JPWO2019088169A1 - Ultrasonic diagnostic system and ultrasonic diagnostic method - Google Patents

Abstract

Generate a density distribution image of the tomographic surface of the subject. In the ultrasonic diagnostic system according to the embodiment of the present invention, ultrasonic waves are transmitted and scattered waves scattered by a subject are received by a plurality of elements. This ultrasonic diagnostic system estimates and estimates the sound velocity distribution of the subject using the data collection unit 132 that collects the actual measurement data which is the data obtained from the element that received the scattered wave and the actual measurement data. The virtual measurement data that the ultrasonic waves propagate in the region having the sound velocity distribution and received by the element is calculated, the difference waveform between the actual measurement data and the virtual measurement data is calculated, and the sound velocity distribution is used using the difference waveform. A calculation unit 133 for calculating an image and a scatterer distribution image is provided.

Description

The present invention relates to an ultrasonic diagnostic system and an ultrasonic diagnostic method for creating a tomographic image of a subject by irradiating ultrasonic waves.

The non-invasive ultrasonic diagnostic system is widely used in the medical field as a technique for diagnosing information inside a subject because it does not require a surgical operation in which a living body is directly incised and observed.

Ultrasound CT (Computed Tomography), which is a method of ultrasonic diagnosis, irradiates a subject with ultrasonic waves and creates a tomographic image of the subject using reflected ultrasonic waves or transmitted ultrasonic waves. Studies have shown that it is useful in detecting breast cancer. In ultrasonic CT, for example, a tomographic image is created by using a ring-type array transducer in which a large number of elements for transmitting and receiving ultrasonic waves are arranged in a ring shape.

In ultrasonic CT, a method of measuring the amount of ultrasonic attenuation and displaying the attenuation rate distribution of the fault plane and a method of measuring the propagation time of ultrasonic waves and displaying the sound velocity distribution of the fault plane are known. There is. In order to make ultrasonic CT a clinically more effective diagnostic method, it is required to image physical quantities other than the attenuation rate distribution and the sound velocity distribution.

International Publication No. 2017/051903

The present invention has been made in view of the above-mentioned conventional conditions, and an object of the present invention is to provide an ultrasonic diagnostic system and an ultrasonic diagnostic method capable of generating a density distribution image of a tomographic surface of a subject.

The ultrasonic diagnostic system according to the present invention is arranged around a subject, and a plurality of elements that transmit and receive at least one of ultrasonic waves and any one of the plurality of elements transmit ultrasonic waves. Data obtained from a control unit that controls the plurality of elements so that at least a part of the plurality of elements receives the scattered wave scattered by the subject, and an element that receives the scattered wave. The sound velocity distribution of the subject is estimated using the data collecting unit that collects the actual measurement data, and the element receives the sound when the ultrasonic wave propagates in the region having the estimated sound velocity distribution. The virtual measurement data is calculated, the difference waveform between the actual measurement data and the virtual measurement data is calculated, and the component used for the calculation of the sound velocity distribution image or the component used for the calculation of the scatterer distribution image is obtained from the difference waveform. A calculation unit that calculates a sound velocity distribution image using the difference waveform of the components used for calculating the sound velocity distribution image, or a scatterer distribution image using the difference waveform of the components used for calculating the scatterer distribution image. It is equipped with.

According to one aspect of the present invention, the component used for calculating the sound velocity distribution image is a forward scattered wave component which is a component of scattered waves scattered on a side other than the side of the element that transmitted the ultrasonic waves, and the scattering The component used for calculating the body distribution image is a backscattered wave component which is a component of the scattered wave scattered on the side of the element that transmitted the ultrasonic wave.

According to one aspect of the present invention, the plurality of elements are arranged at equal intervals in a ring shape, and the calculation unit is an element located on one half side of the ring circumference centering on the element that transmits ultrasonic waves. The corresponding difference waveform is classified into the backscattered wave component, and the difference waveform corresponding to the element located on the other half side of the ring circumference is classified into the forward scattered wave component.

According to one aspect of the present invention, the calculation unit calculates a sound velocity distribution image and a scatterer distribution image for each transmitting element that transmits ultrasonic waves, adds the sound velocity distribution image for each transmitting element, and the transmitting element. An image creation unit that adds the scatterer distribution image for each is further provided.

