A method, device, equipment and storage medium for determining the excitation frequency of shear waves

Abstract

The present invention discloses a method, device, equipment and storage medium for determining the excitation frequency of shear waves. In this solution, after determining the excitation focus within the shear wave imaging area, the optimal target excitation frequency of the current probe at the excitation focus can be determined based on the bandwidth curve function, directivity function of the current probe, and the attenuation coefficient and absorption coefficient of the excited tissue, thereby increasing the acoustic radiation force and shear wave amplitude at the excitation focus, and further increasing the signal-to-noise ratio of the shear wave, ensuring the optimal shear wave excitation effect at the excitation focus.

Description

Technical Field

[0001] The present invention relates to the technical field of shear wave elastic imaging, and more particularly to a method, device, equipment and storage medium for determining an excitation frequency of a shear wave. Background Art

[0002] Shear wave elastography based on acoustic radiation force is an ultrasonic elastography technology for assessing tissue hardness. The imaging steps of shear wave elastography are generally divided into two steps: the first step is to excite the shear wave, and the second step is to detect the shear wave propagation process. Since the shear wave excitation in shear wave elastography based on acoustic radiation force is carried out by relatively strong ultrasonic waves, and the safety intensity and power of ultrasonic waves in the human body are strictly limited by the laws and regulations of various countries, the intensity of the sound beam used to excite the shear wave is generally not very strong, and the corresponding acoustic radiation force is generally weak. The amplitude of the shear wave generated is generally very small, which is very easy to be drowned out by noise in the ultrasonic signal. The signal-to-noise ratio of shear wave detection is generally low.

[0003] Therefore, how to improve the signal-to-noise ratio of shear waves is a problem that those skilled in the art need to solve. Summary of the Invention

[0004] The object of the present invention is to provide a method, device, equipment and storage medium for determining the excitation frequency of shear waves, so as to determine the optimal excitation frequency of shear waves and improve the excitation effect of shear waves.

[0005] To achieve the above object, the present invention provides a method for determining the excitation frequency of a shear wave, comprising:

[0006] determining a focal depth of the excitation focus within the shear wave imaging region;

[0007] Obtaining a bandwidth curve function and a directivity function of the current probe; the bandwidth curve function is used to determine the transmit sensitivity of the current probe at different excitation frequencies; the directivity function is used to determine the transmit sensitivity of each array element in the current probe at different deflection angles;

[0008] Determining the sound intensity of each excitation frequency point using the attenuation coefficient of the excited tissue, the focal depth, the bandwidth curve function, and the directivity function;

[0009] The acoustic radiation force corresponding to each excitation frequency is obtained according to the sound intensity and the absorption coefficient of the excited tissue, and the excitation frequency corresponding to the maximum acoustic radiation force is used as the target excitation frequency.

[0010] The determining of the sound intensity of each excitation frequency point by using the attenuation coefficient of the excited tissue, the focal depth, the bandwidth curve function, and the directivity function includes:

[0011] determining an excitation aperture of the current probe according to the focal depth;

[0012] Determining the array element distance and deflection angle between each array element in the excitation aperture and the excitation focus;

[0013] Determine the first sensitivity of the current probe at each excitation frequency point using the bandwidth curve function;

[0014] Determining a second sensitivity of each array element at a corresponding deflection angle using the directivity function;

[0015] The sound intensity at each excitation frequency point is determined according to the attenuation coefficient of the excited tissue, the first sensitivity, the second sensitivity corresponding to each array element, and the distance between each array element.

[0016] The determining of the sound intensity at each excitation frequency point according to the attenuation coefficient of the excited tissue, the first sensitivity, the second sensitivity corresponding to each array element, and the distance between each array element includes:

[0017] Determine the sound intensity of the target probe at each excitation frequency using a sound intensity determination rule;

[0018] The sound intensity determination rule is:

[0019]

[0020] Among them, f j is the jth excitation frequency, I fj is the excitation frequency f j The sound intensity under the current probe is N, N is the total number of array elements in the excitation aperture of the current probe, i represents the i-th array element in the N array elements, Fbw(f j ) is the first sensitivity, is the second sensitivity, is the deflection angle between the ith array element and the excitation focus, L i is the array element distance between the ith array element and the excitation focus, and β is the attenuation coefficient.

[0021] The step of determining the array element distance and the deflection angle between each array element in the excitation aperture and the excitation focus includes:

[0022] Determining the probe type of the current probe;

[0023] The array element distance and the deflection angle between each array element in the excitation aperture and the excitation focus are determined according to the probe type and the focal depth.

[0024] If the probe type is a linear array probe, the process of determining the array element distance and the deflection angle between each array element in the excitation aperture and the excitation focus includes:

[0025] determining a first distance between a target array element and an aperture center of the excitation aperture;

[0026] An array element distance and a deflection angle between a target array element and the excitation focus are determined according to the first distance and the focal depth.

[0027] If the probe type is a convex array probe, the process of determining the array element distance and the deflection angle between each array element in the excitation aperture and the excitation focus includes:

[0028] Determining a second distance between the center of the convex array probe and the excitation focus;

[0029] Determining the angle between the target array element, the excitation focus and the center of the circle;

[0030] Determining an array element distance between the target array element and the excitation focus according to the radius of the convex array probe, the second distance, and the cosine value of the angle;

[0031] The deflection angle between the target array element and the excitation focus is determined according to the second distance, the radius, and the array element distance.

[0032] The shear wave imaging area includes at least one excitation focus, and different excitation focuses have different focal depths.

[0033] The acoustic radiation force corresponding to each excitation frequency point is obtained according to the sound intensity and the absorption coefficient of the excited tissue, including:

[0034] Using the acoustic radiation force determination rule, determine the acoustic radiation force corresponding to each excitation frequency point;

[0035] The acoustic radiation force determination rule is:

[0036]

[0037] in, is the jth excitation frequency f j The acoustic radiation force, α is the absorption coefficient of the excited tissue, is the jth excitation frequency f j The sound intensity is c, and the sound velocity of the excited tissue is c.

