Ultrasonic image generation method and device

Abstract

An embodiment of the present invention provides an ultrasonic image generation method comprising the steps of: transmitting an HIFU signal to an object by using an HIFU transformer, and receiving an HIFU signal reflected by the object; acquiring frame data for a region of interest by using the received HIFU signal; performing deconvolution on the frame data scan line by scan line; and acquiring ultrasonic image data by performing pulse compression on the frame data after the step of performing deconvolution.

Description

Ultrasonic image generation method and device

[0001] Embodiments of the present invention relate to a method and device for generating an ultrasound image, and more particularly, to a method and device for generating a high-resolution ultrasound image using a HIFU transducer.

[0002] Ultrasound signals can be used to treat biological tissues such as cancer, tumors, and lesions.

[0003] High Intensity Focused Ultrasound (HIFU) is a non-invasive treatment method that uses heat energy generated by focusing high-powered acoustic energy on a target area. It is used in the treatment of lesions such as cancer and tumors, as well as cosmetic treatments such as skin tightening. The non-invasive nature of HIFU has the advantage of minimizing trauma to the patient compared to surgery. However, since the treatment area cannot be observed by the practitioner (doctor) with the naked eye during the procedure, separate monitoring of the treatment area is essential.

[0004] Traditionally, a separate imaging transducer was used in addition to the HIFU transducer for monitoring purposes. While this approach serves the purpose of enabling monitoring of the HIFU treatment and the treatment area, it also presents limitations in terms of convenience for the practitioner and cost-effectiveness.

[0005] To improve this, two types of transducers have been designed to be physically assembled, allowing a single, integrated structure to perform both functions. However, the small apertures of the individual elements within the transducer increase electrical impedance, and the resulting electrical impedance mismatch between the system and the transducer reduces the therapeutic efficacy of the HIFU transducer and reduces the transmit / receive capabilities of the imaging transducer.

[0006] The present invention proposes an ultrasound transmission / reception and signal processing technology that enables an ultrasound image obtained from a HIFU transducer to have an axial resolution and signal-to-noise ratio improved to a level comparable to that of an image obtained from an imaging transducer, and an object of the present invention is to provide a method for forming a high-resolution ultrasound image using a therapeutic ultrasound transducer.

[0007] One embodiment of the present invention provides a method for generating an ultrasound image, including the steps of transmitting a HIFU signal to a target object using a HIFU converter and receiving a HIFU signal reflected from the target object, obtaining frame data for a region of interest using the received HIFU signal, performing deconvolution on the frame data for each scan line, and performing pulse compression on the frame data after the deconvolution step to obtain ultrasound image data.

[0008] In one embodiment of the present invention, the step of transmitting a HIFU signal to the object and receiving a HIFU signal reflected from the object may include the step of modulating the HIFU signal through coded excitation and transmitting the modulated HIFU signal.

[0009] In one embodiment of the present invention, the step of transmitting a HIFU signal to the target object and receiving a HIFU signal reflected from the target object may be modulating the HIFU signal with a center frequency of the HIFU converter.

[0010] In one embodiment of the present invention, the modulated HIFU signal may be any one of a Barker code, a Chirp code, and a Golay code.

[0011] In one embodiment of the present invention, the step of obtaining the frame data may include the step of removing noise from the frame data using a first band-pass filter; and the step of normalizing the frame data from which the noise has been removed using the maximum value of the frame data.

[0012] In one embodiment of the present invention, after the step of performing the deconvolution, a step of removing noise from the deconvolved frame data using a second band-pass filter may be further included.

[0013] In one embodiment of the present invention, the step of acquiring the ultrasound image data may include a step of performing pulse compression on the frame data using a matched filter or a mismatched filter.

[0014] Another embodiment of the present invention provides an ultrasound image generation device, comprising a HIFU converter that transmits a HIFU signal to a target object and receives a HIFU signal reflected from the target object, and a processor that receives the reflected HIFU signal from the HIFU converter and generates ultrasound image data, wherein the processor is configured to execute commands for the steps of: obtaining frame data for a region of interest using the received HIFU signal; performing deconvolution on the frame data for each scan line; and performing pulse compression on the frame data after the step of performing the deconvolution to obtain ultrasound image data.

[0015] In one embodiment of the present invention, the HIFU converter can modulate a HIFU signal through coded excitation and transmit the modulated HIFU signal.

[0016] In one embodiment of the present invention, the HIFU converter can transmit the HIFU signal by modulating it with the center frequency of the HIFU converter.

