A method for improving the focusing efficiency of a ring-shaped ultrasonic transducer array

Abstract

The application discloses a method for improving focusing efficiency of a ring-shaped ultrasonic transducer array, comprising the following steps: firstly, collecting two groups of echo signals of single emission and multiple reception and self emission and self reception of the ring-shaped ultrasonic transducer array, calculating positions of each transducer element, completing position calibration of the ring-shaped ultrasonic transducer array, and reducing focusing deviation caused by transducer assembly error; and secondly, using the ring-shaped ultrasonic transducer array to perform ultrasonic imaging on a target to be heated, analyzing imaging results, and adjusting transmission delay of the transducer element to reduce focusing deviation caused by uneven medium of the object to be heated. Through the above two steps, the ring-shaped ultrasonic transducer array can maximize the concentration of sound energy on the position to be heated in the focusing process, and the purpose of improving the focusing efficiency of the ring-shaped ultrasonic transducer array is achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for improving the focusing efficiency of an array in ultrasonic imaging and processing technology, in particular to a method for improving the focusing efficiency of a ring-shaped ultrasonic transducer array. BACKGROUND

[0002] Traditional ultrasonic heating is usually completed by a single curved transducer, and the geometric focal point of the curved transducer is the focal point of ultrasonic focusing. The focal point of the curved transducer is fixed, and during the heating process, the focal point can only be moved by moving the spatial position of the transducer through a mechanical displacement mechanism. The precise mechanical displacement mechanism is bulky and inconvenient to manufacture, and electronic focusing using an ultrasonic transducer array can solve this problem. Acoustic focusing using a ring-shaped ultrasonic transducer array requires accurate calculation of the time required for sound waves to reach the target to be heated from the transducer elements, and the transducer elements are set with different transmission delays accordingly to ensure that the ultrasonic signal energy is concentrated at the target to be heated. In order to calculate the time required for sound waves to reach the target to be heated from the transducer elements, the position of the transducer elements needs to be accurately known. However, due to the manual assembly of the ultrasonic transducer array, there will be some position deviation between the assembled transducer elements and the designed transducer elements. In addition, the object to be heated is often not a simple homogeneous object, but is composed of multiple media. Different media have different sound speeds, and the paths of the sound waves emitted by different transducer elements to the target to be heated are also different. The distribution of the medium on different paths is often also different, which will cause deviation in the arrival time of the sound waves.

[0003] The assembly error of the transducer and the error caused by the inhomogeneity of the medium of the object to be heated will cause different degrees of focusing deviation when the ring-shaped ultrasonic transducer array is focused, resulting in a significant reduction in focusing efficiency. It takes a longer time to reach the target heating temperature, and the focal point area may be expanded, causing overheating. Therefore, measures need to be taken to reduce the focusing deviation and improve the focusing efficiency of the ring-shaped ultrasonic transducer array. SUMMARY

[0004] The technical problem to be solved by the present application is to provide a method for improving the focusing efficiency of a ring-shaped ultrasonic transducer array to overcome the shortcomings of the prior art.

[0005] In order to solve the above technical problems, the present application discloses a method for improving the focusing efficiency of a ring-shaped ultrasonic transducer array, comprising the following steps:

[0006] Step 1, set the ring-shaped ultrasonic transducer array to a single-transmission multi-reception mode, and the transducer elements sequentially transmit sound signals one by one, and collect the echo signals received by each transducer element;

[0007] Step 2, set a range of non-central positions near the center position of the transducer array, fix a thin wire axially on the annular ultrasonic transducer array, set the transducer array to a self-emission and self-reception mode, and sequentially emit acoustic signals by the transducer elements, and collect echo signals reflected by the thin wire received by the transducer elements;

[0008] Step 3, according to the two groups of echo signals collected in the single emission and multiple reception mode and the self-emission and self-reception mode in steps 1 and 2, calculate the actual distance d between the transducer elements and the actual distance L between the transducer elements and the thin wire, and calculate the positions of the transducer elements according to the actual distance d and the actual distance L, to complete the calibration of the positions of the annular ultrasonic transducer array;

[0009] Step 4, use the annular ultrasonic transducer array to perform ultrasonic imaging on a target to be heated, analyze the imaging results, adjust the transmission delay of the transducer elements, reduce the focusing deviation, and finally realize the improvement of the focusing efficiency of the annular ultrasonic transducer array.

[0010] Further, the calculation of the actual distance d between the transducer elements and the actual distance L between the transducer elements and the thin wire in step 3 specifically includes:

[0011] Step 3-1, calculate the time of flight of the acoustic signal;

[0012] Step 3-2, combine the speed SOS of acoustic signal propagation to calculate the actual distance d between the transducer elements and the actual distance L between the transducer elements and the thin wire.

