of the image generated using the processed signal is increased. can be improved and the image quality can be relatively good.

On the other hand, when the magnitude of the sample value is large, in other words, when the signal strength of the received signal is large, the contribution of noise components in the received signal is relatively small. Therefore, even if the weight given to the first processed signal is set higher than that of the second processed signal, the S/N ratio of the image generated using the processed signal does not decrease so much. In this case, the responsiveness ( trackability) can be improved.

In the example shown in FIG. 4, the weight given to the third processed signal has been omitted for the sake of simplicity. I wish I could.

In the example shown in FIG. 4, it has been described that the magnitude of the weight given to each processed signal is determined based on the magnitude of the sample value of the received signal. It is not necessary to determine the magnitude of the weight based solely on magnitude. For example, the magnitude of the weight given to the first, second, and third processed signals based on the image quality information of the ultrasonic image desired by the user, which is input by the user of the medical image generating apparatus 1 via the operation unit 2. may be adjusted as appropriate.

As described above, since the received signal takes the form of ^a complex ^number , the magnitude of the sample value may be calculated using the L2 norm using the real part and the imaginary part of the complex signal. It may be calculated by a formula using the L ^∞ norm. These calculation methods can reduce the computational load when determining the magnitude of the weight.

(2) Weighted integration unit 732
Weighted integration section 732 assigns a weight to each of the first processed signal, the second processed signal, and the third processed signal based on the magnitude of the weight determined for each processed signal by weight determining section 731. ,Integrate. An integrated signal generated as a result of the integration is input to the image generator 74 . The integrated signal is preferably a first processed signal with high responsiveness to the movement of the ultrasonic probe 101, a second processed signal with a high S/N ratio, and a third processed signal that gives an appropriate afterimage effect. It is generated by integrating by weight. As a result, the C-mode image data generated by the image generation unit 74 is an image having an appropriate combination of responsiveness to the movement of the ultrasound probe 101, an S/N ratio, and an appropriate afterimage effect. For this reason, it is possible to generate an image that exhibits three image effects at the same time: responsiveness to the movement of the ultrasound probe 101, S/N ratio, and moderate afterimage effect.

The configuration and operation of the medical image generating apparatus 1 according to the embodiment of the present disclosure have been described above. Modifications that the medical image generating apparatus 1 can take will be described below.

<Modification 1>
FIG. 5 is a diagram showing the configuration of Modified Example 1 of the medical image generating apparatus 1. As shown in FIG. In Modification 1 shown in FIG. 5 , the medical image generating apparatus 1 has a frame interpolating section 75 between the integrating section 73 and the image generating section 74 .

A frame interpolation unit 75 performs frame interpolation on the integrated signal output by the integration unit 73 . Thereby, the frame rate of the C-mode image data generated by the image generator 74 can be improved. Since the integrated signal takes the form of complex numbers, frame interpolation tends to be highly effective.

Note that since the integrated signal is a signal obtained by integrating a plurality of processed signals (first to third processed signals) in the integration section 73, discontinuity may occur between frames. Since the frame interpolator 75 can interpolate such discontinuity, it is possible to eliminate the unnaturalness of the image caused by the discontinuity.

<Modification 2>
FIG. 6 is a diagram for explaining the configuration of the signal processing unit 72 in Modification 2 of the medical image generating apparatus 1. As shown in FIG. In modification 2, a second signal processing unit 722 and a third signal processing unit 723 are connected in series (cascade connection), and the second processed signal output by the second signal processing unit 722 is the third signal processing unit. is input to the signal processing unit 723 of .

As described above, the second signal processing unit 722 generates a second processed signal with a high S/N ratio using the FIR second discrete time filter. The third signal processing unit 723 uses an IIR-type third discrete time filter to assign a greater weight to the input signal of the newest frame and then to the past multiple frames in order from newer frames to newer frames. A countable third processed signal is generated. In Modified Example 2, by using the second processed signal as the input signal used by the third signal processing unit 723, it is possible to generate a natural image in which an afterimage disappears into noise, for example.

6, the third signal processing unit 723 is connected in series after the second signal processing unit 722. For example, the third signal processing unit 723 is connected after the second A signal processing unit 722 may be arranged. Even in this case, the same effects as in Modification 2 can be obtained.

<Modification 3>
FIG. 7 is a diagram for explaining the configuration of the signal processing unit 72 in Modification 3 of the medical image generating apparatus 1. As shown in FIG. In Modified Example 3 shown in FIG. 7 , the third signal processing section 723 has a sample value suppressing section 724 . The sample value suppression unit 724 is configured to suppress the size of a sample value of the received signal input to the third signal processing unit 723 when the size of the sample value is greater than or equal to a predetermined value. . In FIG. 7, the discrete-time filters included in the second and third signal processing units 722 and 723 are indicated as a second filter unit and a third filter unit, respectively.