[0017] In one embodiment of the present invention, the modulated HIFU signal may be any one of a Barker code, a Chirp code, and a Golay code.

[0018] In one embodiment of the present invention, the step of obtaining the frame data may include the step of removing noise from the frame data using a first band-pass filter and the step of normalizing the frame data from which the noise has been removed using the maximum value of the frame data.

[0019] In one embodiment of the present invention, the step of acquiring the ultrasound image data may include a step of performing pulse compression on the frame data using a matched filter or a mismatched filter.

[0020] Another embodiment of the present invention provides a method for generating an ultrasound image, including the steps of transmitting a HIFU signal to a target object using a HIFU converter, receiving a HIFU signal reflected from the target object, obtaining frame data for a region of interest using the received HIFU signal, and obtaining ultrasound image data from the frame data using a trained neural network.

[0021] In one embodiment of the present invention, the step of obtaining the ultrasound image data may include a step of training the neural network to obtain the ultrasound image data from the frame data based on a transducer impulse response among the frame data.

[0022] In one embodiment of the present invention, the step of obtaining the frame data may include the step of removing noise from the frame data using a first band-pass filter and the step of normalizing the frame data from which the noise has been removed using the maximum value of the frame data.

[0023] Other aspects, features and advantages other than those described above will become apparent from the following drawings, claims and detailed description of the invention.

[0024] The ultrasound image generation method and device according to embodiments of the present invention can obtain an ultrasound image of comparable quality to an ultrasound transducer for imaging through signal processing without a separate additional transducer by performing deconvolution and pulse compression on an ultrasound signal received through a HIFU transducer.

[0025] FIG. 1 is a block diagram schematically showing an ultrasonic image generating device according to one embodiment of the present invention.

[0026] Figure 2 is a flowchart of an ultrasound image generation method according to one embodiment of the present invention.

[0027] FIG. 3 is a flowchart specifically explaining the steps for transmitting and receiving the HIFU signal of FIG. 2.

[0028] FIG. 4 is a flowchart specifically explaining the steps for acquiring frame data for the region of interest of FIG. 2.

[0029] Figure 5 is a drawing for explaining the difference between the impulse response and transmission signal of the image converter and the HIFU converter, respectively.

[0030] FIG. 6 is a diagram for comparing simulation results of an image converter according to one embodiment of the present invention and a HIFU converter applying the proposed method of the present invention.

[0031] FIG. 7 is a diagram illustrating an ultrasound image obtained by (a) an ultrasound transducer for imaging, (b) a HIFU transducer, and (c) a HIFU transducer using the proposed method of the present invention, and a diagram illustrating an envelope of each ultrasound image signal.

[0032] Figure 8 shows ultrasound image images of a cyst target obtained by (a) an ultrasound transducer for imaging, (b) a HIFU transducer, and (c) a HIFU transducer using the proposed method of the present invention, respectively, and (d) shows the result of measuring the signal-to-noise ratio (SNR) of the ultrasound image.

[0033] Figure 9 is a diagram for explaining the axial resolution of an ultrasound image depending on whether deconvolution is performed and the pulse compression method.

[0034] Hereinafter, the following embodiments will be described in detail with reference to the attached drawings. When describing with reference to the drawings, identical or corresponding components are given the same drawing reference numerals, and redundant descriptions thereof will be omitted.

[0035] These embodiments are capable of various modifications. Specific embodiments are illustrated in the drawings and described in detail in the detailed description. The effects and features of these embodiments, as well as the methods for achieving them, will become clearer with reference to the detailed descriptions below, along with the drawings. However, these embodiments are not limited to the embodiments disclosed below and may be implemented in various forms.

[0036] In the examples below, singular expressions include plural expressions unless the context clearly indicates otherwise.

[0037] In the examples below, terms such as “include” or “have” mean that a feature or component described in the specification exists, and do not exclude in advance the possibility that one or more other features or components may be added.

[0038] The term "ultrasound image" as used below refers to an image of an object obtained using ultrasound. Furthermore, "object" may refer to a human, fetus, animal, metal, non-metal, or a portion thereof. For example, the object may include organs such as the liver, heart, uterus, brain, breasts, or abdomen, or blood vessels.

[0039] High Intensity Focused Ultrasound (HIFU) is a non-invasive treatment method that uses heat energy generated by focusing high-powered acoustic energy on a target area. It is used to treat lesions such as cancer and tumors, and for cosmetic treatments such as skin tightening. HIFU focuses and irradiates the area to be treated with ultrasound signals of higher intensity than those typically used for ultrasound imaging.