[0013] Further, the calculation of the time of flight TOF of the acoustic signal in step 3-1 specifically includes:

[0014] TOF=Num×dt

[0015] Wherein, Num represents the number of time points from emission to reception of the acoustic signal, and the calculation method is:

[0016] Num=t r -t t

[0017] Wherein, t r represents the time when the maximum value of the echo signal is reached, t t represents the time when the maximum value of the transmitted signal is reached, and dt represents the sampling time interval, and the calculation method is:

[0018]

[0019] Wherein, Freq represents the frequency of the acoustic signal, and n represents the number of sampling points in a period.

[0020] Further, the calculation of the actual distance d between the transducer elements in step 3-1 includes:

[0021] d = TOF 单发多收 × SOS

[0022] Wherein, TOF 单发多收 is the time of flight of the acoustic signal in the single-transmitting and multi-receiving mode, and SOS is the speed of acoustic signal propagation, i.e. the actual sound speed.

[0023] Further, the calculation of the actual distance L between the transducer elements and the thin wire in step 3-1 includes:

[0024]

[0025] Wherein, TOF 自发自收 is the time of flight of the acoustic signal in the self-transmitting and self-receiving mode.

[0026] Further, the completion of the calibration of the position of the annular ultrasonic transducer array in step 3 includes:

[0027] The calculation of the actual angle θ i ′ of each transducer element includes:

[0028]

[0029] A plane rectangular coordinate system is established with the center of the annular ultrasonic transducer array as the origin in the plane where the annular ultrasonic transducer array is located, and (Posx i , Posy i ) represents the position coordinates of the transducer element i.

[0030] The calculation method of the spatial distance D i,j between the transducer element i and the transducer element j includes:

[0031]

[0032]

[0033] Wherein, (Posx i , Posy i ) and (Posx j , Posy j ) represent the position coordinates of the transducer element i and the transducer element j, respectively, and (Posx i , Posy i ) * represents the minimum value of ∑ i,j (D i,j -d i,j ) 2The position coordinate where the value reaches the minimum;

[0034] Actual radius R of transducer element i on the ring i , the calculation method is as follows:

[0035] R i ′=R+ΔR i

[0036] Wherein, R represents the radius of each transducer element on the ring in ideal case, ΔR i represents the deviation of actual radius of transducer element i compared with R, i.e. radius deviation;

[0037] L 2 (θ′ i ) function is calculated from the self-receiving data, the L 2 (θ′ i ) function represents L 2 -θ′ i relationship function, which is a sinusoidal function, fitting L 2 (θ′ i ) image to obtain a sinusoidal curve k(θ′ i );

[0038] The calculation method of radius deviation ΔR i is as follows:

[0039]

[0040] The calculation method of transducer element position coordinate (Posx i , Posy i ) is as follows:

[0041] Posx i =R i ′×cosθ′ i

[0042] Posy i =R i ′×sinθ′

[0043] The real position (Posx i , Posy i ) of each element in the annular ultrasonic transducer array is calculated by the above method, i.e. the position calibration of the annular ultrasonic transducer array is completed.

[0044] Further, the ultrasonic imaging in step 4 refers to reconstructing B-mode ultrasonic image of the target space by using the annular ultrasonic transducer array, specifically, the beam forming method and the delay and superposition method of the annular ultrasonic transducer array.

[0045] Further, the analysis imaging result in step 4 refers to judging the size of the focusing deviation through the pixel maximum value Q of the ultrasound image I of the to-be-heated region, that is, the larger the pixel maximum value Q is, the smaller the focusing deviation is at this time.

[0046] Further, the adjustment of the transmission delay of the transducer elements in step 4 refers to fine-tuning the transmission delay on the basis of the delay parameter Dly i of the transducer element i, and the specific method is as follows:

[0047] Let Dly i ' be the fine-tuned transmission delay, the adjustment factor be ΔDly i , find the adjustment factor ΔDly i that makes the pixel maximum value Q reach the maximum, and use the adjustment factor ΔDly to compensate for the focusing error in the ultrasonic focusing process, that is:

[0048] Dly′ i =Dly i +ΔDly i

[0049] The transmission delay of each transducer element during ultrasonic focusing is updated to Dly', that is, the adjustment of the transmission delay of the transducer elements is completed.

[0050] Further, the non-central position in step 2, that is, the position of the fixed thin line, does not coincide with the central position of the annular transducer array, and the distance between the position of the thin line and the central position is more than 1mm;

[0051] The central position, that is, the distance between the position of the thin line and the central position is less than 5mm;

[0052] The diameter of the thin line is between 1 / 8 and 1 / 16 of the wavelength of the ultrasonic signal emitted by the ultrasonic transducer array.

[0053] Beneficial effects:

[0054] The application discloses a method for improving the focusing efficiency of an annular ultrasonic transducer array, acquires the positions of transducer elements by collecting two groups of echo signals of single transmission and multiple reception and self-transmission and self-reception of the annular ultrasonic transducer array, reduces the focusing deviation caused by transducer assembly errors, analyzes the ultrasonic imaging result of the transducer on a to-be-heated object, adjusts the transmission delay of the transducer elements, and reduces the focusing deviation caused by the non-uniformity of the medium of the to-be-heated object.

