JP3754142B2 - Ultrasonic tomograph - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ultrasonic tomography apparatus, and more particularly to an ultrasonic tomography apparatus characterized by the manner in which an ultrasonic signal is received.
[0002]
[Prior art]
Conventionally, an ultrasonic tomography apparatus including a multi-channel probe in which a plurality of transducer elements are arranged is known. In such an apparatus, as shown in FIG. 4, the transmission signal generated by the transmission focus circuit 201 is converted into a high voltage signal by the transmission circuit 202, and as a result, a large number of transducer element groups of the probe 1 are formed. It is driven and ultrasonic waves are transmitted from the probe 1 to the subject.
[0003]
On the other hand, the ultrasonic waves reflected from the subject are received by the transducer element groups of the probe 1, amplified by the first stage amplification circuit 203 for each transducer element group, and then digitalized by the A / D converter 204. Converted to a signal. The digital signal is given a predetermined delay by the digital delay circuit 205 and added by the reception channel addition circuit 206 to receive the received signal. The added digital signal is subjected to predetermined processing by the image processing circuit 3, further converted into a display signal for displaying an image by a digital scan converter (DSC) 4, and displayed on the image display 5.
[0004]
In this ultrasonic tomography device, in order to enable real-time measurement without being limited to the complete image time by the speed of sound, the directivity of receiving an ultrasonic beam is slightly smaller than one ultrasonic transmission direction. Shifting by a small amount and simultaneously receiving a plurality of reception beams, so-called simultaneous reception by a plurality of beams can be performed (Japanese Patent Publication No. 56-20017). In this case, the operations of the digital delay circuit 205, the reception channel addition circuit 206, the image processing circuit 3 and the DSC 4 are time-divided into the number of products of the number of reception beams and the sample frequency.
[0005]
On the other hand, as a technique for improving the S / N of a signal, a single transmission / reception uses a smaller number of channels than the number of transducer elements forming the probe 1, and a plurality of transmissions / receptions by changing the channel (transducer element). A technique called aperture synthesis for performing is known. In this aperture synthesis, a single received beam having a good S / N can be obtained by adding a plurality of received beams obtained by a plurality of times of transmission / reception. For example, by performing transmission and reception twice for the even and odd channels and adding them, the resolution and S / N equivalent to a beam with twice the number of channels can be obtained. That is, since a good resolution and S / N can be realized with a small number of channels, the apparatus can be made inexpensive.
[0006]
[Problems to be solved by the invention]
However, the above-described aperture synthesis has a problem in that the frame rate is slow because transmission and reception are performed a plurality of times to obtain one beam.
[0007]
Further, when combining the above-described technique for simultaneously receiving a plurality of beams with the aperture synthesis technique and performing aperture synthesis for a plurality of beams simultaneously received, the first stage amplifier circuit 203, the A / D converter 204, and the digital delay circuit 205 are used. Are required for the number of beams to be simultaneously received, and the hardware becomes large-scale, which is difficult to realize.
[0008]
Therefore, the present invention has an object to provide an ultrasonic tomography apparatus that can synthesize an aperture of a plurality of beams without increasing the scale of hardware and thereby improve the frame rate in the aperture synthesis. .
[0009]
[Means for Solving the Problems]
The ultrasonic tomography apparatus of the present invention that achieves the above-described object includes a probe that is formed into a multi-channel by arranging a plurality of transducer elements, and that transmits and receives ultrasonic waves to and from a subject, and an ultrasonic wave to the probe. An ultrasonic transmission / reception unit that gives a transmission signal, amplifies the ultrasonic reception signal received by the probe, and gives a predetermined delay to receive reception focus, and an ultrasonic reception output from the ultrasonic transmission / reception unit displaying an image processing circuit for a predetermined processing on the signal, and DSC unit for converting a signal outputted from the image processing circuit into a signal for displaying an image, an image based on the signal output from the D SC unit In an ultrasonic tomography apparatus including an image display, an ultrasonic transmission / reception unit transmits a plurality of reception beams having slightly different directivities to one transmission beam in an odd channel or an even channel of a probe. Means for receiving simultaneously by any one of the time division processing , storage means for storing either the received signal received by the odd channel of the probe or the received signal received by the even channel in the time division state, and the storage means Means for performing aperture synthesis by adding the received signals and the time-division received signals received in a channel adjacent to the channel that received the stored received signals to each other.