[0038] To achieve the above object, the present invention further provides a device for determining an excitation frequency of a shear wave, comprising:

[0039] A focus depth determination module, configured to determine a focus depth of an excitation focus within a shear wave imaging region;

[0040] A first acquisition module is used to acquire a bandwidth curve function of the current probe; the bandwidth curve function is used to determine the emission sensitivity of the current probe at different excitation frequencies;

[0041] A second acquisition module is used to obtain a directivity function of the current probe; the directivity function is used to determine the transmission sensitivity of each array element in the current probe at different deflection angles;

[0042] an acoustic intensity determination module, configured to determine the acoustic intensity of each excitation frequency point by using the attenuation coefficient of the excited tissue, the focal depth, the bandwidth curve function, and the directivity function;

[0043] an acoustic radiation force determination module, configured to obtain the acoustic radiation force corresponding to each excitation frequency point based on the sound intensity and the absorption coefficient of the excited tissue;

[0044] The target excitation frequency determination module is used to use the excitation frequency corresponding to the maximum acoustic radiation force as the target excitation frequency.

[0045] To achieve the above object, the present invention further provides an electronic device, comprising:

[0046] Memory for storing computer programs;

[0047] The processor is configured to implement the steps of the above-mentioned method for determining the excitation frequency of the shear wave when executing the computer program.

[0048] To achieve the above object, the present invention further provides a computer-readable storage medium having a computer program stored thereon, which implements the steps of the above-mentioned method for determining the excitation frequency of shear waves when executed by a processor.

[0049] It can be seen from the above scheme that an embodiment of the present invention provides a method for determining the excitation frequency of shear waves, including: determining the focal depth of the excitation focus in the shear wave imaging area; obtaining the bandwidth curve function and directivity function of the current probe; the bandwidth curve function is used to determine the emission sensitivity of the current probe at different excitation frequencies; the directivity function is used to determine the emission sensitivity of each array element in the current probe at different deflection angles; using the attenuation coefficient of the excited tissue, as well as the focal depth, bandwidth curve function, and directivity function, to determine the sound intensity of each excitation frequency; according to the sound intensity and the absorption coefficient of the excited tissue, the sound radiation force corresponding to each excitation frequency is obtained, and the excitation frequency corresponding to the maximum sound radiation force is used as the target excitation frequency.

[0050] It can be seen that in this scheme, after determining the excitation focus in the shear wave imaging area, the optimal target excitation frequency of the current probe at the excitation focus can be determined based on the bandwidth curve function, directivity function of the current probe, and the attenuation coefficient and absorption coefficient of the excited tissue, thereby increasing the acoustic radiation force and shear wave amplitude at the excitation focus, and then improving the signal-to-noise ratio of the shear wave, ensuring the optimal shear wave excitation effect at the excitation focus; the present invention also discloses a shear wave excitation frequency determination device, equipment and storage medium, which can also achieve the above-mentioned technical effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0052] Figure 1 A schematic diagram of an excitation method for shear wave elastography in the prior art;

[0053] Figure 2 A schematic diagram of another excitation method for shear wave elastography in the prior art;

[0054] Figure 3 A schematic flow chart of a method for determining an excitation frequency of a shear wave disclosed in an embodiment of the present invention;

[0055] Figure 4 This is a flow chart of another method for determining the excitation frequency of shear waves disclosed in an embodiment of the present invention;

[0056] Figure 5a A schematic diagram of calculating a deflection angle and array element distance disclosed in an embodiment of the present invention;

[0057] Figure 5b A schematic diagram of calculating another deflection angle and array element distance disclosed in an embodiment of the present invention;

[0058] Figure 6 This is a schematic structural diagram of a device for determining the excitation frequency of a shear wave disclosed in an embodiment of the present invention;

[0059] Figure 7 The figure is a schematic diagram of the structure of an electronic device disclosed in an embodiment of the present invention. DETAILED DESCRIPTION

[0060] Shear wave elastography based on acoustic radiation force is an ultrasound elastography technique used to assess tissue hardness. The principle of shear wave elastography based on acoustic radiation force is as follows: After a probe emits high-energy ultrasound waves to the soft tissue of an organism, the soft tissue in a specific area will vibrate in all directions under the action of the acoustic radiation force and the shear stress of the tissue, thereby generating shear waves. Since the hardness of the soft tissue of an organism is correlated with the speed of the shear wave, the hardness of the soft tissue can be analyzed by detecting the shear wave speed. Therefore, the imaging steps of shear wave elastography are generally divided into two steps: the first step is shear wave excitation, and the second step is shear wave propagation process detection.

[0061] Currently, there are two main excitation methods for shear wave elastography based on acoustic radiation force: one is to continuously focus and emit a long pulse sequence in the area next to the shear wave detection area, with a pulse duration generally less than 1 ms (millisecond), and then detect the shear wave in the shear wave detection area, see Figure 1 , is a schematic diagram of an excitation method for shear wave elastography in the prior art, where 1 is the shear wave excitation beam, 2 is the shear wave excitation focus, 3 is the shear wave detection beam, 4 is the shear wave, 5 is the ultrasonic probe, and ABCD represent the shear wave detection lines. Another method is to continuously excite several focuses in a certain direction (usually longitudinal) in a certain order, so that the shear wave forms two cone-shaped wavefronts on the left and right, similar to the Mach cone formed by a supersonic moving object in the air. Therefore, this shear wave excitation method is also called Mach cone excitation, see Figure 2 , is a schematic diagram of another excitation method for shear wave elastography in the prior art.

