Ultrasonic diagnostic device

Abstract

The objective of this invention is to enable the contrast agent to be easily and appropriately imaged over a wide range of depth directions within the body of the patient. Alternatively, to obtain emission conditions suitable for ultrasound contrast imaging examination for each patient. The ultrasound diagnostic device includes: a biological parameter calculation and processing unit that acquires a set of biological parameters representing the propagation state of ultrasound waves within the patient by implementing pilot emission; a sound pressure distribution simulation execution unit (1102) that estimates the sound pressure distribution by performing sound pressure distribution simulation by taking a set of emission parameters extracted from the ultrasound emission condition storage unit (118) as emission conditions and the set of biological parameters as input; and a sound pressure distribution analysis unit (1104) that analyzes multiple sound pressure distributions estimated by performing multiple sound pressure distribution simulations based on different sets of emission parameters, selects the set of emission parameters that can obtain the best contrast image, and determines the selected set of emission parameters as the emission conditions to be used in ultrasound contrast imaging examination.

Description

Technical Field

[0001] This invention relates to an ultrasound diagnostic device, and more particularly to an ultrasound diagnostic device used in ultrasound contrast imaging examinations. Background Technology

[0002] Contrast-Enhanced Ultrasound (CEUS) is a technique that uses intravenous injection of a contrast agent into a living organism and a beam of ultrasound to generate strong vibrations, thereby extracting nonlinear components such as harmonics from the received echoes to image blood vessels within the organism. The bubble-like contrast agent exhibits three dynamics under ultrasound irradiation: reflection, resonance, and cavitation. These dynamics depend on the sound pressure level of the emitted ultrasound beam. To display blood vessels with high contrast and good image quality, it is preferable to control the ultrasound sound pressure level across the entire depth direction within the subject, between a contrast threshold and a destruction threshold. The contrast threshold serves as the lower limit for imaging with a certain or higher contrast relative to the tissue, while the destruction threshold serves as the upper limit for the contrast agent to remain intact. Since the sound pressure level of the emitted ultrasound beam depends on the emission conditions, these conditions need to be adjusted to ensure that the sound pressure level falls within the aforementioned thresholds.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2002-177270

[0004] Patent Document 2: Japanese Patent Application Publication No. 2003-175038

[0005] Patent Document 3: Japanese Patent Application Publication No. 2020-39821

[0006] Patent Document 4: Japanese Patent Application Publication No. 2009-201651

[0007] However, even under the same emission conditions, the vibrational state of the contrast agent can vary depending on the patient's body size and other factors. Furthermore, even for the same patient, the vibrational state can dynamically change depending on the location of the contrast agent within the tissue and the patient's blood pressure, body temperature, and other conditions during the examination. Therefore, to generate ultrasound images that accurately represent the distribution of the contrast agent across a wide depth range within the patient, the emission conditions used in each ultrasound contrast-enhanced examination must be appropriately set. Summary of the Invention

[0008] The object of this invention is to enable the contrast agent to be readily and appropriately imaged over a wide range of depth directions within the subject. Alternatively, the object of this invention is to obtain emission conditions suitable for ultrasound contrast examination of each subject.

[0009] The ultrasonic diagnostic device of the present invention is characterized by comprising a processor that performs the following processing: selecting a simulated measurement condition from multiple measurement conditions that generate different transmitted beams; generating an intensity distribution as a sound pressure distribution along the depth direction within a specific subject, or a distribution related to harmonics reflecting the sound pressure distribution, by performing simulation or pre-transmission / reception based on the simulated measurement condition; calculating an evaluation value representing the size of a portion of the intensity distribution that satisfies appropriate intensity conditions for contrast agent imaging; selecting a formal measurement condition from the multiple measurement conditions based on multiple evaluation values ​​corresponding to the multiple measurement conditions; performing transmission / reception for ultrasound contrast imaging based on the formal measurement condition, and generating an ultrasound image representing the distribution of contrast agent within the specific subject based on received information obtained from the specific subject.

[0010] Furthermore, the appropriate intensity condition may include a lower intensity threshold for ensuring the lowest contrast of the ultrasound image and an upper intensity threshold for avoiding damage to the contrast agent. The portion that satisfies the appropriate intensity condition is the portion that falls between the lower intensity threshold and the upper intensity threshold of the sound pressure distribution.

[0011] Furthermore, the measurement conditions can be a set of transmission parameters that serve as transmission conditions for generating the transmission beam.

[0012] Furthermore, the processor can perform the following processing: based on the received information obtained from the specific subject, perform pre-transmission and reception of a set of biological parameters, which represents the ultrasonic wave propagation state within the specific subject; and estimate the sound pressure distribution along the depth direction within the specific subject by performing the simulation using the transmission parameter set and the biological parameter set as input parameters.

[0013] Furthermore, the appropriate intensity condition may have an intensity lower limit threshold for ensuring the desired contrast of the ultrasound image, and the portion that satisfies the appropriate intensity condition is the portion of the distribution related to the harmonics that is above the intensity lower limit threshold.

[0014] Furthermore, the measurement conditions may be a set of transmission parameters as transmission conditions and a set of reception parameters as reception conditions, wherein the transmission conditions are the transmission conditions used for the pre-transmission and the ultrasound contrast imaging examination.

[0015] Furthermore, the processor can calculate the evaluation value based on the display range of the ultrasound image or the range of interest in the depth direction of the specific subject.

[0016] -Invention Effects-

[0017] According to the present invention, the contrast agent can be readily and appropriately imaged over a wide range of depth directions within the subject. Alternatively, according to the present invention, emission conditions suitable for ultrasound contrast examination of each subject can be obtained. Attached Figure Description

[0018] Figure 1 This is a block diagram showing the general structure of the ultrasound diagnostic device in Embodiment 1.