[0040] As ultrasound signals propagate within the human body, their magnitude is attenuated due to scattering, reflection, and other factors, reducing the signal-to-noise ratio (SNR) of the image and the penetration depth of the ultrasound signal. This degrades the quantitative and qualitative indices of diagnostic images and reduces their reliability as diagnostic images. To solve the above problems, there is a method of increasing the intensity of the transmitted signal by lengthening the duration of the transmission pulse, but as described below, this brings about another problem of reduced axial resolution in ultrasound images.

[0041] To deliver high ultrasound energy, temporally long pulses or continuous wave (CW) are used. To increase the input-to-output efficiency of the transducer, the HIFU transducer structurally uses air backing and does not use an acoustic matching layer. Therefore, the impulse response of the HIFU transducer is longer than that of an imaging transducer. This means that the spectral bandwidth of the HIFU transducer is narrow, and since the axial resolution of an ultrasound image is proportional to the spectral bandwidth of the transducer, an HIFU transducer cannot acquire ultrasound images with fine axial resolution.

[0042] In addition, HIFU transducers, which are intended for transmitting ultrasound energy, are made of piezoelectric materials such as PZT-4, which have a high transmission constant, but these materials generally have a low reception constant. Consequently, ultrasound images acquired with HIFU transducers have low axial resolution and a low signal-to-noise ratio (SNR). To overcome these problems, the present invention proposes ultrasound transmission / reception and signal processing technologies that enable ultrasound images acquired from HIFU transducers to have improved axial resolution and signal-to-noise ratios comparable to those of images acquired from imaging transducers.

[0043] FIG. 1 is a block diagram schematically illustrating an ultrasound image generating device according to one embodiment of the present invention. As illustrated in FIG. 1, the ultrasound image generating device may include a HIFU converter (110) and a processor (120). In addition, as an optional embodiment, the ultrasound imaging device (10) may further include a display unit (130).

[0044] The HIFU converter (110) transmits and receives a HIFU (High-Intensity Focused Ultrasound) signal. That is, the HIFU converter (110) transmits a HIFU signal (S1) to a target object (M) and receives a HIFU signal (S2) reflected from the target object.

[0045] Specifically, the HIFU converter (110) transmits ultrasound to the object (M) according to a transmission signal provided from the processor (120), and receives echo ultrasound reflected from a specific part inside the object (M) and transmits the echo ultrasound to the processor (120).

[0046] The processor (120) receives the reflected HIFU signal (S2) from the HIFU converter (110) and generates ultrasound image data.

[0047] The processor (120) is configured to execute commands for the steps of obtaining frame data for a region of interest using a received HIFU signal (S2), performing deconvolution on the frame data for each scan line, and performing pulse compression on the frame data after the deconvolution step to obtain ultrasound image data. Specific details for each of the steps will be covered in the description of the ultrasound image generation method below.

[0048] The processor (120) may control one or more other components (hardware, software components, etc.) of electronic devices connected to the processor (120) by executing software, etc., and may perform various data processing or calculations. As part of the data processing or calculations, the processor (120) may load commands and / or data received from other components (HIFU converter (110), display unit (130), etc.) into volatile memory, process the commands and / or data stored in the volatile memory, and store the resulting data in non-volatile memory. The processor (120) may include a main processor (central processing unit, application processor, etc.) and an auxiliary processor (graphics processing unit, image signal processor, sensor hub processor, communication processor, etc.) that can operate independently or together with the main processor.

[0049] The display unit (130) may refer to a main screen that displays ultrasound images. The display unit (130) may display ultrasound images acquired through the HIFU converter (110) in real time, or may read out and display previously stored ultrasound images. In addition, the display unit (130) may also display ultrasound images received from an external server or external device.

[0050] Hereinafter, as an embodiment of the present invention, a method for generating an ultrasound image will be described in detail.

[0051] FIG. 2 is a flowchart of an ultrasound image generation method according to one embodiment of the present invention, FIG. 3 is a flowchart specifically explaining a step of transmitting and receiving a HIFU signal of FIG. 2, and FIG. 4 is a flowchart specifically explaining a step of acquiring frame data for a region of interest of FIG. 2.

[0052] First, referring to FIGS. 2 and 3, in step S100, the HIFU converter (110) transmits a HIFU signal to the target object and receives a HIFU signal reflected from the target object.