[0062] Furthermore, since the intensity of the sound beam used to excite shear waves is generally not very strong, the corresponding acoustic radiation force is generally weak, and the amplitude of the generated shear waves is generally very small, which is very easy to be drowned by noise in the ultrasonic signal, so the signal-to-noise ratio of shear wave detection is generally low. There are also two corresponding methods to improve the signal-to-noise ratio of shear waves: one is to increase the shear wave amplitude. When the shear wave amplitude increases, the signal-to-noise ratio will naturally increase; the other is to improve the signal-to-noise ratio of shear wave detection. The conventional means of the former is to increase the intensity of the sound beam for shear wave excitation as much as possible, while the latter often requires improving the echo detection signal-to-noise ratio of the entire ultrasonic system or equipment. Therefore, the means of improving the shear wave signal-to-noise ratio described in the former are simpler. Moreover, in theory, the greater the acoustic radiation force, the greater the amplitude of the excited shear wave, and thus the higher the signal-to-noise ratio. Therefore, increasing the acoustic radiation force can naturally improve the signal-to-noise ratio of the shear wave.

[0063] The approximate formula for the acoustic radiation force is as follows:

[0064]

[0065] In formula 1, α is the absorption coefficient of the excited tissue for the exciting ultrasonic beam; I is the sound intensity of the exciting ultrasonic beam when it reaches the excited tissue; and c is the sound velocity of the excited tissue.

[0066] The tissue velocity of sound, c, does not vary significantly in soft tissues routinely used for shear wave elastography (generally around 1540 m / s). Therefore, to improve the acoustic radiation force, it is important to focus on the effects of the absorption coefficient α and the acoustic intensity I on the acoustic radiation force. The tissue absorption coefficient is the most important component of tissue attenuation of ultrasound waves. The tissue absorption coefficient and the tissue attenuation coefficient are highly correlated. Generally speaking, the majority of tissue attenuation is due to tissue absorption. Generally speaking, the greater the tissue absorption coefficient, the greater the attenuation coefficient. Some literature directly equates the absorption coefficient with the attenuation coefficient. A characteristic of ultrasound attenuation and absorption in tissue is that both the absorption coefficient and the attenuation coefficient are strongly frequency-dependent: the greater the frequency, the greater the attenuation and absorption coefficient. The attenuation and absorption coefficients increase approximately linearly with increasing frequency, resulting in units of dB / cm / MHz.

[0067] Currently, the corresponding ultrasonic excitation frequency for the shear wave excitation focal position at a specific depth is often determined through manual parameter adjustment. The optimal effect must be determined based on the actual shear wave excitation effects at different frequencies. Better shear wave excitation results indicate greater acoustic radiation force, greater shear wave amplitude, and, consequently, a higher signal-to-noise ratio. Determining the shear wave excitation frequency at a specific depth is currently cumbersome, and manual adjustment often results in misjudgment of the shear wave excitation effect due to other external factors, such as manipulation, which can lead to missing the optimal excitation frequency.

[0068] Furthermore, combined with Formula 1, it can be seen that, at a specific depth and in a specific tissue, a high acoustic radiation force can only be achieved if the tissue absorption coefficient α and the acoustic intensity I are both high. However, for a given transmitting probe's transmission power, the acoustic intensity I of ultrasound waves reaching a specific depth is entirely determined by the tissue attenuation coefficient β. A higher tissue attenuation coefficient β weakens the energy intensity I propagating to the tissue at that specific depth. Conversely, a higher tissue absorption coefficient α increases the acoustic radiation force I. The tissue absorption coefficient α and attenuation coefficient β are strongly positively correlated, with the attenuation coefficient β generally being greater than the absorption coefficient α. The majority of tissue attenuation of ultrasound waves is due to absorption. This presents a contradiction. According to the acoustic radiation force formula, a higher tissue attenuation coefficient β results in a higher acoustic radiation force I under the same ultrasonic excitation intensity. However, higher tissue attenuation results in greater attenuation of the ultrasound waves reaching the shear wave excitation focus, and under the same conditions, the acoustic intensity I decreases. Furthermore, different tissues have different absorption coefficients for different ultrasonic frequencies. Both the tissue attenuation and absorption coefficients are approximately linearly related to the transmission frequency: higher frequencies increase both the attenuation and absorption coefficients for a given tissue. Therefore, it is very difficult to determine the optimal shear wave excitation frequency for tissues at different depths and with different attenuation coefficients. Therefore, in this application, a method, device, equipment, and storage medium for determining the excitation frequency of shear waves are provided. Through this application, the optimal shear wave excitation frequency can be accurately determined, thereby increasing the acoustic radiation force and shear wave amplitude, and further improving the signal-to-noise ratio of the shear wave.

[0069] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0070] See also Figure 3 , a flow chart of a method for determining the excitation frequency of a shear wave provided by an embodiment of the present invention, see Figure 3 , the method specifically comprises the following steps:

[0071] S101, determining the focal depth of the excitation focus in the shear wave imaging area;

[0072] It should be noted that, before determining the target excitation frequency, the present application will determine the shear wave imaging area by means of the machine's default settings or by means of the doctor's modification of the settings. Moreover, after the shear wave imaging area is determined, it is necessary to set the excitation focus of the shear wave according to the depth of the shear wave excitation, thereby determining the focal depth of the excitation focus. Generally, the excitation focus can be set in the middle of the shear wave imaging area. Of course, it can also be modified according to actual conditions, which is not specifically limited here.

[0073] S102. Obtaining a bandwidth curve function and a directivity function of the current probe; wherein the bandwidth curve function is used to determine the transmit sensitivity of the current probe at different excitation frequencies; and the directivity function is used to determine the transmit sensitivity of each array element in the current probe at different deflection angles.

[0074] It should be noted that conventional probes have a limited operating frequency range. Beyond this range, the probe's transmit and receive sensitivity decreases to unacceptable levels. The probe's operating frequency is typically referred to as its operating bandwidth, and is categorized by the degree of sensitivity reduction, with -6dB bandwidth and -20dB bandwidth being common. Common probe bandwidth testing methods include one-way and two-way. The one-way bandwidth test only measures the probe's transmit sensitivity when transmitting waveforms at different frequencies, thereby generating the probe's bandwidth curve function. The two-way bandwidth test involves transmitting different frequencies to a smooth, mirrored metal target, which then reflects back and receives an echo. The probe's sensitivity at different frequencies is calculated based on the energy of the final received echo, thereby generating the probe's bandwidth curve function. Probe bandwidth can be measured using either short pulse excitation or continuous frequency sweep testing.

