CN104905815B - A kind of linear array ultrasonic probe - Google Patents

Abstract

The application discloses a linear array ultrasonic probe, which includes a housing, an array element array, a matching layer and an acoustic lens, the housing is provided with a cavity and an opening is provided at the front end, the acoustic lens is arranged on the opening, the The array element array and the matching layer are arranged in the cavity, and the matching layer is sandwiched between the array element array and the acoustic lens, and the ultrasonic beam passing through the acoustic lens is not focused in the elevation direction , enabling the ultrasonic beam to realize plane wave emission. Since the ultrasonic beam passing through the acoustic lens has no focus in the elevation direction, the ultrasonic beam can be emitted as a plane wave, making the beam more uniform within the data acquisition range, and the imaging range is expected to be extended from the original one surface to three-dimensional scanning. Through the composite imaging algorithm, It can better realize fast and high frame rate imaging, and the hardware cost is much lower than that of a two-dimensional transducer.

Description

A linear array ultrasonic probe

technical field

The present application relates to the field of medical devices, in particular to a linear array ultrasonic probe.

Background technique

With the emergence of imaging technologies such as brain functional imaging, real-time three-dimensional ultrasound imaging, and high-speed Doppler blood flow velocity and flow field imaging, the requirements for imaging frame rates have become higher. Currently, ultrasound imaging probes on the market mostly use electronic scanning. A complete image is generated by performing multiple focused transmissions. The frame rate of this mode of imaging is low, and it is difficult to meet the new imaging requirements. Realizing high frame rate imaging of ultrasonic instruments has become an urgent demand in the market. Plane wave transmission is a method that can quickly increase the imaging frame rate. The frame rate of imaging has been improved. In order to improve the quality of plane wave imaging, some scholars have proposed a method of plane wave coherent composite imaging, which greatly improves the imaging quality. Most of the research is limited to the exploration of ultrasound imaging algorithms, but the research on the relationship between the structure and working mode of the ultrasound probe and the effect of plane wave imaging has been ignored by everyone, and the structure of the linear array ultrasound probe has an important impact on the imaging effect .

Two-dimensional linear array ultrasonic probes are arranged with piezoelectric wafers (usually called array elements) in both vertical and horizontal directions of the probe, while conventional ultrasonic linear array transducers only have array elements arranged in the transverse direction of the probe. The two-dimensional linear array ultrasonic probe can control the beam more flexibly by controlling the emission and reception of the array elements, and its imaging algorithm is still in the research stage. The two-dimensional linear array ultrasound probe can flexibly control the beam, and in principle can realize the three-dimensional scanning of the whole tissue under the probe, but its application is greatly limited due to its high cost and complicated manufacturing process.

Contents of the invention

The technical problem to be solved in this application is to provide a linear array ultrasonic probe for the deficiencies of the prior art.

The technical problem to be solved in this application is solved through the following technical solutions:

A linear array ultrasonic probe, comprising a housing, an array of array elements, a matching layer and an acoustic lens, the housing is provided with a cavity and the front end is provided with an opening, the acoustic lens is arranged on the opening, the array of array elements and the The matching layer is arranged in the cavity, and the matching layer is clamped between the array element array and the acoustic lens, and the ultrasonic beam passing through the acoustic lens has no focus in the elevation direction, so that the Ultrasonic beams achieve plane wave emission.

In the above-mentioned linear array ultrasonic probe, the acoustic lens includes a convex lens, and the focal point of the convex lens is set at infinity.

In the above-mentioned linear array ultrasonic probe, the acoustic lens includes a concave lens, and the focal point of the concave lens is set at infinity.

Above-mentioned linear array ultrasonic probe, the thickness of described matching layer is Wherein, λ is the ultrasonic wavelength, and N is a positive integer.

For the above-mentioned linear array ultrasonic probe, the value of N is 1, 2 or 3.

