Ultrasound diagnostic equipment

Abstract

To provide an ultrasonic diagnostic device capable of improving quality of an ultrasonic image on the basis of an S / N index for each region and for each frequency zone in a data space of reception beam data.SOLUTION: A transmission / reception unit 14 generates a plurality of pieces of reception beam data whose added numbers of a plurality of phased reception channel signals from each variation element that receives a reflective wave from a subject are different from each other. An S / N estimation unit 18 executes frequency analysis for each of the plurality of pieces of reception beam data Rb whose added numbers of the reception channel signals prior to wave detection processing are different from each other for each region Re. The S / N estimation unit 18 calculates an inclination of an approximation straight line AP of spectrum intensity for the added number of the signal of each reception channel for each combination of the region Re and a frequency zone F. The inclination serves as the S / N index. A signal processing unit 20 generates a band-pass filter for each region Re on the basis of the S / N index for each region Re and each frequency zone F, and applies it to the reception beam data Rb prior to the wave detection processing.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] This specification discloses an improvement of an ultrasonic diagnostic apparatus.

Background Art

[0002] Conventionally, an ultrasonic diagnostic apparatus is known in which ultrasonic waves are transmitted and received toward a subject, reception beam data is formed based on the received signal obtained thereby, an ultrasonic image is formed from the reception beam data, and the formed ultrasonic image is displayed on a display. In an ultrasonic diagnostic apparatus, a process of applying a band-pass filter to the received signal is performed for the purpose of noise reduction and the like.

[0003] Conventionally, different band-pass filters have been applied for each depth of the subject.

[0004] For example, Patent Document 1 discloses an ultrasonic diagnostic apparatus including a plurality of STC controls that adjust the gain of time gain control for each depth, and sets a band-pass filter applied to each depth according to the gain specified by each STC control. Further, Patent Document 2 discloses an ultrasonic diagnostic apparatus that performs frequency analysis for each depth on a received signal acquired from an ultrasonic probe, acquires frequency characteristics for each depth, and sets a band-pass filter for each depth based on the acquired frequency characteristics for each depth. Further, Patent Document 3 discloses an ultrasonic diagnostic apparatus that acquires signal characteristic values (for example, frequency) related to each depth by analyzing a received signal acquired from an ultrasonic probe, and sets a band-pass filter for each depth based on the acquired frequency for each depth.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

[0006] Incidentally, it can be beneficial to estimate the signal-to-noise ratio (S / N ratio) for each region and each frequency area (of the received beam data) within the data space of the received beam data. Based on the estimated S / N ratio for each region and frequency area, it becomes possible to perform adaptive image enhancement processing for each region and frequency area of ​​the ultrasound image. One example of adaptive image enhancement processing is applying different bandpass filters to each region.

[0007] The objective of the ultrasound diagnostic apparatus disclosed herein is to provide an ultrasound diagnostic apparatus capable of estimating the signal-to-noise ratio (S / N) for each region and frequency area in the data space of received beam data, and improving the image quality of ultrasound images based on the estimated S / N ratio. [Means for solving the problem]

[0008] The ultrasound diagnostic apparatus disclosed herein is characterized by comprising: an addition data generation unit that generates received beam data by adding a plurality of received channel signals corresponding to a plurality of received channels obtained by transmitting and receiving ultrasound waves to a subject, which are phase-aligned by a phase-alignment process, the addition data generation unit that generates a plurality of received beam data with different sums of the received channel signals; an S / N estimation unit that performs frequency analysis on each of the plurality of received beam data with different sums of the received channel signals before detection processing for each predetermined region in the data space of the received beam data, and estimates an S / N index for each region and frequency area based on the amount of increase in spectral intensity with increasing sums; and an image quality enhancement unit that performs different image quality enhancement processing for each region to enhance the image quality of the ultrasound image based on the S / N index estimated for each region and frequency area.

[0009] The signal components of multiple phase-corrected received channel signals, obtained from the same transmitted beam and corresponding to multiple received channels, will have approximately the same phase and amplitude. Therefore, ideally, when N received channel signals are added together, the signal components in each frequency range will be approximately N times greater. On the other hand, the noise components of each received channel signal have varying phases and amplitudes. Therefore, even when N of these are added together, the noise components in each frequency range will not be N times greater, but will only be smaller. In general, the effective value when multiple uncorrelated noises are added together is expressed as the square root of the sum of the squares of the effective values ​​of each noise, and when N noise components from each received channel are added together, the noise components in each frequency range will be approximately √N times greater.

[0010] Therefore, the more signal components there are in the received beam data in a given region, the larger the S / N ratio becomes as the number of sums increases. In other words, the increase in spectral intensity with respect to the number of sums of signals in the received channel represents the S / N ratio. The S / N estimation unit calculates the increase in spectral intensity with respect to the number of sums of signals in the received channel for each region and each frequency region, thereby estimating the S / N ratio for each region and frequency region. This allows the image enhancement unit to perform image enhancement processing on ultrasound images based on the S / N ratio for each region and frequency region.

[0011] Furthermore, the ultrasound diagnostic apparatus disclosed herein is characterized by comprising: a receiving beam data generation unit that generates received beam data by a phase-correcting summation process on a plurality of receiving channel signals corresponding to a plurality of receiving channels obtained by transmitting and receiving ultrasound waves to a subject; an addition data generation unit that generates added received beam data by adding a plurality of the received beam data corresponding to the same scan line position, wherein the addition data generation unit generates a plurality of the added received beam data in which the number of additions of the plurality of received beam data differs from one another; an S / N estimation unit that performs frequency analysis on each of the plurality of added received beam data before detection processing for each predetermined region in the data space of the received beam data, and estimates an S / N index for each region and frequency area based on the amount of increase in spectral intensity with increasing sums; and an image quality enhancement unit that performs different image quality enhancement processing for each region to enhance the image quality of the ultrasound image based on the S / N index estimated for each region and frequency area.

[0012] Similarly, in this configuration, the more signal components there are in the received beam data in a given region, the larger the S / N ratio becomes as the number of received beam data points corresponding to the same scan line position increases. In other words, the increase in spectral intensity with respect to the number of received beam data points represents the S / N ratio. The S / N estimation unit calculates the increase in spectral intensity with respect to the number of received beam data points for each region and each frequency region, thereby estimating the S / N ratio for each region and each frequency region. This allows the image enhancement unit to perform image enhancement processing on ultrasound images based on the S / N ratio for each region and each frequency region.

