JPH1014917A - Ultrasonic imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve an image display luminance value by a method wherein the distribution of an image signal level is computed corresponding to an interest area set by an ROI setter to control the display luminance value with respect to a received signal level based on the results. SOLUTION: An ROI setter 14 sets ROI about a reflection echo signal stored in a line memory 11. A depth gain control curve computation memory 15 extracts a part representing a depth and the direction of a beam of the reflection echo signal corresponding to the set ROI to compute the histogram of the luminance of the signal. The center and an average luminance of a luminance occurrence frequency distribution are determined for the histogram. Then, an absolute value of a difference between both the values is compared with a fixed value to judge the presence of correction. In other words, when the absolute value is large, a display dynamic range set value is referred to correct a luminance/echo level function coefficient generated by an arithmetic processing section 16. When the absolute value is small, no correction is needed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for transmitting an ultrasonic beam into a subject, receiving an echo signal of the ultrasound beam, obtaining a tomographic image of a diagnostic site inside the subject, and displaying the image on an image display unit. In particular, for a region of interest in a subject, a logarithmic value of an echo signal level such that a display level of the echo signal on an image becomes an appropriate value within a display dynamic range. The present invention relates to an ultrasonic imaging apparatus capable of automatically controlling a display luminance value curve and / or an echo signal detection sensitivity of an ultrasonic circuit.

[0002]

2. Description of the Related Art A conventional ultrasonic imaging apparatus includes a probe for transmitting / receiving an ultrasonic beam to / from an object, and transmitting an ultrasonic pulse to the probe to generate an ultrasonic beam for scanning the object. A transmission / reception circuit that generates and receives and amplifies an echo signal from a diagnostic site and forms a reception beam, and amplifies the echo signal by giving different gains to the echo signal at different depths determined by the arrival time of the reflected echo to the probe. A signal processing circuit for further processing a video signal; inputting and digitizing an echo signal output from the signal processing circuit; storing the echo signal for each scan of the ultrasonic beam; A digital scan converter for reading out stored contents in synchronization with the digital scan converter, and an image display for displaying an output signal from the digital scan converter. Further, within the transmission / reception circuit unit, a transmission circuit for transmitting a transmission pulse to the probe to generate an ultrasonic beam is provided, and a reception circuit for receiving and amplifying an echo signal returned from the diagnostic site is provided. A receiving circuit is provided,
Further, a depth gain control unit for controlling a gain and a frequency band for each depth of the received echo signal is provided. In such a conventional ultrasonic imaging apparatus, automatic control of a display luminance value curve with respect to a reception signal level (Automa
tic Signal-Brightness Curve Control: ASBCC)
The first method is to control the gain of reception amplification instantaneously according to the echo level within the transmission / reception period of one ultrasonic beam. There is a method of controlling the gain of reception amplification on average according to the brightness of an ultrasonic image. The principle of each system is based on AGC (Automatic Gain Control).

[0003]

However, in the ASBCC method using AGC in these conventional ultrasonic imaging apparatuses, in any of the above-mentioned methods, the echo level is simply determined irrespective of the region of interest in the subject to be imaged. Control the gain of the reception amplification instantaneously, or control the gain of the reception amplification on average according to the brightness of the ultrasound image in frame units. Cannot be automatically controlled to obtain an appropriate contrast. Therefore, for example, in the case of a person who is fat and has low ultrasonic permeability, or a person who easily transmits ultrasonic waves such as an infant, the gain setting of the apparatus may not be properly set.

In view of the above problems, the present invention has as its first object to be able to set a good image display luminance value with respect to a received echo signal level for a region of interest in a subject. Another object of the present invention is to make it possible to automatically control the echo detection sensitivity.