[0019] Figure 2 This is a flowchart illustrating the method for determining the launch conditions in Implementation 1.

[0020] Figure 3 (a) is a two-dimensional diagram showing the sound pressure distribution relative to the depth direction of the subject. Figure 3 (b) shows from Figure 3 The diagram shows the sound pressure level obtained from the sound pressure distribution shown in (a).

[0021] Figure 4 (a) is a diagram showing a specific example of a part of the body being examined. Figure 4 (b) is shown by... Figure 4 The sound pressure distribution was obtained by performing a sound pressure distribution simulation on the part shown in (a), and a graph of the sound pressure level obtained from the sound pressure distribution was obtained.

[0022] Figure 5 This is a block diagram showing the general structure of the ultrasound diagnostic device in Embodiment 2.

[0023] Figure 6 This is a flowchart illustrating the method for determining the transmission and reception conditions in Implementation Method 2.

[0024] Figure 7 (a) is a schematic diagram showing the harmonic power distribution relative to the depth direction of the object being examined. Figure 7 (b) shows from Figure 7 The diagram shows the harmonic power level obtained from the harmonic power distribution shown in (a).

[0025] Symbol Explanation

[0026] 10-Ultrasound diagnostic device; 100-Device body; 102-Transmit / receive control unit; 104-Signal processing unit; 106-Image processing unit; 108-Display processing unit; 110-Transmission condition determination unit; 112-Operation unit; 114-Display unit; 116-Control unit; 118-Ultrasound transmission condition storage unit; 120-Transmit / receive condition determination unit; 122-Ultrasound transmit / receive condition storage unit; 200-Probe; 202-Voltage array; 300 - Subject, 302- Subcutaneous fat layer, 304- Muscle, 306- Organ, 308- Tumor, 310- Large blood vessels, 1022- Transmitting beamformer, 1024- Receiving beamformer, 1042- Bioparameter calculation and processing unit, 1044- Harmonic component extraction and processing unit, 1102- Sound pressure distribution simulation execution unit, 1104- Sound pressure distribution analysis unit, 1202- Harmonic power distribution production unit, 1204- Harmonic power distribution analysis unit. Detailed Implementation

[0027] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0028] Implementation method 1.

[0029] (Structure of an ultrasound diagnostic device)

[0030] Figure 1 This is a block diagram showing the schematic structure of the ultrasonic diagnostic apparatus 10 according to this embodiment. The ultrasonic diagnostic apparatus 10 of this embodiment includes a main body 100 and a probe 200. The main body 100 is also referred to as a "control console," and has an operation unit 112 and a display unit 114, described later, serving as a user interface. The probe 200 is a device for transmitting and receiving ultrasonic beams used for ultrasonic diagnosis. A transducer array 202, composed of multiple transducers, is built into the probe 200. Each transducer converts electrical signals to ultrasonic signals via piezoelectric effect. The probe 200 can be of several types, including linear array, sector scan, and convex array.

[0031] The ultrasound diagnostic apparatus 10 can also be referred to as an ultrasound diagnostic system. The ultrasound diagnostic apparatus 10 has the function of performing ultrasound diagnosis using a probe 200. The ultrasound diagnostic apparatus 10 of this embodiment particularly has an ultrasound contrast imaging function. Ultrasound contrast imaging is an examination that uses an ultrasound beam to generate strong vibrations by injecting a bubble-like contrast agent into a vein of a living organism, and receives the resulting nonlinear signals, thereby depicting blood vessels in biological tissue with high contrast.

[0032] Furthermore, in the following description, "imaging in contrast mode" refers to imaging using contrast agents, which in this embodiment has the same meaning as imaging using contrast agents in ultrasound contrast imaging. Also, "contrast" in an image refers to the difference between the bright and dark parts of the image, and "high contrast" means that this difference is large. In this embodiment, "high contrast" means that the brightness difference between the areas where contrast agent is injected and those where no contrast agent is injected is large, allowing for a clear display of the ultrasound image representing the distribution of the contrast agent. In other words, contrast can also be described as the ratio of the intensity of the harmonic components from the contrast agent to the intensity of the harmonic components from the biological tissue.

[0033] The transceiver control unit 102 controls the ultrasonic transceiver based on each transducer within the probe 200. This control includes, for example, supplying electrical transmission signals to each transducer and amplifying electrical reception signals from each transducer. The transmit beamformer 1022 forms an ultrasonic transmission beam by controlling the timing of the transmission signals supplied to each transducer. The receive beamformer 1024 performs delay superposition processing on the received signals from each transducer within the probe 200. This delay superposition processing forms a receive beam. As a result of the delay superposition processing, the receive beamformer 1024 outputs echo data obtained along the receive beam.

[0034] The signal processing unit 104 performs various signal processing operations on the echo data output by the receiving beamformer 1024, including gain compensation, logarithmic amplification, envelope detection, and filtering. This generates beam data corresponding to each echo data point.

[0035] The signal processing unit 104 of this embodiment includes a bio-parameter calculation processing unit 1042. The bio-parameter calculation processing unit 1042 calculates bioacoustic parameters (hereinafter referred to as "bio-parameters") used in the sound pressure distribution simulation calculation performed by the transmission condition determination unit 110. More specifically, the bio-parameter calculation processing unit 1042 acquires a set of multiple bio-parameters (hereinafter referred to as "bio-parameter set") representing the ultrasonic wave propagation state within the subject body by transmitting pilot signals equivalent to pre-transmit / receive.

[0036] As detailed below, this embodiment determines the optimal emission conditions for obtaining an ultrasound image that represents a good contrast agent distribution. At this point, determining the precise sound pressure distribution is crucial. The sound pressure distribution is affected by parameters set in the emission conditions, such as the emission frequency and the input voltage to the probe, but it also varies considerably depending on the aforementioned biological parameters of the subject 300. In particular, since the sound attenuation rate or sound velocity included in the biological parameters can significantly alter the shape of the sound pressure distribution, it is preferable that these parameters be input into the sound pressure distribution simulation. Therefore, in this embodiment, a biological parameter calculation and processing unit 1042 is provided to acquire a set of biological parameters, which can then be input into the sound pressure distribution simulation.