[0053] At this time, step S100 may include a step of setting an image acquisition range (S110), a step of modulating a HIFU signal through coded excitation (S120), and a step of transmitting and receiving the modulated HIFU signal to and from a target object (M) (S130).

[0054] Step S110 can set the image acquisition range to include a region of interest, such as the lesion to be treated. In one embodiment, the image acquisition range may vary depending on the type of region of interest, its size, etc.

[0055] Step S120 can modulate the HIFU signal through coding here.

[0056] Here, coded excitation is a method of transmitting a long coded signal in the time axis, and this technology can improve the transmission energy by 15-20 dB without increasing the transmission peak voltage, resulting in an improvement in the signal-to-noise ratio (SNR), which can be used to increase the resolution or penetration.

[0057] The coding signal used in the coding technique is a signal capable of pulse compression and having a large time-bandwidth product (TBP), and may be any one of a Barker code, a Chirp code, and a Golay code, but is not limited thereto.

[0058] Additionally, as an embodiment, the step of modulating the HIFU signal via the coding here may modulate the HIFU signal at the center frequency of the HIFU converter.

[0059] Referring again to FIGS. 2 and 4, in step S200, the processor (120) obtains frame data for the region of interest using the received HIFU signal.

[0060] Step S200 first removes noise from the frame data using a first band-pass filter (S210).

[0061] Thereafter, step S200 can normalize the frame data from which the noise has been removed (S220). At this time, step S200 can normalize the frame data using the maximum value of the frame data.

[0062] The method for generating an ultrasound image according to one embodiment of the present invention can adjust the amplitude ratio between the impulse response of the HIFU converter (110) and the scan line data before performing deconvolution through the above-described process.

[0063] Referring again to FIG. 2, the processor (120) can perform deconvolution for each scan line on the frame data (S300).

[0064] Step S300 may perform scanline-by-scanline deconvolution on frame data using the converter impulse response among the frame data. In one embodiment, step S300 may be a step for performing Wiener deconvolution.

[0065] Hereinafter, as an embodiment of the present invention, when a Barker code is used as a transmission signal and a Wiener deconvolution method is used, the operational formula and theory for solving this will be described.

[0066] HIFU signal, rx, applied to the surface of the transducer in a three-dimensional space can be expressed as follows.

[0067] rx =tx(t)*h t *m *h r +n(t)

[0068] Here, tx(t) is the electrical signal applied to the HIFU transducer, m is the inhomogeneity of the medium that generates the scattering signal, h t ,h r are the transmit and receive space impulse responses of the converter, n(t) is white noise generated from various sources, and the symbol * represents the convolution operation.

[0069] Here, h t ,h r is the converter impulse response of the HIFU converter, which has a long impulse response characteristic. In the present invention, h having a long impulse response characteristic t ,h r Deconvolution can be performed to remove mtx in the above equation. =tx(t)*m ,h pe =h t *h r If replaced with , it can be expressed in abbreviated form as follows.

[0070] [Mathematical Formula 1]

[0071] rx =mtx *h pe + n(t)

[0072] An ultrasound image generation method according to one embodiment of the present invention uses a Wiener deconvolution method, h pe It takes mtx as an argument and performs inverse filtering. The estimated signal can be inferred as follows.

[0073] [Equation 2]

[0074] =h deconv (t)*rx

[0075] Here, is mtx Estimated signal, h deconv (t) is mtx and It refers to the Wiener deconvolution filter that minimizes the mean square error and can be expressed as follows.

[0076] [Equation 3]

[0077] minimizee(t) = E|mtx - | 2

[0078] The above mathematical expression 3 can be expressed as follows when solved in the frequency domain.

[0079] [Equation 4]

[0080] H deconv (f) = ,

[0081] [Equation 5]

[0082] SNR(f) =

[0083] Here, H deconv (f),MTX ,N(f) is H deconv (t),mtx ,n(t) refers to a frequency domain signal to which a Fourier transform is applied.

[0084] Meanwhile, the following mathematical expression 6 is an expression in which the Fourier transform of mathematical expression 2 is applied, and (·) represents a multiplication operator.

[0085] [Equation 6]

[0086] =H deconv (f)·RX

[0087] A method for generating an ultrasonic image according to one embodiment of the present invention is an estimation signal of the non-uniformity of a medium for obtaining an ultrasonic image. To derive , by substituting Equation 4 into Equation 6 and performing an inverse Fourier transform, it can be expressed as follows.