According to one aspect of the present invention, the image creating unit creates a density distribution image from the sound velocity distribution image and the scatterer distribution image.

According to one aspect of the present invention, the calculation of the sound velocity distribution image includes backscattering of the difference waveform of the forward scattered wave component, and the calculation of the scatterer distribution image includes backscattering of the difference waveform of the backscattered wave component. Including.

According to one aspect of the present invention, the estimated sound velocity distribution is updated using the scatterer distribution image, and the difference waveform is calculated and the sound velocity distribution image is calculated or the sound velocity distribution image is calculated using the updated sound velocity distribution. The scattering body distribution image is calculated.

According to one aspect of the present invention, the plurality of elements are arranged in a ring shape, and a scatterer distribution image is reconstructed by back propagation of the difference waveform from some elements on the circumference of the ring.

The ultrasonic diagnostic method according to the present invention performs a process of transmitting ultrasonic waves from any one of a plurality of elements arranged around a subject and receiving scattered waves at at least a part of the plurality of elements. The step of switching the elements that transmit sound waves in order, the step of collecting measurement data that is the data obtained from the element that received the scattered wave, and the step of estimating the sound velocity distribution of the subject using the actual measurement data. The process, the process of calculating the virtual measurement data received by each element by propagating ultrasonic waves in the region having the estimated sound velocity distribution, and the calculation of the difference waveform between the actual measurement data and the virtual measurement data for each element. A step of classifying the difference waveform for each element into a forward scattered wave component and a backscattered wave component, a step of calculating a sound velocity distribution image using the difference waveform of the forward scattered wave component, and the backscattered wave. It includes a step of calculating a scatterer distribution image using a difference waveform of components.

According to the present invention, it is possible to generate a density distribution image of the tomographic surface of a subject.

It is a schematic block diagram of the ultrasonic diagnostic system in embodiment of this invention. FIG. 1 is a cross-sectional view taken along the line AA of FIG. It is a functional block diagram of an arithmetic unit. It is a flowchart explaining the method of making a tomographic image by the same embodiment. FIG. 5a is a scatterer distribution image, and FIG. 5b is a graph showing the brightness of the point scatterer. FIG. 6a is a scatterer distribution image, and FIG. 6b is a graph showing the brightness of the point scatterer. FIG. 7a is a sound velocity distribution image, and FIG. 7b is a graph showing the brightness of the point scatterer. FIG. 8a is a sound velocity distribution image, and FIG. 8b is a graph showing the brightness of the point scatterer. It is a flowchart explaining the method of making a tomographic image by a modification. 10a and 10b are diagrams showing a simulation model, FIG. 10c shows a backscattered image, and FIG. 10d shows a backscattered image. It is a figure which shows the element which receives a forward scatter wave component and the element which receives a back scatter wave component.

Hereinafter, the present invention will be described in more detail with reference to the drawings. The ultrasonic diagnostic system according to the embodiment of the present invention irradiates a subject such as a human body with ultrasonic waves, and creates a tomographic image of the subject using the received signal. A doctor can diagnose a lesion such as a malignant tumor by confirming the created tomographic image.

As shown in FIG. 1, the ultrasonic diagnostic system 10 according to the present embodiment includes a ring array R, a switch circuit 110, a transmission / reception circuit 120, an arithmetic unit 130, and an image display device 140.

The ring array R is a ring-shaped oscillator having a diameter of preferably 80 to 500 mm, more preferably 100 to 300 mm, which is composed of a combination of a plurality of oscillators. Further, the ring array R can be configured to have a variable diameter. In this embodiment, as an example, a ring-shaped oscillator in which four concave oscillators P01 to P04 are combined is used.

For example, when the concave oscillators P01 to P04 each have 256 strip-shaped piezoelectric elements E (hereinafter, also simply referred to as "elements E"), the ring array R is composed of 1024 elements E. become. The number of elements E provided in the concave oscillators P01 to P04 is not limited, and is preferably 1 to 1000, more preferably 100 to 500.

Each element E has a function of mutually converting an electric signal and an ultrasonic signal. The element E transmits ultrasonic waves to the subject T, receives the scattered waves scattered by the subject T, and forms an electrical signal as measurement data. The scattered wave includes a forward scattered wave, a back scattered wave (refers to a scattered wave other than the forward scattered wave, and includes a side scattered wave) and the like.