[0013] The image enhancement unit generates a bandpass filter for each region and frequency area based on the S / N index estimated for each region and frequency area, and applies the generated bandpass filter for each region to the received beam data before detection processing.

[0014] This configuration allows for the application of different bandpass filters to each region, enabling appropriate noise reduction and other modifications for each region.

[0015] The summing data generation unit generates the summing received beam data by inter-transmission aperture synthesis, and it is preferable to generate a plurality of summing received beam data sets in which the summing number of the received beam data in the inter-transmission aperture synthesis is different from one another.

[0016] The summing data generation unit generates summing received beam data by adding up multiple frame data, which are multiple received beam data for one frame, and it is preferable to generate multiple summing received beam data with different sums of frame data.

[0017] The S / N estimation unit calculates the slope of the approximate straight line for each summation number with respect to the spectral intensity in the two-dimensional data space of the summation number and the spectral intensity for each region and frequency area, and estimates the calculated slope as the S / N index for each region and frequency area.

[0018] According to this configuration, the S / N index for each region and each frequency area can be estimated by determining the slope of the approximate straight line of spectral intensity with respect to the sum of the received channel signal or received beam data.

[0019] The S / N estimation unit calculates a corrected spectral intensity by correcting the spectral intensity based on a predetermined correction coefficient for each summation number, and estimates the slope of the approximate line for the corrected spectral intensity for each summation number in the two-dimensional data space as the S / N index.

[0020] According to this configuration, when the received channel signals to be added are not the same signal, or when the received beam data to be added are not the same signal, the S / N index can be estimated while reducing the influence of differences in spectral intensity between received channels or between received beam data.

Advantages of the Invention

[0021] According to the ultrasonic diagnostic apparatus disclosed in this specification, an ultrasonic diagnostic apparatus capable of enhancing the image quality of an ultrasonic image can be provided based on the S / N index for each region and each frequency band in the data space of the received beam data.

Brief Description of the Drawings

[0022] [Figure 1] It is a schematic configuration diagram of an ultrasonic diagnostic apparatus according to the first embodiment. [Figure 2A] It is a first diagram showing the reception channels to be added. [Figure 2B] It is a second diagram showing the reception channels to be added. [Figure 2C] It is a third diagram showing the reception channels to be added. [Figure 2D] It is a fourth diagram showing the reception channels to be added. [Figure 3A] It is a fifth diagram showing the reception channels to be added. [Figure 3B] It is a sixth diagram showing the reception channels to be added. [Figure 3C] It is a seventh diagram showing the reception channels to be added. [Figure 3D] It is an eighth diagram showing the reception channels to be added. [Figure 4] It is a conceptual diagram showing a plurality of received beam data stored in a beam data memory, where the number of addition of received channel signals is different from each other. [Figure 5] It is a diagram showing the frequency spectrum of received beam data corresponding to one addition number in one region. [Figure 6] It is a diagram showing the relationship between the addition number of received channel signals and the spectrum intensity in one region and one frequency band. [Figure 7] It is a diagram showing the spectrum intensity corrected by a correction coefficient. [Figure 8]This figure shows the signal-to-noise ratio (S / N) for each frequency zone within a single region. [Figure 9] This is a schematic diagram of the configuration of an ultrasound diagnostic apparatus according to the second embodiment. [Figure 10] This figure shows the scan line position and beam position in intertransmission aperture synthesis. [Figure 11] This is a schematic diagram of the configuration of an ultrasound diagnostic apparatus according to the third embodiment. [Modes for carrying out the invention]

[0023] <First Embodiment> Figure 1 is a schematic diagram of the configuration of an ultrasound diagnostic device 10 according to the first embodiment. The ultrasound diagnostic device 10 is a medical device installed in a medical institution such as a hospital and used during ultrasound examinations.

[0024] The ultrasound diagnostic device 10 is a device that scans a subject with an ultrasound beam and forms an ultrasound image based on the received signal obtained thereby. For example, the ultrasound diagnostic device 10 forms a tomographic image (B-mode image) based on the received signal, in which the amplitude intensity of the reflected wave from the scanning surface is converted into brightness. Alternatively, the ultrasound diagnostic device 10 can also form a Doppler image, which is an ultrasound image representing the motion velocity of tissue within the subject, based on the difference in frequency between the transmitted wave and the received wave (Doppler shift). In this embodiment, the process by which the ultrasound diagnostic device 10 forms a B-mode image will be described.

[0025] The ultrasonic probe 12 is a device that transmits and receives ultrasonic waves to a subject. The ultrasonic probe 12 has a vibrating element array consisting of multiple vibrating elements that transmit and receive ultrasonic waves to the subject.

[0026] The transmitting / receiving unit 14 transmits a transmission signal to the ultrasonic probe 12 (specifically, each vibrating element in the vibrating element array) under control from the control unit 34 (described later). As a result, ultrasonic waves are transmitted from each vibrating element toward the subject. Ultrasonic waves are transmitted from multiple vibrating elements at once, and the transmitting / receiving unit 14 controls the transmission timing of ultrasonic waves from each vibrating element, so that ultrasonic beams (transmitting beams) are transmitted from multiple vibrating elements in multiple directions. The transmitting / receiving unit 14 also receives received signals from each vibrating element that has received reflected waves from the subject. In this specification, the received signals received from each vibrating element are referred to as the received signals of each receiving channel, and further, the received signals of a receiving channel are referred to as the receiving channel signals.

[0027] The transmitting / receiving unit 14 has multiple delay units corresponding to each receiving channel, and these multiple delay units perform phase alignment processing to align the phases of the multiple receiving channel signals.

[0028] Furthermore, the transmitting / receiving unit 14 has an adder, which adds up multiple received channel signals obtained by the same transmitted beam and processed to generate received beam data. One received beam data corresponds to one ultrasonic scan line (scan line; in other words, the transmission direction of the transmitted beam) and contains information indicating the signal intensity of the reflected waves from each depth of the subject.

