JPH11104130A - Ultrasonic diagnostic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a transmitted wave focusing to be performed considering sonic non-uniformity in the interior of a subject, in an ultrasonic diagnostic device. SOLUTION: A signal received from each of vibration elements of a probe 1 is recorded in a memory 6, and a difference in the time required for reaching the interior of a subject due to the sonic non-uniformity of the interior of the specimen is sought by a part 7 for detecting a delay time in regenerating an adaptable image, based on the correlationship between the signals recorded and received through two channels. An adaptable image regeneration control part 8 sets an address for initiating a reading operation from memory 6 in each of the channels so that an appropriate delay for the difference in the time required for reaching the interior of the specimen is imparted, and then the received signal which is readh from memory 6 is added using an adder 9. On the other hand, a wave transmission control part 2 controls the timing for the wave transmission by plural vibration elements which form an ultrasonic beam, in accordance with the delay time sought by the part 7 for detecting the delay time in regenerating the adaptable image.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic diagnostic apparatus which obtains a tomographic image of a diagnostic part of a subject by scanning an ultrasonic beam, and more particularly to receiving and transmitting focusing in consideration of nonuniformity of a living body. The present invention relates to an ultrasonic diagnostic apparatus capable of performing the above.

[0002]

2. Description of the Related Art As a conventional ultrasonic diagnostic apparatus, for example, there is one having a configuration as shown in FIG. The probe 1 includes a plurality of transducer elements arranged and transmits / receives ultrasonic waves to / from a subject, and a transmitting / receiving device for performing calculations necessary for forming an ultrasonic beam focused on a predetermined position in the subject. Control unit 2
A transmission pulse generator 3 for generating an ultrasonic pulse at a predetermined time calculated by the transmission control unit 2, a transmission signal to the probe 1 and a reception signal from the probe 1 A transmission / reception separation circuit 4 for separating, a digital phasing unit 12 for converting a reception signal obtained by the transmission / reception separation circuit 4 into a digital signal, and then performing phasing addition between channels, and an image for each scanning line of an ultrasonic beam. It is provided with a scan converter 10 for converting data into image data for a display device, and an image display device 11 for displaying the image data converted by the scan converter 10.

The digital phasing section 12 includes an analog / digital converter 5 for converting a received signal into a digital signal,
Data is sequentially read from the memory 6 in accordance with a read start address specified by an adaptive image reproducing means described later, and is added to the memory 6 for recording digital signals obtained by the analog / digital converter 5 for all channels in a time series. And an adder 9.

Here, the adaptive image reproducing means reads out data of two channels from the memory 6 and calculates a delay time based on a correlation between signals between the two channels. 7 and an adaptive image reproduction controller 8 for designating a read start address for the memory 6 based on the delay time calculated by the adaptive image reproduction delay time detector 7.

The adaptive image reproduction delay time detector 7 analyzes the received signals of the two channels by a cross-correlation method, a phase detection method, or the like, thereby obtaining a difference in arrival time of the reflected echo to each transducer element. A delay time corresponding to the arrival time difference is set. In some cases, a method called the maximum luminance method for determining the delay time may be used so that the focus state of the one-dimensional tomographic image obtained by the phasing addition is optimal.

[0006] In the ultrasonic diagnostic apparatus configured as described above, even if the sound velocity in the living body is non-uniform, it is possible to perform accurate receiving focusing in consideration of the non-uniformity. Is generally called adaptive image reproduction.

[0007]

However, in the ultrasonic diagnostic apparatus configured as described above, the so-called reception focusing is performed in consideration of the non-uniformity of the sound velocity inside the subject. Has performed transmission with a delay time determined only by the distance from the focus point to each transducer element, assuming that the sound speed inside the subject is uniform. For this reason, if there is a non-uniform portion of the sound velocity inside the subject, the convergence of the ultrasonic beam is reduced, and the resolution of the tomographic image is reduced.

