WO2017057221A1

WO2017057221A1 - Ultrasonic diagnostic device and delay data generating method

Info

Publication number: WO2017057221A1
Application number: PCT/JP2016/078164
Authority: WO
Inventors: 将則久津; 栗原　浩
Original assignee: 株式会社日立製作所
Priority date: 2015-10-01
Filing date: 2016-09-26
Publication date: 2017-04-06
Also published as: CN108024798A; CN108024798B; JP2017064249A; JP6059782B1

Abstract

In the present invention, a forward time arithmetic circuit computes forward delay data that corresponds to a forward path from a transmission reference point to a reception focus. A backward time arithmetic circuit computes backward delay data that corresponds to a backward path from the reception focus to reception vibration elements for each reception vibration element. An adder generates delay data by adding the forward delay data and the backward delay data. The forward delay data is shared among a plurality of reception elements. The backward delay data is shared among a plurality of transmission beams for each reception element in a case where a virtual sound source method is applied.

Description

Ultrasonic diagnostic apparatus and delay data generation method

The present invention relates to an ultrasonic diagnostic apparatus and a delay data generation method, and more particularly to generation of delay data for delay processing executed by a reception beamformer.

The receiving beamformer (Receiving Beam Former) of the ultrasonic diagnostic device (Ultrasonic Diagnostic Apparatus) performs phasing and addition processing (Aligning and) on multiple received signals output in parallel from multiple transducers (Transducer Elements) Summing 回路 Processing) is applied to generate beam data corresponding to the received beam. The phasing and adding process is a process of delaying a plurality of received signals and aligning the phases of the plurality of received signals to form a reception focus, and adding them together, which is Delay and Sum (DAS) It is also said. The phasing addition process is roughly divided into a delay process and an addition process.

Usually, a reception dynamic focus technique for continuously changing the reception focal depth in a deep direction is applied to each individual reception beam (see Patent Document 1). The reception focus generally matches the transmission / reception total peak position (maximum sensitivity position). However, when parallel reception technology or the like is applied (that is, when the transmission beam central axis and the reception beam central axis are shifted), the reception focal point is obtained. And the transmission / reception total peak position do not match (see Patent Document 1). In that case, not the reception focus but the transmission / reception total peak position is regarded as the position of the imaging point (observation point). A technique for manipulating a reception beam so that an imaging point is in an appropriate position has also been proposed (see Patent Document 1). The parallel reception (Parallel Receiving) technique forms a plurality of reception beams simultaneously and in parallel with respect to one transmission beam. According to this technique, a plurality of beam data can be obtained by one transmission / reception.

The reception beamformer generally has a plurality of A / D converters, a plurality of delay units, an adder, and the like. Specifically, a plurality of analog reception signals are converted into a plurality of digital reception signals by a plurality of A / D converters. The plurality of digital received signals are delayed by a plurality of delay units, respectively. A plurality of digital received signals after the delay processing are added by an adder, whereby beam data corresponding to the received beam is obtained. The beam data is composed of a plurality of echo data arranged in the depth direction.

The plurality of delay devices described above are actually composed of a plurality of memories, for example. A plurality of received signals are subjected to delay processing by adjusting the read timing of a plurality of data from a plurality of memories. For this reason, a read controller that controls parallel reading of a plurality of data from a plurality of memories based on a plurality of delay data is provided inside (or outside) the reception beamformer. Also, a delay data generation circuit that generates a delay data set to be supplied to the read controller is provided inside (or outside) the reception beamformer. The delay data set is a collection of delay data for realizing reception dynamic focus, parallel reception, and the like according to the electronic scanning method. Typically, a large number of receiving focal points need to be formed per beam scanning plane, and the data for forming them is a delayed data set. The individual delay data constituting the delay data set usually corresponds to a propagation time or a delay time. It is also possible to understand the propagation time as a negative delay time (fast reading time). Note that a parameter group necessary for generating delay data by the delay data generator is calculated in advance, and the calculated parameter group is stored in advance in a parameter memory accessed by the delay data generation circuit.

In general, when forming a certain reception focal point, delay data given to each reception element constituting the reception aperture includes the forward distance from the transmission reference point (transmission origin) to the reception focal point, and the return path from the reception focal point to the reception element. Calculated based on the distance. Specifically, the delay time, that is, the delay data, is obtained by dividing the round trip distance obtained by adding the forward path distance and the return path distance by the speed of sound. It is very difficult and time-consuming to calculate the delay data individually for each receiving element for all receiving focal points on one scanning plane. For this calculation, it is necessary to calculate a large number of parameters in advance, and for this purpose, a parameter memory having a large storage capacity must be provided.

With the above background, in normal ultrasound diagnostic equipment, instead of performing ideal propagation time calculations to reduce the total number of parameters given to the delay data generation circuit and the amount of computation there, piecewise polynomial interpolation A simple calculation method using a method (Piecewise Polynomial Interpolation) (Spline Interpolation), a method using a recurrence formula (Recurrence Formula) (see Non-Patent Document 1), or the like is employed. As a kind of piecewise polynomial interpolation method, a piecewise linear interpolation method (PWL method) is known. In this method, a plurality of representative propagation times are obtained in advance for a relatively small number of representative reception focal points arranged in the depth direction, and in the process of applying the reception dynamic focus, two representative propagation times forming both ends of the target section are obtained. By applying linear interpolation to, propagation time or delay data corresponding to each reception focus is generated.

In any case, in the conventional ultrasonic diagnostic apparatus, delay data corresponding to all paths including the forward path and the return path is generated. There has not yet been proposed a technique for independently generating the delay data corresponding to the forward path and the delay data corresponding to the return path, and a technique for sharing the individual delay data generated as such.