[0075] In this embodiment, since the shear wave excitation process is only to focus the excitation beam to the set focus, it does not receive the echo of the shear wave excitation beam. Therefore, it is a unidirectional or one-way process; and the two-way bandwidth test method takes into account the receiving performance of the probe, which is not necessary to consider in the simple excitation process. Therefore, in this embodiment, the one-way bandwidth test method is specifically used to obtain the bandwidth curve function of the current probe, through which the transmission sensitivity of the current probe at different excitation frequencies can be determined. In this embodiment, the bandwidth curve function can be expressed as: Fbw(f), where f in the bandwidth curve function represents the current excitation frequency, and the value range of the excitation frequency is: f∈[f min f max ], f min Refers to the lower limit of the current probe bandwidth, f max It is the upper limit of the current probe bandwidth.

[0076] Furthermore, since current probes are mostly array probes, each array element can function as a separate ultrasonic transmitter and receiver. However, each array element's ultrasonic transmission has a certain directionality. For example, the transmission sensitivity is generally highest 90° in front of the array element, that is, in the direction normal to the array element. The greater the angle from the normal, the weaker the transmission sensitivity of the array element in that direction. Therefore, in this solution, the directivity function Fdir(θ) of the current probe also needs to be determined. The deflection angle θ in the directivity function is: the deflection angle of the array element in any left or right direction based on the direction of its surface normal. The range of the deflection angle θ is: θ∈[-π / 2 π / 2]. Of course, the range of the deflection angle can also be adjusted according to actual conditions, such as: the range of the deflection angle θ can also be: [-0.4π0.4π]; the directivity function is used to determine the relative emission sensitivity of each array element in the current probe in any left or right deflection angle direction based on the direction of its surface normal. For example: if the deflection angle is 0, it means that the excitation focus is in the normal direction of the array element, and the relative emission sensitivity can be set to 1. If the deflection angle is 30 degrees, it means that the excitation focus is in the direction 30 degrees away from the normal, so the relative emission sensitivity is 0.5.

[0077] S103, determining the sound intensity of each excitation frequency point using the attenuation coefficient of the excited tissue, as well as the focal depth, bandwidth curve function, and directivity function;

[0078] It should be noted that acoustic intensity refers to the energy of the excitation ultrasound beam when it reaches the excited tissue. Because the acoustic intensity of ultrasound reaching a certain depth depends entirely on the attenuation coefficient of the excited tissue, in this embodiment, the acoustic intensity of the excitation ultrasound beam emitted by the current probe at the excitation focus at the current excitation frequency is determined based on the attenuation coefficient of the excited tissue. Since the attenuation coefficient varies between tissues, this solution can determine the attenuation coefficient of the excited tissue from publicly available literature. Furthermore, in order to enable this solution to accurately determine the sound intensity for probes of different types and performances, in this embodiment, the sound intensity also needs to be determined based on the bandwidth curve function and directivity function of the current probe, that is, this embodiment also needs to combine the emission sensitivity of the current probe at each excitation frequency point, and the emission sensitivity of each array element in the current probe used to excite the tissue at the corresponding deflection angle to determine the sound intensity of the excitation ultrasonic beam emitted by the current probe at the current excitation frequency point reaching the excitation focus. Therefore, when determining the sound intensity at the excitation focus point for each excitation frequency point, this solution not only takes into account the attenuation coefficient related to the sound intensity, but also takes into account the sensitivity of the probe through the bandwidth curve function and the directivity function, so that this solution can obtain more accurate sound intensity for probes of specific types and performances.

[0079] S104 , obtaining the acoustic radiation force corresponding to each excitation frequency point according to the sound intensity and the absorption coefficient of the excited tissue, and taking the excitation frequency point corresponding to the maximum acoustic radiation force as the target excitation frequency point.

[0080] In this embodiment, the attenuation coefficient is set to β and the absorption coefficient is set to α. The absorption coefficient of the excited tissue can also be obtained from public books or literature. Since the attenuation coefficient and the absorption coefficient are correlated, the values ​​of the two are very close. For example, the attenuation coefficient of the liver may be 0.9dB / cm / MHz, and the absorption coefficient may be 0.8dB / cm / MHz. Therefore, in this embodiment, the relationship between the two can be set as: β = k × α, where k is the correlation coefficient between the two, which can generally be set between 0.6 and 1.0. In this embodiment, when one of the attenuation coefficient and the absorption coefficient is obtained by β = k × α, the other coefficient can be determined based on this formula. After determining the sound intensity through the above steps, the acoustic radiation force at each excitation point can be obtained according to Formula 1 as shown above or other calculation methods. There is no specific limitation here, as long as the acoustic radiation force of the excitation frequency point can be determined based on the sound intensity.

[0081] It can be understood that the target excitation frequency in this embodiment is the optimal excitation frequency with the maximum acoustic radiation force at the current probe at the excitation focus. Therefore, in order to determine the target excitation frequency, this embodiment needs to determine the excitation frequency range (f min ~f max ) The acoustic radiation force corresponding to each excitation frequency point, so that the excitation frequency point corresponding to the maximum acoustic radiation force is taken as the target excitation frequency point.

[0082] In summary, it can be seen that after this embodiment determines the excitation focus within the shear wave imaging area, it can determine the optimal target excitation frequency of the current probe at the excitation focus based on the bandwidth curve function, directivity function of the current probe, and the attenuation coefficient and absorption coefficient of the excited tissue, thereby increasing the acoustic radiation force and shear wave amplitude at the excitation focus, and then improving the signal-to-noise ratio of the shear wave, ensuring the optimal shear wave excitation effect at the excitation focus.

[0083] See also Figure 4 , a flow chart of another method for determining the excitation frequency of shear waves provided in an embodiment of the present invention; in this embodiment, the specific method for determining the sound intensity is specifically limited, and the similarities between this embodiment and the previous embodiment are not repeated here.