[0055] Compared with directly heating the target, the method can effectively improve the focusing efficiency of the annular ultrasonic transducer array, improve the accuracy of the focal point area control, and make up for the defects of the prior art. Attached Figure Description

[0056] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, and the advantages of the present invention in the above and / or other aspects will become clearer.

[0057] Figure 1 This is a schematic diagram of the annular ultrasonic transducer array heating device involved in the present invention.

[0058] Figure 2 This is a schematic diagram of the process for improving the focusing efficiency of the annular ultrasonic transducer array according to the present invention.

[0059] Figure 3 This is a schematic diagram of a ring ultrasonic transducer array detecting the distance between transducer elements in single-transmitter multi-receiver mode.

[0060] Figure 4 This is a schematic diagram showing the distance between the transducer elements and the thin line placed near the center of the annular ultrasonic transducer array for self-transmission and self-reception detection.

[0061] Figure 5 This is a schematic diagram illustrating the improved focusing efficiency in one embodiment. Detailed Implementation

[0062] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0063] This invention discloses a method for improving the focusing efficiency of a ring-shaped ultrasonic transducer array, such as... Figure 2 As shown, it includes the following steps:

[0064] Step 1: Set the annular ultrasonic transducer array to single-transmitter, multi-receiver mode. Transducer elements sequentially transmit acoustic signals one by one, and the echo signals received by each element are collected. A thin wire is fixed near the center of the transducer. The transducer is set to self-transmitter, self-receiver mode, and the transducer elements sequentially transmit acoustic signals one by one. The echo signals reflected by the wire are collected. Based on the single-transmitter, multi-receiver, and self-transmitter, self-receiver echo signals, the actual distance *d* between transducer elements and the actual distance *L* between a transducer element and the thin wire are calculated. The position of each transducer element can be calculated from *d* and *L*, completing the position calibration of the annular ultrasonic transducer array and reducing focusing deviations caused by transducer assembly errors.

[0065] Step 2: Use a ring ultrasonic transducer array to perform ultrasonic imaging on the target to be heated, analyze the imaging results, and adjust the emission delay of the transducer array elements to reduce the focusing deviation caused by the inhomogeneity of the medium of the object to be heated, so as to improve the focusing efficiency of the ring ultrasonic transducer array.

[0066] Step 1 described the single shot multi-receiving mode, that is, the i-th ultrasonic transducer array element transmits the acoustic signal, and all the remaining transducer array elements are in the receiving state.

[0067] Step 1 described the self-emission self-receiving mode, that is, the i-th transducer array element transmits the acoustic signal, and immediately after transmitting the acoustic signal, the transducer array element is in the receiving state to receive the echo of the acoustic signal reflected by the thin wire, and all the other transducer array elements stop working during this process.

[0068] Step 1 described fixing a thin wire near the center position of the annular transducer, the direction of the thin wire should be parallel to the axial direction of the annular transducer, the position of the fixed thin wire cannot coincide with the center position of the annular transducer, and at least maintains a distance of 1 mm, and the position of the fixed thin wire and the center position of the annular transducer need to be within 5 mm.

[0069] Step 1 described fixing a thin wire, the diameter of the thin wire is closely related to the echo signal-to-noise ratio, if the diameter of the thin wire is too small, it will be difficult to obtain a high signal-to-noise ratio echo signal, and if the diameter of the thin wire is too large, the distance between the transducer array element and the thin wire cannot be accurately calculated according to the echo, which affects the transducer position correction result. The diameter of the thin wire should be between 1 / 8 and 1 / 16 of the wavelength of the ultrasonic signal, so that the transducer array element can detect a high signal-to-noise ratio echo signal.

[0070] Step 1 of the present application described calculating the actual distance d between the transducer array elements and the actual distance L between the transducer array elements and the thin wire, and the calculation formula is:

[0071] First, calculate the time of flight (TOF) according to the single shot multi-receiving and self-emission self-receiving two groups of echo signals.

[0072] TOF = Num x dt

[0073] The calculation formula of Num and dt is:

[0074] Num = t r -t t

[0075]

[0076] t r represent the time when the maximum value of the echo signal is located, t trepresent the time point from the emission to the reception of the sound signal, dt represents the time interval of the sampling, Freq represents the frequency of the sound signal, and n represents the sampling points in a period. In combination with the sound speed SOS, the actual distance d between the transducer array elements and the actual distance L between the transducer array element and the thin line can be calculated, and the calculation formula is:

[0077] d = TOF 单发多收 × SOS

[0078]

[0079] The position of each transducer array element is calculated in step 1, and the position calibration of the annular ultrasonic transducer array is completed, and the specific method is as follows: the actual angle θ i ′ of each transducer array element is calculated first, and the calculation formula is as follows:

[0080]

[0081] wherein Posx i , Posy j represent the position coordinates of the transducer array element i, and the calculation formula is as follows:

[0082]

