阅读说明：本技术 基于反相Golay码的超声微泡空化成像方法及装置 (Ultrasonic microbubble cavitation imaging method and device based on reverse Golay code ) 是由 屠娟 朱逸斐 张国峰 丁波 王建和 于 2019-10-09 设计创作，主要内容包括：一种基于反相Golay码的超声微泡空化成像方法及装置,通过将待发射的若干空化成像脉冲采用Golay码编码后,得到一对正相及其180°反相空化脉冲,经与常规成像超声脉冲协同控制后发射；再通过对回波进行匹配滤波、分通道时延和叠加后解调,与常规成像超声脉冲得到的图像叠加后实现。本发明能够精确采集空化发生时的所有非线性的能量,检测到的空化强度更为准确。同时由于使用了脉冲压缩技术。空化成像的精度提高。(A ultrasonic microbubble cavitation imaging method and device based on reverse phase Golay codes, a pair of positive phase and 180-degree reverse phase cavitation pulses are obtained after a plurality of cavitation imaging pulses to be transmitted are coded by the Golay codes, and the positive phase and 180-degree reverse phase cavitation pulses are transmitted after being cooperatively controlled with conventional imaging ultrasonic pulses; and then the echo is demodulated after matched filtering, channel-division delay and superposition, and is superposed with an image obtained by the conventional imaging ultrasonic pulse. The invention can accurately collect all nonlinear energy when cavitation occurs, and the detected cavitation intensity is more accurate. And simultaneously, the pulse compression technology is used. The accuracy of cavitation imaging is improved.)

1. An ultrasonic microbubble cavitation imaging method based on reverse phase Golay codes is characterized in that a pair of normal phase and 180-degree reverse phase cavitation pulses are obtained by encoding a plurality of cavitation imaging pulses to be transmitted by the Golay codes, and the cavitation imaging pulses are transmitted after being cooperatively controlled with conventional imaging ultrasonic pulses; then, the echo is demodulated after matched filtering, channel-division delay and superposition, and is superposed with an image obtained by a conventional imaging ultrasonic pulse;

the Golay codes, specifically orthogonal complementary Golay (a, B) codes, have lengths matched to corresponding cavitation imaging pulses.

2. The method as claimed in claim 1, wherein the pair of positive and negative cavitation pulses comprises Golay code A sequence, Golay code B sequence coded signals and their negative signals;

Said emission is carried out by inverting A, B and 180 deg. phaseThe four groups of signals are modulated and then transmitted in sequence.

3. the method as claimed in claim 1, wherein the superposition is performed by superposing a pair of positive phase and reverse phase cavitation echo signals obtained after matched filtering to obtain a fundamental component and a nonlinear component of cavitation pulse echo.

4. The method of claim 1, wherein the cooperative control is: controlling cavitation imaging pulses with normal B-mode and/orThe emission time sequence of the contrast mode pulse is completely staggered, so that the interference is obviously reduced, and the time-sharing full duplex is realized, and the method specifically comprises the following steps: the safe time required for the echo intensity obtained after the cavitation pulse is transmitted to be attenuated to be less than or equal to the intensity of the conventional imaging ultrasonic pulse is satisfied, namely:Wherein: f. of_tAt the frequency of cavitation pulses, f_BFor conventional imaging pulse frequency, V_tis a cavitation pulse voltage, V_BThe pulse voltage is the conventional imaging pulse voltage, d is the current imaging depth, and alpha is the attenuation coefficient of the ultrasound in the human body.

5. An ultrasonic microbubble cavitation imaging device based on Golay codes, which is characterized by comprising: the device comprises a transmitting end used for generating single cavitation pulse and imaging pulse, a receiving end used for receiving echo and analyzing cavitation image, and transmitting and receiving switches respectively connected with the receiving end and the receiving end, wherein: the transmitting and receiving switch is connected with the transducer and is opposite to the position to be measured.

6. the imaging apparatus of claim 5, wherein said transmitting end comprises: a bipolar pulse generator and a transmit sequence memory, wherein: the control terminal of the bipolar pulse generator receives the transmit focus delay to transmit normal B-mode, Doppler mode or contrast mode pulses for conventional imaging, and the transmit sequence memory provides Golay codes to encode cavitation imaging pulses.