Recently, a virtual acoustic source method based on a transmission aperture synthesis method is being put into practical use. In this virtual sound source method, individual transmission focal points generated at different timings are regarded as virtual sound sources, and a plurality of waves (spherical waves) arriving from a plurality of virtual sound sources at individual imaging points on the scanning plane. The delay processing is applied to a plurality of received signals so that the phases are matched (see Non-Patent Document 2). A virtual sound source method using a plane wave is also known.

Japanese Patent Laid-Open No. 2-206451

As described above, it can be pointed out that the amount of calculation or the calculation time is increased with respect to the generation of delay data. If a very high-speed circuit or a huge memory is used to cope with this, problems such as a complicated apparatus configuration and an increase in cost occur. In particular, when the number of parallel receptions is increased under application of the virtual sound source method, the above problem becomes more serious.

An object of the present invention is to enable generation of a delay data set used in received signal processing efficiently or efficiently. Alternatively, the amount of computation or computation time is reduced when generating delay data. Alternatively, the number of parallel receptions is increased. Another object is to realize a reception beamformer adapted to the virtual sound source method.

(1) An ultrasonic diagnostic apparatus according to the present invention includes a plurality of vibration elements that output a plurality of reception signals, a generation circuit that generates a plurality of delay data corresponding to the plurality of vibration elements, and the plurality of delay data. A delay processing circuit that delays the plurality of received signals, and the generation circuit generates a forward delay data generator that generates forward delay data corresponding to a forward path from a transmission reference point to a reception focal point, and For each reception vibration element in a plurality of vibration elements, a return path delay data generator that generates return path delay data corresponding to a return path from the reception focus to the reception vibration element, and for each reception vibration element, the forward path delay data and A delay data generator that generates delay data for delaying a reception signal from the reception vibration element based on the return path delay data; That.

According to the above configuration, the forward delay data and the backward delay data are generated separately, and based on them, the delay data that defines the actual delay processing is preferably generated by adding them. Therefore, for example, when the virtual sound source method and the parallel reception method are executed, one forward path delay data (delay data corresponding to the path from the transmission reference point to the reception focus via the transmission focus) is transmitted between the plurality of reception vibration elements. One return path delay data (delay data corresponding to the return path from the reception focal point to the reception vibration element) can be shared between a plurality of transmission beams. Necessary to generate delay data by separating forward delay data and backward delay data in calculation, that is, from the viewpoint of data sharing, by separating delay data into a plurality of components constituting it. The amount of parameters and calculation amount can be reduced.

Delay data is data used in delay processing, such as data representing propagation time, data representing delay time, and the like. For example, when the delay data is data representing the propagation time, the larger the delay data, the later the data stored in the memory among the plurality of data stored in the memory in chronological order (that is, the newer data) ) Data is read out. The transmission reference point corresponds to a calculation or space origin, and is typically the transmission aperture center. Depending on the scanning method, the definition of the transmission reference point may change.

Desirably, the forward path delay data generator generates the forward path delay data as data shared by a plurality of receiving vibration elements. That is, it is possible to share the same forward delay data for each reception focal point among a plurality of vibration elements constituting the reception aperture.

Desirably, the forward delay data generator generates the forward delay data based on the transmission reference point, the transmission focus, and the reception focus when a virtual sound source method as a transmission aperture synthesis method is executed. For example, when the ultrasonic beam is scanned one-dimensionally, forward delay data is generated from the coordinates of the transmission reference point, the coordinates of the transmission focal point, and the coordinates of the reception focal point on the scanning plane.

Preferably, the forward delay data is data corresponding to a forward propagation time, and the forward propagation time is when the distance from the transmission origin to the reception focal point is larger than the distance from the transmission origin to the transmission focal point. Is a time obtained by adding a propagation time corresponding to the distance from the transmission focal point to the reception focal point to a propagation time corresponding to the distance from the transmission origin to the transmission focal point. When the distance from the transmission origin to the reception focal point is smaller than the distance from the transmission time, the propagation time corresponding to the distance from the transmission origin to the transmission focal point corresponds to the distance from the transmission focal point to the reception focal point. This is the time obtained by subtracting the propagation time. That is, the propagation time of the spherical wave is considered according to the virtual sound source method.

Preferably, the forward delay data generator generates the forward delay data according to a piecewise polynomial interpolation method. When this configuration is adopted, for example, a plurality of propagation times for a plurality of representative reception focal points are calculated in advance for each transmission beam, and interpolation is performed for each reception focal point when actually applying reception dynamic focus. The propagation time is sequentially calculated by the processing.

Preferably, the return path delay data generator generates the return path delay data as data shared between a plurality of transmission beams. Preferably, the return path delay data generator generates the return path delay data based on a distance between the reception focus and the reception vibration element. Preferably, the delay data generation circuit is a circuit that adds the forward path delay data and the return path delay data.

Preferably, the generation circuit further includes a correction delay data generator that generates correction delay data as a correction term, and the delay data generator includes the forward delay data and the return delay data for each of the reception vibration elements. And based on the said correction | amendment delay data, the said delay data for carrying out the delay process of the received signal from the said receiving vibration element are produced | generated. Preferably, the correction term corresponds to a reception focus shift amount for adjusting the transmission / reception total peak to a desired imaging point.

(2) The method according to the present invention includes a step of generating first delay data as a component shared among a plurality of reception vibration elements, and a first component as a unique component for the reception vibration element for each reception vibration element. A step of generating two delay data, and for each reception vibration element, delay data for delaying a reception signal from the reception vibration element is generated based on the first delay data and the second delay data. And a process.