[0083]

[0084] (Posx i , Posy i ) and (Posx j , Posy j ) represent the positions of the transducer array element i and the transducer array element j, respectively, D i,j represents the spatial distance between the transducer array element i and the transducer array element j. R represents the radius of each transducer array element on the ring under ideal conditions, ΔR i represents the deviation of the actual radius of the transducer array element i from R, R i ′ indicates the actual radius of the transducer array element i on the ring. R i ′, R, ΔR i satisfy the following relationship:

[0085] R i ′ = R + ΔR i

[0086] Since L 2 - θ′ i the relationship L 2 (θ′ i ) should be a sinusoidal function. L 2 (θ′i ), L 2 (θ′ i ) image fitting into a sinusoidal curve k(θ′ i ) ΔR i is calculated by the following formula:

[0087]

[0088] The formula for calculating the position coordinates (Posx i , Posy i ) of the transducer elements is as follows:

[0089] Posx i = R i ′ × cosθ′ i

[0090] Posy i = R i ′ × sinθ′ i

[0091] The real positions (Posx i , Posy i ) of the elements of the annular ultrasonic transducer array are calculated, i.e., the calibration of the annular ultrasonic transducer array is completed.

[0092] The speed of the sound signal propagation is related to the medium temperature, so the medium temperature needs to be measured to determine the sound speed. Since the medium temperature is affected by the room temperature, the device needs to be placed in a room temperature environment for a period of time before measurement, and when measuring the temperature, the reading of the thermometer needs to be recorded after a long time of stable reading to reduce the deviation of the sound speed. When measuring, the medium sound speed needs to be determined by measuring the temperature of multiple positions of the device to reduce the error caused by the non-uniformity of the medium temperature.

[0093] The method for ultrasonic imaging of the target to be heated using the annular ultrasonic transducer array in step 2 of the present application is the beam forming method and the delay and sum method. The beam forming method is to use the annular transducer to emit ultrasonic signals with different time delays, so that all the ultrasonic signals can be focused in one region. The delay and sum method is an image reconstruction method corresponding to the beam forming method. When receiving the ultrasonic signals, the delay is corresponding to the time delay of the transmitted ultrasonic signals in the beam forming, and the focus imaging region of the transmitted ultrasonic signals can be reconstructed by the delay and sum.

[0094] The delay and sum beam forming can be described as:

[0095]

[0096] wherein n = 1, …, N, u = 1, …, U, Dly i(n) represents the time delay when focusing on the center of the target region to be heated, the value of this item is related to the distance between the ultrasonic transducer element i and the center of the target region to be heated, w i is the weight of beam forming, is the initial sound pressure signal received by the i-th ultrasonic transducer element, corresponding to the emission at an angle θ u According to the above formula, the ultrasonic image of the target region to be heated can be reconstructed.

[0097] The adjustment of the emission delay of the transducer element based on the analysis of the imaging result in step 2 of the present application refers to: extracting the maximum value Q of the pixel of the ultrasonic image I of the target region to be heated. Based on the delay parameter Dly i of the transducer element i, the emission delay is fine-tuned, Dly i ' is the fine-tuned emission delay, and the adjustment factor is ΔDly i The ΔDly i that can make Q reach the maximum value is found. The maximum value of Q indicates that the ΔDly i at this time can minimize the focusing deviation caused by the non-uniformity of the medium of the target object to be heated, and can maximize the focusing efficiency of the annular ultrasonic transducer array. By using ΔDly to compensate for the focusing error in the ultrasonic focusing process, the emission delay of each transducer element in the ultrasonic focusing process is updated to Dly', which can achieve the purpose of improving the focusing efficiency of the annular ultrasonic transducer array.

[0098] Embodiment:

[0099] The embodiment of the present application discloses a method for improving the focusing efficiency of an annular ultrasonic transducer array. In this embodiment, the annular ultrasonic transducer array is used to heat a specific region, and the target temperature for heating is 42.5℃. In this embodiment, the scheme proposed by the present application can effectively reduce the focusing deviation of the annular ultrasonic transducer array, effectively improve the focusing efficiency of the annular ultrasonic transducer array, reduce the time required to reach the target temperature for heating, and improve the focal point control ability to avoid damage to other parts outside the target region to be heated.

