阅读说明：本技术 一种高质量的超声复合成像方法 (High-quality ultrasonic composite imaging method ) 是由 郑驰超 王源果 王亚丹 彭虎 于 2021-09-03 设计创作，主要内容包括：本发明公开了一种高质量的超声复合成像方法,是采用聚焦发射的工作方式并包括：1设置发射聚焦点的位置,保证焦点深度略大于成像区域成像深度；2根据焦点位置,发射时采用探头内全部阵元发射聚焦超声波,并采用全部阵元接收回波信号；3确定每次发射时有效发射声场的作用区域范围,并根据回波信号对该有效作用区域内所有位置的成像点进行成像,得到低质量的成像结果；4将所有低质量成像结果进行复合的高质量的成像结果。本发明能在成像区域保持较强的发射声场能量,有效提高深度较远的成像区域回波信号的信噪比,对成像区域较深的区域实现高质量成像,另外全阵元发射和接收的方式实现了全孔径发射和全孔径接收,具有较好的成像分辨率。(The invention discloses a high-quality ultrasonic composite imaging method, which adopts a working mode of focused emission and comprises the following steps: 1, setting the position of a transmitting focus point to ensure that the depth of the focus is slightly larger than the imaging depth of an imaging area; 2, according to the focal position, all array elements in the probe are adopted to transmit focused ultrasonic waves during transmission, and all array elements are adopted to receive echo signals; 3, determining the range of an effective transmission sound field in each transmission, and imaging the imaging points at all positions in the effective transmission area according to the echo signals to obtain a low-quality imaging result; 4, all the low-quality imaging results are subjected to composite high-quality imaging results. The invention can keep stronger transmitting sound field energy in an imaging area, effectively improve the signal-to-noise ratio of echo signals of the imaging area with a far depth, realize high-quality imaging on the area with a deep imaging area, realize full-aperture transmitting and full-aperture receiving in a full-array element transmitting and receiving mode and have better imaging resolution.)

1. A high-quality ultrasonic composite imaging method is characterized by comprising the following steps:

the method comprises the following steps: in the ultrasonic imaging process, setting a focus point when a probe transmits ultrasonic waves every time, and determining the coordinates of the focus point, wherein the depth of the focus point is greater than the maximum depth of an imaging area;

step two: calculating the emission delay parameters of all array elements in the probe according to the position of the focusing point, so that all array elements in the probe receive echo signals after emitting focused ultrasonic waves to an imaging area according to the emission delay parameters;

step three: determining an effective action area of a transmitting sound field during each transmission according to the coordinates of a focusing point transmitted each time, the coordinates of a first transmitting array element and the coordinates of a last transmitting array element of the probe;

imaging points at all positions in the effective action area according to the echo signals to obtain an imaging result;

directly setting an imaging point which belongs to the outside of the effective action area in the imaging result to be 0, thereby obtaining a low-quality image;

step four: forming imaging results corresponding to each imaging point in the low-quality image into corresponding composite vectors, and respectively averaging nonzero-value elements in the composite vectors of each imaging point to obtain high-quality composite imaging results of the corresponding imaging points; and carrying out logarithmic compression and graying processing on the high-quality imaging results of all imaging points to obtain a high-quality ultrasonic image in the imaging area.

2. The method for high-quality ultrasonic compound imaging according to claim 1, wherein the depth y of the focus point in the first step is obtained by using formula (1)^f：

In the formula (1), Δ x^fIs the interval between the focal points of two adjacent transmissions, y_maxIs the maximum depth of the imaging region; and L is the total length of all array elements of the probe.

3. The method according to claim 1, wherein the determination condition of the effective action area of the transmitted sound field of the imaging point p at the m-th transmission in the step three is obtained by using the formula (2):

in the formula (2), (x)^p,y^p) Coordinates of an imaging point p in the imaging area are obtained;the coordinates of the last transmitting array element in the imaging area are obtained;the coordinates of the focusing point of the imaging point p during the mth emission are shown;

if the coordinate of the imaging point p satisfies the formula (2), it indicates that the imaging point p belongs to the effective sound field region, otherwise, it indicates that the imaging point p does not belong to the effective sound field region.

Technical Field

The invention is suitable for the field of medical ultrasonic imaging, in particular to a high-quality ultrasonic composite imaging technology.