[0008] Since the directivity characteristics of the entire ultrasonic diagnostic apparatus are the product of the directivity of the transmitted wave and the directivity of the received wave, even if the adaptive image reproduction enables accurate focusing of the received wave. In addition, since the accuracy of the wave transmission focusing is reduced due to the non-uniformity of the sound velocity in the living body, the best directivity characteristics have not been obtained as a whole device.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an ultrasonic diagnostic apparatus capable of addressing such a problem and performing reception focusing and transmission focusing in consideration of non-uniform sound velocity in a subject.

[0010]

In order to achieve the above object, an ultrasonic diagnostic apparatus according to the present invention comprises: a probe having a plurality of transducer elements arranged for transmitting and receiving ultrasonic waves; Phasing addition means for delaying and adding a signal for each channel, and delay time detection for obtaining a delay time for each channel in the phasing addition means according to the correlation of the received signal added by the phasing addition means And an ultrasonic diagnostic apparatus comprising: a transmission control unit that controls a transmission timing of ultrasonic waves in the transducer element according to the delay time obtained by the delay time detection unit. is there.

[0011]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a block diagram showing an embodiment of an ultrasonic diagnostic apparatus according to the present invention. In FIG. 1, a probe 1 mechanically or electrically scans an ultrasonic beam to transmit and receive ultrasonic waves to and from a subject, and the probe 1 includes a source of ultrasonic waves. And a plurality of transducer elements for receiving the reflected echo are arranged.

The transmission control unit 2 determines the transmission timing of a plurality of transducer elements forming an ultrasonic beam from a signal from an adaptive image reproduction delay time detection unit 7 to be described later and a focus point corresponding to an imaging condition. Generate

The transmission pulse generator 3 includes the transmission control unit 2
A drive pulse is sent to each transducer element of the probe 1 based on the signal generated in the step (1). The transmission / reception separation circuit 4 amplifies the signal from the transmission pulse generator 3 so as to emit an ultrasonic wave, supplies the amplified signal to the probe 1, and then switches the signal line, thereby converting the reception signal from the probe 1 into a digital signal. This is a circuit that operates so as to be given to the phasing unit 12, and is composed of, for example, a relay.

The digital phasing unit 12 (phasing addition means)
After converting the received signal obtained by the transmission / reception separation circuit 4 into a digital signal, the signal is subjected to phasing addition between the respective channels, and comprises an analog / digital converter 5, a memory 6, and an adder 9. The analog / digital converter 5
The reception signal for each channel obtained by the transmission / reception separation circuit 4 is converted into a digital signal. The memory 6
The received signal converted into a digital signal by the analog / digital converter 5 is recorded in time series for each channel. The adder 9 adds the signals read from the memory 6 according to a read start address determined for each received signal, as described later.

On the other hand, the adaptive image reproduction delay time detecting section 7 (delay time detecting means) calculates a delay time for adaptive image reproduction from the correlation between the signals of the two channels recorded in the memory 6. The delay time is calculated by an algorithm such as a cross-correlation method, a phase detection method, and a maximum luminance method. The obtained delay time for each channel is referred to in the adaptive image reproduction control unit 8 and the transmission control unit 2.

The adaptive image reproduction control unit 8 determines a read start address of the reception signal recorded in the memory 6 from the delay time. On the other hand, the transmission control unit 2 uses the delay time for each channel obtained by the adaptive image reproduction delay time detection unit 7 as the transmission delay time as it is (transmission control means).

The adder 9 sequentially reads data from the memory 6 in accordance with the determined read start address, thereby giving a delay to each signal and delaying the read signal for each channel. to add. Then, the scan converter 10 converts data output from the adder 9 for each scanning line of the ultrasonic beam into data of a tomographic image. The image display device 11 displays a tomographic image created by the scan converter 10, and is, for example, a television monitor.

Hereinafter, the operation of the thus configured ultrasonic diagnostic apparatus will be described in detail. The ultrasonic beam is formed by simultaneously driving a plurality of transducer elements, with the scanning line x of the ultrasonic beam and the point F (x, y) at the depth y being the focus point, and the focus point F (x, y) An example in which the ultrasonic reflection coefficient is obtained.