FIG. 8 is a diagram showing how the sampled value suppression unit 724 suppresses sampled values having a value equal to or greater than a predetermined value. In FIG. 8, the solid line indicates the input sample value, the dashed line indicates the output value before being suppressed by the sample value suppressing section 724, and the one-dot chain line indicates the output value after being suppressed by the sample value suppressing section 724. ing. As shown in FIG. 8, the sample value suppression unit 724 suppresses sample values having a predetermined size or more to a predetermined size.

In this way, the dynamic range of the blood flow signal may be several tens of times wider than the S/N ratio of the blood flow to be expressed. An unnatural image may be generated, such as afterimages remaining too much. By suppressing some large sample values by the sample value suppression unit 724, it is possible to prevent such an unnatural image from being generated.

The third signal processing unit 723 can also prevent the generation of an image having an unnatural afterimage effect by controlling the attenuation rate (persistence coefficient) of the past frame superimposed on the latest frame. is. However, when the attenuation rate is controlled, the entire image is affected, so the image as a whole may appear unnatural. On the other hand, the sample value suppressing unit 724 of the medical image generating apparatus 1 can suppress only some large sample values, so that the unnatural afterimage effect can be suppressed more appropriately.

In Modification 3, the case where the third signal processing unit 723 has the sample value suppression unit 724 has been described. are connected in series, the second signal processing section 722 may have the sample value suppression section 724 .

<Modification 4>
FIG. 9 is a diagram for explaining the configuration of the signal processing unit 72 in Modification 4 of the medical image generating apparatus 1. As shown in FIG. In Modified Example 4 shown in FIG. 9, the second signal processing section 722 has an offset correction section 725 that eliminates the offset caused by the MTI filter processing.

MTI (Moving Target Indication) filter processing is processing performed when the C-mode image generator 7 generates information such as blood flow velocity and blood flow power. MTI filter processing is processing for extracting fast-speed signals in order to distinguish, for example, between the movement of blood flow and the movement of organs and the like.

FIG. 10 is a diagram showing, on the complex plane, the background noise area (shaded area) affected by the MTI filter. Due to the influence of the MTI filter, as shown in FIG. 10, the center of gravity of the signal in the real part direction of the complex signal corresponding to the noise component that should be at the origin may be biased in the negative direction. In the following description, this bias (deviation) is described as an offset.

When the noise component contained in the received signal processed by the MTI filter shifts in the negative direction of the real part due to the influence of the MTI filter as shown in FIG. The image generated in section 74 may be rich in noise components.

In Modified Example 4, the offset correction unit 725 cancels this offset (adds a value equal to the offset in the positive direction of the real part on the complex plane), so that the second signal processing unit 722 outputs the 2, the S/N ratio of the processed signal can be further increased. A known technique can be applied to the offset correction processing by the offset correction unit 725 .

In Modification 4, the case where the second signal processing unit 722 has the offset correction unit 725 has been described. are connected in series, the third signal processing section 723 may have the offset correction section 725 .

<Modification 5>
FIG. 11 is a diagram for explaining the configuration of the signal processing unit 72 in Modification 5 of the medical image generating apparatus 1. As shown in FIG. In Modified Example 5 shown in FIG. 11 , the first signal processing section 721 has a first spatial filter section 726 and the second signal processing section 722 has a second spatial filter section 727 .

The first spatial filter section 726 performs spatial filtering processing on the input signal to the first signal processing section 721 . Also, the second spatial filter unit 727 performs spatial filtering processing on the signal output by the second discrete time filter. Spatial filtering processing is a method of calculating the pixel value of a specific pixel by considering the pixel values of adjacent pixels in the input signal. Here, the high frequency component of the spatial frequency characteristic of the second spatial filter section 727 is set to be smaller than the high frequency component of the spatial frequency characteristic of the first spatial filter section 726 .

With such a configuration, the second processed signal with a high S/N ratio has a stronger spatial average than the first processed signal with high responsiveness to the movement of the ultrasonic probe 101. will be processed. Through such processing, even when the magnitude of the sample value of the received signal is relatively small, it is possible to expect an improvement in the S/N ratio by filtering high-frequency components more strongly.

In Modification 5, the case where the second signal processing unit 722 has the second spatial filter unit 727 has been described. 723 are connected in series, the third signal processing section 723 may have a third spatial filter section.

<Modification 6>
FIG. 12 is a diagram showing a part of the configuration of Modified Example 6 of the medical image generating apparatus 1. As shown in FIG. In Modified Example 6, a motion artifact evaluation section 76 is added before the signal processing section 72, and the first, second, and third signal processing sections 721, 722, and 723 each have a motion artifact suppression section 728. FIG. In FIG. 12, only the signal acquisition unit 71, the motion artifact evaluation unit 76, and the signal processing unit 72 are illustrated, and illustration of the subsequent configuration (integration unit 73, image generation unit 74) is omitted.