According to the above configuration, the first delay data as a component shared between the plurality of reception vibration elements and the second delay data as a component (unique component) that is not shared between the plurality of reception vibration elements are separated. Then, delay data is generated based on both components. Since at least the first delay data can be shared among a plurality of reception oscillating elements constituting the reception aperture, the total number of delay data generation parameters and the amount of calculation can be reduced. Preferably, the first delay data is forward path delay data, and the second delay data is return path delay data. Alternatively, the first delay data is a component that is not affected by the peak correction for matching the transmission / reception total peak to a desired imaging point by the reception point shift, and the second delay data is a component that is affected by the peak correction.

The above method pays attention to a plurality of components constituting the delay data, and reduces the amount of calculation by separately generating components that can be used in common and components that are not. Each of the above steps is executed in the ultrasonic diagnostic apparatus. More specifically, each of the above steps can be realized by a program executed by a processor included in the ultrasonic diagnostic apparatus. The program may be installed on a portable medium or transmitted over a network.

1 is a block diagram showing a preferred embodiment of an ultrasonic diagnostic apparatus according to the present invention. It is a figure which shows the propagation path model in parallel reception. It is a figure which shows the propagation path model based on a virtual sound source method. It is a figure for demonstrating an example of a virtual sound source method. 1 is a block diagram illustrating a first embodiment of a delay data generation circuit. FIG. It is a figure which shows the relationship between a receiving focus and an imaging point (transmission / reception sensitivity peak). It is a block diagram which shows 2nd Embodiment of a delay data generation circuit. It is a figure for demonstrating the effect | action of a correction | amendment term. It is a block diagram which shows 3rd Embodiment of a delay data generation circuit. It is a block diagram which shows 4th Embodiment of a delay data generation circuit.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

(1) Ultrasonic Diagnostic Device FIG. 1 shows a preferred embodiment of an ultrasonic diagnostic device according to the present invention. This ultrasonic diagnostic apparatus is an apparatus that is installed in a medical institution and forms an ultrasonic image by transmitting and receiving ultrasonic waves to and from a living body. The ultrasonic diagnostic apparatus includes an ultrasonic diagnostic apparatus main body and a probe connected thereto. The probe includes a head, a cable, and a connector. An array transducer 50 is provided in the head.

In the present embodiment, the array transducer 50 is a transmission / reception device including a plurality of vibration elements 50a arranged linearly. An ultrasonic beam is formed by the array transducer 50 and scanned electronically. The ultrasonic beam is actually a combined transmission / reception beam that is conceived when a transmission beam and a reception beam are combined. As an electronic scanning method, an electronic linear scanning method, an electronic sector scanning method, and the like are known. An electronic convex scanning system is known as an aspect of the electronic linear scanning system. A 2D array transducer including a plurality of transducer elements arranged two-dimensionally may be provided.

The transmission beam former 52 is an electronic circuit for forming a transmission beam during transmission. Specifically, a plurality of transmission signals having a fixed delay relationship for forming a transmission beam are generated and supplied to the array transducer 50 in parallel. Thereby, ultrasonic waves are radiated from the individual vibration elements in the transmission opening into the living body. As a result, a transmission beam that is focused at the transmission focal point is formed.

The reception beam former 54 is an electronic circuit for forming a reception beam during reception. When reflected waves from the living body reach a plurality of vibration elements in the reception opening, a plurality of reception signals (a plurality of element reception signals) are output in parallel from the plurality of vibration elements. A phasing addition process is applied to the plurality of reception signals in the reception beam former 54, thereby obtaining beam data corresponding to the reception beam. The beam data consists of a plurality of echo data arranged in the depth direction.

Specifically, the reception beamformer 54 includes a plurality of reception channel circuits 56, an adder 64, a delay data generation circuit 66, and a delay controller 70. The number of reception channel circuits 56 is the same as the number of vibration elements constituting the array transducer 50 or the same as the number of vibration elements constituting the maximum reception aperture set for the array transducer 50. Each reception channel circuit 56 includes an amplifier 58, an A / D converter 60, a delay unit (DL) 62, and the like. The amplifier 58 includes a preamplifier, a gain variable amplifier, and the like. The A / D converter 60 converts an analog reception signal into a digital reception signal. The digital reception signal is composed of a plurality of reception data (a plurality of amplitude values) arranged on the time axis. The delay device 62 is configured by a memory (for example, a ring buffer), and a plurality of received data are written in the time series order therein. By adjusting the read timing of each received data from the memory, the phase of each received data is aligned. A plurality of delay devices 62 constitute a delay processing circuit. A plurality of received data (in parallel relation) after the delay processing is added by the adder 64. A reception focus is formed as a result of this phasing addition processing. As a result of repeatedly executing the phasing addition processing while dynamically switching the depth of the reception focus on the reception beam axis, beam data composed of a plurality of echo data arranged in the depth direction is obtained. Each delay unit 62 may be constituted by a coarse delay memory and a fine delay interpolation circuit.

The delay data generation circuit 66 is an electronic circuit that generates a delay data set necessary for the delay processing. It functions as generating means or generating circuit. The delay data generation circuit 66 includes a memory that stores a parameter group, a function calculator, and the like. When a specific transmission / reception condition is set, a delay data set is generated based on the transmission / reception condition and stored in a memory (not shown). Then, simultaneously with the start of transmission / reception, delay data is sequentially read from the memory. However, the delayed data set may be generated in real time, that is, simultaneously with transmission / reception.

The delay controller 70 functions as a control unit that controls the plurality of delay units 62, and specifically adjusts the read timing of received data from each delay unit 62 based on the delay data set. At that time, according to the reception dynamic focus method, a plurality of reception data are read in parallel and added in real time. The delay data generation circuit 66 and the delay controller 70 may be realized as functions of the main control unit 72. The reception beamformer 54 can be configured by a device such as an FPGA or an ASIC.