[0084] See also Figure 4 , the method specifically comprises the following steps:

[0085] S201, determining the focal depth of the excitation focus in the shear wave imaging area;

[0086] It can be understood that in this embodiment, the shear wave imaging area includes at least one excitation focus, and the focal depths of different excitation focuses are different. Therefore, when determining the focal depth of the excitation focus in the shear wave imaging area, this scheme determines the focal depth of each excitation focus, and for each excitation focus, the corresponding target excitation frequency point will be determined through this scheme, thereby ensuring that each excitation focus in the shear wave imaging area has the best shear wave excitation effect.

[0087] S202, obtaining a bandwidth curve function and a directivity function of the current probe; wherein the bandwidth curve function is used to determine the transmit sensitivity of the current probe at different excitation frequencies; and the directivity function is used to determine the transmit sensitivity of each array element in the current probe at different deflection angles;

[0088] S203, determining the excitation aperture of the current probe according to the focal depth;

[0089] It should be noted that the excitation aperture in this embodiment is the array element group used to excite tissue within the current probe. W is used here to represent the excitation aperture, and the number of array elements within the excitation aperture W is N. N can be obtained based on the array element width after calculating the excitation aperture W. Before determining the excitation aperture, it is necessary to establish the F# value of the shear wave excitation. This F# value can represent the focal depth of the excitation focus and the width of the focal aperture. The larger the F# value is set, the smaller the excitation aperture used for excitation. After determining the F# value and the focal depth Fcl, the excitation aperture W can be determined according to the following formula:

[0090]

[0091] That is, in actual application, after the doctor determines the shear wave imaging area, he or shear wave excitation focus and the focal depth of the excitation focus are first determined from the imaging area. Then, the excitation aperture W is calculated by combining the preset F# value and Formula 2. The excitation aperture W can be determined by the method described in Formula 2 or by other methods, which are not specifically limited here.

[0092] S204, determining the array element distance and deflection angle between each array element in the excitation aperture and the excitation focus;

[0093] It should be noted that in this embodiment, when determining the element distance and deflection angle between each element in the excitation aperture and the excitation focal point, the probe type of the current probe must first be determined. Different probe types correspond to different methods for determining the element distance and deflection angle. Only after the probe type is determined are the element distance and deflection angle between each element in the excitation aperture and the excitation focal point determined based on the probe type and focal depth. The probe type of the current probe can be a linear array probe, a convex array probe, or a phased array probe. In this embodiment, only linear array probes and convex array probes are used as examples to illustrate the method for determining the element distance and deflection angle; other probe types are not described here.

[0094] See also Figure 5a , which is a schematic diagram of calculating the deflection angle and element distance of each array element in a linear array probe provided in an embodiment of the present invention; in this embodiment, if the probe type is a linear array probe, it is first necessary to determine a first distance between the target array element and the aperture center of the excitation aperture; and the element distance and deflection angle between the target array element and the excitation focus are determined based on the first distance and the focal depth.

[0095] Specifically, in this embodiment, the target array element is any array element within the excitation aperture of the linear array probe, and the target array element can be referred to as the i-th array element within the excitation aperture. Figure 5a It can be seen that the distance between the i-th array element and the excitation node in the excitation aperture is expressed by L i The deflection angle between the i-th array element and the excitation node in the excitation aperture is expressed as The center of the excitation aperture is O, the focal depth is Fcl, and the first distance between the i-th array element and the aperture center O is OI, which is calculated as follows:

[0096]

[0097] Where abs is the function for finding the absolute value; i is the i-th array element in the excitation aperture; N is the total number of array elements in the excitation aperture; and Pitch is the probe array element width, which is a known parameter.

[0098] After calculating the first distance OI, the array element distance L can be calculated according to the following formula: i and deflection angle

[0099]

[0100] See also Figure 5b, a schematic diagram of calculating the deflection angle and element distance of each array element in a convex array probe provided in an embodiment of the present invention; in this embodiment, if the probe type is a convex array probe, it is necessary to determine the second distance between the center of the convex array probe and the excitation focus, determine the angle between the target array element, the excitation focus, and the center of the circle, and determine the element distance between the target array element and the excitation focus based on the radius of the convex array probe, the second distance, and the cosine value of the angle; and determine the deflection angle between the target array element and the excitation focus based on the second distance, the radius, and the element distance.

[0101] Specifically, in this embodiment, the target array element is any array element within the excitation aperture of the convex array probe, and the target array element can be referred to as the i-th array element within the excitation aperture. Figure 5b It can be seen that the center of the convex array probe is O, and the second distance between the center O and the excitation focus F is OF. OF is the sum of the radius R of the convex array probe and the focal depth Fcl. The i-th array element in the excitation aperture is represented by K on the array element surface. The OK distance from point K on the i-th array element surface to the virtual center O of the convex array probe is also the radius R of the convex array probe. The angle between the target array element, the excitation focus, and the center is the angle α between OK and OF. The method for determining α is:

[0102]

[0103] Then the array element distance L can be determined according to the following formula i and deflection angle

[0104]

[0105]

[0106] It should be noted that the array element distance and deflection angle of the probe can be determined according to the specific type of the probe. In this embodiment, only a linear array probe and a convex array probe are used as examples to illustrate one of the specific calculation methods of the probe. Of course, the array element distance and deflection angle of the probe can also be calculated according to other methods, and are not limited to the calculation method described in this embodiment.

[0107] S205, determining the first sensitivity of the current probe at each excitation frequency point using a bandwidth curve function;

[0108] S206, determining a second sensitivity of each array element at a corresponding deflection angle using the directivity function;

[0109] S207, determining the sound intensity at each excitation frequency point based on the attenuation coefficient of the excited tissue, the first sensitivity, the second sensitivity corresponding to each array element, and the distance between each array element;

[0110] S208 . Obtain the acoustic radiation force corresponding to each excitation frequency point according to the sound intensity and the absorption coefficient of the excited tissue, and use the excitation frequency point corresponding to the maximum acoustic radiation force as the target excitation frequency point.