Owing to adopting above technical scheme, the beneficial effect that makes this application possess is:

In the specific implementation of this application, since the ultrasonic beam passing through the acoustic lens has no focus in the elevation direction, the ultrasonic beam can be emitted as a plane wave, making the beam more uniform within the data collection range, and the imaging range is expected to expand from the original one plane From three-dimensional scanning, fast and high frame rate imaging can be better achieved through composite imaging algorithms, and the hardware cost is much lower than that of two-dimensional transducers.

Description of drawings

FIG. 1 is a schematic structural view of a linear array ultrasonic probe of the present application in an embodiment;

Figure 2 is a schematic diagram of the focusing principle of the acoustic lens;

Figure 3 shows the imaging effects of different types of probes on different types of phantom scatterers;

Figure 4 is a comparison of phantom data collected by two probes on the ultrasound platform.

Detailed ways

The present application will be described in further detail below through specific embodiments in conjunction with the accompanying drawings.

The commonly used linear array ultrasonic probe has focus in the elevation direction, and the focus depth varies with different probes. This application refers to this type of linear array ultrasonic probe as an elevation-focused probe (Elevation-Focused Probe, EFP). By improving the matching layer of the linear array probe and the longitudinal radian of the acoustic lens, it can produce a fully meaningful plane wave emission sound field, which is called the non-elevation-focused probe (Non-Elevation-Focused Probe, NEFP).

This application mainly improves the traditional linear array ultrasonic probe. When the traditional linear array ultrasonic probe emits plane waves, it only adopts non-delayed emission in the transverse direction (the width direction of the probe) to form a plane wave, while there is a plane wave in the elevation direction of the probe. The physical focusing achieved by the acoustic lens is not a true pure plane wave. This application improves the ordinary linear array ultrasonic probe, so that it has no focus in the elevation direction, so as to emit complete plane waves.

As shown in Fig. 1 and Fig. 2, the linear array ultrasonic probe of the present application, one embodiment thereof, includes a housing 11, an array element array 12, a matching layer 13 and an acoustic lens 14, the housing 11 is provided with a cavity, and the housing 11 The front end is provided with an opening through the cavity, the acoustic lens 14 is arranged on the opening, the array element array 12 and the matching layer 13 are arranged in the cavity, and the matching layer 13 is clamped between the array element array 12 and the acoustic lens 14, passing through The ultrasonic beam passing through the acoustic lens 14 is not focused in the elevation direction, so that the ultrasonic beam can be emitted as a plane wave. In Figure 1, the horizontal X is the array arrangement direction, the vertical Y is the elevation direction, and the depth Z is the emission direction.

In order to enable the linear array ultrasonic probe to emit a complete plane wave, the radian of the acoustic lens is improved, and the acoustic convex lens and the acoustic concave lens are used to realize the plane wave emission. The sound velocity c1 of ultrasound in the lens is different from the sound velocity c2 in the human body. When c1<c2, a convex lens is used, and when c1>c2, a concave lens is used. When using a convex lens, the middle is thicker and the edge is thinner, and the speed of sound in the convex lens is lower than the speed of sound in the human body. Ultrasonic waves are delayed less when passing through the edge of the lens, but are delayed more when passing through the center of the convex lens; therefore, the sound waves at the edge and center There will always be a point that converges on the axis of the sound beam at a certain moment, which is the acoustic focus and focuses the sound field. Concave lenses are used when the speed of sound in the lens is greater than the speed of sound propagating in human tissue. The thicker the edge of the concave lens, the shorter the total propagation time, and the same can form an acoustic focal point. If plane waves are needed, the curvature of the acoustic lens can be adjusted to set its focal point at infinity.

In the linear array ultrasound probe of the present application, in an implementation manner, the acoustic lens may include a convex lens, and the focal point of the convex lens is set at infinity. In another implementation manner, the acoustic lens may further include a concave lens, and the focal point of the concave lens is also set at infinity.