[0010]
Preferably, in this ultrasonic tomography apparatus, the ultrasonic transmission / reception unit shifts the directivity of the received beam by a small amount and digitizes a plurality of received signals simultaneously, delays and adds them, and digital processing means A storage means for temporarily storing the output of the processing means; a selection means for selectively connecting the digital processing means to the storage means; a combining means for reading the received signal stored in the storage means and combining it with the output of the digital processing means; It is equipped with.
[0011]
In such an ultrasonic tomography apparatus, the ultrasonic transmission / reception unit simultaneously receives a plurality of reception beams in a time-division manner by shifting the directivity of the reception beam by a small amount with respect to one ultrasonic transmission direction. Then, this simultaneous reception is performed a plurality of times, and a signal obtained by digitizing the reception signal obtained by the simultaneous reception of the plurality of times is combined for each directivity of the received beam (aperture synthesis).
[0012]
Specifically, a plurality of received signals simultaneously received are each subjected to delay processing by a digital processing means, then added for each received beam, converted into a digitized received signal, and time-division processed. These received signals are temporarily stored in a storage means such as a line memory by the selection means. Subsequently, simultaneous reception and digital processing of such a plurality of reception signals are repeated, and the reception signal obtained here is combined with the reception signal previously stored in the storage unit read by the combining unit. In this way, reception signals corresponding to the number of reception beams received simultaneously are obtained.
[0013]
As a result, the delay in frame rate due to multiple transmission / reception by the aperture synthesis technique can be canceled by simultaneous reception by time division using multiple beams, and good S / N and resolution can be achieved without reducing the frame rate. Can be realized.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the ultrasonic tomography apparatus of the present invention will be described with reference to FIG.
[0015]
The ultrasonic tomography apparatus includes a probe 1 in which a large number of transducer element groups are arranged to form a multi-channel, and transmits and receives ultrasonic waves to and from a subject. An ultrasonic transmission / reception unit 2 that performs reception focusing after amplifying an ultrasonic reception signal received by the toucher 1 to give a predetermined delay, and a predetermined process for an output signal output from the ultrasonic transmission / reception unit 2 An image processing circuit 3 for performing the above, a DSC 4 for converting a signal output from the image processing circuit 3 into a display signal for image display, and an image display 5 such as a TV monitor for displaying the output from the DSC 4. Yes.
[0016]
The ultrasonic transmission / reception unit 2 generates, as a transmission system, an ultrasonic transmission signal and a transmission focus circuit 201 that applies a transmission focus by giving a predetermined delay, and converts the ultrasonic transmission signal into a high-voltage signal. And a transmission circuit 202 for driving the transducer element group of the probe 1. Further, as a reception system, the first stage amplification circuit 203 for amplifying the reception signal in an analog manner and the first stage amplification circuit 203 are used. An A / D converter 204 that converts a signal into a digital signal, a digital delay circuit 205 that gives a predetermined delay, and a reception channel addition circuit 206 that performs reception focus in combination with the action of the digital delay circuit 205 are provided.
[0017]
In the ultrasonic tomography apparatus according to the present invention, the ultrasonic transmission / reception unit 2 further stores a line memory 207 as storage means for temporarily storing the digitized reception signal, and the reception signal is stored in the line memory 207. And a beam adder circuit 209 that combines the received signal saved in the line memory 207 and the received signal directly transferred from the beam selector 208 as selection means for selecting whether or not to save. Yes.
[0018]
In such an ultrasonic tomography apparatus, the transmission signal generated by the transmission focus circuit 201 is converted into a high-voltage signal by the transmission circuit 202, and is transmitted from the transducer element group of the probe 1 formed in multiple channels to the subject. In contrast, an ultrasonic beam is transmitted. The ultrasonic beam reflected from the subject is received by the multi-channel transducer element group of the probe 1. The received signal is amplified by the first stage amplifier circuit 203 for each channel, and then converted into a digital signal by the A / D converter 204. These digital signals for each channel are given a predetermined delay by the digital delay circuit 205 and added by the reception channel addition circuit 206 to become a reception signal that is received and focused.