7. The imaging device of claim 5 or 6, wherein the transmitting end adopts four times of transmission, and the separation of the fundamental wave component and the strong nonlinear component in the echo is realized by respectively transmitting the pulses after the A sequence and the B sequence are coded and the reverse pulses after the A sequence and the B sequence are coded.

8. The imaging apparatus of claim 5, wherein said receiving end comprises: matched filter, receive channel with time delay, receive beam synthesizer, accumulator and demodulator, wherein: the matched filter is connected with a memory in which filter coefficients are prestored, the received echo signals are convoluted with receiving codes corresponding to the transmitting signals and then output to a receiving channel for corresponding time delay, amplification and analog-to-digital conversion processing, the accumulator superposes the synthesized matched filtering signals at the same transmitting focus position to realize pulse compression of harmonic signals and suppression of fundamental wave signals, and the demodulator demodulates the signals output by the accumulator and outputs the signals to a subsequent signal processor for corresponding envelope detection, edge enhancement and/or logarithmic compression processing.

9. The imaging device of claim 8, wherein the receiving end performs matched filtering and phase inversion processing corresponding to the sequence A and the sequence B on the four received groups of signals through a matched filter to obtain R_AAnd R_BAnd anti-phase filtered signalAnd

The on-off setting of the matched filter is the same as the sequence A and the sequence B of the transmitting end;

The accumulators are overlapped to respectively obtain fundamental wave componentsAnd a nonlinear component

the signal processor calculatesObtaining the cavitation intensity of each echo point and obtaining the normal B mode, Doppler mode or contrast mode map for imaging through scanning conversionand (5) superposing the images to obtain cavitation imaging.

10. The imaging device according to any one of claims 6 to 11, wherein the transmitting end is further provided with a cooperative control module for controlling the transmitting timing of the single cavitation pulse and the imaging ultrasonic pulse;

when the emission gap meets the condition, namely, a plurality of times of cavitation pulses are emitted in one period under an ideal state, and the time interval of adjacent cavitation pulses is 1/prf; transmitting the conventional imaging pulse Image for several times after the interval of the safe time slot after the last time of cavitation pulse transmission, wherein the time interval of the adjacent conventional imaging pulses isWherein: c is the propagation speed of sound waves in a human body, d is the imaging depth, and extra is the extra waiting time; generally d is inversely proportional to extra;

When the transmission gap does not meet the condition, namely the safe time slot obtained according to the current imaging depth information and the time required by the transmission end for any one or any four of the four transmissions exceed the transmission gap, the cooperative control module temporarily suspends the bipolar pulse generator, and ensures that the conventional imaging pulses are not interfered by forcibly increasing the gap between cavitation pulses.

Technical Field

The invention relates to a technology in the field of ultrasonic treatment, in particular to an ultrasonic microbubble cavitation imaging method and device based on an inverse Golay code.

Background

Cavitation imaging is a necessary means for monitoring microbubble cavitation intensity, and proper cavitation intensity is a very necessary parameter for doctors and experimenters. Generally, continuous strong ultrasonic pulses are needed for cavitation excitation, the cavitation intensity is judged according to the nonlinear intensity of echoes, and the higher the nonlinear component of the echoes is, the higher the cavitation intensity is; whereas the greater the number of cavitation imaging pulses, the lower the resolution. The resolution of cavitation imaging and the cavitation intensity create a pair of contradictions.

Disclosure of Invention

Aiming at the defects in the prior art, the invention provides an ultrasonic microbubble cavitation imaging method and device based on an inverse Golay code, and cavitation excitation ultrasonic and imaging ultrasonic are fused and simultaneously transmitted through coding transmission and pulse compression technologies.

The invention is realized by the following technical scheme:

The invention relates to an ultrasonic microbubble cavitation imaging method based on reverse phase Golay codes, which is characterized in that a pair of normal phase and 180-degree reverse phase cavitation pulses are obtained by encoding a plurality of cavitation imaging pulses to be transmitted by the Golay codes, and the cavitation imaging pulses are transmitted after being cooperatively controlled with conventional imaging ultrasonic pulses; and then the echo is demodulated after matched filtering, channel-division delay and superposition, and is superposed with an image obtained by the conventional imaging ultrasonic pulse.