In the linear array ultrasonic probe of the present application, the thickness of the matching layer is Wherein, λ is the ultrasonic wavelength, and N is a positive integer. In one embodiment, the value of N is 1, 2 or 3. The main function of the matching layer of the probe is to match the acoustic impedance between the linear array ultrasound probe and human tissue. The acoustic lens is in contact with the array element array 12 and the human tissue at the same time. The acoustic impedance of the two is very different. In this case, the sound wave cannot enter the human tissue smoothly. The interface emission will cause a large energy loss. In order to make more sound wave energy incident on the human body, it is often necessary to use a matching layer to achieve the matching between the probe and the tissue. In addition, the matching layer also plays a role of isolating the array element array 12 and human tissue, which can protect the array element array 12 from external damage, and protect the human body from the damage of substances and current in the probe. There are requirements on the thickness, acoustic impedance and damping of the matching layer to reduce the loss of ultrasonic energy during propagation. Therefore the purpose of the matching layer is to make the sound wave propagate smoothly, and the design is designed according to the shape of the acoustic lens. The thickness of the matching layer 13 can be a quarter wavelength or its multiple (within 3 times), and it may be too thick Cause unnecessary sound wave attenuation.

The imaging speed of the improved NEFP probe is obviously superior to that of the traditional probe, and the plane wave coherent composite imaging algorithm is used, and the imaging quality is better. Compared with the plane wave coherent compound imaging of the EFP probe, the imaging contrast of the NEFP probe is higher, the imaging at each depth is more uniform, and the imaging effect of the non-central plane is also achieved. It can realize single-shot acquisition Multiple data, to achieve direct three-dimensional data acquisition. Moreover, the improved probe does not require too much additional expenditure, and has a good market application prospect.

Figure 2 shows the schematic diagram of the acoustic lens focusing, the position of the array element crystal, the matching layer and the acoustic lens are shown in the figure, the length direction of the array element represents the longitudinal direction of the probe, the width represents the thickness of the array element, and the matching layer is located between the acoustic lens and the crystal Between, the thickness is small. The curvature of the acoustic lens determines the depth of focus. If you want to get a longitudinal plane wave, you can set the focus at infinity (the focal length is much longer than the length of the array element).

This application has been verified by simulation and experiment, and the detailed verification scheme is as follows:

(1) Simulate two kinds of plane wave transmitting probes, use MATLAB tool software to conduct simulation experiments by setting transducer parameters through the Field II ultrasonic simulation program. Assuming that the sound propagation medium is uniform human tissue, the sound velocity is uniformly set to 1540m/s without considering the sound attenuation and the non-uniformity of the tissue. The transducer adopts a transmission frequency of 7.5MHZ, the number of array elements is 128, the array element spacing is 2.7mm, and the length in the elevation direction is 5mm. In order to simulate and realize its acoustic lens focusing effect in the elevation direction, the EFP probe array is placed It is divided into 10 equal parts in the elevation direction to realize electronic focusing, and the EFP probe sets the elevation focusing depth to 30mm. The NEFP probe is divided into the same 10 equal parts as the EFP probe in the elevation direction of the array element, but it does not perform electronic focusing. The remaining parameters of the two probes are the same. The simulation experiment uses 30 point scattering targets for verification, the simulation imaging depth is 0-80mm, the 30 points are regularly distributed between 11-65mm, the point spacing in the depth direction is 6mm, and the lateral positions are at -5mm and 10mm. Vertically set the position of the elevation focus center plane as 0mm, and mark the simulated phantom as phantom 1. All the scatterers of the phantom are offset longitudinally by 1.5mm, and the other parameters are the same, which is marked as phantom 2. The simulation experiment is carried out through the composite imaging algorithm, and the composite angle starts from θ=-((N-1)/2)*pi/180, (if N is an even number, start with θ=-(N/2)*pi/180) to Δθ=pi/180 interval transformation, N represents the number of composite imaging pairs, and this simulation uses N=9. Composite imaging results are shown in Figure 2. In order to further analyze the resolution and contrast of different methods, a cross-section was taken at a depth of 30mm and 60mm in Figure 2 for analysis, and the data results are listed in Table 1.