In the present embodiment, each element E is described as having both functions of transmitting and receiving ultrasonic waves, but the present invention is not limited to this. For example, a transmitting element or a receiving element having only one of an ultrasonic transmitting function and a receiving function may be used, and a plurality of transmitting elements and a plurality of receiving elements may be arranged in a ring shape. Further, an element having both transmission and reception functions, a transmission element, and a reception element may be mixed.

FIG. 2 is a cross-sectional view taken along the line AA of FIG. For example, the ring array R is installed under the bed with holes so that the holes in the bed and the insertion portion SP overlap each other. The subject inserts a body part (subject T, for example, breast) to be imaged into the insertion portion SP through the hole in the bed.

The insertion portion SP for inserting the subject T is provided in the center of the ring array R. The plurality of elements E of the ring array R are provided along the ring around the insertion portion SP at equal intervals. A convex lens called an acoustic lens is attached to the inner peripheral side of the ring array R. By applying such surface processing to the inner peripheral side of the ring array R, the ultrasonic waves transmitted by each element E can be converged in the plane including the ring array R. The space between the ring array R and the subject T is filled with, for example, water.

In the present embodiment, the elements E are arranged in a ring shape at equal intervals, but the shape of the ring array R is not limited to a circle, and any polygon such as a hexagon, a square, or a triangle, at least a part thereof. It may be a shape including a curve or an arc, any other shape, or a part of these shapes (for example, a semicircle or an arc). That is, the ring array R can be generalized to the array R.

The ring array R is connected to the transmission / reception circuit 120 via the switch circuit 110. The transmission / reception circuit 120 (control unit) transmits a control signal (electrical signal) to the element E of the ring array R to control the transmission / reception of ultrasonic waves. For example, the transmission / reception circuit 120 instructs the element E of the frequency and magnitude of the ultrasonic waves to be transmitted, the type of wave (continuous wave, pulse wave, etc.), and the like.

The switch circuit 110 is connected to each of a plurality of elements E of the ring array R, transmits a signal from the transmission / reception circuit 120 to an arbitrary element E, drives the element E, and transmits / receives a signal. For example, the switch circuit 110 controls to switch the element E that supplies the control signal from the transmission / reception circuit 120, so that any one of the plurality of elements E functions as a transmission element that transmits ultrasonic waves. The scattered wave is received by the element E (for example, all).

The measurement data may be collected by driving all the elements E at the same time, or the plurality of elements E of the ring array R may be divided into several groups and the measurement data may be collected in order in group units. By switching the group within a few μs to ms order or less, measurement data can be collected in almost real time.

The ring array R is installed so as to be vertically movable by a stepping motor or the like. The entire data of the subject T is collected by moving the ring array R up and down.

The arithmetic unit 130 is composed of, for example, a computer including a CPU, a storage unit (RAM, ROM, hard disk, etc.), a communication unit, and the like. By executing the program stored in the storage unit, the functions of the transmission element determination unit 131, the data collection unit 132, the calculation unit 133, the image creation unit 134, and the like as shown in FIG. 3 are realized, and the calculation result is stored. Area 135 and measurement data storage area 136 are secured in the storage unit. The processing by each part will be described later.

Next, the tomographic image creating method according to the present embodiment will be described with reference to the flowchart shown in FIG. In the following description, it is assumed that the ring array R is provided with ₂₅₆ elements E _{1 to} E ₂₅₆ . The elements E _{1 to} E ₂₅₆ are arranged at equal intervals on the circumference in this order.

First, a state in which the subject T is not inserted into the insertion unit SP (any state may be used as long as there is no subject T, for example, a housing into which the subject T is inserted or a state in which water may exist). Then, the ultrasonic waves are transmitted while switching the transmitting elements, and are received by the plurality of elements (step S1). For example, ultrasonic waves are transmitted from the element _{E 1,} to receive the transmission waves in all elements _E 1 _{to E 256.} While switching the transmitting element from element E ₁ to element E _{256 in} order, all the elements E _{1 to} E ₂₅₆ receive the transmitted wave.

