JPH0473053A - Ultrasonic diagnosing apparatus - Google Patents

Abstract

PURPOSE:To check effect of a time difference by selecting a constant alternate scanning in an ultrasonic beam scan mode when a diagnosing depth position desired by an operation is under a specified value and a sequentially alternate scanning when it exceeds the specified value. CONSTITUTION:A scan controller 15a is provided as control means to perform a switching between a sequentially alternate scanning and a constant interval alternate scanning with respect to a transducing circuit 2 as transducing means according to a raster alternate frequency and a frequency for driving a probe 1. A desired diagnosing depth data D1 at an object to be inspected is inputted to a controller 12. As a result, a scan controller 15a is operated and a data on a probe information table possessed thereby is referred to select sequentially alternate scanning in an ultrasonic beam scan mode according to a depth input data, that is, when the data exceeds a set value D1. As for the remaining area under the D1, a constant interval alternate scanning is implemented thereby enabling the obtaining of a diagnosis image with eased effect of a time phase difference.

Description

Detailed Description of the Invention [Purpose of the Invention (Industrial Application Field) The present invention utilizes ultrasound transmission/reception waves and the Doppler effect to obtain blood flow velocity information as functional information accompanying the movement of a moving object within a living body. The present invention relates to an ultrasonic diagnostic device that obtains images and displays them.

(Prior Art) An ultrasound diagnostic apparatus obtains blood flow information and a tomographic image (B-mode image) using an ultrasound probe using ultrasound transmission/reception and ultrasound Doppler method. Blood flow velocity is measured using this device as follows. In other words, when ultrasound is transmitted to the blood flow in a living body, the center frequency fc of this ultrasound beam is scattered by flowing blood cells and changes by the frequency fd due to the Doppler shift, and the delivery frequency is f-fc+fd. becomes. The frequencies fc and fd at this time are displayed as shown in the following equation.

fd-2vcosθ·fC/nikodeV; blood flow velocity θ; angle C between the ultrasound beam and the blood vessel; sound velocity. Therefore, the blood flow velocity V can be obtained by detecting the Doppler shift fd.

The two-dimensional image display of the blood flow velocity (2) obtained in this manner is performed as follows. First, as shown in Fig. 6, by performing scan control of ultrasound pulses, ultrasound pulses are sequentially transmitted from the ultrasound probe 1 to the subject in directions A, B, C, etc. Perform sector or linear scan.

Here, for example, when an ultrasound pulse is transmitted in the A direction several times, the ultrasound is reflected by the blood flow inside the subject, and the 7th
As shown in the figure, the waves are received by the same probe 1. This reflected ultrasonic wave is then converted into an electrical signal and output to the wave transmitting/receiving circuit 2.

Next, the phase detection circuit 3 detects the Doppler shift signal. This Doppler shift signal is captured at each of, for example, 256 sample points SP set in the transmission direction of the ultrasound pulse. The Doppler shift signal captured at each sample point SP is frequency analyzed by the frequency analyzer 4a, and the DS
The signal is output to a digital scan converter (C) 6, where it is scan-converted and output to a display section 7.

In this way, the blood flow velocity distribution image in the A direction is displayed in real time as a two-dimensional image. Similarly, B.

The operation is repeated in each direction of C...,
A blood flow image (flow velocity distribution image) corresponding to each scanning direction is displayed.

(Problem to be Solved by the Invention) By the way, the detectability of low flow velocity depends on the length of data to be frequency analyzed. The sampling frequency of the Doppler signal is fr
, if the number of samplings is n, the data length T of the wave to be frequency analyzed is T-n/fr (1), and the frequency resolution fd at this time is fd=1/T
...(2). therefore,
The lower limit fdmin of the measurable flow rate is also f dmin −1/T−fr/n −(
3) can be displayed. Therefore, if you want to detect even low-velocity blood flow, the Doppler signal sampling frequency fr
, or the number of data n may be increased.