[0088] [Equation 7]

[0089] =iFT[ ] =iFT[H deconv (f)·RX ]

[0090] Through the above method, the ultrasound image generation method can remove the long impulse response component of the HIFU transducer from the received ultrasound data, thereby improving the pulse compression performance and the axial resolution of the ultrasound image. In the present invention, the Barker code is used as the transmission signal applied to the transducer, so mtx and can be expressed as follows.

[0091] [Equation 8]

[0092] mtx = tx(t)*m =txBarker (t)*m

[0093] [Equation 9]

[0094] =tx Barker (t)*

[0095] Here, tx Barker (t) is the Barker code transmission signal, represents an estimated signal for the inhomogeneity of the medium.

[0096] As an example, the method for generating an ultrasound image may include, after the step of performing deconvolution (S300), a step of removing noise from the deconvolved frame data using a second band-pass filter.

[0097] Specifically, the ultrasound image generation method can perform deconvolution for each scan line using pre-stored noise information and a correlation signal of an impulse response, and then perform bandpass filtering to remove out-of-band noise caused by inverse filtering.

[0098] In an ultrasound image generation method according to one embodiment of the present invention, after the step of performing deconvolution (S300), pulse compression is performed on the frame data (S400).

[0099] Pulse compression method theoretically transmits the signal, tx, through a matched or mismatched filter. Barker (t) is a method that can be converted into a Dirac delta function.

[0100] As an example, the present invention provides a mismatch filter, h, capable of minimizing the peak sidelobe of a correlation function. PSL (t) As shown in the following mathematical expression 10, the present invention estimates the non-uniformity of the medium using a pulse compression method, Only can be extracted.

[0101] [Equation 10]

[0102] h PSL (t)* =h PSL (t)*tx Barker (t)* δ(t)*

[0103] As described above, the ultrasound imaging method according to one embodiment of the present invention can extract only an estimation signal for the inhomogeneity of a medium by combining deconvolution and pulse compression on a HIFU signal, thereby producing information on the medium scattering function without a significant loss in axial resolution and signal-to-noise ratio (SNR).

[0104] Thereafter, the method for generating an ultrasonic image according to one embodiment of the present invention can obtain ultrasonic image data using information about the calculated medium scattering function (S500).

[0105]

[0106] Meanwhile, a method for generating an ultrasound image according to another embodiment of the present invention can also produce ultrasound image data by training a machine learning model using a HIFU signal as input data.

[0107] According to another embodiment, a method for generating an ultrasound image can obtain ultrasound image data by performing steps S100 and S200 as shown in FIG. 2 to obtain preprocessed frame data, and then learning the obtained frame data as input data.

[0108] As another embodiment, the method for generating an ultrasound image may acquire ultrasound image data by, after step S200, training to output an estimation signal for the inhomogeneity of a medium using frame data as input data, and then performing pulse compression using the estimation signal for the inhomogeneity of the medium.

[0109] The artificial intelligence-related functions according to the present disclosure are performed through a processor (120) and memory. The processor (120) may be composed of one or more processors. In this case, one or more processors may be general-purpose processors such as a CPU, an AP, a DSP (Digital Signal Processor), or an artificial intelligence-specific processor such as an NPU. The one or more processors control the processing of input data according to predefined operation rules or artificial intelligence models stored in the memory. Alternatively, if one or more processors are artificial intelligence-specific processors, the artificial intelligence-specific processors may be designed with a hardware structure specialized for processing a specific artificial intelligence model.

[0110] The predefined operation rules or artificial intelligence models are characterized by being created through learning. Here, being created through learning means that the basic artificial intelligence model is trained using a learning algorithm using a plurality of learning data, thereby creating a predefined operation rules or artificial intelligence model set to perform a desired characteristic (or purpose). This learning may be performed on the device itself on which the artificial intelligence according to the present disclosure is performed, or may be performed through a separate server and / or system. Examples of the learning algorithm include, but are not limited to, supervised learning, unsupervised learning, semi-supervised learning, or reinforcement learning.

[0111] An artificial intelligence model may be composed of multiple neural network layers. Each of the multiple neural network layers has multiple weight values, and performs neural network operations through operations between the operation results of the previous layer and the multiple weights. The multiple weights of the multiple neural network layers may be optimized based on the learning results of the artificial intelligence model. For example, the multiple weights may be updated so that the loss value or cost value obtained from the artificial intelligence model is reduced or minimized during the learning process. The artificial neural network may include a deep neural network (DNN), and examples thereof include, but are not limited to, a convolutional neural network (CNN), a deep neural network (DNN), a recurrent neural network (RNN), a restricted boltzmann machine (RBM), a deep belief network (DBN), a bidirectional recurrent deep neural network (BRDNN), or deep Q-networks.