[0005]

SUMMARY OF THE INVENTION In order to achieve the first object, the present invention provides an ultrasonic probe for transmitting and receiving ultrasonic waves to and from a subject, and transmitting a transmission pulse to the probe. An ultrasonic circuit unit that receives and amplifies an echo signal returned from a diagnostic site in the subject while giving an ultrasonic beam, amplifies the received echo signal by applying a gain corresponding to the depth at which the reflected echo occurs, and then performs video signal processing; and A digital scan converter section for digitally converting and storing the echo signal output from the sound wave circuit section and reading out the stored content in synchronization with the scanning signal of the image display section; and converting the output signal from the digital scan converter section into a video signal. An image display unit that converts and displays an ultrasonic image, and an ultrasonic imaging apparatus that controls each of the components and scans the inside of the subject with an ultrasonic beam to obtain the ultrasonic image In the digital scan converter unit, an ROI setting device that sets a region of interest to be diagnosed by an operator on a displayed image, and a video signal level corresponding to the region of interest set by the ROI setting device. An arithmetic processing unit for calculating the distribution; and a region-of-interest luminance control means for generating a display luminance value curve with respect to the reception signal level of the region of interest using the operation result of the arithmetic processing unit; The area portion is automatically controlled to an appropriate luminance and displayed.

In order to achieve the first object of the present invention, the region-of-interest luminance value control means generates a display luminance value curve for a received signal level comprising a plurality of continuous logarithmic functions according to the received signal level. Preferably, it occurs.

According to another aspect of the present invention, there is provided an ultrasonic probe for transmitting and receiving ultrasonic waves to and from an object, and transmitting a transmission pulse to the probe to generate an ultrasonic beam. An ultrasonic circuit unit that receives and amplifies an echo signal that is generated and returned from a diagnostic site in the subject, applies a gain according to the depth at which the reflected echo has occurred, amplifies the signal, and performs video signal processing after amplification.
A digital scan converter for digitally converting and storing the echo signal output from the ultrasonic circuit unit and reading out the stored content in synchronization with the scanning signal of the image display unit; and converting the output signal from the digital scan converter unit into a video signal. An image display unit that converts the signal into a signal and displays the same as an ultrasonic image; and an ultrasonic imaging apparatus that controls the components and scans the inside of the subject with an ultrasonic beam to obtain the ultrasonic image. In the department,
An ROI setting unit that sets a region of interest to be diagnosed by the scanner on the displayed image; a calculation processing unit that calculates a distribution of a video signal level corresponding to the region of interest set by the ROI setting unit; A depth gain control curve calculation memory for calculating and storing a gain control curve for a beam direction and a depth corresponding to a region of interest based on a calculation result of a calculation processing unit, and a display brightness value curve for a received signal level from a target ROI. Means for correcting and calculating according to the received signal level, and / or controlling a gain for each depth in the ultrasonic circuit section by the gain control curve.

[0008] In order to achieve the second object of the present invention, the gain control means generates a display luminance value curve for a received signal level composed of a plurality of continuous logarithmic functions according to the received signal level. It is preferred that

In the above arrangement, the range of the echo level including the low-level and high-frequency appearance echoes and the high-level and high-frequency appearance echo is set within the subject so that the luminance range has good visibility on the image. The function of the display brightness with respect to the received echo signal level is controlled so that the display brightness of the echo signal is automatically controlled so as to have an appropriate contrast at the diagnosis site for the region of interest, and the function alone cannot control with sufficient accuracy. In this case, a depth gain control curve is generated and controlled according to the beam direction and the depth.