However, in two-dimensional Doppler, FN-n-m
・(1/f r)=1-(4) where FN: number of frames, m: number of scanning lines, f'; ultrasound transmission pulse repetition frequency (PRF). The number of frames FN is the two-dimensional blood flow image. It is usually a value of 8 to 30, related to the real-time nature of
This makes it possible to obtain 8 to 30 images per second.

In addition, in the case of sector electronic scanning, for example, the number of scanning lines m
-32, Ultrasonic pulse repetition frequency (PRF) f r
-4KHz and the number of samplings is n-8, the number of frames FN will be approximately 16. Also, maximum depth of field I) wax
and PRFfr is Dmax −C/ (2・f
There is a relationship: r) - (5). Therefore, to improve the detection ability of low flow rates, PRF f r
When increasing , there was a problem that the maximum depth of field could not be increased. Furthermore, if the number m of scanning lines is reduced, the scanning line density becomes coarser, resulting in deterioration of image quality. Improving the detectability of low flow rates in this manner has the problem of degrading other characteristics.

Therefore, as a method to improve this, sequential alternating scan (scanning)
For example, Japanese Patent Application No. 62-201244 is known, which adopts this method. In this method, as shown in FIG. 9, the ultrasonic scanning order is changed and controlled. In other words, sequential alternating scans refer to a plurality of predetermined sample points (for example, 8
The ultrasonic waves are sequentially transmitted and received at points), and the sequential transmission and reception is performed alternately for each rate with respect to different ultrasound rasters at a predetermined number of raster alternations (for example, the number of alternating stages is 4).

Specifically, when scanning the ultrasonic transmission beam from the right end of the probe 1 as shown in FIG. , 1 points 1a-1h).

2nd scanning line (Nα2 points 2a to 2h), 3rd scanning line (NQ, 3 points 3a to 3h), 4th scanning line (magnetic 4 points 48 to 4h), 1st scanning line (1a of Nα1~
Ih)... are scanned sequentially. In this case, the repetition effective rate frequency fr- of the ultrasonic transmission beam in the same direction is f r - f r/4 - (6), and as can be seen from equation (3) above, the lower limit fda+in of the measurable flow velocity is method, the ultrasonic transmission beam is n
This can be improved to 1/4 compared to the method of repeatedly transmitting waves in the same direction several times, and then repeating the same process n times for adjacent scanning lines.

If the number of ultrasound transmissions in the same direction (the number of samplings of Doppler signals) is n, then n-g. However, if 8 pieces of data are retrieved from a memory (not shown) for each scanning line according to the order of transmission and reception of ultrasound waves, block scanning is performed every 4 rasters, so each block is scanned as shown in (b). Because the time phase difference between rasters is large, 1
This was causing image discontinuity within the frame. This phenomenon is
In particular, as the number of stages of alternate scanning increases, the time phase difference becomes even worse.

Therefore, as a method for reducing this time phase difference, there is a constant interval alternating scan as shown in FIG.

In other words, this means that ultrasonic rasters having different raster alternating numbers are alternately scanned at each rate.

Specifically, as shown in Fig. 10, when scanning starts from the right end of the probe 1, the scanning order is changed to, for example, when using four-stage alternating regular interval scanning as shown in (a) and (C). , point 1a of scanning line NO,1.

Point 2a of scanning line No. 2, point 3a of scanning line No. 3, point 4a of scanning line N014, point 1b of scanning line Nα1, point 2b of scanning line No. 2, point 3b of scanning line No. 3, scanning Line No.
4 point 4b... In this way, as in the case of Fig. 9, it is possible to reduce the repetition frequency (sampling frequency of the Doppler signal) fr of the ultrasonic transmission beam in the same direction to 1/4, and also to set the data output timing at regular intervals. Therefore, the time phase difference within one frame can be equalized.