The Golay codes, specifically orthogonal complementary Golay (a, B) codes, have lengths matched to corresponding cavitation imaging pulses.

The pair of positive phase cavitation pulse and the opposite phase cavitation pulse thereof comprise signals coded by an A sequence and a B sequence of Golay codes and signals after the opposite phase of the signals.

Said emission is carried out by inverting A, B and 180 deg. phasethe four groups of signals are modulated and then transmitted in sequence.

And in the superposition, a pair of normal phase signals and reverse phase cavitation echo signals obtained after the matched filtering are superposed to obtain a fundamental wave component and a nonlinear component of the cavitation pulse echo.

The conventional imaging ultrasonic pulse comprises a normal B mode, Doppler mode or contrast mode pulse or a combination thereof.

the coordinated control preferably controls the timing of the transmission of the cavitation imaging pulses and the normal B-mode and/or contrast mode pulses.

The cooperative control means that: the method comprises the following steps of controlling the emission time sequence of cavitation imaging pulse and conventional imaging ultrasonic pulse, and completely staggering the time sequence of the cavitation imaging pulse and the conventional imaging ultrasonic pulse, so that the interference is obviously reduced, and the time-sharing full duplex is realized, specifically: the safe time required for the echo intensity obtained after the cavitation pulse is transmitted to be attenuated to be less than or equal to the intensity of the conventional imaging ultrasonic pulse is satisfied, namely: wherein: f. of_tAt the frequency of cavitation pulses, f_BFor imaging pulse frequency, V_tIs a cavitation pulse voltage, V_BFor the imaging pulse voltage, d is the current imaging depth, and alpha is the attenuation coefficient of ultrasound in the human body, generally 0.5dB MHz/cm.

Technical effects

Compared with the prior art, the invention innovatively uses the matched filter to naturally filter out the second harmonic wave, and then separates the fundamental wave from the nonlinear component by the inverse phase technology, thereby accurately collecting all nonlinear energy when cavitation occurs, and the detected cavitation intensity is more accurate. And simultaneously, the pulse compression technology is used. The accuracy of cavitation imaging is improved.

Drawings

FIG. 1 is a schematic view of a transmitting device of the present invention;

FIG. 2 is a schematic diagram of a transmission process of the present invention;

Fig. 3 is a diagram of an example Golay code transmit waveform;

In the figure: a. b are respectively complementary sequences;

FIG. 4 is a diagram of a receiving end matched filter according to an embodiment;

In the figure: a. b are respectively used for receiving AB complementary sequences;

FIG. 5 is a waveform diagram of the compressed pulses obtained by separately matched filtering and summing AB;

Fig. 6 is a schematic diagram of cooperative control according to an embodiment.

Detailed Description

As shown in fig. 1, the present embodiment relates to an ultrasonic microbubble cavitation imaging apparatus based on Golay codes, which includes: the device comprises a transmitting end used for generating single cavitation pulse and imaging pulse, a receiving end used for receiving echo and analyzing cavitation image, and transmitting and receiving switches respectively connected with the receiving end and the receiving end, wherein: the transmitting and receiving switch is connected with the transducer and is opposite to the position to be measured.

the transmitting end comprises: a bipolar pulse generator and a transmit sequence memory, wherein: the control terminal of the bipolar pulse generator receives the transmit focus delay to transmit normal B-mode, Doppler mode or contrast mode pulses for conventional imaging, and the transmit sequence memory provides Golay codes to encode cavitation imaging pulses.

The Golay code is specifically an orthogonal complementary Golay (a, B) code, i.e., a (a) (N), N ═ 1.., N, B (B) (N), N ═ 1.., N, and satisfies a (N) × a (-N) + B (N) × 2N δ (N), where: is convolution, N is a natural constant, and δ (N) is a pulse sequence.