[0111] It should be noted that since the bandwidth curve function and directivity function are known functions, once the current excitation frequency is determined, the excitation frequency can be substituted into the bandwidth curve function to obtain the current probe's first sensitivity at each excitation frequency. After determining the deflection angle of each array element, the deflection angle can be substituted into the directivity function to obtain the second sensitivity of each array element at the corresponding deflection angle. The sound intensity at each excitation frequency, and ultimately the acoustic radiation force, can then be determined based on the attenuation coefficient of the excited tissue, the first sensitivity, the second sensitivity corresponding to each array element, and the distance between each array element.

[0112] In this embodiment, a specific method for determining sound intensity is disclosed, specifically: using a sound intensity determination rule to determine the sound intensity of the target probe at each excitation frequency point; the sound intensity determination rule is:

[0113]

[0114] Among them, f j is the jth excitation frequency point, is the excitation frequency f j The sound intensity under the current probe is N, N is the total number of array elements in the excitation aperture of the current probe, i represents the i-th array element in the N array elements, Fbw(f j ) is the first sensitivity, is the second sensitivity, is the deflection angle between the ith array element and the excitation focus, L i is the array element distance between the ith array element and the excitation focus, and β is the attenuation coefficient.

[0115] It can be seen that the above formula 9 can be used to calculate the excitation frequency of each array element at f j When the relative intensity of the light focused on the focal point F is It should be noted that the above formula 9 is an approximate calculation of the sound intensity of the focused sound field at a certain frequency point and a specific depth. The actual strict and accurate formula is much more complicated, but it is sufficient for this solution to solve the problem of the relative maximum sound radiation force within the probe bandwidth. For example: when determining the sound intensity, the energy loss of the sound wave due to the cumulative reflection during the propagation process can also be considered. Then the sound intensity determination rule can also be:

[0116]

[0117] Where bf(s) is the reflection coefficient of the sound wave at each depth, and 1-bf(s) is the remaining sound wave energy coefficient after reflection within a certain depth range s. This reflection coefficient is independent of frequency and therefore does not affect the final process of finding the frequency of the maximum acoustic radiation force.

[0118] That is to say, in this embodiment, the specific method for determining the sound intensity is not limited. The sound intensity can be determined by Formula 9, Formula 10, or other methods, which are not specifically limited here.

[0119] Furthermore, after the sound intensity is determined, the acoustic radiation force corresponding to each excitation frequency can be obtained based on the sound intensity and the absorption coefficient of the excited tissue. In this embodiment, the acoustic radiation force can be calculated in the manner described in Formula 1 above, that is, the acoustic radiation force corresponding to each excitation frequency is determined using the acoustic radiation force determination rule. The acoustic radiation force determination rule is:

[0120]

[0121] in, is the jth excitation frequency f j The acoustic radiation force, α is the absorption coefficient of the excited tissue, is the jth excitation frequency f j The sound intensity is c, and the sound velocity of the excited tissue is c.

[0122] Here, in order to specifically explain the method of determining the target excitation frequency, the sound intensity determination rule described in Formula 9 is substituted for Formula 11 to obtain the acoustic radiation force determination rule:

[0123]

[0124] It can be seen from formula 12 that the parameters affecting the sound radiation force are the bandwidth curve function Fbw, the directivity function Fdir, and the deflection angle Array element distance L i , attenuation coefficient β, absorption coefficient α, speed of sound c, excitation frequency f j However, after the probe and excitation focus are determined, the bandwidth curve function Fbw and the directivity function Fdir are fixed, and the deflection angle and array element distance L i is also fixed, and for a specific excited tissue, its attenuation coefficient β for the emitted ultrasound is related to the excitation frequency f j The absorption coefficient α is also related to the excitation frequency f j Therefore, considering the actual application scenario, the parameter that can be adjusted is the excitation frequency f of the acoustic radiation force. jThat is, under the conditions of a specific focal depth, specific tissue, and specific probe, the acoustic radiation force at the excitation focus is a function that depends on the excitation frequency. At the focal depth of the excitation focus, from the acoustic radiation force results at the above different excitation frequencies, find the excitation frequency corresponding to the maximum acoustic radiation force, and use it as the optimal target excitation frequency for shear wave excitation at the excitation focus of the current probe, that is, the target excitation frequency f Tx The method of determining is:

[0125]

[0126] In summary, it can be seen that this solution, through the bandwidth curve function and directivity function of the probe, as well as the absorption coefficient and attenuation coefficient of the detected tissue, can perform shear wave elastic imaging and detection on tissues and organs of different properties under probes of different types and performances. It can automatically find the optimal shear wave target excitation frequency at different imaging and detection depths, thereby obtaining the optimal shear wave signal-to-noise ratio at each depth, ensuring the best shear wave excitation effect at the excitation focus, and also reducing the shear wave excitation sound power at the same signal-to-noise ratio to a certain extent.

[0127] The following describes an excitation frequency determination apparatus, device, and storage medium provided by embodiments of the present invention. The excitation frequency determination apparatus, device, and storage medium described below can be referenced to the excitation frequency determination method described above.

[0128] See also Figure 6 , a schematic diagram of a structure of a shear wave excitation frequency determination device provided by an embodiment of the present invention, see Figure 6 , the device comprises:

[0129] A focus depth determination module 11 is used to determine the focus depth of the excitation focus in the shear wave imaging area;

[0130] The first acquisition module 12 is used to obtain a bandwidth curve function of the current probe; the bandwidth curve function is used to determine the emission sensitivity of the current probe at different excitation frequencies;

[0131] A second acquisition module 13 is configured to acquire a directivity function of the current probe; the directivity function is used to determine the transmit sensitivity of each array element in the current probe at different deflection angles;

[0132] The sound intensity determination module 14 is configured to determine the sound intensity of each excitation frequency point by using the attenuation coefficient of the excited tissue, the focal depth, the bandwidth curve function, and the directivity function;

[0133] an acoustic radiation force determination module 15, configured to obtain the acoustic radiation force corresponding to each excitation frequency point based on the sound intensity and the absorption coefficient of the excited tissue;

[0134] The target excitation frequency determination module 16 is configured to use the excitation frequency corresponding to the maximum acoustic radiation force as the target excitation frequency.