The transmission element determination unit 131 instructs the transmission / reception circuit 120 so that ultrasonic waves are transmitted in order from the elements E _{1 to} E ₂₅₆ . Data collection unit 132 through the switch circuit 110 and the transmitting and receiving circuit 120, for collecting the measurement data (received data) is data obtained by the element _E 1 _{to E 256} (including the receiving or obtaining). The measurement data (transmitted wave data) is stored in the measurement data storage area 136.

The transmitted wave data may be measured in advance.

Next, with the subject T inserted from the insertion unit SP, ultrasonic waves are transmitted while switching the transmitting element, and scattered waves are received by the plurality of elements (step S2). For example, ultrasonic waves are transmitted from the element _{E 1,} and receives the scattered wave in all elements _E 1 _{to E 256.} While switching the transmitting element from element E ₁ to element E _{256 in} order, all the elements E _{1 to} E ₂₅₆ receive the scattered wave.

The actual measurement data (scattered wave data), which is the data obtained by the elements E _{1 to} E ₂₅₆ , is stored in the measurement data storage area 136.

The measurement data obtained in steps S1 and S2 is three-dimensional data in which the first axis is the receiving element number, the second axis is the signal arrival time, and the third axis is the transmitting element number.

The calculation unit 133 calculates an estimated value of the sound velocity distribution in the imaging region using the actual measurement data acquired in step S2 (step S3). For example, the tomographic image obtained by the aperture synthesis method is generated using the actual measurement data acquired in step S2, and the contour of the subject T is extracted. Then, the average sound velocity in the subject T is calculated from the signal arrival time of the transmitted wave. Alternatively, the sound velocity distribution is calculated using a known ray-base sound velocity distribution reconstruction method. The calculation result is stored in the calculation result storage area 135.

The element of unselected selects one of the elements _E 1 _{to E 256} (step S4). Using the estimated value of the sound velocity distribution calculated in step S3, the calculation unit 133 calculates virtual measurement data (emulated data) received by each element when ultrasonic waves are transmitted from the element selected in step S4. (Step S5).

For example, the calculation unit 133 numerically solves the wave equation and the Helmholtz equation, calculates the behavior of the ultrasonic waves propagating in the region having the sound velocity distribution calculated in step S3, and obtains the virtual measurement data received by each element. ..

The calculation unit 133 extracts from the measurement data storage area 136 the data in which the transmitting element is the element selected in step S4 from the actual measurement data acquired in step S2. The calculation unit 133 subtracts the virtual measurement data calculated in step S5 from the extracted actual measurement data for each receiving element to calculate the difference waveform (step S6).

The actual measurement data acquired in step S2 includes a first wave scattered from a large structure related to the sound velocity distribution and a second wave scattered from a fine structure related to the sound velocity distribution and a structure of density change. On the other hand, the virtual measurement data calculated in step S5 is a wave scattered from a large structure related to the sound velocity distribution calculated in step S3, and corresponds to the above-mentioned first wave. Therefore, by subtracting the virtual measurement data from the actual measurement data, the component of the first wave is canceled, and the component of the wave containing the component of the second wave as the main component remains.

The calculation unit 133 classifies the difference waveform for each receiving element into a component used for calculating the sound velocity distribution image and a component used for calculating the scatterer distribution image, for example, a backscatter wave component and a forward scattered wave component (step). S7). The forward scattered wave component is a component of the scattered wave scattered on the side other than the side of the element that transmitted the ultrasonic wave, and the backscattered wave component is a component of the scattered wave scattered on the side of the element that transmitted the ultrasonic wave. (See FIG. 11). For example, the difference waveform of the receiving element located on one half side of the ring array R about the transmitting element is classified into a backscattered wave component. The difference waveform of the receiving element located on the other half side of the ring array R is classified into the forward scattered wave component.

For example, when the element _{E 1} is the transmission device, the differential waveform of the element _E 193 _{to E 256,} E 1 _{to E 64} located on one half side of the ring array R around the element _{E 1} is classified into backscattered wave component To. Further, the difference waveforms of the elements E _{65 to} E ₁₉₂ located on the other half side of the ring array R are classified as forward scattered wave components.