[0037] In addition, as a method for estimating the sound attenuation rate, the technique described in, for example, Japanese Patent No. 6457107 can be used; as a method for estimating the sound velocity, the technique described in, for example, Japanese Patent No. 7493481 can be used.

[0038] The image processing unit 106 has coordinate transformation and interpolation functions, and forms a display frame, i.e., an ultrasound image, based on multiple beam data output from the signal processing unit 104. The beam data from the signal processing unit 104 is data in a beam scanning coordinate system, consisting of multiple data points along the beam direction corresponding to the beam data. The image processing unit 106, for example, converts the signal values ​​of each data point of the beam data into the coordinate system of the display coordinate system, i.e., the coordinate system of the ultrasound image (usually a Cartesian coordinate system composed of x and y coordinates). Furthermore, the image processing unit 106 interpolates the values ​​of pixels without values ​​based on the values ​​of surrounding pixels. Through this coordinate transformation and interpolation, the image processing unit 106 forms ultrasound images such as B-mode tomographic images. When performing ultrasound contrast imaging, the image processing unit 106 uses CHI (Contrast Harmonic Imaging) to generate an ultrasound image representing the distribution of the contrast agent. CHI is a method that selectively displays harmonic signals generated by the nonlinear effects of ultrasound waves incident on an ultrasound contrast agent (usually microbubbles). In the following description, the image formed using CHI will be referred to as a "contrast image". As described above, the transceiver control unit 102, the signal processing unit 104, and the image processing unit 106 work together to generate a contrast image of the subject 300 based on the received information obtained from the subject 300.

[0039] The display processing unit 108 combines the ultrasound image generated by the image processing unit 106 with images or text displaying various information to form display screen data. The information combined with the ultrasound image includes, for example, ROIs (Regions of Interest) indicating the display range of various display modes such as color Doppler mode, and sampling volumes in pulse Doppler mode along with lines showing the beam containing those sampling volumes. The display screen data generated by the display processing unit 108 is displayed on the display unit 114.

[0040] The emission condition determination unit 110 determines the emission conditions for emission beamforming. In this embodiment, the emission condition determination unit 110 determines emission conditions particularly suitable for contrast imaging. As detailed below, the emission condition determination unit 110 in this embodiment uses multiple sets of emission parameters pre-set and registered in the ultrasonic emission condition storage unit 118 as emission conditions. The emission condition determination unit 110 includes a sound pressure distribution simulation execution unit 1102 and a sound pressure distribution analysis unit 1104.

[0041] The sound pressure distribution simulation execution unit 1102 estimates the sound pressure distribution by performing sound pressure distribution simulation using a set of emission parameters (as emission conditions) and a set of biological parameters calculated by the biological parameter calculation and processing unit 1042 (hereinafter, the emission parameter set and the biological parameter set are collectively referred to as "input parameters"). In the sound pressure distribution simulation, the sound pressure distribution is output assuming that a contrast agent has been injected into the subject 300. In particular, in this embodiment, by using the biological parameters of the subject 300 as input to the sound pressure distribution simulation, the sound pressure distribution along the depth direction within the subject can be estimated. The sound pressure distribution simulation execution unit 1102 obtains multiple sound pressure distributions by performing multiple sound pressure distribution simulations using different sets of emission parameters as emission conditions.

[0042] The sound pressure distribution analysis unit 1104 refers to multiple sound pressure distributions obtained by the sound pressure distribution simulation execution unit 1102 and selects the emission conditions estimated to be optimal for ultrasound contrast imaging of the subject 300. Essentially, emission conditions are selected where the range (referred to as the "appropriate range") estimated to provide good contrast in the depth direction of the subject 300 is maximized. In the ultrasound contrast imaging, the emission conditions determined by the emission condition determination unit 110 are used to perform emission beamforming. Furthermore, in this embodiment, unless otherwise specified, "depth direction" refers to the direction from the surface of the subject 300 toward the interior of the body.

[0043] The operation unit 112 is a device operated by the surgeon or other operator (hereinafter also referred to as "user") to input parameters and perform display control during ultrasound diagnosis. The display unit 114 is a device for displaying images, and is configured, for example, by a liquid crystal panel or an organic EL panel. Display screen data generated by the display processing unit 108 is displayed on the display unit 114. The control unit 116 controls the execution of ultrasound diagnostic processing by controlling the operation of each component included in the control device main body 100.

[0044] In the ultrasonic emission condition storage unit 118, multiple sets of emission parameters used in performing emission beamforming through sound pressure distribution simulation and other methods are pre-set and registered as measurement conditions. The emission parameter sets are created by combining multiple emission parameters. The emission parameters included in the emission parameter set can themselves have the same structure as the emission parameters specified in normal emission beamforming. Specifically, the emission parameters include the input voltage, frequency, pulse length, ultrasonic waveform (sine wave or waveform formed by superimposing multiple sine waves, etc.), apodization, aperture, and focus of the probe 200. By changing the setting value of at least one of these emission parameters, multiple sets of emission parameters with setting values ​​that are not completely consistent with other emission parameter sets are set. Multiple emission parameter sets with different settings are combined into emission conditions that generate different emission beams. Furthermore, since the emission parameter set is used as the emission condition for performing emission beamforming, it is sometimes referred to as "emission condition" for convenience.