[0029] The transmitting / receiving unit 14 generates multiple received beam data sets with different summation counts of multiple phase-aligned received channel signals, controlled by the control unit 34. Figures 2A to 2D and 3A to 3D show the received channels Ch that are to be added. As a simulated example, 12 received channels Ch included in the effective receiving aperture are shown in Figures 2A to 2D and 3A to 3D. The dashed line indicates the center M of the effective receiving aperture. The center M of the effective receiving aperture is also the transmission direction (center) of the transmitted beam. In Figures 2A to 2D and 3A to 3D, the received channels Ch shown in black indicate the received channels Ch whose received channel signals are to be added, and the received channels Ch shown in white indicate the received channels Ch whose received channel signals are not to be added.

[0030] As shown in Figures 2A to 2D, for example, the transmitting / receiving unit 14 generates multiple received beam data, such as received beam data obtained by adding the received channel signals of two receiving channels Ch (Figure 2A), received beam data obtained by adding the received channel signals of four receiving channels Ch (Figure 2B), received beam data obtained by adding the received channel signals of six receiving channels Ch (Figure 2C), and received beam data obtained by adding the received channel signals of eight receiving channels Ch (Figure 2D). Note that all received channel signals of each receiving channel Ch are stored in the receiving channel memory (not shown), regardless of whether or not they are added for the generation of received beam data. Therefore, the transmitting / receiving unit 14 only needs to select the receiving channel to be used for generating received beam data (i.e., the channel to be added) from the multiple received channel signals stored in the receiving channel memory.

[0031] In Figures 2A to 2D, the received channel signals of the received channel Ch on the center M side of the effective receiving aperture are added together, but this is not necessarily required. For example, as shown in Figures 3A to 3C, the received channel Ch to which the received channel signal is added may be selected at intervals of one or more from the edge of the effective receiving aperture. In the example shown in Figures 3A to 3D, the transmitting and receiving unit 14 generates multiple received beam data sets: received beam data with the received channel signals of 3 received channel Ch added together (Figure 3A), received beam data with the received channel signals of 4 received channel Ch added together (Figure 3B), received beam data with the received channel signals of 6 received channel Ch added together (Figure 3C), and received beam data with the received channel signals of 12 received channel Ch added together (Figure 3D).

[0032] In this embodiment, the transmitting / receiving unit 14 generates multiple frames of received beam data, each with a different sum of received channel signals. In this specification, the received beam data for one frame is referred to as frame data. Frame data corresponds to one ultrasound image. The transmitting / receiving unit 14 does not necessarily need to generate received beam data for the entire frame for each sum; it only needs to generate received beam data that covers at least the area to be improved in the ultrasound image.

[0033] As described above, in the first embodiment, the transmitting / receiving unit 14 corresponds to the addition data generation unit.

[0034] Multiple received beam data sets, each with a different sum of received channel signals, generated by the transmitting / receiving unit 14, are stored in the beam data memory 16. Figure 4 is a conceptual diagram showing multiple received beam data sets Rb, each with a different sum of received channel signals, stored in the beam data memory 16. In Figure 4, one frame of received beam data Rb (i.e., frame data) corresponding to one sum is represented in a two-dimensional data space in the azimuthal and depth directions. In Figure 4, multiple frame data sets with different sums are arranged in the sum direction, which is orthogonal to the azimuthal and depth directions.

[0035] In the data space of the received beam data Rb, multiple regions Re are defined in advance. In this embodiment, multiple regions Re are defined in the data space of the received beam data Rb for one frame, arranged in a two-dimensional direction without gaps. Note that a region Re does not necessarily need to cover the entire data space of the received beam data Rb for one frame; it is sufficient if it is defined to cover at least the area targeted for high-quality improvement of the ultrasound image. Each region Re in the data space of the received beam data Rb corresponds to each area on the ultrasound image. For convenience, in this specification, the area on the ultrasound image that corresponds to a region Re in the data space of the received beam data Rb is also referred to as region Re.

[0036] The S / N estimation unit 18 performs frequency analysis (e.g., FFT (Fast Fourier Transform)) on each of the multiple received beam data Rb, each with a different sum of received channel signals, before detection processing (i.e., possessing frequency information), for each region Re. Figure 5 shows the frequency spectrum of the received beam data Rb corresponding to one sum in one region Re. Frequency analysis processing by the S / N estimation unit 18 obtains a frequency spectrum for each region Re and for each sum of received channel signals.

[0037] As shown in Figure 5, multiple frequency regions F are predefined. A frequency region F represents a certain frequency range (for example, XX Hz to YY Hz). The S / N estimation unit 18 then calculates the spectral intensity Si for each frequency region F based on the acquired frequency spectrum. The spectral intensity Si may be a representative value (for example, the mean or median) of the spectral intensity included in that frequency region F. In this way, spectral intensity Si is acquired for each region Re, for each sum of received channel signals, and for each frequency region F.

[0038] Figure 6 shows the relationship between the summation number and spectral intensity in one region Re and one frequency region F. The S / N estimation unit 18 plots the spectral intensity against the summation number of the signal for each received channel in one region Re and one frequency region F in a two-dimensional data space of the summation number and spectral intensity of the received channel signal. The S / N estimation unit 18 then finds an approximate straight line AP of spectral intensity against the summation number of the signal for each plotted received channel and calculates the slope of the approximate straight line AP.

[0039] Here, the slope of the approximate straight line AP is a parameter that indicates the signal-to-noise ratio (S / N) index in the frequency range F of the region Re. The S / N index indicates the ratio of signal components to noise components; a larger S / N index indicates fewer noise components and more signal components, while a smaller S / N index indicates more noise components and fewer signal components.

[0040] Referring to Figures 2A-2D or 3A-3D, the signal components of the phase-corrected received channel signals of each received channel Ch included in the effective receiving aperture for the same transmitted beam are approximately the same in both phase and amplitude. Therefore, ideally, when these are added together N times, the signal components of each frequency range F become approximately N times greater. On the other hand, the noise components of each received channel signal are different in both phase and amplitude. Therefore, even when these are added together N times, the noise components of each frequency range F do not become N times greater, but rather smaller. When the N noise components of each received channel Ch are added together, the noise components of each frequency range F become approximately √N times greater.