A motion artifact is noise that occurs on an image due to, for example, the movement of a subject. When a motion artifact occurs, a signal component other than blood flow may be reflected in an image by being superimposed on blood flow information, so countermeasures are desired.

A motion artifact evaluation unit 76 evaluates the influence of motion artifacts for each sample value of the received signal. As for the motion artifact evaluation method by the motion artifact evaluation unit 76, a known method can be appropriately adopted. For example, when the phase angle of the sample value (complex signal) is too small for specifying the MTI filter, motion artifact information is generated indicating that many motion artifacts are occurring.

The motion artifact evaluation unit 76 generates motion artifact information indicating the motion artifact evaluation result for each sample value, and outputs the motion artifact information to the motion artifact suppression unit 728 .

The motion artifact suppression unit 728 performs processing to suppress motion artifacts for each sample value based on the motion artifact information. A known method can be appropriately adopted for the process of suppressing motion artifacts by the motion artifact suppression unit 728 as well. As a method of suppressing motion artifacts, for example, a sample value with a high motion artifact evaluation is extracted as a target sample, and the target sample is multiplied by a coefficient that selectively suppresses the sample value, thereby suppressing the motion artifact. etc.

When motion artifacts occur, the above-described effects of the first, second, and third signal processing units 721, 722, and 723 may not be obtained due to the influence of the motion artifacts. In Modified Example 6, by performing processing to suppress motion artifacts, the processed signal output from the signal processing unit 72 can sufficiently exhibit the above-described effects.

Further, in Modification 6, a motion artifact spatial filter section that performs selective spatial filtering processing based on motion artifact information may be further arranged between the integration section 73 and the image generation section 74 . When some of the sample values are suppressed by the motion artifact suppression unit 728, information may be missing from some of the pixels and the image may appear unnatural. The effect of improving the visibility can be obtained by interpolating the pixels from the surrounding pixels.

Note that the motion artifact spatial filter section may be provided in each of the first, second, and third signal processing sections 721, 722, and 723 instead of between the integration section 73 and the image generation section 74. FIG.

<Other Modifications>
In the above-described embodiment, the medical image generating apparatus 1 that configures the ultrasonic diagnostic apparatus 100 by being connected to the ultrasonic probe 101 has been described as an example of the medical image generating apparatus according to the present disclosure. However, the medical image generating apparatus according to the present disclosure does not necessarily have to be connected to the ultrasound probe 101 . For example, a received signal generated by an ultrasound probe is stored in advance in an external storage device such as an HDD, and the medical image generating apparatus 1 according to the present disclosure receives such an external storage device via the receiving unit 4. Received signals may be obtained by wired or wireless communication from.

Further, in the above-described embodiment, the internal signal indicating the internal structure of the object is exemplified by the received signal of the reflected ultrasound, but the present disclosure is not limited to this. Any signal that indicates the internal structure of the subject can be used as appropriate, in addition to the received signal from the reflected ultrasonic waves.

Further, in the above-described embodiment, the medical image generating apparatus according to the present disclosure has been described as being configured with software alone. Personal Computer), a tablet terminal, or a mobile terminal such as a smart phone.

Also, in the above-described embodiment, the example in which the first signal processing unit 721 outputs the input signal as it is has been described. However, for example, the first signal processing section may also perform filtering processing using an FIR filter in the same manner as the second signal processing section. Even in this case, the duration of the first processed signal output by the first signal processing unit is made shorter than the duration of the second processed signal output by the second signal processing unit. As in the embodiment, it is possible to output the first processed signal with high responsiveness to the movement of the ultrasonic probe.

INDUSTRIAL APPLICABILITY The present invention is suitable for medical image generation apparatuses that generate images based on input signals.

1 medical image generation apparatus 2 operation unit 3 transmission unit 4 reception unit 5 B-mode image generation unit 6 ROI setting unit 7 C-mode image generation unit 71 signal acquisition unit 72 signal processing unit 721 first signal processing unit 722 second signal Processing unit 723 Third signal processing unit 724 Sample value suppression unit 725 Offset correction unit 726 First spatial filter unit 727 Second spatial filter unit 728 Motion artifact suppression unit 73 Integration unit 731 Weight determination unit 732 Weighted integration unit 74 Image generation unit 75 Frame interpolation unit 76 Motion artifact evaluation unit 8 Display processing unit 9 Control unit 10 Frame data storage unit 100 Ultrasound diagnostic apparatus 101 Ultrasound probe 101a Transducer 102 Display unit