In the conventional ultrasonic diagnostic apparatus, since the sound velocity inside the subject is assumed to be uniform, the apparatus operates.
The transmission timing is determined only according to the length from the focus point to each transducer element. For example, as shown in FIG. 2, a value T1 obtained by dividing the distance from each transducer element El to E5 to the focus point F (x, y) by the sound velocity in water.
To T5 are focus points F (x, x) from the transducer elements El to E5 when the inside of the subject is formed of a uniform medium.
It is the time to reach y). And the focus point F
When the transducer element E3 having the shortest distance to (x, y) is used as a reference, each transducer element En transmits waves earlier than the transducer element E3 by the time of Tn-T3. The transmission signal from the slave element En is the focus point F (x, y)
Are equal, and transmission focusing can be performed.

However, when a non-uniform portion exists in the medium inside the subject, Sn deviation occurs in the propagation time in each path as shown in the figure. This time deviation S
An example of a method for obtaining n will be described below.

The ultrasonic reflected wave from the focus point F (x, y) is received by the probe 1 and then stored in the memory 6 via the transmission / reception separation circuit 4 and the analog / digital converter 5. Here, the memory 6 has a two-dimensional arrangement of the number of receiving elements (the number of channels) of the probe 1 and data of one scanning line. For the following description, it is assumed that data on the memory 6 is defined by an array of M (ch, t). For example, M (3, 30) is 30 units from the start of reception on channel 3. It shall represent the received data value after a time.

The adaptive image reproduction delay time detecting section 7 calculates a delay time for adaptive image reproduction. Here, a cross-correlation method will be described as a typical algorithm. Assuming that a reference reception channel is S and a channel for which a delay time is to be obtained is i, each data is M (S,
t), M (i, t), and the two cross-correlation values are R (τ _si ) = {M (S, t) · M (i), where τ _si is the delay time given to the channel i. , T−τ _i ) dt.

Here, a delay time τ _si that maximizes the cross-correlation value R (τ _si ) is obtained, and is set as a delay time of the channel i with respect to the reference reception channel S. In FIG. 2, for example, a reception channel S serving as a reference is denoted by E.
3. If the channel i for which the delay time is to be obtained is E4,
Time difference to reach the transducer element, ie, (T4 + S4)
- (T3 + S3) is next to tau _34, channel E4 is E3
It is sufficient to quickly transmit only obtained comparing τ ₃₄ in. By performing such calculation for each transducer element from El to E5, even if there is an uneven portion in the medium inside the subject, at the focus point F (x, y), the superposition from each transducer element is obtained. The sound waves arrive at the same time.

On the other hand, in the received signal, after obtaining the delay time for each channel, the delay time is converted into a read start address of the memory 6. Then, a read start address is set for each channel, the data is read out in order, and the adder 9 delays and adds the data.

According to the above configuration, it is possible to transmit a wave with a propagation time in consideration of nonuniformity of the medium in each path, and it is possible to generate an ultrasonic beam having high convergence. In combination with focusing (adaptive image reproduction), the directional characteristics of the entire apparatus are improved, and a high-resolution tomographic image can be obtained.

[0026]

The present invention has been configured as described above.
Considering the sound velocity non-uniformity inside the subject, the accuracy of the reception focusing can be improved, and the accuracy of the transmission focusing can be increased at the same time. An image can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a system configuration of an ultrasonic diagnostic apparatus according to the present invention.

FIG. 2 is a diagram illustrating characteristics of a transmission delay process according to the present invention.

FIG. 3 is a block diagram showing a system configuration of a conventional ultrasonic diagnostic apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Probe 2 ... Transmission control part 3 ... Transmission wave pulse generator 4 ... Transmission / reception separation circuit 5 ... Analog / Digital converter 6 ... Memory 7 ... Adaptive image reproduction delay time detection part 8 ... Adaptive image reproduction control part 9 … Adder 10… Scan converter 11… Image display device

Claims (1)

[Claims] 1. A probe in which a plurality of transducer elements are arranged to transmit and receive ultrasonic waves, phasing addition means for delaying and adding a signal received from the probe for each channel, and phasing addition. Delay time detecting means for obtaining a delay time for each channel in the phasing and adding means in accordance with the correlation of the received signals added by the means. An ultrasonic diagnostic apparatus provided with transmission control means for controlling transmission timing of ultrasonic waves in the transducer element according to the delay time.