[0041] Therefore, the more signal components there are in the received beam data Rb in a given region Re, the larger the S / N index becomes as the summation number increases. In other words, the slope of the approximate straight line AP of spectral intensity with respect to the summation number of signals for each received channel represents the S / N index. For example, ideally, if the received beam data Rb consists entirely of signal components, the spectral intensity also increases by N times when the summation number is N, so the slope of the approximate straight line AP is N / N, or 1. Conversely, if the received beam data Rb consists entirely of noise components, the spectral intensity increases by √N times when the summation number is N, so the slope of the approximate straight line AP is only √N / N times. As the signal components of the received beam data Rb increase (the noise components decrease), the slope of the approximate straight line AP increases from √N / N towards 1.

[0042] As described above, ideally, the signal components of the phase-corrected signals of each receiving channel Ch included in the effective receiving aperture for the same transmitting beam should be approximately the same. However, there may be cases where the signal components of the phase-corrected signals of each receiving channel Ch are not the same. For example, generally, the vibrating element of the ultrasonic probe 12 has sensitivity directivity that depends on the element size and the signal frequency, so the signal component of the receiving channel Ch closer to the center of the transmitting beam (e.g., receiving channel Cha in Figure 2D) may be larger than the signal component of the receiving channel Ch farther from the center of the transmitting beam (e.g., receiving channel Chb in Figure 2D). In this case, ideally, even if the received beam data Rb consists entirely of signal components, the spectral intensity may not be multiplied by N when the summation number is N.

[0043] Therefore, the S / N estimation unit 18 should correct the spectral intensity for each sum based on a correction coefficient that is predetermined for each sum of the received channel signal. The correction coefficient is predetermined based on the position of the receiving channel Ch to be added relative to the transmission beam center for each sum of the received channel signal, and can be stored in the memory 32. Then, as shown in Figure 7, the S / N estimation unit 18 calculates the corrected spectral intensity (black triangle in Figure 7) by correcting the spectral intensity (black circle in Figure 7) for each sum based on the correction coefficient for each sum. The S / N estimation unit 18 then finds an approximate straight line AP of the corrected spectral intensity for each sum in the two-dimensional data space of the sum of the received channel signal and the spectral intensity, and estimates the slope of the approximate straight line AP as the S / N index.

[0044] The S / N estimation unit 18 performs the above processing for each combination of region Re and frequency region F, and calculates the slope of the approximate straight line AP for each combination of region Re and frequency region F. In other words, the S / N estimation unit 18 estimates the S / N index for each combination of region Re and frequency region F based on the amount of increase in spectral intensity associated with an increase in the number of sums of received channel signals.

[0045] Figure 8 shows the S / N index for each frequency region F within a single region Re. As described above, the S / N estimation unit 18 estimates the S / N index for each combination of region Re and frequency region F. Therefore, for a single region Re, the S / N index is estimated for each frequency region F, as shown in Figure 8.

[0046] The signal processing unit 20 performs various signal processing operations on the received beam data from the transmitting / receiving unit 14, including filtering, such as applying a bandpass filter. In particular, the signal processing unit 20 generates a bandpass filter for each region Re and each frequency region F based on the S / N index estimated by the S / N estimation unit 18.

[0047] Referring to Figure 8, specifically, the signal processing unit 20 generates a bandpass filter for each region Re such that the estimated S / N index allows signals in frequency region F that are equal to or greater than a predetermined S / N threshold to pass through. For example, for a region Re having the S / N index for each frequency region F shown in Figure 8, a bandpass filter is generated that allows signals from frequency f1 to frequency f2 to pass through. Since the S / N index for each frequency region F can be different between each region Re, the bandpass filters generated for each region Re can also be different.

[0048] The signal processing unit 20 applies a bandpass filter generated for each region Re to the received beam data Rb before detection processing as an image quality enhancement process to improve the image quality of the ultrasound image. In other words, even if the S / N index for each frequency region F differs for each region Re, a bandpass filter suitable for each region Re can be applied. This makes it possible to adaptively enhance the image quality of each region Re of the ultrasound image. For example, in the ultrasound image, appropriate noise reduction can be performed for each position (region Re) without excessive noise suppression and loss of resolution. Thus, the signal processing unit 20 corresponds to the image quality enhancement unit.

[0049] The signal processing unit 20 can apply the above-described bandpass filter to multiple received beam data Rb stored in the beam data memory 16, each with a different sum of received channel signals, and to received beam data Rb of the same frame (i.e., frame data obtained by the same transmitted beam).

[0050] Furthermore, from the viewpoint of suppressing delays caused by the generation process of multiple received beam data Rb with different sums of received channel signals, and the S / N index estimation process by the S / N estimation unit 18, the signal processing unit 20 may use the received beam data Rb to which the bandpass filter is applied as the received beam data Rb of one or more frames later than the multiple received beam data Rb with different sums of received channel signals used to generate the bandpass filter.

[0051] Furthermore, if there is no change in the cross-section of the subject shown in the ultrasound image, the S / N index of each frequency area F in each region Re is not expected to change significantly. Therefore, the signal processing unit 20 may continue to use the bandpass filter for each region Re that has been generated once until the cross-section of the subject shown in the ultrasound image changes. Whether or not the cross-section of the subject shown in the ultrasound image has changed can be determined by comparing the ultrasound images formed by the image forming unit 24 (described later) between frames. Alternatively, an acceleration sensor may be provided on the ultrasound probe 12, and the orientation of the ultrasound probe 12 may be detected based on the signal from the acceleration sensor. If the orientation of the ultrasound probe 12 changes, it may be determined that the cross-section of the subject shown in the ultrasound image has changed.

[0052] The detection processing unit 22 performs detection processing (e.g., envelope detection processing) and logarithmic compression processing on the received beam data Rb after processing by the signal processing unit 20. Due to the detection processing by the detection processing unit 22, the received beam data Rb loses phase information (frequency information).

[0053] The image forming unit 24 forms an ultrasonic image (B-mode image) based on frame data that has been detected and processed in the detection processing unit 22.

[0054] The display control unit 26 controls the display of the ultrasound image formed by the image forming unit 24 and various other information on the display 28. The display 28 is a display device made of, for example, a liquid crystal display or an organic EL (Electro-Luminescence) display.

[0055] The input interface 30 consists of, for example, buttons, a trackball, a touch panel, etc. The input interface 30 is used to input user commands to the ultrasound diagnostic device 10.