In this embodiment, as will be described in detail later, in the first step and the second step, the forward delay data and the backward delay data are independently generated separately, and in the third step, the forward delay data And the return delay data are added to generate delay data that is actually used in the delay process. The forward delay data is data representing the time required for the ultrasonic wave to propagate in the forward path from the transmission reference point to the reception focus in the present embodiment. The return path delay data is data representing the time required for the ultrasonic wave to propagate along the return path from the reception focus to the receiving element (vibration element) in the present embodiment. Such parallel generation makes it possible to vary the generation methods of the forward delay data and the backward delay data. For example, forward delay data can be generated by the first generation method, and backward delay data can be generated by a second generation method different from the first generation method. Further, the same forward path delay data can be shared among a plurality of vibration elements or the same return path delay data can be shared among a plurality of transmissions under a certain condition. Furthermore, delay data correction using a correction term to be described later can be realized with a simple circuit configuration.

The ultrasonic diagnostic apparatus of the present embodiment is an apparatus that can perform a transmission / reception operation according to the virtual sound source method and the parallel reception method. For example, 32 reception beams arranged in the scanning direction are simultaneously formed per transmission beam. If such transmission / reception is repeated while shifting the transmission beam position, a plurality of pre-transmission aperture synthesis data (data after reception aperture synthesis) is acquired for each reception focus (imaging point). If a plurality of pre-transmission aperture synthesis data is added for each reception focus, one post-transmission aperture synthesis data can be obtained. The delay time generation under the virtual sound source method will be described in detail later.

Each beam data output from the reception beam former 54 is input to the signal processing circuit 76. The signal processing circuit 76 includes a detection circuit, a logarithmic compression circuit, and the like. When the virtual sound source method is applied, the transmission aperture synthesis process is executed by the signal processing circuit 76. Each beam data output from the signal processing circuit 76 is input to a DSC (digital scan converter) 78. The DSC 78 is a known electronic circuit that generates a display frame based on a reception frame made up of a plurality of beam data. It has a coordinate conversion function, an interpolation processing function, a frame rate conversion function, and the like. The display frame is, for example, a B-mode tomographic image. The display frame output from the DSC 78 is sent to the display 82 via the display processing circuit 80. A B-mode tomographic image is displayed on the display device 82. Other ultrasonic images may be displayed there.

The main control unit 72 controls the operation of each circuit in the ultrasonic diagnostic apparatus. In this embodiment, it is constituted by a CPU and a program. The main control unit 72 has a transmission / reception control function, which is shown as a transmission / reception control unit 74 in FIG. The transmission / reception control unit 74 controls the operations of the transmission beam former 52 and the reception beam former 54. Data necessary for generating delay data (transmission delay data, reception delay data) is given to these circuits. For example, the transmission / reception control unit 74 provides the delay data generation circuit 66 in the reception beamformer 54 with a parameter group necessary for executing the above-described PWL and other parameter groups. In the ultrasonic diagnostic apparatus, a Doppler signal processing unit, a three-dimensional image forming unit, and the like are further provided as necessary. *

(2) Description of Delay Data Generation Method and Virtual Sound Source Method FIG. 2 shows a general propagation path model according to the parallel reception method. A transmission beam 84 is formed by radiating ultrasonic waves from a plurality of vibration elements in the transmission aperture set on the array transducer 50. The transmit beam 84 has a form of focusing at the transmit focal point 90. The transmission reference point (transmission origin) 88 is typically a point on the central axis 86 of the transmission beam 84, and the transmission reference point 88 is a temporal and spatial reference when calculating the reception delay time. Is done. The reception focal point 92 is on the center line 91 of the specific reception beam of interest. The reception focal point 92 can generally be regarded as an imaging point (observation point). However, when the transmission / reception total peak shift phenomenon occurs (or when it cannot be ignored), the reception focus and the transmission / reception total peak do not match. In that case, the position of the reception focus is corrected in order to match the transmission / reception total peak to a desired imaging point. This will be described later. The receiving element 94 is a vibrating element to be noticed now.

In the model shown in FIG. 2, the straight path from the transmission reference point 88 to the reception focal point 92 is the forward path, and the straight path from the reception focal point 92 to the reception element 94 is the backward path. The total route is the sum of the outbound route and the inbound route. By dividing the total path length by the speed of sound, the propagation time corresponding to the total path can be obtained. Delay processing is to eliminate the difference in propagation time between a plurality of receiving elements and to align the phases.

In the receive beamformer of the present embodiment, the propagation time corresponding to the forward path (forward path propagation time) and the propagation time corresponding to the backward path (return path propagation time) are calculated separately, and then the forward path delay time and the backward path By adding the delay time, the total propagation time corresponding to all paths is generated. The delay data given to the delay controller is data representing such total propagation time. However, the delay data can be configured as data representing the delay time itself.

In the model shown in FIG. 2, the forward path 96 is common to all the receiving elements in the receiving aperture, that is, it is possible to use the same forward path propagation time in these receiving elements. On the other hand, the propagation time of the return path 98 can be shared among a plurality of transmission beams in the virtual sound source method described below. That is, when paying attention to a certain reception focus, it is possible to use the same return path propagation time for each reception element between a plurality of transmission beams. Even when the reception focus and the imaging point are different, it is possible to share some data. This will be described later.

FIG. 3 shows a propagation path model according to the virtual sound source method. The same elements as those shown in FIG. 2 are denoted by the same reference numerals, and the description thereof is omitted.