[0045] The functions provided by each component 102-116 in the device main body 100 are realized through the cooperative operation of a computer mounted on the device main body 100 and a program running on the processor mounted on the computer. The computer may be configured to have multiple processors, and the functions provided by each component 102-116 may be appropriately distributed among the processors for execution. The multiple processors may include processors focused on specific processing functions. The control unit 116 may be implemented by a single processor or multiple processors. The ultrasonic emission condition storage unit 118 is implemented by a storage device such as an HDD (Hard Disk Drive) mounted on the device main body 100. Alternatively, it may be implemented via a network using an external storage device.

[0046] The above uses Figure 1 The structure of the ultrasound diagnostic device 10 described herein can be basically set to the same hardware structure as in the past.

[0047] (Method for determining launch conditions)

[0048] As described above, in contrast-enhanced ultrasound examination, a contrast agent is intravenously injected into a living organism (i.e., "subject 300"). An ultrasound beam is used to cause the contrast agent to vibrate strongly, and the resulting nonlinear signal is received as receiving information to depict the blood vessels of the subject 300. However, even under the same emission conditions, the vibration state of the bubble-like contrast agent can vary depending on factors such as the size of the subject 300. Furthermore, even for the same subject 300, the vibration state may dynamically change depending on the location of the contrast agent in the tissue and the subject's blood pressure, body temperature, and other conditions during the examination. Therefore, it is preferable to set emission conditions suitable for the differences in the subject 300 or the subject's physical condition during beamforming, resulting in good contrast images in the contrast-enhanced ultrasound examination.

[0049] Therefore, in this embodiment, ultrasound pre-transmission and reception are performed before performing ultrasound contrast imaging to obtain biological parameters that represent the state of the subject 300 being examined, and these biological parameters are used as input to perform sound pressure distribution simulation. A feature of this embodiment is that by performing sound pressure distribution simulation using a set of biological parameters and various sets of transmission parameters as transmission conditions, the transmission conditions that yield the optimal contrast imaging image for the subject 300 during ultrasound contrast imaging are determined. The optimal contrast imaging image referred to here is a high-contrast and good contrast imaging image along the depth direction of the subject 300 within the imaging field of view. Furthermore, a high-contrast and good contrast imaging image is essentially equivalent to the sound pressure distribution obtained through ultrasound transmission and reception falling within the range of a contrast threshold and a destruction threshold within the imaging field of view, as described later. In this embodiment, the condition that the sound pressure level falls within the range of the contrast threshold and the destruction threshold is defined as an appropriate intensity condition, and is considered as obtaining a good contrast imaging image with high contrast when the appropriate intensity condition is met. Incidentally, the "contrast threshold" refers to the lower limit threshold of intensity used to ensure the minimum contrast of the ultrasound image. The "destruction threshold" is an upper limit threshold for contrast agent intensity used to avoid destruction of the contrast agent. Both the contrast threshold and the destruction threshold can be determined using known methods.

[0050] The following uses Figure 2 The flowchart shown illustrates the method for determining the launch conditions in this embodiment.

[0051] First, the ultrasound diagnostic device 10 acquires biological parameters representing the body condition or current status of the organism, i.e., the subject 300. Specifically, the ultrasound diagnostic device 10 transmits a pilot signal based on a first ultrasound frequency toward a predetermined location on the subject 300, such as an organ or tumor (step S110). The first ultrasound frequency can be a frequency commonly used in ultrasound diagnostics. For example, the first ultrasound frequency can be 2 to 20 MHz.

[0052] The bioparameter calculation and processing unit 1042 calculates bioparameters based on the received signal obtained through pilot transmission (step S120). Bioparameters include, for example, the sound attenuation rate, sound velocity, and subcutaneous fat thickness at a specified location on the subject, estimated based on the received signal. In this embodiment, these bioparameters are aggregated to obtain a bioparameter set.

[0053] If a biological parameter set is obtained, the sound pressure distribution simulation execution unit 1102 selects a set of emission parameters for sound pressure distribution simulation from the set of emission parameters registered in the ultrasonic emission condition storage unit 118 (step S130).

[0054] As described above, the ultrasonic emission condition storage unit 118 stores multiple sets of emission parameters with different values ​​for at least one emission parameter. The sound pressure distribution simulation execution unit 1102 reads emission parameter sets that have not yet been used for simulation execution from the ultrasonic emission condition storage unit 118. Reading these emission parameter sets is equivalent to selecting simulation measurement conditions for performing sound pressure distribution simulation from the measurement conditions registered in the ultrasonic emission condition storage unit 118.

[0055] Then, the sound pressure distribution simulation execution unit 1102 uses the read emission parameter set as emission conditions, and uses the emission conditions and the biological parameter set calculated by the biological parameter calculation processing unit 1042 as input parameters to perform sound pressure distribution simulation, thereby estimating the sound pressure distribution (step S140). In this embodiment, a sound pressure distribution representing the intensity of the sound pressure is generated as an intensity distribution.

[0056] Thus, if a sound pressure distribution is obtained by performing a sound pressure distribution simulation using a set of emission parameters as emission conditions, the sound pressure distribution analysis unit 1104 analyzes this sound pressure distribution to extract and determine the range from the entire depth direction in which a high-contrast and good imaging image can be obtained in the depth direction of the subject 300 (step S150). The range determined here is referred to as the "suitable range" as described below. The details of the processing in this sound pressure distribution analysis unit 1104 will be explained later.

[0057] Next, when the sound pressure distribution simulation is performed using all the emission parameter sets registered in the ultrasonic emission condition storage unit 118 as emission condition candidates ("Yes" in step S160), the sound pressure distribution simulation execution unit 1102 proceeds to step S170. If there is an emission parameter set that has not yet been used to perform the sound pressure distribution simulation ("No" in step S160), the process proceeds to step S130, and the aforementioned steps S140 to S150 are repeated.

[0058] Here, the processing in the sound pressure distribution analysis unit 1104 will be explained.