[0100] The annular ultrasonic transducer array heating device used in this embodiment is shown in Figure 1 . The annular ultrasonic transducer array is composed of four quarter rings, each quarter ring contains 16 elements, the center frequency of the transducer is 1MHz, the bandwidth is 200KHz, the size of a single transducer is 4mm×4mm, and the material is PZT. According to the design when the transducer is manufactured, under ideal conditions (without internal assembly error), the positions of every two adjacent transducer elements form a 5° angle, the positions of the two transducer elements on the edge and the edge of the quarter ring are separated by 7.5°, and the angle of each transducer element can be described by the following formula:

[0101]

[0102] i represents the transducer element number, and 1 ≤ i ≤ 64. R represents the radius of each transducer element on the ring under ideal conditions; in this embodiment, the transducer used has R = 50 mm. ΔR i R represents the deviation of the actual radius of transducer element i from R. i ′ represents the actual radius of transducer element i on the ring. R i ′、R、ΔR i The following relationship must be satisfied:

[0103] R i ′=R+ΔR i

[0104] θ i This represents the angle of transducer element i on the circular ring under ideal conditions. Due to assembly errors, the radius and angle of each transducer element will deviate to varying degrees, and the angular deviation is expressed as Δθ. i The actual angle of each transducer element on the ring is represented by θ. i ′。 θ i ′、θ i , Δθ i The following relationship exists:

[0105] θ i ′=θ i +Δθ i

[0106] like Figure 2 As shown, this embodiment of the invention discloses a method for improving the focusing efficiency of a ring-shaped ultrasonic transducer array, comprising:

[0107] Step 1: Set the annular ultrasonic transducer array to single-transmitter, multi-receiver mode. Transducer elements sequentially transmit acoustic signals one by one, and collect the echo signals received by each element. Fix a thin line near the center of the transducer. Set the transducer to self-transmitter, self-receiver mode. Transducer elements sequentially transmit acoustic signals one by one, and collect the echo signals reflected by the thin line. Based on the single-transmitter, multi-receiver, and self-transmitter, self-receiver echo signals, calculate the actual distance *d* between transducer elements and the actual distance *L* between a transducer element and the thin line. From *d* and *L*, the position of each transducer element can be calculated, completing the position calibration of the annular ultrasonic transducer array and reducing focusing deviations caused by transducer assembly errors. The specific method is as follows:

[0108] The annular ultrasonic transducer array is immersed and fixed in the water tank. After the device is left to stand for 30 minutes at room temperature, the bubbles attached to the transducer elements in the water are removed using a plastic rod. The transducer is set to a single-transmit multi-receive mode, that is, the transducer element i transmits an acoustic signal, and the remaining 63 transducer elements are all in a receiving state, receiving the acoustic signal transmitted by the transducer element i, as shown in FIG. 6. Figure 3 Since the maximum distance between the transducer elements is about the diameter of the circle, the sampling depth is set to be slightly larger than the diameter of the circle, that is, l1. In this embodiment, l1 = 10 mm. The total sampling point number Num sam1 of the receiving transducer elements in the single-transmit multi-receive mode is calculated according to the following formula:

[0109]

[0110] wherein λ represents the wavelength of the transmitted acoustic signal, and n represents the sampling point number of a single period. The receiving transducer element records Num sam1 sampling points from the signal transmission time.

[0111] A thin wire is fixed near the center position of the transducer, and the direction of the thin wire should be parallel to the axial direction of the annular transducer. The position of the fixed thin wire should not be too close to the center position, and a distance of more than 1 mm should be left. In addition, the position of the fixed thin wire should not be too far from the center position of the annular transducer, and the distance should be kept within 5 mm. At this time, according to the cosine theorem, the square of the distance L 2 of each transducer element to the thin wire should be a sinusoidal function in the ideal case. If the distance between the thin wire position and the center of the circle is too close, the transducer itself will be affected by the error, and the resolution of the transducer will be difficult to fit using the sinusoidal function. If the distance is too large, the correction is no longer a radial error.

[0112] In this embodiment, the diameter of the thin wire used is 0.08 mm, and the material is metal. The transducer is set to a self-transmit self-receive mode, the transducer element i transmits an acoustic signal, and immediately after the acoustic signal is transmitted, the transducer element is in a receiving state, receiving the echo obtained by reflecting the acoustic signal through the thin wire, and the other 63 transducer elements stop working in this process, as shown in FIG. 7. Figure 4 Since the distance between the thin wire and the center of the circle is within 5 mm, the sampling depth is set to be larger than the diameter of the circle, that is, l2. In this embodiment, l2 = 20 mm. The total sampling point number Num sam2 of the receiving transducer elements in the single-transmit multi-receive mode is calculated according to the following formula:

[0113]

[0114] The time of flight (TOF) can be calculated from the echo data, and the calculation formula is as follows:

[0115] TOF = Num x dt

[0116] Wherein, the calculation formula of Num and dt is:

[0117] Num = t r -t t

[0118]

[0119] t r representing the time when the maximum value of the echo signal is located, t t representing the time when the maximum value of the transmitted signal is located, Num representing the time point number of the sound signal from being emitted to being received, dt representing the time interval of sampling, Freq representing the frequency of the sound signal, and n representing the sampling point number in a period. The larger n is, the more accurate the calculation result of TOF is. In the embodiment, Freq = 1 MHz, and n = 32.