The calculation unit 133 calculates the sound velocity distribution image from the forward scattered wave component (step S8). The wave equation is calculated by retyping the difference waveform classified as the forward scattered wave component in the opposite direction from the receiving element position toward the transmitting element, that is, by separating the space and time and using an algorithm such as the time region finite difference method. The sound velocity distribution image is calculated using the so-called back propagation method, in which the focused scattering position is detected by solving and propagating the wave into the ring array R.

The calculation unit 133 calculates a scatterer distribution image from the backscattered wave component (step S9). The same method as in step S8 described above can be used for the calculation of the scatterer distribution image.

The processing of steps S5 to S9 is performed for all the transmitting elements (step S10). As a result, the same number of sound velocity distribution images and scatterer distribution images as the number of transmitting elements (for example, 256) can be obtained.

The image creation unit 134 adds the obtained sound velocity distribution images to generate a final sound velocity distribution image (step S11). In addition, the image creation unit 134 adds all the scatterer distribution images to generate the final scatterer distribution image. RF data may be added, or absolute value data or data after envelope detection may be added.

Scattering is a spatial derivative of acoustic impedance Z = ρc (ρ: density, c: sound velocity), and the scatterer distribution image includes sound velocity distribution and density distribution. The image creation unit 134 compares the sound velocity distribution image and the scatterer distribution image, and generates a density distribution image by, for example, subtracting the sound velocity distribution image from the scatterer distribution image (step S12). The image generated by the image creation unit 134 is displayed on the image display device 140.

As described above, according to the present embodiment, the forward scattered wave component and the backscattered wave component are classified, and after separating the influence of the transmitted wave (forward scattered wave) having a larger amplitude than the backscattered wave, the backscattered wave Invert the ingredients over time and remake. Therefore, the density distribution and the sound velocity distribution can be evaluated independently. By imaging the density distribution, ultrasonic CT can be a clinically more effective diagnostic method.

Simulation Using the tomographic image creation method according to the above embodiment, the effectiveness of the scatterer distribution image based on the backscattered wave component will be demonstrated by simulation.

<Simulation 1>
Eight point scatterers were arranged at equal intervals on the circumference of concentric circles on the radial inside of the ring array. The calculation was performed by the method according to the above embodiment, and a scatterer distribution image based on the backscattered wave component was created. The simulation conditions are as follows. The following five conditions are common to simulations 1 to 4.
Number of ring array elements: 256 Ring array radius: 50 mm
Sampling frequency: 5MHz
Excitation: Unit Impulse Distance from the center of the ring array to eight point scatterers: 7.5 mm

Point scatterer, counterclockwise from 12 o'clock position, increased density stepwise by 10 kg / m ^3.

The results are shown in FIGS. 5a and 5b. FIG. 5a shows a scatterer distribution image. FIG. 5b is a graph showing the brightness of the point scatterer. Numbers 1 to 8 on the horizontal axis of FIG. 5b correspond to point scatterers arranged in order counterclockwise from the 12 o'clock position.

<Simulation 2>
The densities of the eight point scatterers were each increased by 10 kg / m ³ over Simulation 1. In addition, the size (radius) of the point scatterer was gradually increased by 1/8 mm from 1/8 mm to 1 mm in a counterclockwise direction from the 12 o'clock position. Other conditions were the same as in Simulation 1.

The results are shown in FIGS. 6a and 6b. FIG. 6a shows a scatterer distribution image. FIG. 6b is a graph showing the brightness of the point scatterer.

<Simulation 3>
The speed of sound of the eight point scatterers was gradually increased by 2 m / s counterclockwise from the 12 o'clock position. Other conditions were the same as in Simulation 1, and a sound velocity distribution image based on the forward scattered wave component was created.

The results are shown in FIGS. 7a and 7b. FIG. 7a shows a sound velocity distribution image. FIG. 7b is a graph showing the brightness of the point scatterer.

<Simulation 4>
The speed of sound of each of the eight point scatterers was increased by 10 m / s compared to Simulation 3. Further, as in Simulation 2, the size (radius) of the point scatterer was gradually increased by 1/8 mm from 1/8 mm to 1 mm in a counterclockwise direction from the 12 o'clock position. Other conditions were the same as in Simulation 3.