However, even with this method, FIG. 10(a) (
As shown in b), the residual echo signal outside the depth of field enters the next rate because the previous raster direction changes. Therefore, the residual echo signal becomes a phase difference, and residual multiple color noise is generated in the Q section. For example, the 9th
In the case shown in the figure, the immediately preceding rates for ultrasonic scanning line No. 3 are those from No. 2 and those from No. 4. For this reason, when the residual echo signal is present, a considerably large phase difference occurs if the scanning line positions differ, and color noise due to residual multiplexing becomes a Doppler signal, resulting in a problem of deterioration of image quality.

Therefore, in order to eliminate the time phase difference between color and B-mode images due to sequential alternating scans and to eliminate the influence of residual multiple color noise due to regular interval alternate scans, the following installation has already been proposed. It has been filed as No. 192g51. In other words, when ultrasonic waves are transmitted and received from the probe to the subject by the wave transmitting/receiving means, a Doppler shift signal is detected from the received signal obtained, and ultrasound information is displayed based on this, when the same ultrasound Sequential alternating scanning, in which ultrasonic waves at multiple predetermined sample points of a raster are sequentially transmitted and received, and the transmission and reception are performed alternately at each rate for different ultrasonic rasters with a predetermined number of raster alternations; and The wave transmitting/receiving means is configured to perform switching between constant interval alternating scanning in which scanning is alternately changed for each rate, depending on the raster alternation number and the frequency at which the probe is driven.

By using the above-mentioned means, sequential alternating scanning or regular interval alternating scanning can be switched by changing the raster alternating number, that is, the number of alternating scan stages, and the probe frequency as parameters. Therefore, for example, at a relatively low frequency, such as the probe frequency, the degree of attenuation of the reflected Doppler signal is small, so if sequential alternating scanning is used in two-stage alternating scanning, the time phase difference and residual multiple color noise will be reduced.

Furthermore, when the probe frequency is relatively high, the degree of attenuation of the reflected Doppler signal is large, so by using regular interval alternating scanning, residual multiple echoes are not generated much, and there is no time phase difference.

Now, let's focus on the case where an image is obtained at a relatively short distance from the shallow part of the subject, that is, from the body surface.

In this case, the image will be displayed as an enlarged image. In such a case, sequential alternating scanning with two alternating stages is selected at a relatively low driving frequency according to the above-mentioned conditions. As a result of selecting sequential alternating scanning in this manner, the time phase difference, which is a weakness of this means, may become noticeable, for example, between the rasters of a black-and-white B-mode image. In such cases, the continuity of tomographic images deteriorates,
Because the shape may be distorted, there is a risk of misdiagnosis by doctors.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an ultrasonic diagnostic apparatus that can create an image of a shallow part of a subject, that is, a region that is close to the body surface, without being affected by time phase differences, with excellent continuity, and without distortion. It is in.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention transmits and receives ultrasonic waves from a probe to a subject using a wave transmitting/receiving means, and obtains received waves. In an ultrasound diagnostic apparatus that detects a Doppler shift signal from a signal and displays ultrasound information based on the detected Doppler shift signal, there is provided a means for selecting a display depth region or a display magnification ratio in the subject; Sequential alternating scanning in which ultrasonic waves at a sample point are sequentially transmitted and received and the sequential transmission and reception is performed alternately at each rate for different ultrasonic rasters with a predetermined number of raster alternations; The switching between fixed-interval alternating scanning and alternating scanning is performed by the wave transmitting/receiving means based on the raster alternation number, the frequency for driving the probe, the display depth area, or the selection information by the display magnification selection means. The ultrasonic diagnostic apparatus is characterized in that it is equipped with a control means that performs the operation accordingly.

(Function) By changing the number of raster alternations, that is, the number of alternating scan stages, and the probe frequency as parameters, sequential alternating scanning or regular interval alternating scanning can be switched. Therefore, for example, when the probe frequency is relatively low, the degree of attenuation of the reflected Doppler signal is small, so if sequential alternating scanning is used in two-stage alternating scanning, the time phase difference and residual multiple color noise will be reduced.

Furthermore, when the probe frequency is relatively high, the degree of attenuation of the reflected Doppler signal is large, so by using regular interval alternating scanning, residual multiple echoes are not generated much, and there is no time phase difference.