[0019]
Furthermore, in the present invention, in order to realize aperture synthesis without slowing down the frame rate, simultaneous reception of a plurality of beams is performed a plurality of times as shown in FIG. Simultaneous reception of a plurality of beams can be performed by a known method. For example, directivity in a plurality of directions can be obtained by controlling a delay amount given to the received signal by the digital delay circuit 205. In this embodiment, as shown in FIG. 2, the directivity of reception of the ultrasonic beam is shifted by a small amount with respect to one ultrasonic transmission direction (for example, the transmission beam α), and two time-divisions are simultaneously performed. Receive beams A and B are received. Simultaneous reception of these two beams is performed a plurality of times to perform aperture synthesis. In this embodiment, a method of aperture synthesis will be described below in the case where simultaneous reception is performed twice.
[0020]
First, as shown in FIG. 3, according to the timing of the reception synchronization signal, the transducer elements arranged oddly in the probe 1, that is, odd channels CH1, CH3... Receive. The reception signals A and B are time-divided for each sample of the A / D converter 204 and added by the reception channel addition circuit 206. At this time, as shown in FIG. 3, the output of the reception channel adding circuit 206 is A1 (0), B1 (0), A1 (1), B1 (1), A1 (2), B1 (2). The received signal array is as follows. A indicates that the received signal is obtained from the received beam A, B indicates that the received signal is obtained from the received beam B, and the number “1” after A and B is an odd number. Indicates that the channel is being used. The numbers in parentheses indicate sample numbers. The larger the sample number, the deeper the depth. The number of samples depends on the sample frequency and is usually 256 or 512.
[0021]
When multiple beams are received simultaneously in this way, in the time division process, in order to secure the signal band of the received signal, in the case of two beams, a sample frequency more than twice the normal sample frequency is required. Become.
[0022]
The output of the reception channel adding circuit 206 is transferred to the line memory 207. That is, when the odd number channel is used, the beam selector 208 selects the line memory 207 side, whereby the received signal is transferred to the line memory 207, and the time division state (A1 (0), B1 (0), A1 (1), B1 (1), A1 (2), B1 (2).
[0023]
Next, according to the timing of the next reception synchronization signal, reception is performed in the same manner using the even-numbered channels CH2, CH4,... (The transducer shown in white in FIG. 2) of the probe 1. In this case as well, time-division is similarly performed, and addition is performed by the reception channel addition circuit 206, and the output is A2 (0), B2 (0), A2 (1), B2 (1), A2 ( 2), B2 (2)... Note that “2” after A and B indicates that an even channel is used. When the even channel is used, the beam selector 208 selects the beam addition circuit 209 side, and the reception signal output from the reception channel addition circuit 206 is transferred to the beam addition circuit 209 as it is.
[0024]
The beam adder circuit 209 receives received signals (A1 (0), B1 (0), A1 (1), B1 (1), A1 (2), B1 (2)...) Temporarily stored in the line memory 207. The reception signals (A2 (0), B2 (0), A2 (1), B2 (1), A2 (2), B2 (2)...) From the reception channel addition circuit 206 are added, and FIG. The received signals A (0), B (0), A (1), B (1), A (2), B (2). The received signals (A (0), B (0), A (1), B (1), A (2), B (2)...) Obtained by aperture synthesis in this way are double channels. Such data is obtained for two receive beams A and B per transmit beam α, with a resolution and S / N equivalent to those received in numbers. Thereby, the delay of the frame rate due to the two transmissions / receptions performed for aperture synthesis can be canceled by simultaneous reception of two beams, and therefore aperture synthesis can be performed without reducing the frame rate.
[0025]
A similar scanning process is performed for the transmission beam β with the transmission beam direction slightly changed, and the reception beams C and D corresponding thereto.
[0026]
A series of outputs from the beam addition circuit 209 obtained in this way is subjected to predetermined processing such as interpolation and FFT in the image processing circuit 3, and is further converted into a display signal for displaying an image by the DSC 4, and the image It is displayed on the display 5 as an ultrasonic image.