[0056] Memory 32 is composed of a hard disk drive (Hard Disk Drive), SSD (Solid State Drive), eMMC (embedded Multi Media Card), or ROM (Read Only Memory). Memory 32 stores ultrasound diagnostic programs for operating each part of the ultrasound diagnostic device 10. The ultrasound diagnostic programs can also be stored on a computer-readable non-temporary storage medium such as a USB (Universal Serial Bus) memory or CD-ROM. The ultrasound diagnostic device 10 can read and execute ultrasound diagnostic programs from such storage media.

[0057] The control unit 34 is comprised of at least one general-purpose processor (e.g., a CPU (Central Processing Unit)) and a dedicated processor (e.g., a GPU (Graphics Processing Unit), an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or a programmable logic device). The control unit 34 may not consist of a single processing unit, but rather of multiple processing units located in physically separate locations working together. The control unit 34 controls each part of the ultrasound diagnostic device 10 according to the ultrasound diagnostic program stored in the memory 32.

[0058] The transmitting / receiving unit 14, S / N estimation unit 18, signal processing unit 20, detection processing unit 22, image forming unit 24, and display control unit 26 are each composed of one or more processors, chips, electrical circuits, etc. These units may also be realized through the cooperation of hardware and software.

[0059] <Second Embodiment> Figure 9 is a schematic diagram of the configuration of the ultrasound diagnostic apparatus 10-2 according to the second embodiment. In Figure 9, components that perform the same processing as the ultrasound diagnostic apparatus 10 according to the first embodiment are denoted by the same reference numerals as in Figure 1, and their descriptions are omitted.

[0060] The transmitting / receiving unit 40, acting as a received beam data generation unit, transmits a transmission signal to the ultrasonic probe 12 under control from the control unit 34. As a result, ultrasonic waves are transmitted from each vibrating element toward the subject. Ultrasonic waves are transmitted from multiple vibrating elements simultaneously, and the transmitting / receiving unit 14 controls the transmission timing of ultrasonic waves from each vibrating element, thereby transmitting ultrasonic beams in multiple directions from multiple vibrating elements. The transmitting / receiving unit 14 also receives received channel signals from each vibrating element that receives reflected waves from the subject. The transmitting / receiving unit 40 performs phase-alignment summation processing on multiple received channel signals corresponding to multiple received channels, thereby generating received beam data Rb.

[0061] The signal processing unit 42 performs various signal processing operations on the received beam data Rb from the transmitting / receiving unit 40, including filtering, such as applying a bandpass filter. In particular, the signal processing unit 42 generates a bandpass filter for each region Re and each frequency region F based on the S / N index for each region Re and each frequency region F estimated by the S / N estimation unit 48, which will be described later. Details of the bandpass filter generation process will be described later.

[0062] Furthermore, the signal processing unit 42 may skip (not perform bandpass filtering) on ​​the received beam data Rb used by the S / N estimation unit 48 described later. Alternatively, as preprocessing, a bandpass filtering with broadband characteristics that cuts only the DC (direct current) component may be performed.

[0063] The received beam data Rb processed by the signal processing unit 42 is stored in a memory (not shown) called the LRI memory. The LRI memory has a memory capacity that is sufficient to store at least enough received beam data Rb to generate one frame's worth of summed received beam data by the aperture synthesis process described later.

[0064] The aperture synthesis processing unit 44 performs intertransmittent aperture synthesis, which adds up multiple received beam data obtained based on different transmitted beams. Intertransmittent aperture synthesis will be described with reference to Figure 10. In Figure 10, scan line positions are shown in the lateral direction, and the scan line positions are numbered sequentially from the end. In this specification, the scan line position is represented by the variable j.

[0065] The transmitting / receiving unit 40 transmits a first transmit beam (hereinafter referred to as "transmit beam #1") and generates multiple received beam data Rb corresponding to multiple scan line positions (hereinafter, multiple received beam data Rb corresponding to transmit beam #1 will be referred to as "receive beam #1"). In the example in Figure 10, the transmitting / receiving unit 40 transmits transmit beam #1 centered on scan line position j=5, thereby generating received beam #1 corresponding to scan line positions j=1 to 9. In this specification, in the multiple received beam data Rb for a single transmit beam, numbers indicating the position within the beam are assigned sequentially from one end. In this specification, the position within the beam is represented by the variable k. In received beam #1, k=j. Note that the example in Figure 10 is a diagram that simulates the aperture synthesis process; in reality, the aperture synthesis processing unit 44 generates received beam data Rb for approximately 8 to 48 scan line positions for a single transmit beam.

[0066] Next, the transmitting / receiving unit 40 transmits a transmitting beam #2 that is shifted in position in the scanning direction relative to transmitting beam #1, and receives a receiving beam #2 in response to it. In the example in Figure 10, transmitting beam #2 is transmitted with scan line position j=6 as the center, and as a result, receiving beam #2 corresponding to scan line positions j=2 to 10 is received. In receiving beam #2, k=j-1. Subsequently, the transmitting / receiving unit 40 transmits a transmitting beam #3 that is further shifted in position in the scanning direction relative to transmitting beam #2, and receives a receiving beam #3 in response to it. In the example in Figure 10, transmitting beam #3 is transmitted with scan line position j=7 as the center, and as a result, receiving beam #3 corresponding to scan line positions j=3 to 11 is received. In receiving beam #3, k=j-2.

[0067] By repeating this process, multiple received beam data Rb can be obtained for a single scan line position j. The maximum number of received beam data Rb obtained for a single scan line position j is the same as the number of transmissions of the transmitted beam. If we let the transmitted beam number (received beam number) be h, and the received beam data Rb corresponding to the in-beam position k in the received beam #h be represented as LRI(h,k), then if the number of received beam data Rb contained in the received beam #h is 9, then for example, the received beam data Rb corresponding to the scan line position j=12 will be the following 9. LRI(4,9), LRI(5,8), LRI(6,7), LRI(7,6), LRI(8,5), LRI(9,4), LRI(10,3), LRI(11,2), LRI(12,1)

[0068] The aperture synthesis processing unit 44 generates summed received beam data corresponding to each scan line position j by adding (combining) multiple received beam data Rb corresponding to the same scan line position j. The aperture synthesis process provides effects such as improved signal-to-noise ratio or resolution in the azimuthal direction.