[0010]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a block diagram showing a schematic configuration of an embodiment of an ultrasonic imaging apparatus according to the present invention. This ultrasonic imaging apparatus transmits and receives an ultrasonic beam to and from a subject, obtains a tomographic image of a diagnostic site, and displays the tomographic image on an image display unit. As shown in FIG.
, An ultrasonic circuit unit 2, a digital scan converter unit (hereinafter abbreviated as a DSC unit) 3, and an image display unit 4. The probe 1 transmits and receives an ultrasonic beam to and from the subject. Although not shown, the probe 1 includes, for example, n elongated rod-shaped piezoelectric vibrators that transmit ultrasonic waves and receive reflected echoes. Are arranged in a vibrator element array. The ultrasonic circuit unit 2 transmits a transmission pulse to the probe 1 to generate an ultrasonic beam, receives and amplifies an echo signal from a diagnostic site, and converts the echo signal into a probe of the reflected echo. And a video signal is processed by giving a gain for each depth determined by the arrival time of the signal, and further includes a transmitting circuit 5 and a receiving circuit 6 therein.
, A transmission / reception separation circuit 7, a probe switching scanning section 8, a depth gain control section 9, and a video signal processing section 10.

The transmission circuit 5 delays transmission pulses of m (m: 1, 2, 3,...) Channels which are simultaneously transmitted to form an ultrasonic beam, and controls the transmission of the ultrasonic beam. The transmission signal is changed to n (n: 1, 2, 2,
3,..., N ≧ m) are sent to the probe 1 having the elements. The receiving circuit 6 inputs and amplifies the echo signals reflected by the diagnostic site in the subject and received by the probe 1, and corrects the phase difference or delay time difference between the echo signals of each channel. It adds and forms a receiving beam and deflects it. The transmission / reception separation circuit 7
The effect of the transmission signal from the transmission circuit 5 on the reception circuit 6 is minimized or the reception signal 6 is separated so as not to be destroyed. The probe switching and scanning unit 8 scans an ultrasonic beam by selecting m channels from the transducer element array of n elements of the probe 1 and sequentially selecting channels for forming beams, or This is to switch to a probe having a different number of transducer elements. Further, the depth gain control section 9 amplifies the echo signal received and amplified by the wave receiving circuit 6 by giving a gain for each depth determined by the arrival time at the probe. Each gain and a frequency band for taking in an echo with respect to a depth for preventing attenuation by the depth of the echo are controlled. The video signal processing unit 10 performs processes such as logarithmic conversion of the level, detection, and linearity equalization (Equalization) on the gain-controlled echo signal.

The DSC unit 3 is provided with the ultrasonic circuit unit 2.
And input the echo signal from
An echo signal obtained based on the ultrasonic beam scanning method is stored and converted into the X, Y scanning method of the display device and output. More specifically, one or more echo signals are provided for each line of the ultrasonic beam. A line memory 11 for storing signals, converting the level shift or γ characteristics as necessary, and outputting the signals; interpolating the echo signals stored in the line memory 11 in accordance with an X, Y two-dimensional display format and performing scan conversion And a control circuit 13 for controlling the operation of each of the above components.

The image display unit 4 is provided with the DSC unit 3
Is converted into a video signal and displayed as an ultrasonic image, and is composed of, for example, a CRT.

Here, in the present invention, an ROI setting unit 14, a depth gain control curve calculation memory 15, and a calculation processing unit 16 are provided inside the DSC unit 3.
The ROI setting unit 14 sets a region of interest (hereinafter abbreviated as ROI) that is significant on a diagnosis target on the screen of the image display unit 4. The depth gain control curve calculation memory 15 calculates, stores, and outputs a gain control curve (hereinafter, referred to as a TGC curve) for the beam direction and the depth corresponding to the ROI set by the ROI setting unit 14. The depth gain control unit 9 in the ultrasonic circuit unit 2 controls the gain for each depth using the value read from the depth gain control curve calculation memory 15. The arithmetic processing unit 16 extracts a video signal corresponding to the ROI set by the ROI setting unit 14 of the image formed by the scan converter 12, and according to the set display dynamic range, as shown in FIG. (Luminance) histogram is calculated, and if the luminance appearance frequency distribution is shifted toward higher luminance than the average luminance, the luminance at that part is decreased. The image display luminance for the received signal level is corrected and calculated so as to increase the luminance, and the signal level after A / D conversion and storage of the echo signal is shifted to automatically adjust the luminance of the image to an appropriate level. Control.