Furthermore, when obtaining an image (enlarged image) of a short distance region from the shallow part of the subject, that is, the body surface, desired depth information is selected by the depth selection means. At this time, if the selected depth is less than a desired set value, the ultrasonic beam scanning mode is forcibly switched to regular interval alternating scanning, which is less affected by time phase differences. As a result, it is possible to obtain a shallow image of the subject with excellent continuity and no distortion.

(Embodiment) FIG. 1 is a schematic block diagram showing an embodiment of an ultrasonic diagnostic apparatus according to the present invention. Note that the same parts as those shown in FIGS. 6 to 10 are designated by the same reference numerals, and the details thereof will be omitted.

In FIG. 1, an ultrasound probe 1 transmits and receives ultrasound pulses to and from a subject.

The wave transmitting/receiving circuit 2 drives the ultrasonic probe 1 to generate ultrasonic waves, and receives reflected ultrasonic waves from the subject.

The phase detection circuit 3a detects the phase of the received signal from the wave transmitting/receiving circuit 2 to obtain a Doppler shift signal.

The B mode processing section 3b detects the B mode from the received signal from the wave transmitting/receiving circuit 2 and outputs the detection signal to the DSC 6. MT
I4 (also referred to as a CFM unit) filters the signal from the phase detection circuit 3 to extract only the Doppler signal, and also calculates the average velocity, dispersion, and power of blood flow. The FFT 5 performs frequency analysis on the blood flow signal from the phase detection circuit 3a to obtain a frequency spectrum.

DSC 6 includes the B mode processing section 3b, MTI4°FFT
The signal from 5 is written, converted into a TV scan, and output to the monitor 7.

The controller 12 issues a command for the number of alternate scan stages (command signal sl that commands 2 stages or 3 or more stages).

The scan controller 15a is controlled by a command signal from the panel SWIO which instructs to input s2).

The feature of this embodiment is that the switching between the sequential alternating scan shown in FIG. 9 and the regular interval alternating scan shown in FIG. The present invention is provided with a scan controller 15a as a control means that performs control according to the number of alternating stages) and the frequency at which the probe 1 is driven. Also scan controller 1
5a is MTI4. It controls DSC6.

FIG. 2 is a schematic diagram showing the functions of the scan controller 15a. That is, the scan controller 15a has a probe information table as shown in FIG. 2, and as shown in FIG.
. The wave transmitting/receiving circuit 2 drives the probe 1 at probe drive frequencies Fl and F2 corresponding to the probe information.

FIG. 3 is a schematic diagram showing the advantages and disadvantages of sequential alternating scans and regular interval alternating scans.

Furthermore, the feature of this embodiment is that the controller 12
is equipped with a means for selectively setting the display depth in the subject. This means receives the display depth data signal specified by the panel switch 10 and controls the wave transmitting/receiving circuit 2, MT I 4, and DSC 6 according to the probe information table provided in the scan controller 15a shown in FIG. do.

That is, depending on the information table, one point I of the display depth
) + (determined by taking into account the attenuation characteristics of the low-frequency ultrasound beam. For example, D + = 10 cm), and for less than 03, constant interval alternating scan is performed as ultrasonic scan moto, and D1 Alternate scans are sequentially assigned to each of the above. Furthermore, the fourth
The information table shown in the figure is for the case where two alternate stages are selected in the BDF mode.

Next, the operation of the ultrasonic diagnostic apparatus configured as described above will be explained with reference to the drawings. First, as shown in FIG. 1, when the number of alternate scan stages is input from the panel 5WIO, this instruction signal is sent to the controller 12. Further, the controller 12 automatically reads out from the probe 1 which type of probe 1 is attached, and outputs this information to the scan controller 15a. The type of alternate scan based on the instruction signal and the probe 1 are determined from the probe information table shown in FIG. 2 inside the scan controller 15a.
The probe drive frequency Fl, F2 information is read out.