[0059] Figure 3 (a) is a schematic diagram showing the sound pressure distribution obtained by performing a sound pressure distribution simulation. Figure 3 (b) shows from Figure 3 The diagram shows the sound pressure level obtained from the sound pressure distribution shown in (a).

[0060] exist Figure 3 In (a), the sound pressure distribution relative to the depth direction is shown in two dimensions by transmitting and receiving ultrasonic beams from the transducer array 202. Figure 3 In (a), the darker the color, the higher the sound pressure. That is, if an ultrasonic beam is emitted from the transducer array 202, the sound pressure increases as it moves toward the focal point (i.e., as the color deepens). Then, it can be seen that the sound pressure decreases after passing the focal point.

[0061] Figure 3 In (b), from Figure 3 The sound pressure level is extracted and shown in one dimension along the central axis represented by the dashed line C in the two-dimensional sound pressure distribution shown in (a). Figure 3 In (b), the sound pressure S is the sound pressure level, which means that the level is higher the closer to the right of the figure.

[0062] exist Figure 3 (b) shows the contrast threshold t1 and the destruction threshold t2. When the sound pressure S falls within the range SR between these thresholds, a high-contrast and good contrast image can be obtained. Furthermore, a high-contrast and good contrast image refers to a contrast image that is useful and suitable for ultrasound contrast examination; therefore, for convenience, it will be referred to as a "suitable image" in the following description.

[0063] For example, in Figure 3 In (b), the sound pressure S when the depth from the oscillator array 202 does not reach the depth d1 does not reach the contrast threshold t1, so sufficient contrast is not obtained, which means that a suitable image is not obtained.

[0064] The sound pressure S at a distance from the oscillator array 202 between depth d1 and depth d2 is above the contrast threshold t1 but below the damage threshold t2. In other words, it falls within the range between the contrast threshold t1 and the damage threshold t2. Therefore, within this range L1, a suitable image can be obtained.

[0065] The sound pressure S at a depth between depth d2 and depth d3 from the oscillator array 202 is above the destruction threshold t2, which causes the contrast agent to be destroyed, indicating that a suitable image cannot be obtained.

[0066] The sound pressure S at a depth of d3 to d4 from the oscillator array 202 is similar to the range L1, being above the contrast threshold t1 but not reaching the damage threshold t2. In other words, it is the part falling between the contrast threshold t1 and the damage threshold t2. Therefore, within this range L2, a suitable image can be obtained.

[0067] Moreover, the sound pressure S when the depth from the oscillator array 202 exceeds the depth d4 does not reach the contrast threshold t1, so sufficient contrast is not obtained, which means that a suitable image is not obtained.

[0068] As described above, in this embodiment, ranges L1 and L2 are extracted as the range within which a suitable image can be obtained in ultrasound contrast imaging (hereinafter referred to as the "suitable range"). The suitable range can also be described as the length in the depth direction, but the longer the length in the depth direction, the better the suitable image can be obtained.

[0069] The sound pressure distribution analysis unit 1104 analyzes the sound pressure distribution obtained from a single sound pressure distribution simulation and calculates a suitable range as an evaluation value. This evaluation value represents the size of the portion of the sound pressure distribution that satisfies the appropriate intensity condition for contrast agent imaging (i.e., generating a contrast image). Specifically, the sound pressure distribution analysis unit 1104 defines the appropriate intensity condition as the case where the sound pressure S level falls between a contrast threshold t1 and a destruction threshold t2, and calculates the portion that satisfies this appropriate intensity condition, i.e., the suitable range. In this embodiment, the number of evaluation values ​​obtained is the same as the number of times steps S130 to S150 are repeated; in other words, the number of evaluation values ​​obtained is the same as the number of emission parameter sets registered in the ultrasonic emission condition storage unit 118.

[0070] Then, the emission condition determination unit 110 determines the emission condition with the best evaluation value, that is, the emission condition (i.e., the emission parameter set) in which the total length of the suitable range in the depth direction is maximized, as the emission condition to be used in the ultrasound contrast imaging examination (step S170). Determining the emission condition to be used in the ultrasound contrast imaging examination according to the suitable range is equivalent to selecting the formal measurement condition from the multiple emission parameter sets (i.e., measurement conditions) registered in the ultrasound emission condition storage unit 118.

[0071] As described above, once the emission conditions are determined, the ultrasound diagnostic apparatus 10 uses those emission conditions to perform an ultrasound contrast imaging examination. During the ultrasound contrast imaging examination, by using these emission conditions, a suitable image, i.e., a high-contrast and well-contrast image, can be displayed.

[0072] (Variation example)

[0073] Figure 4 (a) is a diagram showing a specific example of a part that becomes the object of examination for subject 300. Figure 4(a) schematically illustrates the subcutaneous fat layer 302, muscle 304, and organs 306 such as the liver. Furthermore, it shows the presence of a tumor 308 and a large blood vessel 310 within organ 306. Figure 4 The part of the subject 300 shown in (a) becomes Figure 3 The transmitting and receiving objects of the ultrasonic beam shown in (a) become the object of sound pressure distribution simulation.

[0074] exist Figure 4 In (a), the following is omitted: Figure 3 The diagram showing the sound pressure distribution in (a) is shown, but... Figure 4 In (b), along Figure 4 The central axis, represented by a single-dotted dashed line C, is shown in (a), and the sound pressure level is extracted and illustrated in one dimension. Figure 4 The suitable range in (b) can be achieved by using Figure 3 (b) is used to determine this. That is, when the sound pressure S falls within the range SR between the contrast threshold t1 and the destruction threshold t2, in Figure 4 In (b), range L3 becomes the suitable range.

[0075] In the above description, the suitable range is calculated based on the entire display range of the contrast-enhanced image; a longer suitable range is considered a better contrast-enhanced image. However, users sometimes desire a clearer image of a specific area of ​​the subject (300°) during ultrasound contrast-enhanced examinations, even if the suitable range is slightly shortened. Emission conditions can be selected to meet such user requirements.