[0120] The speed of the sound signal propagating in water can be represented by SOS. Since the value of SOS is related to water temperature Tem, the water temperature needs to be measured to determine the sound speed. The method for measuring the water temperature is as follows: a thermometer is placed near the center position of the transducer and near the transducer array element into the water. After the reading of the thermometer is stable and unchanged for more than 20 minutes, the reading is taken and recorded. The degree of the thermometer near the center position of the transducer is represented as Tem1, and the degree of the thermometer near the transducer array element is represented as Tem2. The water temperature is recorded as Tem, which can be calculated by the following formula:

[0121]

[0122] The calculation formula of SOS is:

[0123] SOS = 1402.5 + 3.15 Tem - 0.037 Tem 2 + 1.7 x 10 -4 x Tem, 3 - 1.8 x 10 -7 x Tem 4

[0124] Combined with SOS and TOF, the actual distance d between the transducer array elements and the actual distance L between the transducer array element and the fine line can be calculated, and the calculation formula is:

[0125] d = TOF 单发多收 x SOS

[0126]

[0127] The specific calculation method of the position deviation of each transducer array element is to calculate the actual angle θ i ′ of each array element of the transducer, and the calculation formula is:

[0128]

[0129] Among them, Posx i Posy j The position coordinates of transducer element i are represented by the following formula:

[0130]

[0131]

[0132] (Posx i Posy i ) and (Posx j Posy j ) represent the positions of transducer element i and transducer element j, respectively, D i,j This represents the spatial distance between transducer array element i and transducer array element j.

[0133] Because of R i ′=R+ΔR i Find ΔR i R can then be obtained i Let c be the distance between the thin line and the center of the ring transducer, L be the distance from each element of the transducer to the thin line, and α be the angle between the line connecting the transducer element to the center of the ring and the line connecting the center of the ring to the position of the thin line. By the law of cosines, L... 2 =R′ 2 +c 2 -2R′·c·cosα. Since R and c are both constants, in the ideal case, L 2 -θ′ i Relationship L 2 (θ′ i L should be a sinusoidal function. It can be obtained from the self-transmitted and self-received data. 2 (θ′ i ), will L 2 (θ′ i The image is fitted into a sinusoidal curve k(θ′). i Since R >> c, ΔL can be approximated as equal to ΔR. i ΔR i The calculation formula is:

[0134]

[0135] At this point, θ′ i R i All of these have been calculated, including the transducer element position coordinates (Posx). i Poxy i The formula for calculating ) is:

[0136] Posx i = R i ' x cos θ ' i

[0137] Posy i = R i ' x sin θ ' i

[0138] The real position (Posx i , Posy i ) of each element of the annular ultrasonic transducer array is calculated, that is, the calibration of the position of the annular ultrasonic transducer array is completed.

[0139] Step 2, using the annular ultrasonic transducer array to perform ultrasonic imaging on the target to be heated, analyzing the imaging result, adjusting the transmission delay of the transducer element to reduce the focusing deviation caused by the non-uniformity of the medium of the object to be heated, and finally achieving the purpose of improving the focusing efficiency of the annular ultrasonic transducer array. The specific method is as follows:

[0140] The annular ultrasonic transducer array is fixed on the reference object, and sufficient acoustic coupling agent is applied at the contact part of the transducer array and the heating area to ensure good acoustic coupling. The B-mode ultrasonic image of the heating area is reconstructed by using the annular ultrasonic transducer array, and the specific reconstruction method is based on the beam forming method and the delay and add method of the aforementioned annular transducer. The beam forming method is to use the annular transducer to transmit ultrasonic signals with different time delays, so that all the ultrasonic signals can be focused in a region. The delay and add method is an image reconstruction method corresponding to the beam forming method. When the received ultrasonic signals are delayed and added, the delay is corresponding to the transmission ultrasonic signal delay in the beam forming process. Through the delay and addition, the focusing imaging area of the transmitted ultrasonic signal can be reconstructed.

[0141] In this embodiment, during the beam forming transmission process, the acoustic pressure field of the transmitted acoustic signal can be represented as:

[0142]

[0143] Where (x, y) represents the coordinates of any point in the ultrasonic propagation area, t represents time, K represents the number of ultrasonic transducer elements, K = 64 in this embodiment, w i is the transmission weight of the ultrasonic transducer element i located at (Posx i , Posy i ), Dly i is the transmission delay of the ultrasonic transducer element i, and p0 is the acoustic pressure field generated by the transmission of the acoustic signal of the ultrasonic transducer element located at the origin of the coordinate system.

[0144] The sound pressure emitted by each transducer element can be represented by a spatial-time shift of the sound pressure value at the ultrasonic transducer element; at the receiving end, the echo signal received by the ultrasonic transducer element is compensated for delay according to the different transmission times of the sound waves. The delayed signal is then weighted and superimposed to form a beam forming signal. The weights used in the weighted summation form the aperture function at the receiving end.