The results are shown in FIGS. 8a and 8b. FIG. 8a shows a sound velocity distribution image. FIG. 8b is a graph showing the brightness of the point scatterer.

As shown in FIGS. 7a and 7b, the brightness of the sound velocity distribution image was proportional to the speed of sound. Further, as shown in FIGS. 8a and 8b, in the sound velocity distribution image, the brightness also depends on the scatterer size.

On the other hand, as shown in FIGS. 5a and 5b and 6a and 6b, it was confirmed that the brightness of the scatterer distribution image is proportional to the density, but the brightness dependence of the scatterer size is small.

So far, in FIGS. 5 to 8, the scatterer model in which the density is changed and the scatterer model in which the sound velocity is changed are examined by separate simulations. In addition, the shape of the scatterer is circular, which is significantly different from the actual structure in the living body.

FIG. 10 shows the results of examination in a model having a sound velocity distribution and a density distribution at the same time. For the sound velocity distribution, tissue segmentation was performed according to the brightness of the image from clinical images obtained by MRI, and a structure that could actually exist as an object was modeled.

Specifically, segmentation was performed on the four tissues of water (outside the breast area), skin, mammary gland tissue, and adipose tissue based on the judgment of brightness and the inside and outside of the contour, and the sound velocities of each were 1500, 1640, 1550, and 1450 m / s. (See FIG. 10a). A model was created in which the point scatterers with varying densities shown in FIG. 10b were superimposed on this.

The speed of sound of the point scatterer is the same as the speed of sound of the surroundings, and the density is 1100 kg / m ³ . All other tissues have a density of 1000 kg / m ³ . The results of calculating the echo data and reconstructing the image are the backscattered image shown in FIG. 10c and the forward scattered image shown in FIG. 10d, respectively.

In general, the estimated value of the initial sound velocity distribution corresponding to step S3 does not exceed the true value in spatial resolution (resolution limit in imaging). In this calculation, a model in which a low-pass filter was applied in the spatial direction to the set model was used as the initial sound velocity distribution estimated value in step S3.

The sound velocity distribution and the density distribution are given at the same time in one model. The backscattered image shown in FIG. 10c is an image reflecting the sound velocity distribution, and the forward scattered image shown in FIG. 10d is an image reflecting the density distribution. It can be confirmed that it is imaged.

Further, as another embodiment, the method shown in FIG. 9 will be described. In the implementation method shown in FIG. 4, step S3 was a method of constructing the final image in a state already set by a known method. When a sound velocity distribution image with higher accuracy than step S3 is obtained in step S11, as a method of utilizing this, the sound velocity distribution of step S3 may be updated based on the calculation result of step S11, and steps S4 and subsequent steps may be repeated. It is possible.

At this time, in step S11, since the absolute value of the difference between the true value and the sound velocity distribution image in step S3 is obtained, strictly speaking, the sign information of "true value-estimated value in step S3" is lost. Therefore, the sound velocity distribution in step S3 is updated so that the predetermined cost function is minimized, considering that the code of the information in step S11 may be both positive and negative. As the cost function, for example, the sum of the absolute differences between adjacent pixels is assumed.

The update of the sound velocity distribution in step S3 is effective from the following viewpoints. When calculating the difference waveform in step S6, when the difference ΔT = T _{1 −} T ₂ between the actual pulse propagation time T ₁ and the estimated pulse propagation time T ₂ becomes larger than the pulse width PW, the difference The received pulse whose waveform is emulated with the actual received pulse is separated on the time axis. As a result, the accuracy of focusing on the scatterer source in backpropagation is reduced. Therefore, by updating the sound velocity distribution in step S3 using the sound velocity distribution information newly obtained in step S11 and performing the reconstruction process again, it is possible to expect an improvement in calculation accuracy.

At this time, at the stage where the accuracy cannot be ensured, the loop is updated from step S13 to step S3 by using the condition that the pulse width PW is long (using a low frequency pulse or a pulse having a long number of cycles). The pulse width PW is shortened each time. In this case, more accurately, the loop returns from step S13 to step S2, the transmission waveform in step S2 is also changed, and transmission and imaging are performed again.

Although the present invention has been described in detail using specific embodiments, it will be apparent to those skilled in the art that various modifications can be made without departing from the intent and scope of the invention.
This application is based on Japanese Patent Application 2017-210737 filed on October 31, 2017, which is incorporated by reference in its entirety.