The Golay codes have the same length as the cavitation imaging pulses: when the null imaging pulse has 10 periods, a Golay (a, B) code of 10 codewords is used, for example, a is 1, -1, -1,1, -1,1, -1, -1, -1, 1; b is 1, -1, -1, -1,1, -1,1, -1, -1, 1.

As shown in fig. 2, the transmitting end adopts four transmissions, and the separation of the fundamental wave component and the strong nonlinear component in the echo is realized by respectively transmitting the pulse coded by the a sequence and the B sequence and the reverse pulse coded by the a sequence and the B sequence.

The receiving end comprises: matched filter, receive channel with time delay, receive beam synthesizer, accumulator and demodulator, wherein: the matched filter is connected with a memory in which filter coefficients are prestored, the received echo signals are convoluted with receiving codes corresponding to the transmitting signals and then output to a receiving channel for corresponding time delay, amplification and analog-to-digital conversion processing, the accumulator superposes the synthesized matched filtering signals at the same transmitting focus position to realize pulse compression of harmonic signals and suppression of fundamental wave signals, and the demodulator demodulates the signals output by the accumulator and outputs the signals to a subsequent signal processor for corresponding envelope detection, edge enhancement and/or logarithmic compression processing.

as shown in fig. 2 and 4, the receiving end performs matched filtering and phase inversion processing on the received four groups of signals corresponding to the sequence a and the sequence B through a matched filter to obtain R_Aand R_BAnd anti-phase filtered signalAnd

As shown in fig. 4a and 4B, the on/off settings of the matched filter are the same as those of the a sequence and the B sequence on the transmitting side. This embodiment is implemented by a transmission sequence memory and a filter coefficient memory, and the ordinate ± 0.05 in the figure corresponds to 1 and-1 in the A, B sequence, respectively, and the abscissa is time (20 in the figure is schematic).

The accumulators are overlapped to respectively obtain fundamental wave componentsAnd a nonlinear component

the demodulator respectively carries out Hilbert transform on the fundamental component and the nonlinear component to correspondingly obtain fundamental component energy EX and nonlinear component energy EY, and the fundamental component energy EX and the nonlinear component energy EY are output to the signal processor.

The signal processor calculatesObtaining the cavitation intensity of each echo point, and obtaining the cavitation imaging by overlapping the scanning transformation and the normal B mode, Doppler mode or contrast mode image for imaging.

Preferably, the transmitting end is further provided with a cooperative control module for controlling the transmitting time sequence of the single cavitation pulse and the imaging ultrasonic pulse.

As shown in fig. 6a, for the case when the emission gap satisfies the condition: ideally, several cavitation pulses are emitted in one period, and the time interval between adjacent cavitation pulses is 1/prf. Transmitting a plurality of times of conventional imaging pulses Image after the interval of the safety time slot after the last time of cavitation pulse transmission, wherein the time interval of the adjacent conventional imaging pulses is determined according to the interval of the imaging system, and generally:Wherein: c is the propagation speed of sound waves in a human body, d is the imaging depth (which can be acquired by the prior art), and extra is the extra waiting time; generally d is inversely proportional to extra.

As shown in fig. 6b, for the case when the transmission gap does not satisfy the condition: that is, when the safe time slot obtained according to the current imaging depth information and the time required by any one or any four of the four transmissions adopted by the transmitting end exceed the transmission gap, the cooperative control module temporarily suspends the bipolar pulse generator, and the interference of the conventional imaging pulse is ensured by forcibly increasing the gap between the cavitation pulses (the part of the treatment pulse with the frame of the dotted line is closed).

The forced increase specifically includes: the cooperative control module shortens the number of cavitation pulses in one period in a mode of sequentially increasing the step length by 1 and tries to calculate the safe time slot again, namely, the transmitting gap of the bipolar pulse transmitter is enlarged until the number of the corresponding cavitation pulses shortened when the transmitting gap is larger than the sum of the time required by the safe time slot and the imaging pulse.

the increased gap in this embodiment is determined by the number of transmit packets (packetsize), which controls the proportion of therapeutic ultrasound that pauses 1 time every n transmissions.

The foregoing embodiments may be modified in many different ways by those skilled in the art without departing from the spirit and scope of the invention, which is defined by the appended claims and all changes that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.