Claims (16)

first to third signal processing units that respectively perform filtering processing on sample values obtained by sampling an internal signal based on the internal structure of a subject at predetermined discrete times and output first to third processed signals;
an integration unit that integrates the first to third processed signals to generate an integrated signal;
an image generator that generates an image based on the integrated signal;
with
The duration of the impulse response possessed by the first signal processing unit is shorter than the duration of the impulse response possessed by the second signal processing unit, and the duration of the impulse response possessed by the second signal processing unit is shorter than the duration of the impulse response possessed by the second signal processing unit. is equal to or less than the duration of the impulse response possessed by the signal processing unit of 3,
Medical imaging equipment. The integration unit
a weight determining unit that determines a magnitude of weight to be applied to each of the internal signal or the first to third processed signals output by the first to third signal processing units;
a weighted integration unit that weights each of the processed signals output from the first to third signal processing units based on the determined weight to generate the integrated signal;
having
The medical image generating apparatus according to claim 1. The weight determination unit determines the magnitude of the weight for each sampling period corresponding to the discrete time for the first to third processed signals.
The medical image generating apparatus according to claim 2. wherein the weight determination unit determines the magnitude of the weight according to the magnitude of the sample value;
4. The medical image generating apparatus according to claim 2 or 3. The first to third signal processing units sample the sample value for each frame of the internal signal.
The medical image generation apparatus according to any one of claims 1 to 4. The second discrete-time filter of the second signal processing unit is a finite impulse response (FIR) type filter,
The third discrete-time filter of the third signal processing unit is an infinite impulse response (IIR) type filter,
The medical image generation device according to any one of claims 1 to 5. The weight determination unit determines a weight to be given to the processed signal generated by the first signal processing unit based on the internal signal when the magnitude of the internal signal in a specific sampling period is smaller than a predetermined value. determining the weight so that the magnitude is smaller than the magnitude of the weight given to the processed signal generated by the second signal processing unit based on the internal signal;
The medical image generating apparatus according to claim 3. further comprising an interpolating unit that interpolates the internal signal based on the integrated signal;
The medical image generation device according to any one of claims 1 to 7. At least one of the second and third signal processing units outputs the generated processed signal to the other signal processing unit as a processing target;
The medical image generating device according to any one of claims 1 to 8. At least one of the second and third signal processing units reduces the magnitude of the internal signal in a particular sampling period to the predetermined magnitude when the magnitude of the internal signal in the particular sampling period is greater than the predetermined magnitude. having a suppressor that suppresses below
The medical image generating apparatus according to claim 3. The first to third signal processing units further have an offset correction unit that adds a predetermined offset in the direction of the real part of the complex plane of the first to third processed signals when the internal signal is a complex signal. ,
The medical image generation device according to any one of claims 1 to 10. The first to third signal processing units each have first to third spatial filter units,
12. Any one of claims 1 to 11, wherein high frequency components in the spatial frequency characteristics of the second or the third spatial filter section are smaller than the high frequency components of the spatial frequency characteristics of the first spatial filter section. 1. The medical image generation device according to claim 1. further comprising a motion artifact evaluation unit that evaluates motion artifacts caused by the movement of the subject;
At least one of the first to third signal processing units includes a motion artifact suppression unit that suppresses the motion artifact for each sample value based on the evaluation result of the motion artifact evaluation unit.
13. The medical image generation device according to any one of claims 1-12. Further comprising a motion artifact spatial filter unit that performs spatial filtering processing to reduce the motion artifact on the integrated signal based on the evaluation result of the motion artifact evaluation unit,
14. The medical image generation device according to claim 13. performing filtering processing on sample values obtained by sampling an internal signal based on the internal structure of a subject at predetermined discrete times, and outputting first to third processed signals;
Integrating the first to third processed signals to generate an integrated signal;
generating an image based on the integrated signal;
An image generation method comprising:
The duration of the impulse response of the first signal processing unit that generates the first processed signal is shorter than the duration of the impulse response of the second signal processing unit that generates the second processed signal, and The duration of the impulse response of the second signal processing unit is less than or equal to the duration of the impulse response of the third signal processing unit that generates the third processed signal.
Medical image generation method. to the computer,
a procedure of performing filtering processing on sample values obtained by sampling an internal signal based on the internal structure of a subject at predetermined discrete times, and outputting first to third processed signals;
a step of integrating the first to third processed signals to generate an integrated signal;
generating an image based on the integrated signal;
A program that executes
The duration of the impulse response of the first signal processing unit that generates the first processed signal is shorter than the duration of the impulse response of the second signal processing unit that generates the second processed signal, and The duration of the impulse response of the second signal processing unit is less than or equal to the duration of the impulse response of the third signal processing unit that generates the third processed signal.
program.

Images