[0145] In the present embodiment, the process of delay superposition is as follows: when u focused beams are emitted through 64 ultrasonic transducer elements, the final reconstructed ultrasonic image is composed of each group of received sound pressure signals, each group of results being from the transmitted signal at angle θ u , where u ∈ {1,..., U}, according to the above process, the delay superposition beam forming can be described as:

[0146]

[0147] where n = 1,..., N, u = 1,..., U, Dly i (n) represents the delay when focusing on the heating area, the value of this term is related to the distance between the ultrasonic transducer element i and the center of the heating area, w u is the weight of beam forming, is the initial sound pressure signal received by the i-th ultrasonic transducer element, which corresponds to the transmission at angle θ u According to the above formula, the ultrasonic image of the heating area can be reconstructed.

[0148] Extract the maximum value Q of the pixels of the ultrasonic image I of the heating area. The larger Q is, the smaller the focusing deviation is at this time. The calculation formula of Q is:

[0149] Q = max(I)

[0150] The delay of the emission of the transducer element i is represented as Dly i , max(·) is the maximum value symbol, and the calculation formula of Dly i is:

[0151] Dly i = T i '-max(T' i )

[0152] where T i ' represents the time required for the ultrasonic wave to travel from the transducer element i to the center of the heating area. The coordinates of the center position of the heating area are represented as (x t , y t ), and the calculation formula of T' i is:

[0153]

[0154] The delay parameter Dly of transducer element i i Based on this, the launch delay was fine-tuned, Dly i ′ represents the fine-tuned transmit delay, with an adjustment factor of ΔDly. i Find the ΔDly that maximizes Q. i The Q value reaching its maximum indicates that ΔDly is at this point. i This minimizes the focusing deviation caused by the inhomogeneity of the medium in the object being heated, thus maximizing the focusing efficiency of the annular ultrasonic transducer array. Dly′ i The calculation formula is:

[0155] Dly′ i =Dly i +ΔDly i

[0156] By using ΔDly to compensate for focusing errors during ultrasonic focusing heating of the area to be heated, the emission delay of each transducer array element during ultrasonic focusing is updated to Dly′, which improves the focusing efficiency of the annular ultrasonic transducer array. During the heating process, the area to be heated reaches the target heating temperature of 42.5℃ more quickly, improving the effect of ultrasonic focusing heating. At the same time, it improves the accuracy of focal area control and enhances the safety of heating.

[0157] like Figure 5 As shown, after direct heating for 10 minutes, the temperature at the center of the area to be heated was 41.65℃, while after heating for 10 minutes using this method, the temperature at the center of the area to be heated was 42.58℃. Compared with directly heating the target, this method can effectively improve the focusing efficiency of the annular ultrasonic transducer array, while also improving the accuracy of focal area control, thus overcoming the shortcomings of existing technologies.

[0158] In its specific implementation, this application provides a computer storage medium and a corresponding data processing unit. The computer storage medium is capable of storing a computer program, which, when executed by the data processing unit, can run the invention's content regarding a method for improving the focusing efficiency of a ring-shaped ultrasonic transducer array, as well as some or all of the steps in various embodiments. The storage medium can be a magnetic disk, optical disk, read-only memory (ROM), or random access memory (RAM), etc.

[0159] Those skilled in the art can clearly understand that the technical solutions in the embodiments of the present application can be implemented by means of a computer program and a corresponding general hardware platform. Based on such understanding, the technical solutions in the embodiments of the present application can be embodied in the form of a computer program, i.e., a software product, which can be stored in a storage medium, including a plurality of instructions for causing a device (which can be a personal computer, a server, a single-chip microcomputer, a MUU or a network device, etc.) comprising a data processing unit to execute the method described in various embodiments or some parts of the embodiments of the present application.

[0160] The present application provides a method for improving the focusing efficiency of a ring-shaped ultrasonic transducer array. There are many ways to implement this technical solution, and the above description is only the preferred embodiment of the present application. It should be noted that for those skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, which should also be considered within the scope of protection of the present application. The components not explicitly described in the embodiments can be implemented using existing technology.

Claims

1. A method of improving focusing efficiency of an annular ultrasonic transducer array, characterized by, The method comprises the following steps: Step 1, setting the annular ultrasonic transducer array in a single emission and multi-reception mode, and sequentially transmitting the sound signals by the transducer array elements, and collecting the echo signals received by each transducer array element; Step 2, fixing a thin wire axially at a non-central position within a range near the central position of the transducer array, setting the transducer array in a self-emission and self-reception mode, sequentially transmitting the sound signals by the transducer array elements, and collecting the echo signals received by the transducer array elements and reflected by the thin wire; Step 3, calculating the actual distance d between the transducer array elements and the actual distance L between the transducer array elements and the thin wire according to the two groups of echo signals collected in the single emission and multi-reception mode and the self-emission and self-reception mode in steps 1 and 2, and calculating the positions of the transducer array elements according to the actual distances d and L, thereby completing the calibration of the positions of the annular ultrasonic transducer array; Step 4, using the annular ultrasonic transducer array to perform ultrasonic imaging on a target to be heated, analyzing the imaging result, adjusting the transmission delay of the transducer array elements, reducing the focusing deviation, and finally realizing the improvement of the focusing efficiency of the annular ultrasonic transducer array.