[0112] Fig. 5 is a diagram for explaining the difference between the impulse response and transmission signal of an image converter and a HIFU converter, respectively. Fig. 5 (a) shows the impulse response of the image converter model, and Fig. 5 (c) shows the transmission signal input to the image converter model. Fig. 5 (b) shows the impulse response of the 3 MHz HIFU converter model, and Fig. 5 (d) shows the Barker code with a code length of 13 applied to the HIFU converter model. To compare the performance of the proposed method, a simulation was also performed using an ideal image converter model.

[0113] Fig. 6 is a diagram for comparing simulation results of an ultrasound image generation method using a HIFU converter according to an embodiment of the present invention and an ultrasound image generation method using an image converter according to a comparative example. Fig. 6 shows the Field-II simulation results for a wire target image. Fig. 6 (a) is an image to which a general backend processing is applied using an image converter, and Fig. 6 (b) is an ultrasound image to which the proposed algorithm is applied using a HIFU converter.

[0114] In order to obtain an ultrasound image as shown in (b) of FIG. 6, a method for generating an ultrasound image according to one embodiment of the present invention transmitted a Barker code of length 13 as shown in (d) of FIG. 5, and the received signal was subjected to signal processing using a Wiener deconvolution and a mismatch filter for pulse compression.

[0115] (c) of Fig. 6 is an envelope obtained through an ultrasound image generation method according to a comparative example and an embodiment of the present invention, and represents an envelope in the axial direction based on the center of a wire target.

[0116] The -6 dB axial resolution of the wire target image was measured to be approximately 0.42 mm in both cases. This result demonstrates the effectiveness of the proposed method of the present invention, which removes the transmit and receive impulse responses of the HIFU transducer using Wiener deconvolution and applies pulse compression using a mismatched filter.

[0117] FIG. 7 is a diagram illustrating an ultrasound image obtained by (a) an ultrasound transducer for imaging, (b) a HIFU transducer, and (c) a HIFU transducer using the proposed method of the present invention, and a diagram illustrating an envelope of each ultrasound image signal.

[0118] Figure 7 shows an ultrasound image acquired targeting a 100 μm thick tungsten wire. Figure 7 (a) is an image acquired using an imaging ultrasound transducer. A two-cycle pulse was applied as an input signal to the transducer, and an image was output using a general back-end ultrasound signal processing method. Figure 7 (b) is an image acquired using a HIFU transducer. A two-cycle pulse was applied as an input signal to the HIFU transducer, and an image was also output using a general back-end ultrasound signal processing method.

[0119] Figure 7(c) shows an ultrasound image obtained from a HIFU transducer to which the proposed algorithm was applied. As in the simulation, a Barker code of length 13 was used as the transmission signal, and the received signal was processed using Wiener deconvolution and a mismatch filter for pulse compression.

[0120] Referring to the drawings, it can be seen that the image acquired with the HIFU converter (Fig. 7(b)) is significantly different from the image acquired with the imaging ultrasound converter (Fig. 7(a)). In contrast, it can be confirmed that the ultrasound image acquired according to one embodiment of the present invention (Fig. 7(c)) is almost identical to the image acquired with the imaging ultrasound converter (Fig. 7(a)).

[0121] Meanwhile, Fig. 7 (d) is a graph representing the ultrasound images of Fig. 7 (a) to (c) as envelopes in the axial direction for the wire target. Here, the dashed line (A1) represents the case where an ultrasound transducer for imaging is used, the dotted line (A2) represents the case where only a HIFU transducer is used, and the solid line (P) represents the case where the proposed method of the present invention is applied using a HIFU transducer.

[0122] As can be seen from Fig. 7 (d), the axial resolution of the ultrasound image (A2) by the HIFU transducer is severely degraded due to the narrow spectral bandwidth. Specifically, the -6 dB axial resolution of the transducer used in the experiment was measured to be 0.37 mm for the imaging ultrasound transducer (A1) and 1.36 mm for the general HIFU transducer (A2). In contrast, the ultrasound image (A3) acquired according to the present invention using the HIFU transducer but applying the Barker code excitation and the proposed algorithm before the conventional backend processing was confirmed to be significantly improved to 0.39 mm.

[0123] As such, it can be seen that the axial resolution of the ultrasonic image obtained by the ultrasonic image generation method according to the embodiment of the present invention is similar to the resolution of the ultrasonic image when an ultrasonic transducer for imaging is used, and thus matches well with the simulation results.