FIG. 3 shows a center line 91 for one reception beam among a plurality of reception beams according to the parallel reception method. The reception focal point 92 exists on the center line 91. In the virtual sound source method, delay data is calculated on the assumption that the transmission focal point 90 is regarded as a virtual sound source and a wave (spherical wave) therefrom reaches the reception focal point 92. First, for the forward path, the forward path propagation time is calculated as described above. Specifically, the propagation time corresponding to the first portion 100 from the transmission origin 88 to the transmission focal point 90 and the propagation time corresponding to the second portion 102 from the transmission focal point 90 to the reception focal point 92 are calculated. The forward propagation time (propagation time corresponding to the first part 100 and the second part 102) is common to a plurality of receiving elements. Further, the return path propagation time corresponding to the return path 104 from the reception focal point 92 to each receiving element is the same among a plurality of transmission beams.

FIG. 4 schematically shows the virtual sound source method. In the illustrated example, a transmission signal line string 24 is connected to the array transducer 10, and a reception signal line string 26 is drawn from the middle of the signal line string 24. A transmission aperture X0 is set for the array transducer 10, and a plurality of transmission signals having a delay relationship indicated by a delay curve 28 are supplied to a plurality of vibration elements belonging to the array aperture 10. As a result, a transmission beam 30a is formed. The transmission beam 30a has a transmission focal point 32a. Similarly, the transmission beam 30b, the transmission beam 30c,... Are formed while changing the transmission position in the scanning direction. They have a transmission focal point 32b, a transmission focal point 32c,. In FIG. 4, the depths of their transmission focal points are the same, that is, Z0. Although not shown in FIG. 4, in this example, for each transmission beam, a plurality of reception beams are formed in one transmission / reception by applying a parallel reception technique.

Pay attention to the imaging point (reception focal point) p. The imaging point p is covered with three

transmission beams

30a, 30b, and 30c in the illustrated example. In other words, it belongs to three

transmission beams

30a, 30b and 30c. Each transmission

focal point

32a, 32b, 32c can be regarded as a virtual sound source (hereinafter, "transmission focal point" will be referred to as "virtual sound source" in some cases). That is, it is possible to think of spherical waves with each virtual sound source as the origin on the near side and the back side of each virtual sound source. FIG. 4 shows a spherical wave emitted from the virtual sound source 32a. Three

spherical wave components

36a, 36b, and 36c derived from the three

virtual sound sources

32a, 32b, and 32c arrive at the imaging point p. A large amplitude can be observed at the imaging point p by combining the phases. That is, for example, in the reception processing after the transmission beam 30a is formed, in addition to the delay condition for realizing normal reception dynamic focus at the imaging point p, according to the distance between the virtual sound source 32a and the imaging point p. Delay processing is executed in consideration of the delay conditions. In FIG. 4, the distance from the imaging point p to the specific vibration element 11a in the reception aperture is indicated by reference numeral 38a, and the propagation time at that time is t2. Propagation time obtained by adding the forward propagation time from the transmission reference point to the reception focal point via the transmission focal point (including the spherical wave component t1) and the return propagation time t2 from the reception focal point to the receiving element 11a. The delay data is given to the received signal output from the receiving element 11a. Similar reception processing is executed in the reception processing after the transmission beams 30b and 30c are formed. As the number of transmission beams covering the imaging point p increases (the transmission aperture synthesis number increases), a larger amplitude can be obtained at the reception point, that is, the image quality of the ultrasonic image can be improved. In other words, in the virtual sound source method, the image quality of the ultrasonic image can be improved, so that the number of transmission beams can be reduced by that amount and the frame rate can be improved.

(3) First Embodiment of Delay Data Generation Circuit FIG. 5 shows a first embodiment of the delay data generation circuit. The delay data generation circuit 66 includes a forward path time (forward path propagation time) calculation circuit 110, a return path time (return path propagation time) calculation circuit 112, an adder 114, a delay data memory 116, and the like. The forward path time calculation circuit 110 functions as a forward path delay data generator, and is configured by a PWL circuit in the first embodiment. A parameter group necessary for executing the PWL is calculated in advance and written in the parameter memory 122 in advance. For example, in the main control unit, when various conditions such as a diagnostic range, a transmission focal depth, a transmission condition, a parallel reception condition, and the number of sections are determined, a parameter group for PWL is calculated and stored in the parameter memory 122. Stored in The forward time calculation circuit 110 reads out necessary parameters from the parameter memory 122 by specifying the transmission beam number, parallel reception number, and the like for each reception focal depth in executing each reception dynamic focus. PWL is executed with reference to parameters necessary for calculation, and as a result, forward path delay data corresponding to each reception focus is output. The forward delay data is shared between a plurality of receiving vibration elements under the same transmission / reception conditions. A memory for storing return path delay data is provided in the forward path time calculation circuit 110. Such a memory may be provided in the adder 114.

The return path time calculation circuit 112 functions as a return path delay data generator, and calculates the propagation time by dividing the path length of the return path from the reception point to each receiving element by the sound velocity. This corresponds to return path delay data. In the parameter memory 124, coordinate data for each receiving element is stored as necessary. The coordinate data specifies the x coordinate and the y coordinate for each receiving element. By holding such two-dimensional coordinate data, it is possible to cope with convex scanning. The return control time calculation circuit 112 is given parameters necessary for the calculation from the main control unit. In that case, the scanning line number to which the reception dynamic focus is applied may be given as a parameter, or the scanning line number may be generated from the transmission beam number and the parallel reception number. In the virtual sound source method, one imaging point corresponds to a plurality of transmission beams. The return delay data of each receiving element is shared between the plurality of transmission beams. A memory for storing a plurality of return path delay data corresponding to a plurality of receiving elements is provided in the return time calculation circuit 112. Such a memory may be provided in the adder 114. The return time calculation circuit is configured by, for example, a general function calculator. It may be composed of a circuit such as an FPGA or an ASIC. The entire reception beam former or the delay data generation circuit 66 may be configured by an FPGA or an ASIC.