[0027]
In the above embodiment, the case where two reception beams are simultaneously received with respect to one transmission beam has been described. However, the number of beams simultaneously received is not limited to two, and any number of beams can be realized. . If the number of beams simultaneously received increases in this way, the sample frequency increases in the time division processing in order to secure the signal band of the received beam. For example, in the case of four beams, it is four times the normal sample frequency. Since the above sampling frequency is required, it is desirable to use a component that has been recently developed as an A / D converter or the like and that has a high processing speed.
[0028]
In addition, the case where the channels are divided into the even channels and the odd channels when performing aperture synthesis has been described as an example. Further, the number of transmissions / receptions performed for aperture synthesis is not limited to two, but can be performed in a plurality of arbitrary times.
[0029]
In addition, as described in the embodiment, the line memory 207 may be provided in the same number as the number of simultaneous receptions performed for aperture synthesis or one less than that, and in order to store reception signals for one image. It is also possible to provide as many transmission beams as there are transmission beams.
[0030]
Further, when the same number of line memories 207 as the number of simultaneous receptions are provided, the beam selector 207 sequentially assigns a predetermined line memory 207 for each reception, and temporarily stores all received signals in the line memory 207. Thereafter, the beam addition circuit 209 can combine the signals while reading out the received signals from the line memory 207.
[0031]
【The invention's effect】
The ultrasonic tomography apparatus of the present invention receives a plurality of reception beams at the same time by shifting the directivity of the reception beam by a minute amount with respect to one transmission direction of ultrasonic waves, and performs this simultaneous reception at least twice. By synthesizing the reception signals for the number of times of simultaneous reception, aperture synthesis can be performed without reducing the frame rate, and an ultrasonic tomographic image with excellent resolution and S / N can be obtained.
[0032]
Further, according to the present invention, by digitizing the received signal, it becomes possible to process the received signal in a time-sharing manner. For this reason, aperture synthesis of a plurality of beams simultaneously received without increasing the hardware scale is possible. Can be realized.
[Brief description of the drawings]
FIG. 1 is a block diagram of an embodiment of an ultrasonic tomography apparatus according to the present invention.
FIG. 2 is a diagram illustrating simultaneous reception of a plurality of beams according to the present invention.
FIG. 3 is an explanatory view of aperture synthesis of a plurality of beams simultaneously received according to the present invention.
FIG. 4 is a block diagram of a conventional ultrasonic tomography apparatus.
[Explanation of symbols]
1... Probe 2... Ultrasonic transceiver 3... Image processing circuit 4... Digital scan converter (DSC)
5 .... Image display 204 ... A / D converter (digital processing means)
205... Digital delay circuit (digital processing means)
206 ··· Receive channel adding circuit (digital processing means)
207... Line memory (storage means)
208 ・ ・ ・ ・ ・ ・ Beam selector (selection means)
209 ・ ・ ・ ・ ・ ・ Beam addition circuit (combining means)

Claims (1)

A plurality of transducer elements are arranged to form a multi-channel, and a probe for transmitting and receiving ultrasonic waves to a subject, and an ultrasonic transmission signal is given to the probe and received by the probe An ultrasonic transmission / reception unit that amplifies the received ultrasonic signal and then applies a predetermined delay to receive focus, and image processing that performs predetermined processing on the ultrasonic reception signal output from the ultrasonic transmission / reception unit A circuit, a digital scan converter that converts a signal output from the image processing circuit into a signal for image display, and an image display that displays an image based on the signal output from the digital scan converter In the equipped ultrasonic tomography device,
The ultrasonic transmission / reception unit is configured to simultaneously receive a plurality of reception beams having slightly different directivities with respect to one transmission beam by time- division processing in either an odd channel or an even channel of the probe; Storage means for storing in a time-division state any one of the reception signal received on the odd channel and the reception signal received on the even channel of the probe, and the reception signal stored in the storage means and the stored An ultrasonic tomography apparatus comprising: means for performing aperture synthesis by adding a time-division received signal received by a channel adjacent to a channel that receives the received signal between the received beams.

Images