2. The method of claim 1, wherein, The calculation of the actual distance d between the transducer array elements and the actual distance L between the transducer array elements and the thin wire in step 3 specifically comprises: Step 3-1, calculating the time of flight of the sound signal; Step 3-2, combining the speed SOS of the sound signal propagation to calculate the actual distance d between the transducer array elements and the actual distance L between the transducer array elements and the thin wire.

3. The method of claim 2, wherein, The calculation of the time of flight TOF of the sound signal in step 3-1 specifically comprises: TOF = Num × dt Wherein, Num represents the number of time points from the emission of the sound signal to the reception, and the calculation method is: Num = t r -t t Where, t r represents the moment when the maximum value of the echo signal is located, t t represents the moment when the maximum value of the transmitted signal is located, and dt represents the time interval of the sampling, and the calculation method is as follows: Wherein, Freq represents the frequency of the sound signal, and n represents the number of sampling points in a period.

4. The method of claim 3, wherein, The calculation of the actual distance d between the transducer array elements in step 3-1 specifically comprises: d = TOF 单发多收 x SOS where TOF is the time of flight of the acoustic signal in the single transmit, multiple receive mode, and SOS is the speed of sound, i.e., the actual speed of sound. 单发多收 where TOF is the time of flight of the acoustic signal in the single transmit, multiple receive mode, and SOS is the speed of sound, i.e., the actual speed of sound.

5. The method of claim 4, wherein the method further comprises, The calculation of the actual distance L between the transducer array elements and the thin wire in step 3-1 specifically comprises: where TOF 自发自收 is the time of flight of the acoustic signal in the self-emission self-reception mode.

6. The method of claim 5, wherein, The completion of the calibration of the positions of the annular ultrasonic transducer array in step 3 specifically comprises: The actual angle θ of each array element of the transducer is calculated i The calculation method is as follows: A plane rectangular coordinate system is established with the center of the annular ultrasonic transducer array as the origin in the plane where the annular ultrasonic transducer array is located, and (Posx i ,Posy i ) represents the position coordinates of the transducer element i. The spatial distance D between transducer elements i and j i,j The calculation method is as follows: wherein (Posx i ,Posy i ) and (Posx j ,Posy j ) represent the position coordinates of transducer elements i and j, respectively, and (Posx i ,Posy i ) represents the position coordinates that minimize the sum i,j (D i,j -d i,j ) 2 . Actual radius R of transducer array element i on ring i The calculation method is as follows: R i ′= R + ΔR i where R represents the ideal radius of each transducer element on the ring, ΔR i represents the deviation of the actual radius of transducer element i from R, i.e., the radius deviation; L(θ) is calculated from the spontaneous emission and the collected data 2 (θ i ′) function, the L 2 (θ i ′) function represents L 2 -θ i ′ relationship function, is a sinusoidal function, fitting the L 2 (θ i ′) image to a sinusoidal curve k(θ i ′); The radius deviation ΔR i The calculation method is: The calculation method of transducer array element position coordinates (Posx i , Posy i ) is as follows: Posx i = R i ' x cos θ i ' Posy i = R i ' x sin θ i ' The real positions (Posx i , Posy i ) of each array element in the annular ultrasonic transducer array are calculated by the above method, that is, the calibration of the positions of the annular ultrasonic transducer array is completed.

7. The method of claim 6, wherein the method further comprises, The ultrasonic imaging in step 4 refers to reconstructing the B-mode ultrasonic image of the target space by using the annular ultrasonic transducer array, and specifically refers to the beam forming method and the delay and superposition method of the annular ultrasonic transducer array.

8. The method of claim 7, wherein, The analysis of the imaging result in step 4 refers to judging the size of the focusing deviation by the maximum pixel value Q of the ultrasonic image I of the target to be heated, that is, the larger the maximum pixel value Q, the smaller the focusing deviation at this time.

9. The method of claim 8, wherein, The adjustment of the transmit delay of the transducer elements in step 4 refers to fine tuning of the transmit delay based on the delay parameter Dly i of the transducer element i, in the following way: Let Dly i be the fine-tuned transmit delay, and the adjustment factor be ΔDly i , find the adjustment factor ΔDly i that maximizes the pixel maximum Q i Compensate for focusing errors during the ultrasound focusing process, i.e.: Dly i ′= Dly i + ΔDly i The transmit delays of the transducer elements are updated as Dly when the ultrasound is focused i ′, i.e. the adjustment of the transmit delays of the transducer elements is completed.

10. The method of claim 9, wherein, The non-central position in step 2, i.e. the position of the fixed thin wire, does not coincide with the central position of the annular transducer array, and the distance between the position of the thin wire and the central position is more than 1 mm; The central position near the thin wire refers to the distance between the position of the thin wire and the central position being within 5 mm; The diameter of the thin wire is between 1 / 8 and 1 / 16 of the wavelength of the ultrasonic signal emitted by the ultrasonic transducer array.

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