[0124] Figure 8 shows ultrasound image images of a cyst target obtained by (a) an ultrasound transducer for imaging, (b) a HIFU transducer, and (c) a HIFU transducer using the proposed method of the present invention, respectively, and (d) shows the result of measuring the signal-to-noise ratio (SNR) of the ultrasound image.

[0125] According to (a) and (c) of FIG. 8, the ultrasound image of the cyst obtained by the ultrasound transducer for imaging and the HIFU transducer according to the embodiment of the present invention clearly shows the speckle pattern and the cyst, but in (b) of FIG. 8, the image is unclear and the speckle pattern and the cyst could not be confirmed.

[0126] Meanwhile, referring to (d) of Fig. 8, it can be clearly seen that the maximum value of SNR appears around the depth of focus. Here, when an ultrasound transducer for imaging was used (A1), the maximum value was 27.8 dB at 19.5 mm, and when only a HIFU transducer was used (A2), the maximum value was 16.5 dB at 19.9 mm. On the other hand, when the ultrasound image generation method according to the embodiment of the present invention was applied (P), the overall SNR was improved and the maximum value was 29.1 dB at 19.2 mm, which can be confirmed to be similar to the SNR measured by an ultrasound transducer for imaging.

[0127] Fig. 9 is a diagram for explaining the axial resolution of an ultrasound image depending on whether deconvolution is performed and the pulse compression method. Both (a) and (b) of Fig. 9 are cases where deconvolution is not performed. Fig. 9 (a) is an ultrasound image when a received signal is compressed with a matched filter (mathed filtering), and Fig. 9 (b) is an ultrasound image when compressed with a mismatched filter (mismatched filtering). Fig. 9 (c) and (d) are cases where deconvolution is performed. Fig. 9 (c) is an ultrasound image when a received signal is compressed with a matched filter, and Fig. 9 (d) is an ultrasound image when compressed with a mismatched filter.

[0128] Figure 9 (e) shows the envelope in the axial direction based on the center of the wire target in each of cases (a) to (d) of Figures 9, and the B1, B2, D1, and D2 graphs correspond to Figures 9 (a), (b), (c), and (d), respectively. The -6dB axial resolution is measured as (a) 1.07 mm, (b) 1.30 mm, (c) 0.40 mm, and (d) 0.39 mm, respectively.

[0129] A key feature of the ultrasound image formation method of the present invention is to eliminate the influence of the narrow spectral bandwidth of the HIFU transducer by using Wiener deconvolution before pulse compression.

[0130] Referring to FIG. 9, the advantages of the ultrasound image generation method of the present invention in enhancing the effectiveness of pulse compression can be seen. That is, when using the Barker-13 code without performing deconvolution, pulse compression was ineffective regardless of whether a matched or mismatched filter was used. Conversely, pulse compression was effective when deconvolution was performed, regardless of whether a matched or mismatched filter was used.

[0131] Compared to imaging ultrasound transducers, HIFU transducers have a temporally longer impulse response, or in other words, a narrower spectrum, which reduces the axial resolution of ultrasound images. However, despite applying a temporally longer transmission signal, which reduces the axial resolution, to the HIFU transducer, the ultrasound image generation method according to embodiments of the present invention was able to obtain ultrasound images comparable to those of imaging ultrasound transducers in both simulations and actual experiments.

[0132] As described above, the ultrasound image generation method and device according to embodiments of the present invention can obtain an ultrasound image of a quality comparable to that of an ultrasound transducer for imaging through signal processing without a separate additional transducer by performing deconvolution and pulse compression on the HIFU signal received through the transducer.

[0133] The present invention has been described above, focusing on preferred embodiments. Those skilled in the art will appreciate that variations and modifications can be made to the invention without departing from its essential characteristics. Therefore, the disclosed embodiments should be considered illustrative rather than limiting. The scope of the present invention is set forth in the claims, not the foregoing description, and all differences within the scope equivalent thereto should be construed as being encompassed by the invention.

[0134] [Explanation of symbols]

[0135] 100: Ultrasonic image generation device

[0136] 110: HIFU Transducer

[0137] 120: Processor

[0138] 130: Display section

[0139]

[0140] The present invention relates to a method and device for generating an ultrasound image, and more particularly, to a method and device for generating a high-resolution ultrasound image using a HIFU transducer. The ultrasound image generating method and device according to embodiments of the present invention perform deconvolution and pulse compression on an ultrasound signal received through a HIFU transducer, thereby obtaining an ultrasound image of comparable quality to an ultrasound transducer for imaging through signal processing without a separate additional transducer, and thus has high industrial applicability.