[0076] For example, by inputting a preset location (e.g., the name of an organ such as the liver or pancreas, or a general location such as the abdomen or lower limbs), the area the user wants to observe can be roughly determined; in other words, the area of ​​interest (hereinafter referred to as the "range of interest"). For example, in the case of a Japanese male's liver, the average distance from the skin to the liver surface is 3-4 cm, and to the diaphragm is 12-15 cm. The 3-15 cm range containing the liver becomes the imaging range to be depicted. Thus, as one method of specifying the range of interest in the depth direction within the subject, the user inputs a preset location.

[0077] Alternatively, the area of ​​interest can be specified from the entire display area of ​​the contrast image. For example, in Figure 4 In (a), if you want to observe only a certain area where tumor 308 is located, you can manually specify the area of ​​interest A as the range from depth d6 to depth d7.

[0078] Given a specified area of ​​interest, the sound pressure distribution analysis unit 1104 calculates the proportion (length) of the area of ​​interest that is included within the suitable area. Here, the proportion of overlap between the area of ​​interest and the suitable area within the area of ​​interest is called the "overlap rate." For example, according to... Figure 4 In the example shown, the area of ​​interest A overlaps with the suitable area L3 by 100%, so the overlapping area (length) is A. Therefore, the overlap rate in the area of ​​interest A can be calculated as the overlap length (=A) / area of ​​interest (=A) = 100%.

[0079] Furthermore, when multiple sets of transmission parameters exist that maximize overlap, any one of them can be selected, or a selection can be made based on a certain criterion, or the user can make the selection. For example, a suitable range of transmission parameters could be selected as the maximizing criterion. Alternatively, for example, in... Figure 4 In the attached figure (b), the emission parameter set with the largest area can be selected, which is enclosed by depths d6 and d7, contrast threshold t1, and sound pressure S at both ends of the area of ​​interest A. Conversely, the emission parameter set with the smallest area enclosed by depths d6 and d7, destruction threshold t2, and sound pressure S can also be selected. Alternatively, a threshold t3 can be set between the contrast threshold t1 and the destruction threshold t2, and the emission parameter set with the largest range (length) exceeding the threshold t3 can be selected.

[0080] In this embodiment, the emission conditions used in the contrast-enhanced ultrasound examination are determined as described above. The contrast-enhanced ultrasound examination itself can be performed using the same methods as before, so description is omitted. However, by using the emission conditions determined in the aforementioned method, a good contrast image can be displayed.

[0081] In addition, in this embodiment, when performing sound pressure distribution simulation, all emission parameter sets registered in the ultrasonic emission condition storage unit 118 are used, but the user can also select the emission parameter set.

[0082] Furthermore, the range of possible values ​​for each emission parameter is essentially defined. Therefore, users can select values ​​for the emission parameters used in sound pressure distribution simulation from the available range. That is, this is equivalent to providing the function of allowing users to manually create their own emission parameter sets. Alternatively, the emission parameter sets created by the user can be registered in the ultrasonic emission condition storage unit 118, or they can remain unregistered. Alternatively, the information can be managed separately from the ultrasonic emission condition storage unit 118 as customized data.

[0083] In this embodiment, a good contrast image can be evaluated and displayed by magnifying it along the depth direction. Furthermore, the state of the subject 300 at the time of the ultrasound contrast examination (i.e., the aforementioned "biological parameters") is acquired by pilot transmission prior to the ultrasound contrast examination. This allows for the determination of transmission conditions suitable for the subject 300 at the time of the ultrasound contrast examination, and by using these transmission conditions, a good contrast image suitable for the subject 300 can be displayed during the ultrasound contrast examination.

[0084] Furthermore, in this embodiment, the sound pressure distribution along the central axis, i.e., the sound pressure distribution in one dimension, has been described. However, a suitable range can also be obtained by comprehensively considering the sound pressure distribution in two or three dimensions.

[0085] Implementation method 2.

[0086] (Structure of an ultrasound diagnostic device)

[0087] Figure 5 This is a block diagram showing the schematic structure of the ultrasonic diagnostic apparatus 10 according to this embodiment. The structure of the ultrasonic diagnostic apparatus 10 in this embodiment is basically the same as that in Embodiment 1. The ultrasonic diagnostic apparatus 10 in this embodiment has the internal structure of a signal processing unit 104, and a transceiver condition determination unit 120 is provided instead of a transmission condition determination unit 110. Furthermore, in Embodiment 1, only the transmission parameter set is registered in the ultrasonic transmission condition storage unit 118, but in the ultrasonic transceiver condition storage unit 122 of this embodiment, in addition to the transmission parameter set, a reception parameter set is also registered.

[0088] The signal processing unit 104 of this embodiment includes a harmonic component extraction processing unit 1044. The harmonic component extraction processing unit 1044 estimates the sound pressure distribution based on the received signal obtained through pilot transceiver equivalent to pre-transmit and extracts harmonic components from the sound pressure distribution.

[0089] The transmit / receive condition determination unit 120 of this embodiment determines the transmit conditions for transmitting beamforming and the receive conditions for receiving beamforming. The transmit / receive condition determination unit 120 includes a harmonic power distribution generation unit 1202 and a harmonic power distribution analysis unit 1204. The harmonic power distribution generation unit 1202 generates a harmonic power distribution based on the harmonic components extracted by the harmonic component extraction processing unit 1044. The harmonic power distribution generation unit 1202 generates one harmonic power distribution each time the pilot is transmitted or received. The harmonic power distribution analysis unit 1204 analyzes the multiple harmonic power distributions generated by the harmonic power distribution generation unit 1202 to select the transmit / receive conditions for obtaining the optimal imaging image.