The display brightness B of the image can be expressed as a function of the received signal level S as follows. B = 20 · a · Log10 (S) + C (1)

However, since the display dynamic range is generally set and determined on the device, it is necessary to assign the signal level of the nominal dynamic range to the entire range of the display screen luminance. Since the range range is generally wider than the nominal display dynamic range as shown in FIG. 3, the low level range of the received signal level and the high level range of the received signal level are:
If the signal level is assigned to the outside or the end of the display screen luminance range, and the signal level difference is not displayed in that range, or even if it is displayed, the difference is very small, so if there is a signal level of the lesion in that range Is very difficult to diagnose,
The lesion may be missed.

Therefore, according to the present invention, as shown in FIG. 3, the coefficient a and the coefficient a of the above equation (1) are adjusted so that the curve is continuous according to the three level ranges of the low level range, the nominal display dynamic range, and the high level range. c is separately controlled to compensate the echo signal. That is, the low level range (S0 ≦ S ≦ S
For the echo signal level S (dB) of 1), B1 = a
1 · S + c1, within the display dynamic range (S1 ≦ S ≦
For the echo signal level of S2), B2 = a2 · S +
c2, B3 = a3 · S + c3 for the echo signal level in the high level range (S2 ≦ S ≦ S3). Of these, the slope a2 of the curve within the display dynamic range is
It is necessary to allocate most of the full scale of the display screen luminance to this area from the demand for diagnosis, and the constant is determined by the set value DR of the dynamic range in order to keep the contrast of the image in the diagnosis area constant. Here, the relationship between S1 and S2 according to the set value DR of the dynamic range is DR
= S2-S1. Further, the slopes a1 and a3 of the curves with respect to the echo signal levels in the low level range and the high level range are not required to have a contrast resolution, but are constant values smaller than a2 so that the general structure of the subject can be understood. In this method, S1 and S2 for the signal level S or B1 and B2 for the display screen brightness B
Is adaptively controlled according to the signal level, it is possible to control the display brightness of the diagnostic area to be constant or to have a desired level range while keeping the contrast constant.

This control process is performed by the scan converter 12
1 can be scaled in the line memory 11 and sent to the scan converter as a video signal as shown in FIG. 1, and if the bit length of the scan converter 12 is sufficient, 2, the same effect can be achieved by converting the output of the scan converter 12 into brightness by the level conversion unit 17 and sending it to the image display unit 4.

When the dynamic range of the ultrasonic reception signal is so wide that it cannot be captured with the same gain, it is necessary to control the gain at the same time. In that case, the depth gain control curve calculation memory 15 takes out a portion of the echo signal stored in the line memory 11 corresponding to the depth and beam direction corresponding to the ROI set by the ROI setting unit 14, and the level (luminance) thereof. Is calculated, and a correction value is added to the TGC curve so that if the appearance frequency distribution of the luminance is shifted to a higher luminance than the average luminance, the gain in that part is reduced.
When a distribution deviated to a low luminance is shown, a correction value is added to the TGC curve so that the gain at that portion is increased, and stored and output as a TGC curve. Since the gain is controlled by the corrected TGC curve, an image is formed by the corrected TGC gain curve after the next frame to be visualized, so that the luminance of the image is evenly averaged.

In summary, a mechanism for setting an ROI on an ultrasonic image display screen, a mechanism for calculating and storing a histogram of a video signal level corresponding to the ROI, and a mechanism for performing a phasing and video signal processed A mechanism for performing A / D conversion / storage and level shift of the sound wave circuit section output, and correcting / calculating an image display luminance curve with respect to the received signal level so as to reduce the deviation of the histogram distribution;
A line memory for shifting the signal level after the A / D conversion and storage and / or storing a plurality of echo levels in a depth of interest range on one line of the ultrasonic beam, and a histogram of the echo levels on the memory And a mechanism for calculating and generating a depth gain curve so that the deviation of the histogram distribution is reduced. When sufficient correction is not possible with the former correction calculation, the depth gain curve is calculated. It operates to calculate and generate a curve.