Claims

1. A step of transmitting a HIFU signal to a target object using a HIFU converter and receiving a HIFU signal reflected from the target object; A step of obtaining frame data for a region of interest using the received HIFU signal; A step of performing deconvolution for each scan line on the above frame data; and A method for generating an ultrasound image, comprising: a step of performing pulse compression on the frame data to obtain ultrasound image data after performing the deconvolution step; 2. In paragraph 1, The step of transmitting a HIFU signal to the target object and receiving a HIFU signal reflected from the target object is as follows: A method for generating an ultrasound image, wherein a HIFU signal is modulated using coded excitation and the modulated HIFU signal is transmitted.

3. In paragraph 2, The step of transmitting a HIFU signal to the target object and receiving a HIFU signal reflected from the target object is as follows: A method for generating an ultrasound image, wherein the HIFU signal is modulated with the center frequency of the HIFU converter.

4. In paragraph 2, A method for generating an ultrasound image, wherein the above modulated HIFU signal is any one of a Barker code, a Chirp code, and a Golay code.

5. In paragraph 1, The step of acquiring the above frame data is: A step of removing noise from the frame data using a first bandpass filter; and A method for generating an ultrasound image, comprising: a step of normalizing the frame data from which noise has been removed using the maximum value of the frame data.

6. In paragraph 1, The step of performing the above deconvolution is: An ultrasound image generation method, which performs deconvolution on each scan line of the frame data using a converter impulse response among the frame data.

7. In paragraph 6, A method for generating an ultrasound image, wherein the step of performing the above deconvolution is a step of performing Wiener deconvolution.

8. In paragraph 6, A method for generating an ultrasound image, further comprising, after the step of performing the deconvolution, a step of removing noise from the deconvolved frame data using a second band-pass filter.

9. In paragraph 1, The step of acquiring the above ultrasound image data is: A method for generating an ultrasound image, wherein pulse compression is performed on the frame data using a matched filter or a mismatched filter.

10. A HIFU converter that transmits a HIFU signal to a target object and receives a HIFU signal reflected from the target object; and A processor that receives the reflected HIFU signal from the HIFU converter and generates ultrasound image data; The above processor, A step of obtaining frame data for a region of interest using the received HIFU signal; A step of performing deconvolution for each scan line on the above frame data; and An ultrasound image generation device configured to execute commands for: performing pulse compression on the frame data to obtain ultrasound image data after performing the deconvolution step; 11. In paragraph 10, The above HIFU converter is, An ultrasound image generating device that modulates a HIFU signal through coded excitation and transmits the modulated HIFU signal.

12. In paragraph 11, The above HIFU converter is, An ultrasound image generating device that modulates the HIFU signal with the center frequency of the HIFU converter.

13. In paragraph 11, An ultrasound image generating device, wherein the above modulated HIFU signal is one of a Barker code, a Chirp code, and a Golay code.

14. In paragraph 10, The step of acquiring the above frame data is: A step of removing noise from the frame data using a first bandpass filter; and An ultrasound image generation device, comprising: a step of normalizing the frame data from which noise has been removed using the maximum value of the frame data; 15. In paragraph 10, The step of performing the above deconvolution is: An ultrasound image generation device that performs deconvolution on each scan line of the frame data using a converter impulse response among the frame data.

16. In paragraph 15, An ultrasound image generating device, wherein the step of performing the above deconvolution is a step of performing Wiener deconvolution.

17. In paragraph 10, The step of acquiring the above ultrasound image data is: An ultrasound image generation device that performs pulse compression on the frame data using a matched filter or a mismatched filter.

18. A step of transmitting a HIFU signal to a target object using a HIFU converter and receiving a HIFU signal reflected from the target object; A step of obtaining frame data for a region of interest using the received HIFU signal; and A method for generating an ultrasound image, comprising: a step of obtaining ultrasound image data from the frame data using a learned neural network.

19. In paragraph 18, The step of acquiring the above ultrasound image data is: A method for generating an ultrasound image, comprising: a step of training the neural network to obtain the ultrasound image data from the frame data based on a converter impulse response among the frame data; 20. In paragraph 18, The step of acquiring the above frame data is: A step of removing noise from the frame data using a first bandpass filter; and A method for generating an ultrasound image, comprising: a step of normalizing the frame data from which noise has been removed using the maximum value of the frame data.

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