10 Ultrasonic diagnostic system 110 Switch circuit 120 Transmission / reception circuit 130 Arithmetic logic unit 140 Image display device

Claims (9)

A plurality of elements arranged around the subject and performing at least one of transmission and reception of ultrasonic waves, and
One of the plurality of elements transmits ultrasonic waves, and at least a part of the plurality of elements controls the plurality of elements so that the ultrasonic waves receive scattered waves scattered by the subject. Control unit and
A data collection unit that collects actual measurement data, which is data obtained from the element that received the scattered wave,
The sound velocity distribution of the subject is estimated using the actual measurement data, and the virtual measurement data received by the element when the ultrasonic wave propagates in the region having the estimated sound velocity distribution is calculated, and the actual measurement data and the said The difference waveform from the virtual measurement data is calculated, the component used for the calculation of the sound velocity distribution image or the component used for the calculation of the scatterer distribution image is obtained from the difference waveform, and the difference waveform of the component used for the calculation of the sound velocity distribution image is obtained. A calculation unit that calculates the sound velocity distribution image used, or a scatterer distribution image that uses the difference waveform of the components used to calculate the scatterer distribution image.
Ultrasonic diagnostic system equipped with. The component used for calculating the sound velocity distribution image is a forward scattered wave component which is a component of scattered waves scattered on a side other than the side of the element that transmitted the ultrasonic wave, and the component used for calculating the scatterer distribution image is. The ultrasonic diagnostic system according to claim 1, wherein the backscattered wave component is a component of a scattered wave scattered on the side of the element that transmits the ultrasonic wave. The plurality of elements are arranged in a ring shape at equal intervals.
The calculation unit classifies the difference waveform corresponding to the element located on one half side of the ring circumference around the element that transmitted the ultrasonic wave into the backscattered wave component, and the element located on the other half side of the ring circumference. The ultrasonic diagnostic system according to claim 2, wherein the difference waveform corresponding to the above is classified into the forward scattered wave component. The calculation unit calculates the sound velocity distribution image and the scatterer distribution image for each transmitting element that transmits ultrasonic waves.
The ultrasonic diagnosis according to any one of claims 1 to 3, further comprising an image creating unit that adds the sound velocity distribution image for each transmitting element and the scatterer distribution image for each transmitting element. system. The ultrasonic diagnostic system according to claim 4, wherein the image creating unit creates a density distribution image from the sound velocity distribution image and the scatterer distribution image. The calculation of the sound velocity distribution image includes backscattering of the difference waveform of the forward scattered wave component, and the calculation of the scatterer distribution image includes backscattering of the difference waveform of the backward scattered wave component. The ultrasonic diagnostic system according to any one of 5 to 5. The estimated sound velocity distribution is updated using the scattered body distribution image, and the difference waveform is calculated, and the sound velocity distribution image or the scattered body distribution image is calculated using the updated sound velocity distribution. The ultrasonic diagnostic system according to any one of claims 2 to 6, wherein the ultrasonic diagnostic system is characterized. The plurality of elements are arranged in a ring shape.
The ultrasonic diagnostic system according to claim 1, wherein the scatterer distribution image is reconstructed by back propagation of the difference waveform from a part of the elements on the ring circumference. A step of transmitting ultrasonic waves from any one of a plurality of elements arranged around a subject and receiving scattered waves at at least a part of the plurality of elements.
The process of collecting measurement data, which is the data obtained from the element that received the scattered wave, and
A step of estimating the sound velocity distribution of the subject using the actual measurement data, and
The process of calculating the virtual measurement data received by each element as ultrasonic waves propagate through the region with the estimated sound velocity distribution, and
The process of calculating the difference waveform between the actual measurement data and the virtual measurement data,
A step of acquiring a component used for calculating the sound velocity distribution image or a component used for calculating the scatterer distribution image from the difference waveform, and
The process of calculating the sound velocity distribution image using the difference waveform of the components used for calculating the sound velocity distribution image, and
The step of calculating the scatterer distribution image using the difference waveform of the components used for calculating the scatterer distribution image, and
Ultrasound diagnostic method comprising.