[0090] The set of transmission parameters registered in the ultrasonic transceiver condition storage unit 122 can be the same as that in the ultrasonic transmission condition storage unit 118 in Embodiment 1. The receiving parameters included in the receiving parameter set can themselves have the same structure as the receiving parameters specified in normal receiving beamforming. Specifically, receiving parameters include apodization, bandpass filter threshold (cutoff frequency when extracting harmonics), number of receiving channels, aperture, etc. Only one set of receiving parameters can be prepared. Alternatively, similar to the transmission parameter set, multiple sets of receiving parameters with setting values ​​that are not completely consistent with other sets of receiving parameters can be prepared by changing the setting value of at least one of the receiving parameters. The harmonic power distribution generation unit 1202 selects any one set of transmission parameters registered in the ultrasonic transmission condition storage unit 118 as the transmission condition and selects any one set of receiving parameters registered in the ultrasonic transmission condition storage unit 118 as the receiving condition, thereby generating a harmonic power distribution.

[0091] (Method for determining sending and receiving conditions)

[0092] As described above, the vibration state of the contrast agent bubbles injected intravenously into the subject 300 can dynamically change according to differences in the body size, etc., of the subject 300, and even for the same subject 300, it can dynamically change depending on the location of the contrast agent bubbles in the tissue or the condition of the subject 300. Therefore, it is desirable to perform ultrasound contrast imaging examinations suitable for the differences in the subject 300 or the physical condition of the subject 300. Therefore, in the above-described embodiment 1, the optimal transmission conditions were determined using sound pressure distribution simulation. In this embodiment, by actually performing pre-transmission and reception, i.e., pilot transmission and reception, on the subject 300, the set of transmission and reception conditions used in the ultrasound contrast imaging examination (hereinafter collectively referred to as "transmission and reception conditions") is determined.

[0093] The following uses Figure 6 The flowchart shown illustrates the method for determining the transmission and reception conditions in this embodiment.

[0094] First, for example, the harmonic power distribution generation unit 1202 in the transceiver condition determination unit 120 selects a set of transmission parameters that is not used in the pilot transceiver described later from the set of transmission parameters registered in the ultrasonic transceiver condition storage unit 122. Then, an arbitrary set of reception parameters is selected from the set of reception parameters registered in the ultrasonic transceiver condition storage unit 122 (step S210).

[0095] Next, the harmonic power distribution generation unit 1202 performs pilot transmission and reception using the selected set of transmission parameters as transmission conditions and the selected set of reception parameters as reception conditions (step S220). Thus, in this embodiment, when the set of transmission parameters and the set of reception parameters registered in the ultrasonic transceiver condition storage unit 122 are used as measurement conditions, the set of transmission parameters and the set of reception parameters selected from the ultrasonic transceiver condition storage unit 122 are used as simulation measurement conditions to perform pilot transmission and reception.

[0096] Next, the harmonic component extraction processing unit 1044 extracts the harmonic components originating from the contrast agent from the sound pressure distribution estimated based on the received signal obtained through pilot transceiver (step S230). Then, the harmonic power distribution generation unit 1202 generates a harmonic power distribution with reference to the harmonic components extracted by the harmonic component extraction processing unit 1044 (step S240). The harmonic power distribution is a distribution related to harmonics that reflect the sound pressure distribution, equivalent to an intensity distribution.

[0097] Thus, if a harmonic power distribution is obtained by performing a pilot transmission and reception operation using a set of transmission and reception parameters as transmission and reception conditions, the harmonic power distribution analysis unit 1204 analyzes this harmonic power distribution to extract and determine the suitable range (step S250) from the entire depth direction where a high-contrast and good contrast image can be obtained in the depth direction of the subject 300. The details of the processing in this harmonic power distribution analysis unit 1204 will be explained later.

[0098] Next, when pilot transmission is performed using all transmission parameter sets registered in the ultrasonic transceiver condition storage unit 122 as transmission condition candidates ("Yes" in step S260), the harmonic power distribution generation unit 1202 proceeds to step S270. If there are transmission parameter sets that have not yet been used for simulation ("No" in step S260), the process proceeds to step S210, and the aforementioned steps S210 to S250 are repeated.

[0099] For example, if m sets of transmission parameters and n sets of reception parameters are registered in the ultrasonic transceiver condition storage unit 122, the harmonic power distribution generation unit 1202 performs m×j (j=1~n) pilot transceivers. Furthermore, the combination of transmission and reception parameter sets used in the pilot transceivers can be selected by the user.

[0100] Here, the processing in the harmonic power distribution analysis unit 1204 will be explained.

[0101] Figure 7 (a) is a schematic diagram showing the harmonic power distribution produced by performing pilot transceiver. Figure 7 (b) shows from Figure 7The diagram shows the harmonic power level obtained from the harmonic power distribution shown in (a).

[0102] exist Figure 7 In (a), the harmonic power distribution relative to the depth direction is shown in two dimensions by transmitting and receiving ultrasonic beams from the oscillator array 202. Figure 7 In (a), the darker the color, the stronger the harmonic power. That is, if an ultrasonic beam is emitted from the oscillator array 202, the harmonics increase with depth and gradually become undetectable as the bubble-like contrast agent begins to break down.

[0103] Figure 7 In (b), from Figure 7 The two-dimensional harmonic power distribution shown in (a) is along the central axis represented by the dashed line C, and the level of the harmonic power is extracted and shown in one dimension. Figure 7 In (b), the harmonic power P refers to power, or in other words, the level of harmonic intensity. It indicates that the level is higher the closer to the right of the graph. Intensity can also be called sensitivity.

[0104] exist Figure 7 (b) shows the harmonic threshold t3. The harmonic threshold t3 is a lower limit threshold representing the intensity required to ensure the desired contrast of the contrast image. When the harmonic power P is above the harmonic threshold t3, it can be said that a high-contrast and good contrast image is a suitable image.