The adder 114 is a circuit that generates delay data by adding the forward path delay data and the backward path delay data, and functions as a delay data generator. That is, the adder 114 calculates the total propagation time by adding the forward propagation time and the backward propagation time. This is performed for each receiving element. The delay data memory 116 stores a delay data set for a predetermined unit, for example, one frame. Of course, individual delay data may be generated in real time.

As shown in FIG. 5, according to the present embodiment, it is possible to apply different calculation methods for the forward path and the backward path. In addition, individual calculation results can be shared by such component separation. Furthermore, as will be described below, it is possible to greatly reduce the parameters required for calculation (a group of parameter values calculated or prepared in advance in the main control unit).

(4) Comparison of data amount In the formation of transmission / reception beams in the ultrasonic diagnostic apparatus, a reception focus is usually formed at all imaging points in the display area. As shown in FIG. 2, when paying attention to a certain receiving element, it is ideal to calculate the total propagation distance accurately, divide it by the speed of sound to obtain the propagation time, and use it as delay data. However, since such an operation is actually difficult, conventionally, for example, delay data is generated using a piecewise polynomial interpolation method or the like. The total amount of parameters required for such calculation is proportional to the number of transmission beams, the number of parallel receptions, and the number of reception elements.

When using piecewise linear interpolation (PWL), which is a kind of piecewise polynomial interpolation, it is assumed that the number of transmitted beams is 192, the number of parallel reception is 32, the number of receiving elements is 192, and the number of sections is 32. Assuming that the delay data (representative depth delay data) is expressed in 2 bytes, the total amount of parameters required in the PWL is calculated as in the following equation (1).

[Equation 1]
Number of transmitted beams (192) * Number of parallel receptions (32) * Number of receiving elements (192)
* Number of sections (32) * 2 [byte] = 75,497,472 [byte] ... (1)

As described above, it is necessary to prepare enormous parameters even for PWL. This is a major factor that makes it impossible to increase the number of reception beams in parallel reception.

On the other hand, this embodiment is also calculated under the same conditions. First, when calculating the forward delay data, the receiving element is irrelevant, and the total amount of parameters is as follows.

[Equation 2]
Number of transmission beams (192) * Number of parallel receptions (32) * Section (32) * 2 [byte]
= 786,432 [byte] (2)

Next, the return delay data can be calculated regardless of the transmission beam number, and since it has become relatively easy to perform square root calculation and the like due to recent advances in electronic circuit technology, the return delay data Can be computed mathematically and sequentially without using PWL. The parameter required for the calculation is about the coordinates (x, y) for each receiving element constituting the receiving aperture per receiving beam. That is, the parameter amounts that should be prepared in advance are as follows, for example.

[Equation 3]
Number of scanning lines (384) * Number of receiving elements (192) * Element coordinates (2) * 2 [byte]
= 294,912 [byte] (3)

When the calculation result of the above formula (2) and the calculation result of the above formula (3) are added, the required total amount of parameters in this embodiment is, for example, as follows.

[Equation 4]
Calculation result of formula (2) + calculation result of formula (3) = 1,081,344 [bytes] (4)

Comparing the calculation result of the above formula (4) with the calculation result of the above formula (1), it can be understood that according to the present embodiment, the total parameter amount can be greatly reduced.

In the configuration shown in FIG. 5, when the virtual sound source method is not applied, the calculation of the forward path time becomes very simple, that is, the calculation of the straight path from the transmission reference point to the reception focus, and the straight path The forward delay data can be easily calculated from the calculation of dividing by the speed of sound.

(5) Second Embodiment First, a transmission / reception sensitivity peak shift from the reception focal point and a coping method thereof will be described with reference to FIG. Although the content of FIG. 6 is based on electronic sector scanning, the concept described below can be applied to other scanning methods.

Numeral 128 indicates a center line that crosses the center of the array transducer 50. Transmit beam 130 is deflected with respect to centerline 128. The imaging point 134 is a point at which imaging is desired on the scanning plane. If the reception focal point is formed at the position of the imaging point 134, a reception beam 136 having a deflection angle θ is formed. However, in that case, the transmission / reception comprehensive peak (transmission / reception combined sensitivity peak) shifts closer to the transmission beam 130 than the imaging point 134 (see Patent Document 1). As a method for coping with this, there is a method of shifting the position of the reception point outward so that the imaging point 134 becomes the position of the transmission / reception total peak. In this case, the reception beam is indicated by reference numeral 144, and the corrected reception focus is indicated by reference numeral 142. The deflection angle of the reception beam 144 actually formed is obtained by adding a correction angle Δθ to the original deflection angle θ. That is, the angle is (θ + Δθ). Reference numeral 144 denotes a forward path from the transmission reference point 126 to the reception focal point 142. This is the same as the distance from the transmission reference point 126 to the imaging point 134. Reference numeral 138 indicates a path from the imaging point 134 to the receiving element 140 (return path before correction), and reference numeral 146 indicates a path from the reception focal point 142 to the receiving element 140 (return path after correction).

When the reception focal point 142 and the imaging point 134 are compared, the length of the forward path from the transmission reference point 126 is the same (both are r), and a difference occurs in the return path length, so correction is necessary.