[0135] Wherein, the sound intensity determination module includes:

[0136] an excitation aperture determination unit, configured to determine an excitation aperture of a current probe according to the focal depth;

[0137] a distance and deflection angle determination unit, configured to determine an array element distance and a deflection angle between each array element in the excitation aperture and the excitation focus;

[0138] a first sensitivity determination unit, configured to determine a first sensitivity of the current probe at each excitation frequency point using the bandwidth curve function;

[0139] a second sensitivity determining unit, configured to determine a second sensitivity of each array element at a corresponding deflection angle using the directivity function;

[0140] The sound intensity determination unit is used to determine the sound intensity at each excitation frequency point according to the attenuation coefficient of the excited tissue and the first sensitivity, the second sensitivity corresponding to each array element, and the distance between each array element.

[0141] The sound intensity determination unit is specifically configured to determine the sound intensity of the target probe at each excitation frequency using a sound intensity determination rule; the sound intensity determination rule is:

[0142]

[0143] Among them, f j is the jth excitation frequency point, is the excitation frequency f j The sound intensity under the current probe is N, N is the total number of array elements in the excitation aperture of the current probe, i represents the i-th array element in the N array elements, Fbw(f j ) is the first sensitivity, is the second sensitivity, is the deflection angle between the ith array element and the excitation focus, L i is the array element distance between the ith array element and the excitation focus, and β is the attenuation coefficient.

[0144] The distance and deflection angle determination unit is specifically configured to: determine the probe type of the current probe; and determine the array element distance and deflection angle between each array element in the excitation aperture and the excitation focus according to the probe type and the focal depth.

[0145] If the probe type is a linear array probe, the distance and deflection angle determination unit includes:

[0146] A first determining subunit, configured to determine a first distance between a target array element and an aperture center of the excitation aperture;

[0147] The second determining subunit is configured to determine an array element distance and a deflection angle between a target array element and the excitation focus according to the first distance and the focal depth.

[0148] If the probe type is a convex array probe, the distance and deflection angle determination unit includes:

[0149] a third determining subunit, configured to determine a second distance between the center of the convex array probe and the excitation focus;

[0150] a fourth determining subunit, configured to determine an angle between the target array element, the excitation focus, and the center of the circle;

[0151] a fifth determining subunit, configured to determine an array element distance between the target array element and the excitation focus according to the radius of the convex array probe, the second distance, and the cosine value of the angle;

[0152] A sixth determining subunit is configured to determine a deflection angle between the target array element and the excitation focus according to the second distance, the radius, and the array element distance.

[0153] The shear wave imaging area includes at least one excitation focus, and different excitation focuses have different focal depths.

[0154] The acoustic radiation force determination module is specifically configured to determine the acoustic radiation force corresponding to each excitation frequency point using an acoustic radiation force determination rule; the acoustic radiation force determination rule is:

[0155]

[0156] in, is the jth excitation frequency f j The acoustic radiation force, α is the absorption coefficient of the excited tissue, is the jth excitation frequency f j The sound intensity is c, and the sound velocity of the excited tissue is c.

[0157] See also Figure 7 , which is a schematic diagram of the structure of an electronic device provided by an embodiment of the present invention, see Figure 7 , the device specifically includes:

[0158] Memory 21, for storing computer programs;

[0159] The processor 22 is configured to implement the steps of the method for determining the excitation frequency of the shear wave described in any of the above method embodiments when executing the computer program.

[0160] In this embodiment, the device may be a PC (Personal Computer), or may be a terminal device such as a smart phone, a tablet computer, a PDA, or a portable computer.

[0161] The device may include a memory 21 , a processor 22 , and a bus 23 .

[0162] Among them, the memory 21 includes at least one type of readable storage medium, and the readable storage medium includes a flash memory, a hard disk, a multimedia card, a card-type memory (for example, an SD or DX memory, etc.), a magnetic memory, a magnetic disk, an optical disk, etc. In some embodiments, the memory 21 can be an internal storage unit of the device, such as the hard disk of the device. In other embodiments, the memory 21 can also be an external storage device of the device, such as a plug-in hard disk equipped on the device, a smart memory card (SmartMedia Card, SMC), a secure digital (Secure Digital, SD) card, a flash card (Flash Card), etc. Furthermore, the memory 21 can also include both an internal storage unit of the device and an external storage device. The memory 21 can not only be used to store application software and various types of data installed in the device, such as program code for executing the excitation frequency determination method, but can also be used to temporarily store data that has been output or is to be output.

[0163] In some embodiments, the processor 22 may be a central processing unit (CPU), a controller, a microcontroller, a microprocessor, or other data processing chip, configured to execute program codes or process data stored in the memory 21, such as program codes for executing the excitation frequency determination method.

[0164] The bus 23 may be a peripheral component interconnect (PCI) bus or an extended industry standard architecture (EISA) bus. The bus may be divided into an address bus, a data bus, a control bus, etc. For ease of representation, Figure 7 Only one thick line is used in the diagram, but this does not mean that there is only one bus or one type of bus.

[0165] Furthermore, the device may also include a network interface 24, which may optionally include a wired interface and / or a wireless interface (such as a WI-FI interface, a Bluetooth interface, etc.), which is generally used to establish a communication connection between the device and other electronic devices.

[0166] Optionally, the device may further include a user interface 25, which may include a display and an input unit such as a keyboard. The optional user interface 25 may also include a standard wired interface or a wireless interface. Optionally, in some embodiments, the display may be an LED display, a liquid crystal display, a touch-sensitive liquid crystal display, or an OLED (Organic Light-Emitting Diode) touchscreen. The display may also be appropriately referred to as a display screen or display unit, and is used to display information processed in the device and to display a visual user interface.