Background

Medical ultrasonic imaging equipment is one of the commonly used imaging equipment and has important value in diagnosis of many important diseases. The imaging mode influences the architecture of the imaging device, has important influence on the imaging quality, and is the core technology of the medical ultrasonic imaging device. Spatial compound imaging is a highly studied high-quality imaging mode, which is implemented by means of multiple shots. The ultrasonic probe transmits ultrasonic waves to enter an imaging area, then receives echo signals scattered back by the imaging area, and then images by adopting a beam forming technology according to the echo signals. After each emission, the obtained ultrasonic image is called as a low-quality image, and then the low-quality image is compounded to obtain the final high-quality image. Common complex imaging methods include plane wave coherent recombination, synthetic aperture imaging, and diverging wave complex imaging. The plane wave coherent recombination adopts a mode of emitting the plane wave in a full aperture, the plane wave is continuously dispersed in the transmission process, the imaging intensity of a deeper part of an imaging area is reduced, and the imaging quality is reduced. The divergent wave complex imaging adopts a mode of emitting divergent waves by using a sub-aperture, although the resolution is higher, the energy attenuation of a sound field is faster, and the quality of remote imaging is obviously reduced. In addition, there is a kind of compound imaging method that uses sub-aperture to emit focusing wave, when the depth of focus is larger, the sub-aperture emission mode will reduce the focusing performance, the imaging quality of the deep imaging area will be improved a little, and the resolution of the image will be reduced.

Disclosure of Invention

The invention provides a high-quality ultrasonic composite imaging method for overcoming the defects in the prior art, so as to improve the imaging quality of a deep imaging area and effectively improve the image resolution of an ultrasonic imaging system.

In order to achieve the purpose, the invention adopts the following technical scheme:

the invention discloses a high-quality ultrasonic composite imaging method which is characterized by comprising the following steps:

the method comprises the following steps: in the ultrasonic imaging process, setting a focus point when a probe transmits ultrasonic waves every time, and determining the coordinates of the focus point, wherein the depth of the focus point is greater than the maximum depth of an imaging area;

step two: calculating the emission delay parameters of all array elements in the probe according to the position of the focusing point, so that all array elements in the probe receive echo signals after emitting focused ultrasonic waves to an imaging area according to the emission delay parameters;

step three: determining an effective action area of a transmitting sound field during each transmission according to the coordinates of a focusing point transmitted each time, the coordinates of a first transmitting array element and the coordinates of a last transmitting array element of the probe;

imaging points at all positions in the effective action area according to the echo signals to obtain an imaging result;

directly setting an imaging point which belongs to the outside of the effective action area in the imaging result to be 0, thereby obtaining a low-quality image;

step four: forming imaging results corresponding to each imaging point in the low-quality image into corresponding composite vectors, and respectively averaging nonzero-value elements in the composite vectors of each imaging point to obtain high-quality composite imaging results of the corresponding imaging points; and carrying out logarithmic compression and graying processing on the high-quality imaging results of all imaging points to obtain a high-quality ultrasonic image in the imaging area.

The high-quality ultrasonic composite imaging method is also characterized in that the depth y of the focusing point in the step I is obtained by using the formula (1)^f：

In the formula (1), Δ x^fIs the interval between the focal points of two adjacent transmissions, y_maxIs the maximum depth of the imaging region; and L is the total length of all array elements of the probe.

Obtaining the judgment condition of the effective action area of the emission sound field of the imaging point p in the mth emission in the third step by using the formula (2):

in the formula (2), (x)^p,y^p) Coordinates of an imaging point p in the imaging area are obtained;the coordinates of the last transmitting array element in the imaging area are obtained;the coordinates of the focusing point of the imaging point p during the mth emission are shown;

if the coordinate of the imaging point p satisfies the formula (2), it indicates that the imaging point p belongs to the effective sound field region, otherwise, it indicates that the imaging point p does not belong to the effective sound field region.

Compared with the prior art, the invention has the beneficial effects that:

the invention adopts a full array element transmitting mode and has higher transmitting sound field energy. The mode that the full array receives and the focus point is arranged outside the imaging area can enable the transmitting sound field to keep higher energy in the whole imaging area, and particularly for the deeper imaging area, the transmitting sound field keeps the focusing characteristic. Compared with an ultrasonic composite imaging mode, the ultrasonic composite imaging method has the advantages that the divergence of a sound field is reduced, the signal to noise ratio of echo signals of an imaging area with a far depth can be effectively improved, and the imaging quality of the imaging area in the deep depth is improved. In addition, the full-aperture transmission and the full-aperture reception are realized by the full-array element transmission and reception mode, and the imaging resolution ratio is better compared with the sub-aperture transmission or reception mode. The imaging method has certain clinical application value.

Drawings

FIG. 1 is a flow chart of a method of the present invention;

FIG. 2 is a diagram of the relationship between the imaging area and the focal point and the probe array element of the present invention;

FIG. 3 is a low quality ultrasound image at the 21 st shot of the simulated scattering point of the present invention;

FIG. 4 is a low quality ultrasound image at the 64 th transmission of the simulated scattering point of the present invention;

FIG. 5 is a graph of the final composite imaging results of scattering sites of the present invention.