First, calculation of the propagation distance (total path length) d when the above correction is not performed is as follows. Xe is the distance from the center 126 to the receiving element 140. As described above, the reception beam deflection angle is θ.

In the above equation (5-2), r in the first term indicates the forward path length, and the second and subsequent terms indicate the return path length. Here, division by sound speed is omitted.

Next, calculation of the propagation distance d 'when correction is performed is as follows. The correction angle of the reception beam is Δθ.

In the above equation (6), Δθ is a minute angle, so sin (Δθ) can be approximated by Δθ, and cos (Δθ) can be approximated by 1. Δθ varies according to r. As a result, the following equation (7) can be derived.

In the equation (7), the corrected propagation distance d ′ is obtained by adding a fixed correction term (−Δθ · cos θ · xe) to the propagation distance d before correction. Therefore, in order to specify the calculation result after correction from the calculation result before correction, the correction term should be considered. The second embodiment considers such a correction term.

FIG. 7 shows the configuration of the delay data generation circuit 66A according to the second embodiment. The delay data generation circuit 66A includes a straight forward time (straight forward propagation time) calculation circuit 150, a correction term calculation circuit 152, a return time calculation circuit 154, and the like. The straight forward time calculation circuit 150 executes a calculation of dividing the forward path length r by the speed of sound c. The straight forward time calculation circuit 150 can be configured as a normal function calculation circuit. Parameters necessary for the calculation are passed from the main control unit. The return time calculation circuit 154 is a circuit that executes the second term in the equation (5-1). However, in that circuit, the return path propagation time may be calculated by dividing the return path length (after the second term) in the equation (5-2) by the speed of sound. The return time calculation circuit 154 can also be constituted by a normal function calculation circuit. Parameters necessary for the calculation are passed from the main control unit.

The correction term calculation circuit 152 functions as a correction delay data generator. In the example shown in the figure, the correction term calculation circuit 152 calculates a correction term using PWL, and specifically, calculates (Δθ · cos θ) / c. Then, xe is multiplied by the multiplier 156 with respect to the calculation result. As a result, a correction term is generated. The correction term can be thought of as correction delay data. A parameter group necessary for calculating PWL is written in the parameter memory 166 in advance. Other necessary parameters are passed from the main controller. Note that a parameter memory 168 may be provided in the previous stage of the return time calculation circuit 154, and necessary parameter groups may be written in advance there.

In the adder 158, the above three calculation results, the straight forward propagation time, the correction term, and the backward propagation time are added, thereby calculating the total propagation time. It is written into the delay data memory as delay data. In the delay process, the delay data in the delay data memory 160 is sequentially read by the delay controller.

As described above, also in the second embodiment, the forward delay data and the backward delay data are generated separately. The number of correction terms may be increased according to the dimension of the element coordinates. Further, the correction term may be calculated using the element number.

FIG. 8 shows the effect of correcting the reception point. The horizontal axis indicates the deflection angle. The vertical axis represents the sound pressure (sensitivity). A characteristic to be realized is indicated by reference numeral 172. This sets the transmission / reception total peak at 0.5 degrees. Accordingly, when the reception beam deflection angle is set to 0.5 degrees (when correction is not performed), the characteristics indicated by reference numeral 170 are obtained. That is, the transmission / reception total peak becomes smaller than 0.5 degrees, in other words, the transmission / reception total peak is drawn toward the center of the transmission beam. On the other hand, when the reception focus is corrected by the deflection angle Δθ (when the received beam deflection angle after correction is set to 0.9 degrees), the characteristic indicated by reference numeral 174 can be formed, and the transmission / reception total peak of the characteristic is obtained. Can be set to 0.5 degrees (see reference numeral 176).

(6) Third Embodiment Using the same delay data generation circuit, the virtual sound source method (first transmission / reception mode) shown in FIGS. 3 and 4 is executed, and sensitivity peak correction (second) shown in FIG. In order to realize (transmission / reception mode), a circuit configuration as shown in FIG. 9 may be employed.

In FIG. 9, the delay data generation circuit 66B has a straight forward path time calculation circuit 180, a forward path time / correction term calculation circuit 182 and a return path time calculation circuit 184, similarly to the delay data generation circuit 66A shown in FIG. is doing. 9 corresponds to the linear forward time calculation circuit 150 shown in FIG. 7, and operates in the second transmission / reception mode. The return path time calculation circuit 184 in FIG. 9 corresponds to the return path

time calculation circuits

112 and 154 shown in FIGS. It operates in both the first transmission / reception mode and the second transmission / reception mode. The forward path time / correction term calculation circuit 182 in FIG. 9 corresponds to the forward path time calculation circuit 110 shown in FIG. 5 and the correction term calculation circuit 152 shown in FIG. 7, which performs calculations according to the PWL method. . In the first transmission / reception mode, the arithmetic circuit 182 functions as a forward path time arithmetic circuit, and in the second transmission / reception mode, the arithmetic circuit 182 functions as a correction term arithmetic circuit. Note that a parameter memory 200 is provided before the arithmetic circuit 182, and a parameter memory 202 is provided before the return time arithmetic circuit 184. The multiplier 186 and the adder 188 function in the second transmission / reception mode, and the selector (SEL) selects the direct output from the arithmetic circuit 182 in the first transmission / reception mode and adds in the second transmission / reception mode. The output from the unit 188 is selected. The adder 192 adds the output of the selector 190 and the output of the return path time calculation circuit 184 in both the first transmission / reception mode and the second transmission / reception mode, thereby generating delay data. It is once written into the delay data memory 194.

As described above, according to the circuit configuration shown in FIG. 9, it is possible to support two transmission / reception modes while sharing a plurality of processors.