[0167] Figure 7 Only the device with components 21-25 is shown, and it will be understood by those skilled in the art that Figure 7 The structure shown does not constitute a limitation of the device, and may include fewer or more components than shown, or combine certain components, or arrange the components differently.

[0168] An embodiment of the present invention further discloses a computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, the steps of the method for determining the excitation frequency of shear waves described in any of the above method embodiments are implemented.

[0169] The storage medium may include any medium capable of storing program codes, such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk.

[0170] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0171] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for determining the excitation frequency of a shear wave, characterized in that: include: determining a focal depth of the excitation focus within the shear wave imaging region; Obtaining a bandwidth curve function and a directivity function of the current probe; the bandwidth curve function is used to determine the transmit sensitivity of the current probe at different excitation frequencies; the directivity function is used to determine the transmit sensitivity of each array element in the current probe at different deflection angles; determining an excitation aperture of the current probe according to the focal depth; Determining the array element distance and deflection angle between each array element in the excitation aperture and the excitation focus; Determine the first sensitivity of the current probe at each excitation frequency point using the bandwidth curve function; Determining a second sensitivity of each array element at a corresponding deflection angle using the directivity function; determining the sound intensity at each excitation frequency point according to the attenuation coefficient of the excited tissue, the first sensitivity, the second sensitivity corresponding to each array element, and the distance between each array element; The acoustic radiation force corresponding to each excitation frequency is obtained according to the sound intensity and the absorption coefficient of the excited tissue, and the excitation frequency corresponding to the maximum acoustic radiation force is used as the target excitation frequency.

2. The method for determining the excitation frequency according to claim 1, wherein: Determining the sound intensity at each excitation frequency point according to the attenuation coefficient of the excited tissue, the first sensitivity, the second sensitivity corresponding to each array element, and the distance between each array element includes: Use the sound intensity determination rule to determine the sound intensity of the current probe at each excitation frequency point; The sound intensity determination rule is: Among them, f j is the jth excitation frequency point, is the excitation frequency f j The sound intensity under the current probe is N, N is the total number of array elements in the excitation aperture of the current probe, i represents the i-th array element in the N array elements, Fbw(f j ) is the first sensitivity, is the second sensitivity, is the deflection angle between the ith array element and the excitation focus, L i is the array element distance between the ith array element and the excitation focus, and β is the attenuation coefficient.

3. The method for determining the excitation frequency according to claim 1, wherein: Determining the array element distance and deflection angle between each array element in the excitation aperture and the excitation focus includes: Determining the probe type of the current probe; The array element distance and the deflection angle between each array element in the excitation aperture and the excitation focus are determined according to the probe type and the focal depth.

4. The method for determining the excitation frequency according to claim 3, wherein: If the probe type is a linear array probe, the process of determining the array element distance and the deflection angle between each array element in the excitation aperture and the excitation focus includes: determining a first distance between a target array element and an aperture center of the excitation aperture; An array element distance and a deflection angle between a target array element and the excitation focus are determined according to the first distance and the focal depth.

5. The method for determining the excitation frequency according to claim 3, wherein: If the probe type is a convex array probe, the process of determining the array element distance and the deflection angle between each array element in the excitation aperture and the excitation focus includes: Determining a second distance between the center of the convex array probe and the excitation focus; Determining the angle between the target array element, the excitation focus and the center of the circle; Determining an array element distance between the target array element and the excitation focus according to the radius of the convex array probe, the second distance, and the cosine value of the angle; The deflection angle between the target array element and the excitation focus is determined according to the second distance, the radius, and the array element distance.

6. The method for determining the excitation frequency according to claim 1, wherein: The shear wave imaging region includes at least one excitation focus, and different excitation focuses have different focal depths.

7. The method for determining the excitation frequency according to any one of claims 1 to 6, characterized in that: Obtaining the acoustic radiation force corresponding to each excitation frequency point according to the sound intensity and the absorption coefficient of the excited tissue includes: The acoustic radiation force corresponding to each excitation frequency point is determined by using the acoustic radiation force determination rule; The acoustic radiation force determination rule is: in, is the jth excitation frequency f j The acoustic radiation force, α is the absorption coefficient of the excited tissue, is the jth excitation frequency f j The sound intensity is c, and the sound velocity of the excited tissue is c.

8. A device for determining the excitation frequency of a shear wave, characterized in that: include: A focus depth determination module, configured to determine a focus depth of an excitation focus within a shear wave imaging region; A first acquisition module is used to obtain a bandwidth curve function of the current probe; The bandwidth curve function is used to determine the emission sensitivity of the current probe at different excitation frequencies; A second acquisition module is used to obtain a directivity function of the current probe; the directivity function is used to determine the transmission sensitivity of each array element in the current probe at different deflection angles; an acoustic intensity determination module, configured to determine an excitation aperture of the current probe based on the focal depth; determine an array element distance and a deflection angle between each array element within the excitation aperture and the excitation focus; determine a first sensitivity of the current probe at each excitation frequency using the bandwidth curve function; determine a second sensitivity of each array element at a corresponding deflection angle using the directivity function; and determine an acoustic intensity at each excitation frequency based on an attenuation coefficient of the excited tissue, the first sensitivity, the second sensitivity corresponding to each array element, and the distance between each array element; an acoustic radiation force determination module, configured to obtain the acoustic radiation force corresponding to each excitation frequency point based on the sound intensity and the absorption coefficient of the excited tissue; The target excitation frequency determination module is used to use the excitation frequency corresponding to the maximum acoustic radiation force as the target excitation frequency.

9. An electronic device, characterized in that: include: Memory for storing computer programs; A processor is configured to implement the steps of the method for determining the excitation frequency of shear waves as claimed in any one of claims 1 to 7 when executing the computer program.

10. A computer-readable storage medium, characterized in that The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the method for determining the excitation frequency of shear waves according to any one of claims 1 to 7 are implemented.

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