Detailed Description

In this embodiment, fig. 1 is a flowchart of a method according to the present invention, and a high-quality ultrasound composite imaging method includes the following steps:

the method comprises the following steps: in the ultrasonic imaging process, an ultrasonic probe is arranged to have N array elements, the total length of all the array elements of the probe is L, and the coordinate of the nth array element isIn a complete imaging process, the probe always transmits for M times, and each time the probe transmits ultrasonic waves, a focus point is set, namely M transmitting focus points are set in the imaging process. Let the focus point of the m-th emission be F_mThe coordinates areThe focusing points are arranged at intervals along the transverse direction. The interval between adjacent focus points is Deltax^fThe maximum depth of the imaging region is set to y_maxAnd the depth of the focus point is greater than the maximum depth of the imaging area;

in specific implementation, the depth y of the focusing point is obtained by using the formula (1)^f：

In the imaging process, in order to ensure focusing performance, the focal depth is set to be not more than 85mm, and the difference between the focal depth and the maximum depth of the imaging region is not more than 5 mm. In order to ensure the imaging quality on both sides of the imaging area, the 1 st focal point and the Mth focal point are arranged outside the imaging area. As shown in fig. 2.

Step two: calculating the emission delay parameters of all array elements in the probe according to the position of the focusing point, so that all array elements in the probe receive echo signals after transmitting focused ultrasonic waves to an imaging area according to the emission delay parameters; namely, the imaging system works in a full-aperture transmitting and receiving mode in the whole imaging process.

Step three: determining an effective action area of a transmitting sound field during each transmission according to the coordinates of a focusing point transmitted each time, the coordinates of a first transmitting array element and the coordinates of a last transmitting array element of the probe;

specifically, the judgment condition of the effective action area of the emission sound field of the imaging point p at the m-th emission in the step three is obtained by using the formula (2):

in the formula (2), (x)^p,y^p) Coordinates of an imaging point p in the imaging area are obtained;the coordinates of the last transmitting array element in the imaging area are obtained;the coordinates of the focusing point of the imaging point p during the mth emission are shown;

if the coordinate of the imaging point p satisfies the formula (2), it indicates that the imaging point p belongs to the effective sound field region, otherwise, it indicates that the imaging point p does not belong to the effective sound field region.

Imaging points at all positions in the effective action area according to the echo signals to obtain an imaging result; directly setting an imaging point outside the effective action area in the imaging result to be 0, thereby obtaining a low-quality image;

specifically, when the m-th emission is carried out, the nth array element of the probe receives an echo signal, and the signal strength value obtained after delaying is v_m,n(p), mth emission, obtaining a low quality imaging result S_m(p) obtainable from formula (3):

step four: forming imaging results corresponding to each imaging point in the low-quality image into corresponding composite vectors, and respectively averaging nonzero-value elements in the composite vectors of each imaging point to obtain high-quality composite imaging results of the corresponding imaging points;

specifically, the low-quality imaging results obtained by M times of emission are combined into an imaging composite vector S (p) ([ S) ]₁(p),S₂(p),…,S_m(p),…,S_M(p)]. If the number of elements with values other than 0 in the composite vector is K, the p-point composite imaging result is given as formula (4):

and carrying out logarithmic compression and graying processing on the high-quality imaging results of all imaging points to obtain a high-quality ultrasonic image in the imaging area.

Example (b):

in this embodiment, a simulation ultrasound imaging system is first established, and the system uses a 128-element linear array probe. The array element spacing is 0.3mm, the center frequency of the emission signal is 5MHz, and the system sampling frequency is 40 MHz. The sound velocity of the imaging region is 1540m/s, the maximum depth of the imaging region is 40mm, the emission frequency of each imaging is 128 times, namely 128 focuses are set, and then as can be seen from formula 1, the 128 focuses are transversely arranged at equal intervals, the distance is 0.3mm, and the depths of the 128 focuses are set to be 40.31 mm. In order to verify the effectiveness of the algorithm, Gaussian white noise with certain intensity is added to the simulated echo signal. The imaging area is 36mm x 30mm in size, with a lateral distance of-18 mm to 18mm and a depth of 10mm to 40 mm. The object within the imaging zone consists of a plurality of strong scattering spots evenly distributed with a lateral spacing of 2mm and a longitudinal spacing of 4 mm. The low quality ultrasound images obtained at the 20 th emission and the 64 th emission are shown in fig. 3 and 4, which illustrate the effective sound field areas of different focal points. The noise inside fig. 3 and 4 is large. Fig. 5 shows the high-quality imaging result obtained after the 128 low-quality images are compounded, and it can be seen that the imaging quality of the scattering point is obviously improved, and the noise of the background area of the image is also obviously reduced.