As described above, by dividing the delay data into a plurality of components, it is possible to obtain advantages such as sharing of components, reduction in parameter amount, and parallel computation, and in turn, effects such as high-speed computation and increase in the number of parallel receptions. . Further, according to the above configuration, even when the transmission / reception conditions are changed, the parameter calculation time for generating the delay data can be shortened, so that the transmission start waiting time can be shortened.

(7) Fourth Embodiment The above formula (7) is modified as follows.

[Equation 8]
D ′ = 2r−xe (sin θ + Δθ · cos θ) (8)

After executing the operation ((sin θ + Δθ · cos θ) / c) in the parenthesis of the second term in the above equation (8), the operation result is multiplied by xe, the multiplication result, and (8 ) (2r / c) with respect to the first term in the equation may be added. In that case, the delay data generation circuit 66C shown in FIG. 10 can be used. In FIG. 10, a first arithmetic circuit 204 is a straight path arithmetic circuit, and executes the calculation of (2r / c). The first arithmetic circuit 204 can be configured by a simple calculation circuit. The calculation result can be shared among a plurality of receiving vibration elements in the receiving aperture.

The second calculation circuit 206 executes the calculation of ((sin θ + Δθ · cos θ) / c) as described above. For example, it may be constituted by a PWL circuit. The calculation result cannot be shared among the plurality of vibration elements.

The computing unit 208 includes a circuit that multiplies the computation result of the second computation circuit 206 by xe, and a circuit that adds the multiplication result and the computation result of the first computation circuit 204. Delay data is output from the arithmetic unit 208 and stored in the delay data memory 210. The parameter memory 212 stores parameters necessary for the calculation in the first calculation circuit 204, and the parameter memory 214 stores parameters required for the calculation in the second calculation circuit 206.

In the configuration shown in FIG. 10 as well, a specific component in the delay data can be shared among a plurality of receiving vibration elements. When the virtual sound source method is applied, it is possible to calculate the forward delay data in the first arithmetic circuit 204 and to calculate the backward delay data in the second arithmetic circuit 206.

In any case, in the past, one piece of delay data was generated at a time based on the parameter group. However, by using the stepwise or parallel generation method as described above, the calculation amount or the parameter amount The advantage that can be reduced is obtained. According to the above configuration, the parameter group can be calculated in a short time even when the transmission / reception conditions are changed, so that the user's stress associated with the delay of the transmission start timing can be reduced or eliminated.

Claims

A plurality of vibration elements that output a plurality of received signals;
A generation circuit for generating a plurality of delay data corresponding to the plurality of vibration elements;
A delay processing circuit that delays the plurality of received signals according to the plurality of delay data;
Including
The generation circuit includes:
An outbound delay data generator that generates outbound delay data corresponding to the outbound path from the transmission reference point to the reception focus;
A return delay data generator for generating return delay data corresponding to a return path from the reception focus to the reception vibration element for each reception vibration element in the plurality of vibration elements;
A delay data generator for generating delay data for delaying a reception signal from the reception vibration element based on the forward path delay data and the return path delay data for each reception vibration element;
An ultrasonic diagnostic apparatus comprising:
The apparatus of claim 1.
The forward delay data generator generates the forward delay data as data shared among a plurality of receiving vibration elements;
An ultrasonic diagnostic apparatus.
The apparatus of claim 2.
The forward delay data generator generates the forward delay data based on the transmission reference point, the transmission focus, and the reception focus when a virtual sound source method as a transmission aperture synthesis method is executed.
An ultrasonic diagnostic apparatus.
The apparatus of claim 3.
The forward path delay data is data corresponding to the forward path propagation time,
The outward propagation time is
When the distance from the transmission origin to the reception focus is larger than the distance from the transmission origin to the transmission focus, the transmission focus with respect to the propagation time corresponding to the distance from the transmission origin to the transmission focus. Is a time obtained by adding a propagation time corresponding to the distance from the reception focal point to
When the distance from the transmission origin to the reception focus is smaller than the distance from the transmission origin to the transmission focus, from the propagation time corresponding to the distance from the transmission origin to the transmission focus, from the transmission focus to the transmission focus. This is the time obtained by subtracting the propagation time corresponding to the distance to the reception focus.
An ultrasonic diagnostic apparatus.
The apparatus of claim 1.
The forward delay data generator generates the forward delay data according to piecewise polynomial interpolation;
An ultrasonic diagnostic apparatus.
The apparatus of claim 1.
The return path delay data generator generates the return path delay data as data shared between a plurality of transmission beams.
An ultrasonic diagnostic apparatus.
The apparatus of claim 6.
The return path delay data generator generates the return path delay data based on a distance between the reception focus and the reception vibration element.
An ultrasonic diagnostic apparatus.
The apparatus of claim 1.
The delay data generation circuit is a circuit that adds the forward delay data and the backward delay data.
An ultrasonic diagnostic apparatus.
The apparatus of claim 1.
The generation circuit further includes a correction delay data generator that generates correction delay data as a correction term,
The delay data generator is configured to delay the received signal from the reception vibration element based on the forward path delay data, the return path delay data, and the correction delay data for each reception vibration element. Generate data,
An ultrasonic diagnostic apparatus.
The apparatus of claim 9.
The correction term corresponds to a reception focus shift amount for adjusting the transmission / reception total peak to a desired imaging point.
An ultrasonic diagnostic apparatus.
Generating first delay data as a component shared among a plurality of receiving vibration elements;
Generating second delay data as a unique component for the reception vibration element for each reception vibration element;
Generating delay data for delaying a reception signal from the reception vibration element based on the first delay data and the second delay data for each reception vibration element;
A method for generating delay data in an ultrasonic diagnostic apparatus.