[0069] In this embodiment, the aperture synthesis processing unit 44 generates multiple summed received beam data sets with different sums of multiple received beam data Rb corresponding to the same scan line position j, under control from the control unit 34. For example, the aperture synthesis processing unit 44 generates multiple summed received beam data sets with sums of 3, 5, 7, and 9 of the received beam data Rb. For example, summed received beam data at the scan line position j=12 is generated as RF J=12 When written as (N) (where N is the number of additions), as described above, if 9 received beam data Rb lines corresponding to the scan line position j=12 are acquired, the summed received beam data RF will be calculated when the number of additions is 3, 5, 7, or 9. J=12 (N) could be, for example, as follows: RF J=12 (3)=LRI(7,6)+LRI(8,5)+LRI(9,4) RF J=12(5)=LRI(6,7)+LRI(7,6)+LRI(8,5)+LRI(9,4)+LRI(10,3) RF J=12 (7)=LRI(5,8)+LRI(6,7)+LRI(7,6)+LRI(8,5)+LRI(9,4)+LRI(10,3)+LRI(11,2) RF J=12 (9)=LRI(4,9)+LRI(5,8)+LRI(6,7)+LRI(7,6)+LRI(8,5)+LRI(9,4)+LRI(10,3)+LRI(11,2)+LRI(12,1) Of course, the received beam data Rb to be added is not limited to the above; for example, if the number of additions is 3, LRI(6,7), LRI(8,5), and LRI(10,3) may be added together.

[0070] In this embodiment, the aperture synthesis processing unit 44 generates multiple summed received beam data (summed frame data) for one frame, each with a different sum of received beam data Rb. The aperture synthesis processing unit 44 does not necessarily need to generate summed received beam data for the entire frame for each sum; it only needs to generate summed received beam data that covers at least the target area for improving the image quality of the ultrasound image.

[0071] As described above, in the second embodiment, the aperture synthesis processing unit 44 corresponds to the addition data generation unit.

[0072] Multiple summed received beam data sets, each with a different sum of received beam data Rb, generated by the aperture synthesis processing unit 44, are stored in the beam data memory 46. Figure 4 shows multiple summed received beam data sets SRb, each with a different sum of received beam data Rb, stored in the beam data memory 46. Similar to the first embodiment, in the second embodiment as well, multiple regions Re are defined in advance in the data space of the summed received beam data SRb. Note that the data space of the summed received beam data SRb, like the data space of the received beam data Rb, is a data space defined by the azimuthal direction and the depth direction; therefore, the data space of the summed received beam data SRb and the data space of the received beam data Rb are substantially synonymous.

[0073] The S / N estimation unit 48 performs frequency analysis on each of several summed received beam data SRb, each with a different sum of received beam data Rb before detection processing (i.e., containing frequency information), for each region Re. As a result, a frequency spectrum (see Figure 5) is obtained for each region Re and for each sum of received beam data Rb.

[0074] The S / N estimation unit 48, similar to the first embodiment, calculates the spectral intensity Si for each frequency region F based on the acquired frequency spectrum, and obtains the spectral intensity Si for each region Re, each sum of received beam data Rb, and each frequency region F. The S / N estimation unit 48 then plots the spectral intensity for each sum of received beam data Rb for one region Re and one frequency region F in a two-dimensional data space of the sum of received beam data Rb and spectral intensity (see Figure 6). The S / N estimation unit 48 then finds an approximate straight line AP of spectral intensity for each plotted sum of received beam data Rb, and calculates the slope of the approximate straight line AP.

[0075] Here again, the slope of the approximate straight line AP is a parameter that indicates the S / N ratio index in the frequency region F of the region Re. Similar to the received channel signal in the first embodiment, the signal components of multiple received beam data Rb corresponding to the same scan line position are signals with approximately the same phase and amplitude. Therefore, ideally, when these are added together N times, the signal components of each frequency region F become approximately N times greater. On the other hand, the noise components of multiple received beam data Rb corresponding to the same scan line position are different in phase and amplitude. Therefore, when these are added together N times, the noise components of each frequency region F do not become N times greater, but only a smaller value (approximately √N times).

[0076] Therefore, the more signal components there are in multiple received beam data Rb corresponding to the same scan line position, the larger the S / N index becomes as the summation number increases. In other words, the slope of the approximate straight line AP of spectral intensity with respect to the summation number of each received beam data Rb represents the S / N index.

[0077] As described above, ideally, when the signal components of multiple received beam data Rb corresponding to the same scan line position are added together N times, the signal component of each frequency area F will be N times greater. However, there are cases where this is not the case. For example, the signal component of the received beam data Rb corresponding to a scan line position close to the center of the transmitted beam (for example, the received beam data Rb corresponding to scan line position 5 in received beam #1 in Figure 10) may be larger than the signal component of the received beam data Rb corresponding to a scan line position far from the center of the transmitted beam (for example, the received beam data Rb corresponding to scan line position 1 in received beam #1 in Figure 10). Therefore, for example, if the summation number is 2, and two received beam data Rb values ​​close to the center of the transmitted beam (e.g., LRI(8,5) and LRI(9,4)) are added together, and if the summation number is 4, and received beam data Rb values ​​including those far from the center of the transmitted beam (e.g., LRI(5,8), LRI(8,5), LRI(9,4), and LRI(12,1)) are added together, even if all of the received beam data Rb values ​​are signal components, the spectral intensity when the summation number is 4 may not be twice that when the summation number is 2.

[0078] Therefore, the S / N estimation unit 48 should correct the spectral intensity for each sum of received beam data Rb based on a correction coefficient that is predetermined for each sum of received beam data Rb. The correction coefficient is predetermined based on the in-beam position k of the received beam data Rb to be added for each sum of received beam data Rb, and can be stored in the memory 32. Then, the S / N estimation unit 48 calculates a corrected spectral intensity for each sum based on the correction coefficient for each sum, finds an approximate straight line AP of the corrected spectral intensity for each sum (see Figure 7), and estimates the slope of the approximate straight line AP as the S / N index.

[0079] The S / N estimation unit 48 performs the above processing for each combination of region Re and frequency region F, and calculates the slope of the approximate straight line AP for each combination of region Re and frequency region F. In other words, the S / N estimation unit 48 estimates the S / N index for each combination of region Re and frequency region F based on the amount of increase in spectral intensity associated with an increase in the number of sums of received beam data Rb (see Figure 8).