Next, a procedure for calculating a function control curve of luminance and an echo level in the ultrasonic imaging apparatus thus configured will be described with reference to the flowchart of FIG. First, in FIG. 1, an echo signal is collected by the probe 1 and the ultrasonic circuit unit 2 for a diagnostic part of a subject in the same manner as a normal ultrasonic imaging apparatus. The collected echo signals are sent to the DSC unit 3 via the video signal processing unit 10. The DSC unit 3 temporarily stores the transmitted echo signal in the line memory 11 in the DSC unit 3.

Next, the echo signal read from the line memory 11 is sent to a depth gain control curve calculation memory 15 in the DSC unit 3. Then, the depth gain control curve calculation memory 15 inputs a luminance distribution corresponding to the level of each time of the echo signal. (Step A in FIG. 2). On the other hand, in this state, the reflected echo signal stored in the line
OI is set (step B). Next, the depth gain control curve calculation memory 15 extracts a portion corresponding to the depth and beam direction corresponding to the ROI set for the reflected echo signal stored in the line memory 11, and generates a histogram of the level (luminance). Calculation is performed (step C). Then, for this histogram, the center of gravity of the appearance frequency distribution of the luminance is calculated (step D), and the average luminance is calculated (step E).

Next, the difference between the luminance frequency centroid obtained as described above and the average luminance is calculated (step F), and the presence or absence of correction is determined depending on whether the absolute value of the difference is larger or smaller than a certain fixed value ε. Is determined (step G). When the absolute value of the difference is larger than a certain value ε, the set value of the display dynamic range is referred to (Step H), and the process proceeds to Step J to correct the luminance / echo level function coefficient generated by the arithmetic processing unit 16. Calculate and set. That is, when the luminance appearance frequency distribution is offset to the higher luminance side than the average luminance, the coefficient is calculated so that the luminance at that part is reduced (step J), and the obtained coefficient is set as a limit. If it is determined that the calculated coefficient range is exceeded (step K), the TGC curve is calculated so as to add a correction value to the TGC curve by changing the gain so as to reduce the gain in the corresponding portion. (Step L), the corrected TGC curve is changed and stored in the depth gain control curve calculation memory 15 (Step M), and the corrected TGC curve read from the depth gain control curve calculation memory 15 is stored in the ultrasonic circuit. Depth gain control unit 9 in 2
The gain control is performed by the depth gain control unit 9 using the corrected TGC curve.

If the above-mentioned luminance appearance frequency distribution is shifted to a lower luminance side than the average luminance, the coefficient is calculated so that the luminance at that portion increases (step J).
The subsequent steps K to M proceed as the same processing as described above.
In these cases, since the gain control is performed by the corrected TGC curve in the depth gain control unit 9, an image is formed with the corrected gain after the next frame to be visualized, and the luminance of the image is reduced. Evenly averaged.

On the other hand, when the absolute value of the difference is smaller than a certain value ε, the process jumps from the step G to the subsequent stage of the step K, and an image is formed in the same manner as before without performing the above-mentioned correction.

[0026]

The present invention has been configured as described above.
An ROI setting unit for setting a region of interest to be diagnosed on the screen of the image display unit is provided inside the DSC unit, and the luminance of the video signal with respect to the echo signal level corresponding to the region of interest set by the ROI setting unit And / or a depth gain control curve for calculating, storing and outputting a gain control curve for a beam direction and a depth corresponding to a region of interest set by the ROI setting device. An arithmetic memory for controlling a coefficient of a function of the luminance of the video signal with respect to the echo signal level, and / or
Alternatively, by controlling the gain for each depth in the ultrasonic circuit by the gain control curve, the luminance is automatically adjusted so that the display contrast of the reflected echo becomes appropriate for the region of interest in the subject. Can be controlled. From this, it is possible to guarantee a uniform image luminance distribution of the video device including the probe, and it is possible to improve the image display performance near the luminance including much useful information.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a schematic configuration of an embodiment of the present invention.