[0105] Incidentally, considering that the contrast of the imaging mode and the destruction of the contrast agent can be determined based on the harmonic values, instead of setting a contrast threshold t1 and a destruction threshold t2 as in Embodiment 1, a harmonic threshold t3 is set instead. The harmonic threshold t3 is the threshold at which the desired contrast can be estimated to be obtained when harmonics above this value are acquired. Furthermore, more harmonics can be obtained when the contrast agent vibrates appropriately. And, when the contrast agent is destroyed, the values ​​of the harmonic components decrease.

[0106] For example, in Figure 7 In (b), the harmonic power P when the distance from the oscillator array 202 to the depth d8 does not reach the harmonic threshold t3, so sufficient contrast is not obtained, which means that a suitable image is not obtained.

[0107] The harmonic power P at a depth between depth d8 and depth d9 of the oscillator array 202 is above the harmonic threshold t3, thus indicating that a suitable image can be obtained within the range L4 of depth d8 to depth d9.

[0108] Moreover, the harmonic power P when the distance from the oscillator array 202 exceeds the depth d9 does not reach the harmonic threshold t3, thus insufficient contrast is not obtained, meaning that a suitable image is not obtained.

[0109] From the above, we can see the suitable range for ultrasound contrast imaging examinations. Figure 7 In the example shown in (b), a fit image is obtained within the range L4, and the longer the length of the range L4 in the depth direction, i.e. the larger the total fit range, the better the fit image is obtained.

[0110] Thus, in this embodiment, an appropriate intensity condition is set for the harmonic power P to be above the harmonic threshold t3. Therefore, the portion that satisfies the appropriate intensity condition is the portion where the harmonic power P is above the harmonic threshold t3, such as range L4. In this embodiment, a suitable range is also calculated as an evaluation value, which represents the size of the portion that satisfies the appropriate intensity condition for generating the contrast image.

[0111] The harmonic power distribution analysis unit 1204 calculates the following based on the harmonic power distribution: Figure 7 (b) shows the range in which a suitable image can be obtained in the depth direction of the subject 300. Then, the transceiver condition determination unit 120 determines the transceiver conditions (i.e., the set of transmission parameter sets and reception parameter sets) that can obtain the maximum range (i.e., the total length in the depth direction) from the range in which the determined suitable image can be obtained as the transceiver conditions to be used in the ultrasound contrast imaging examination (step S270). Determining the transceiver conditions to be used in the ultrasound contrast imaging examination based on the suitable range is equivalent to selecting the formal measurement conditions from the multiple transceiver parameter sets (i.e., measurement conditions) registered in the ultrasound transceiver condition storage unit 122.

[0112] As described above, once the transmit and receive conditions are determined, an ultrasound contrast-enhanced imaging examination is performed using those conditions. In ultrasound contrast-enhanced imaging, by using these transmit and receive conditions, a suitable image, i.e., a high-contrast and well-formed contrast image, can be displayed. In this embodiment, the harmonic components contained in the received signal can be effectively extracted and imaged, rather than directly displaying the received signal. In other words, the desired vascular portion, to which contrast agent has been injected, can be displayed brightly, while other biological portions can be displayed dimly.

[0113] In addition, although the description is omitted in this embodiment, the user can specify the scope of interest in the same way as in embodiment 1.

Claims

1. An ultrasonic diagnostic device, characterized in that, Equipped with a processor The processor performs the following processing: Select simulation measurement conditions from multiple measurement conditions that generate different transmitted beams; By simulating or pre-transmitting based on the simulated measurement conditions, the sound pressure distribution along the depth direction within a specific test subject or the distribution related to the harmonics reflecting the sound pressure distribution is generated as the intensity distribution. Calculate an evaluation value representing the size of the portion of the intensity distribution that satisfies the appropriate intensity conditions for contrast agent imaging; Based on the multiple evaluation values ​​corresponding to the multiple measurement conditions, a formal measurement condition is selected from the multiple measurement conditions; By transmitting and receiving data for ultrasound contrast examination based on the formal measurement conditions, and generating an ultrasound image representing the distribution of contrast agent within the specific subject based on the received information obtained from the specific subject.

2. The ultrasonic diagnostic device according to claim 1, characterized in that, The appropriate intensity conditions include a lower intensity threshold to ensure the lowest possible contrast in the ultrasound image, and an upper intensity threshold to prevent damage from the contrast agent. The portion that satisfies the appropriate intensity condition is the portion that falls between the lower intensity threshold and the upper intensity threshold of the sound pressure distribution.

3. The ultrasonic diagnostic device according to claim 1, characterized in that, The measurement conditions are a set of transmission parameters used as transmission conditions for generating the transmission beam.

4. The ultrasonic diagnostic device according to claim 3, characterized in that, The processor performs the following processing: Based on the received information obtained from the specific subject, a set of biological parameters is pre-transmitted and received, which represents the ultrasonic wave propagation state within the specific subject. The simulation is performed by using the emission parameter set and the biological parameter set as input parameters to estimate the sound pressure distribution along the depth direction within the specific subject.

5. The ultrasonic diagnostic device according to claim 1, characterized in that, The appropriate intensity condition has an intensity lower limit threshold to ensure the desired contrast of the ultrasound image. The portion that satisfies the appropriate intensity condition is the portion of the distribution related to the harmonics that is above the lower intensity threshold.

6. The ultrasonic diagnostic device according to claim 1, characterized in that, The measurement conditions are a set of transmission parameters as transmission conditions and a set of reception parameters as reception conditions, wherein the transmission conditions are the transmission conditions used for the pre-transmission and the ultrasound contrast imaging examination.

7. The ultrasonic diagnostic device according to claim 1, characterized in that, The processor calculates the evaluation value based on the display range of the ultrasound image or the range of interest in the depth direction of the specific subject.

Images