[0080] The signal processing unit 42 generates a bandpass filter for each region Re such that the estimated S / N index allows signals in frequency region F to pass through if the S / N index is equal to or greater than a predetermined S / N threshold. For example, for a region Re having the S / N index for each frequency region F shown in Figure 8, a bandpass filter is generated that allows signals from frequency f1 to frequency f2 to pass through. Since the S / N index for each frequency region F can be different between each region Re, the bandpass filters generated for each region Re can also be different.

[0081] The signal processing unit 42 applies a bandpass filter generated for each region Re to the received beam data Rb before detection processing as an image quality enhancement process to improve the image quality of the ultrasound image. In other words, even if the S / N index for each frequency region F differs for each region Re, a bandpass filter suitable for each region Re can be applied. This makes it possible to adaptively enhance the image quality of each region Re of the ultrasound image. For example, in the ultrasound image, appropriate noise reduction can be performed for each position (region Re) without excessive noise suppression and loss of resolution. Thus, in the second embodiment as well, the signal processing unit 42 corresponds to the image quality enhancement unit.

[0082] The signal processing unit 42 can apply the above-described bandpass filter to the received beam data Rb of the same frame as the received beam data Rb that was the source of the multiple summed received beam data SRb stored in the beam data memory 46. Furthermore, from the viewpoint of suppressing delays caused by the generation process of multiple summed received beam data SRb with different sums of received beam data Rb, and the S / N index estimation process by the S / N estimation unit 48, the signal processing unit 42 may choose the received beam data Rb to which the bandpass filter is applied to be the received beam data Rb of the frame immediately following the received beam data Rb that was the source of the multiple summed received beam data SRb. Moreover, if there is no change in the cross-section of the subject shown in the ultrasound image, it is considered that the S / N index of each frequency area F in each region Re will not change so significantly. Therefore, in the second embodiment as well, the signal processing unit 42 may continue to use the bandpass filter for each region Re that has been generated once until the cross-section of the subject shown in the ultrasound image changes.

[0083] <Third Embodiment> Figure 11 is a schematic diagram of the configuration of the ultrasound diagnostic apparatus 10-3 according to the third embodiment. In Figure 11, components that perform the same processing as the ultrasound diagnostic apparatus 10 according to the first embodiment are denoted by the same reference numerals as in Figure 1, and their descriptions are omitted.

[0084] The transmitting / receiving unit 50, acting as a received beam data generation unit, transmits a transmission signal to the ultrasonic probe 12 under control from the control unit 34. As a result, ultrasonic waves are transmitted from each vibrating element toward the subject. Ultrasonic waves are transmitted from multiple vibrating elements simultaneously, and the transmitting / receiving unit 14 controls the transmission timing of ultrasonic waves from each vibrating element, thereby transmitting ultrasonic beams in multiple directions from multiple vibrating elements. The transmitting / receiving unit 14 also receives received channel signals from each vibrating element that receives reflected waves from the subject. The transmitting / receiving unit 50 performs phase-alignment summation processing on multiple received channel signals corresponding to multiple received channels, thereby generating received beam data Rb.

[0085] The signal processing unit 52 performs various signal processing operations on the received beam data Rb from the transmitting / receiving unit 50, including filtering, such as applying a bandpass filter. In particular, the signal processing unit 52 generates a bandpass filter for each region Re and each frequency region F based on the S / N index for each region Re and each frequency region F estimated by the S / N estimation unit 58, which will be described later. Details of the bandpass filter generation process will be described later.

[0086] Furthermore, the signal processing unit 52 may choose not to perform bandpass filtering on the received beam data Rb that constitutes the frame data used by the S / N estimation unit 58, described later. Alternatively, as a preprocessing step, a bandpass filter with broadband characteristics that cuts only the DC-near component may be performed.

[0087] The received beam data Rb processed by the signal processing unit 52 is stored in a memory called LRI memory (not shown). The LRI memory has a memory capacity capable of storing at least multiple frames of received beam data Rb.

[0088] The frame summer 54 generates one frame of added received beam data by adding up multiple frame data, which are received beam data Rb for one frame. Specifically, the frame summer 54 generates one frame of added received beam data by adding up multiple frame data so that received beam data Rb corresponding to the same scan line position are added together. The frame summer 54 also generates multiple frames of added received beam data (hereinafter referred to as "added frame data") with different numbers of added frame data.

[0089] The multiple frame data added by the frame summer 54 are frame data obtained based on transmitted beams sent to the same scanning plane. In other words, each frame data consists of received beam data Rb corresponding to the same scan line position. For example, the multiple frame data added by the frame summer 54 are frame data acquired continuously in time series while the orientation of the ultrasonic probe 12 is maintained.

[0090] As described above, in the third embodiment, the frame addition unit 54 corresponds to the addition data generation unit.

[0091] Multiple added frame data, each with a different number of additions to the frame data, generated by the frame summing unit 54, are stored in the frame data memory 56. Similar to the first embodiment, in the third embodiment, multiple regions Re are defined in advance in the data space of the frame data (i.e., received beam data Rb).

[0092] The S / N estimation unit 58 performs frequency analysis on each of the received beam data Rb that constitutes multiple summed frame data with different sums of frame data, before detection processing (i.e., possessing frequency information), for each region Re. As a result, a frequency spectrum (see Figure 5) is obtained for each region Re and for each sum of frame data.

[0093] The S / N estimation unit 58, similar to the first embodiment, calculates the spectral intensity Si for each frequency region F based on the acquired frequency spectrum, and obtains the spectral intensity Si for each region Re, each number of frame data additions, and each frequency region F. The S / N estimation unit 58 then plots the spectral intensity for each number of frame data additions for one region Re and one frequency region F in a two-dimensional data space of the number of frame data additions and spectral intensity (see Figure 6). The S / N estimation unit 58 then finds an approximate straight line AP of spectral intensity for each plotted number of frame data additions, and calculates the slope of the approximate straight line AP.