⑵ Use EFP probe and NEFP probe to collect phantom data. The experimental data collection platform The Verasonics System is developed and produced by Verasonics Company of the United States. This platform has good compatibility with matlab. The specific imaging system parameters of the ultrasonic probe are: 128 array elements, the array element spacing is 0.49mm, the center frequency is 7.5MHz, and the sampling frequency is 100MHz. The speed of sound is 1540m/s. The imaging dynamic range was set to 60dB, and the acoustic wave emission voltage was kept at 30V during the data acquisition process. In order to analyze the imaging effect at each depth, the acquisition image depth was selected in the range of 0-110mm. The imaging result is shown in Figure 4.

The results show that the contrast of the NEFP probe is significantly better than that of the EFP probe in the near-field region. Analyzing the different depths of the same probe, it was found that the resolution of the NEFP probe decreased slightly in the far field, but the contrast did not change significantly; the contrast of the EFP probe increased in the far field, but the resolution did not change significantly. Comparing the images of the two probes at the central position and the non-central position, the imaging quality of the two probes is reduced at the offset center, but the imaging quality of the EFP probe is seriously degraded. From the comparison of the above data, it can be seen that the NEFP probe is indeed superior to the EFP probe in some aspects, which is of great significance for further improving the quality of ultrasonic plane wave imaging.

Figure 3 shows the imaging effects of different types of probes on different types of phantom scatterers. a represents the imaging of scatterers on the center plane of focus by NEFP probe, b represents the imaging of scatterers on the center plane of focus by EFP probe, c represents the imaging of scatterers at 1.5mm away from the center plane by EFP probe, and d represents the imaging of scatterers on the center plane of focus by EFP probe Imaging of scatterers 1.5mm away from the center plane. In order to distinguish the imaging effects more clearly, the quantitative analysis of the data in Figure 3 is listed in Table 1.

Table 1 shows the comparative analysis of the two probes under various imaging modes. The scatterers in phantom 1 are all on the elevation focusing center plane, and the scatterers in phantom 2 are all off the center plane by 1.5mm. The parameter FWHM (Full Width at Half Maximum) represents the full width at half maximum, and the smaller it is, the better the image resolution is. PSL (Peak Side-lobe Level) refers to the peak side-lobe level. The smaller the PSL, the better the side-lobe suppression and the better the image contrast. In the table, the depths of 30mm and 60mm are selected for analysis.

Table 1: Comparative analysis of two probes under various imaging modalities

Figure 4 is a comparison of phantom data collected by the two probes on the ultrasound platform. Figure a shows the imaging results of the EFP probe, and b shows the imaging results of the NEFP probe. It can be seen from the figure that there is little difference in the resolution of the two pictures, and the imaging contrast of the picture b higher than Figure a.

The above content is a further detailed description of the present application in conjunction with specific implementation modes, and it cannot be considered that the specific implementation of the present application is limited to these descriptions. For those of ordinary skill in the technical field to which the present application belongs, some simple deduction or replacement can also be made without departing from the concept of the present application.

Claims (5)

1. A linear array ultrasonic probe, comprising a shell, an array of array elements, a matching layer and an acoustic lens, the shell is provided with a cavity and the front end is provided with an opening, the acoustic lens is arranged on the opening, and the array element The array and the matching layer are arranged in the cavity, and the matching layer is sandwiched between the array element array and the acoustic lens, and it is characterized in that the ultrasonic beam passing through the acoustic lens is Without focusing, the ultrasonic beam can realize plane wave emission. 2. The linear array ultrasonic probe according to claim 1, wherein the acoustic lens comprises a convex lens, and the focal point of the convex lens is set at infinity. 3. The linear array ultrasonic probe according to claim 1, wherein the acoustic lens comprises a concave lens, and the focal point of the concave lens is set at infinity. 4. The linear array ultrasonic probe according to any one of claims 1 to 3, wherein the thickness of the matching layer is Wherein, λ is the ultrasonic wavelength, and N is a positive integer. 5. The linear array ultrasonic probe according to claim 4, wherein the value of N is 1, 2 or 3.