FIG. 2 is a flowchart showing a procedure of the present invention.

FIG. 3 is a diagram illustrating a part of the operation of the present invention.

FIG. 4 is a block diagram illustrating a schematic configuration of another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Probe 2 Ultrasonic circuit part 3 DSC part 4 Image display part 5 Transmitting circuit 6 Receiving circuit 9 Depth gain control part 10 Video signal processing part 11 Line memory 12 Scan converter 13 Control circuit 14 ROI setting device 15 Depth gain Control curve calculation memory 16 Calculation processing unit.

Claims (4)

[Claims] An ultrasonic probe for transmitting / receiving an ultrasonic wave to / from a subject, an ultrasonic signal being transmitted to the probe to generate an ultrasonic beam, and an echo signal returning from a diagnostic site in the subject. An ultrasonic circuit for receiving and amplifying and applying a gain corresponding to the depth of occurrence of the reflected echo to amplify and then perform video signal processing, an echo signal output from the ultrasonic circuit is digitally converted, stored and imaged A digital scan converter unit for reading stored contents in synchronization with a scanning signal of a display unit, an image display unit for converting an output signal from the digital scan converter unit into a video signal and displaying the video signal as an ultrasonic image, and In the ultrasonic imaging apparatus that controls the inside of the subject to scan with an ultrasonic beam to obtain the ultrasonic image, the digital scan converter unit displays An ROI setting device for setting a region of interest to be diagnosed by an operator on an image, an arithmetic processing unit for calculating a distribution of a video signal level corresponding to the region of interest set by the ROI setting device, and an arithmetic processing unit And a region-of-interest luminance control means for generating a display luminance value curve with respect to the received signal level of the region of interest using the calculation result of the region of interest. The region of interest of the displayed image is automatically controlled to an appropriate luminance and displayed. An ultrasonic imaging apparatus characterized by the following. 2. The apparatus according to claim 1, wherein said region-of-interest luminance value control means generates a display luminance value curve for a received signal level comprising a plurality of continuous logarithmic functions according to the received signal level. Ultrasound imaging device. 3. An ultrasonic probe for transmitting and receiving an ultrasonic wave into and from an object, and transmitting an ultrasonic wave pulse to the probe to generate an ultrasonic beam and an echo signal returned from a diagnostic site in the object. An ultrasonic circuit for receiving and amplifying and applying a gain corresponding to the depth of occurrence of the reflected echo to amplify and then perform video signal processing, an echo signal output from the ultrasonic circuit is digitally converted, stored and imaged A digital scan converter unit for reading stored contents in synchronization with a scanning signal of a display unit, an image display unit for converting an output signal from the digital scan converter unit into a video signal and displaying the video signal as an ultrasonic image, and In the ultrasonic imaging apparatus that controls the inside of the subject to scan with an ultrasonic beam to obtain the ultrasonic image, the digital scan converter unit displays An ROI setting device for setting a region of interest to be diagnosed by a scanner on an image, an arithmetic processing unit for calculating a distribution of a video signal level corresponding to the region of interest set by the ROI setting device, and an arithmetic processing unit A depth gain control curve calculation memory for calculating and storing a gain control curve for a beam direction and a depth corresponding to a region of interest based on the calculation result, and a reception signal level from a target ROI for a display luminance value curve for a reception signal level Means for performing correction / calculation and / or adaptively controlling the gain for each depth in the ultrasonic circuit section by the gain control curve. 4. The ultrasonic image according to claim 3, wherein said gain control means generates a display luminance value curve for a received signal level composed of a plurality of continuous logarithmic functions according to the received signal level. apparatus.