[0094] Here again, the slope of the approximate straight line AP is a parameter that indicates the S / N ratio index in the frequency region F of the region Re. Similar to the received channel signal in the first embodiment, the signal components of multiple received beam data Rb corresponding to the same scan line position are signals with approximately the same phase and amplitude. Therefore, ideally, when these are added together N times, the signal components of each frequency region F become approximately N times greater. On the other hand, the noise components of multiple received beam data Rb corresponding to the same scan line position are different in phase and amplitude. Therefore, when these are added together N times, the noise components of each frequency region F do not become N times greater, but only a smaller value (approximately √N times).

[0095] Therefore, the more signal components there are in multiple received beam data Rb corresponding to the same scan line position, the larger the S / N index becomes as the number of sums increases. In other words, the slope of the approximate straight line AP of spectral intensity with respect to the number of sums of each frame data represents the S / N index.

[0096] The S / N estimation unit 58 performs the above processing for each combination of region Re and frequency region F, and calculates the slope of the approximate straight line AP for each combination of region Re and frequency region F. In other words, the S / N estimation unit 58 estimates the S / N index for each combination of region Re and frequency region F based on the amount of increase in spectral intensity due to the increase in the number of added frame data (see Figure 8).

[0097] The signal processing unit 52 generates a bandpass filter for each region Re such that the estimated S / N index allows signals in frequency region F that are equal to or greater than a predetermined S / N threshold to pass through. For example, for a region Re having the S / N index for each frequency region F shown in Figure 8, a bandpass filter is generated that allows signals from frequency f1 to frequency f2 to pass through. Since the S / N index for each frequency region F can be different between each region Re, the bandpass filters generated for each region Re can also be different.

[0098] The signal processing unit 52 applies the bandpass filters generated for each region Re to the received beam data Rb before detection processing as an image quality enhancement process to improve the image quality of the ultrasound image. In other words, even if the S / N index for each frequency region F differs for each region Re, a bandpass filter suitable for each region Re can be applied. This makes it possible to adaptively enhance the image quality of each region Re of the ultrasound image. For example, in the ultrasound image, appropriate noise reduction can be performed for each position (region Re) without excessive noise suppression and loss of resolution. Thus, in the third embodiment as well, the signal processing unit 52 corresponds to the image quality enhancement unit.

[0099] The signal processing unit 52 can apply the above-described bandpass filter to the received beam data Rb of the next frame of the received beam data Rb that constitutes multiple frame data stored in the frame data memory 56. Furthermore, if there is no change in the cross-section of the subject shown in the ultrasound image, the S / N index of each frequency area F in each region Re is not expected to change significantly. Therefore, in the third embodiment as well, the signal processing unit 42 may continue to use the bandpass filter for each region Re that has been generated once until the cross-section of the subject shown in the ultrasound image changes.

[0100] Although embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications are possible without departing from the spirit of the invention. [Explanation of Symbols]

[0101] 10,10-2,10-3 Ultrasound diagnostic device, 12 Ultrasound probe, 12a Vibration element, 14,40,50 Transmitting / receiving unit, 16,46 Beam data memory, 18,48,58 S / N estimation unit, 20,42,52 Signal processing unit, 22 Detection processing unit, 24 Image forming unit, 26 Display control unit, 28 Display, 30 Input interface, 32 Memory, 34 Control unit, 44 Aperture synthesis processing unit, 56 Frame data memory, 54 Frame summing unit, Ch Received channel, Rb Received beam data, Re Region, F Frequency division, AP Approximate straight line.

Claims

1. An additive data generation unit that generates received beam data by adding together multiple received channel signals corresponding to multiple received channels obtained by transmitting and receiving ultrasound waves to a subject, and which have been phase-corrected by a phase-correction process, wherein the additive data generation unit generates multiple received beam data sets in which the sum of the received channel signals differs from one another, An S / N estimation unit performs frequency analysis on each of the multiple received beam data sets, each with a different sum of the received channel signals before detection processing, for each predetermined region in the data space of the received beam data, and estimates the S / N index for each region and frequency area based on the increase in spectral intensity with increasing sum. A high-image-quality enhancement unit that performs different high-image-quality processing for each region in order to enhance the image quality of the ultrasound image based on the S / N index estimated for each region and each frequency area, An ultrasound diagnostic device characterized by being equipped with the following features.

2. A received beam data generation unit generates received beam data by performing a phase-aligned summation process on multiple received channel signals corresponding to multiple received channels obtained by transmitting and receiving ultrasound waves to a subject, An additive data generation unit that generates added received beam data by adding up a plurality of received beam data corresponding to the same scan line position, the additive data generation unit that generates a plurality of added received beam data where the number of additions of the plurality of received beam data differs from one another, An S / N estimation unit performs frequency analysis on each of the multiple summed received beam data before detection processing for each predetermined region in the data space of the received beam data, and estimates the S / N index for each region and frequency area based on the amount of increase in spectral intensity with increasing summation. A high-image-quality enhancement unit that performs different high-image-quality processing for each region in order to enhance the image quality of the ultrasound image based on the S / N index estimated for each region and each frequency area, An ultrasound diagnostic device characterized by being equipped with the following features.

3. The image enhancement unit generates a bandpass filter for each region and frequency area based on the S / N index estimated for each region and frequency area, and applies the generated bandpass filter for each region to the received beam data before detection processing. The ultrasound diagnostic apparatus according to claim 1 or 2.

4. The summing data generation unit generates the summing received beam data by inter-transmission aperture synthesis, and generates a plurality of summing received beam data sets in which the summing number of the received beam data in the inter-transmission aperture synthesis is different from each other. The ultrasound diagnostic apparatus according to feature 2.

5. The summing data generation unit generates summing received beam data by adding up multiple frame data, which are multiple received beam data for one frame, and generates multiple summing received beam data with different summing counts for each frame data. The ultrasound diagnostic apparatus according to feature 2.

6. The S / N estimation unit calculates the slope of the approximate straight line for each summation number and spectral intensity in the two-dimensional data space of the summation number and spectral intensity for each region and frequency area, and estimates the calculated slope as the S / N index for each region and frequency area. The ultrasound diagnostic apparatus according to claim 1 or 2.

7. The S / N estimation unit calculates a corrected spectral intensity by correcting the spectral intensity based on a predetermined correction coefficient for each sum, and estimates the slope of the approximate line for the corrected spectral intensity for each sum in the two-dimensional data space as the S / N index. The ultrasound diagnostic apparatus according to feature 6.

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