For example, if the BDF mode has two alternating stages and the driving frequency F1, the alternating scan information is sequentially read out, and this scanning information and the probe driving frequency F1 are sent to the wave transmitting/receiving circuit 2. Similarly, from the scan controller 15a to the MTI4. A control signal is sent to the DSC6. As a result, the probe 1 is driven by the wave transmitting/receiving circuit 2 at the frequency F1, and alternate scanning is performed sequentially.

That is, scanning is performed alternately in sequence as shown in FIG. 9, and the reflected ultrasound waves from the living body are received by the wave transmitting/receiving circuit 2 via the probe 1, and detected by the phase detection circuit 3a to produce a Doppler signal. and a clutter component. Furthermore, this signal is converted into a digital signal by an ADC (not shown),
Clutter components are removed by MTI 4, and Doppler shift signals due to blood flow are frequency analyzed by a frequency analyzer to obtain Doppler velocity 1 dispersion, power, etc. These pieces of information are then color-processed and written into the frame memory of the DSC 6.

Further, the signal from the wave transmitting/receiving circuit 2 is subjected to envelope detection by the B mode processing section 3b and sent to the DSC 6 as black and white data. Furthermore, the detection signal from the phase detection circuit 3a is subjected to FFT
5 performs frequency analysis and sends it to the DSC 6.

Furthermore, when data of, for example, n-g is taken in for each scanning line from this DSC 6, eight pieces of data for that scanning line are read out, and blood flow information can be output to the monitor 7.

On the other hand, if the probe drive frequency F2 information is read out from the probe information table in two stages alternately, the regular interval alternate scan information and the probe drive frequency F2 are sent to the wave transmitting/receiving circuit 2, and the sequential alternate scanning is performed. The mode is switched to regular interval alternating scan.

Further, in the BDF mode, when there are three or more stages of alternation, constant interval alternating scans are performed regardless of the probe drive frequencies Fl and F2. Similarly, in the BDF/FFT simultaneous mode, constant interval alternating scans are performed regardless of the number of alternating stages and the probe drive frequency.

As described above, according to the present embodiment, by changing the number of alternate scan stages and the frequency of the probe 1 as parameters, the sequential alternate scan or regular interval alternate scan can be switched. Therefore, for example, when the probe frequency is relatively low, the degree of attenuation of the reflected Doppler signal is also small, so 2
In the stage alternating scan, by using successive alternating scans, the time phase difference is small and residual multiple color noise is also small.

Furthermore, when the frequency of the probe 1 is relatively high, the degree of attenuation of the reflected Doppler signal is large, so by using regular interval alternating scans, residual multiple echoes are not generated much, and there is no time phase difference. That is, as shown in FIG. 3, by effectively utilizing the advantages of sequential alternating scans or regular interval alternating scans, it is possible to improve the detection ability of low flow velocities and obtain good ultrasound images.

Incidentally, a constant interval alternating scan other than the above-mentioned constant interval alternating scan has already been filed as Japanese Patent Application No. 1-174426.

FIG. 5 is a schematic diagram showing another embodiment of the fixed interval alternating scan using four alternating stages, and FIG. 6 is a schematic diagram showing another embodiment of the fixed interval alternating scanning using two alternating stages. The constant interval alternating scan shown in FIG. MTI4
．． By controlling the DSC 6, the sampling frequency of Doppler information can be reduced to 1/4 without changing the ultrasound pulse repetition frequency, and the scanning order of the ultrasound raster obtained by multiple ultrasound receptions can be changed in the scanning direction θ. In contrast, the direction is reversed (in the -θ direction).

That is, as shown in the figure, the scanning order of the ultrasonic raster is in the opposite direction (-○ direction) to the scanning direction θ, and (a) (b)
) As shown in 4. Scanning line No. 3. scanning line N
o, 2. Scanning line Nα1. Scanning line No. 4.

This is an alternate scan in which four-stage scans are performed alternately with scanning lines Nα3, . . . .

According to this, the echoes before the ultrasonic raster NCL3 are mainly from NO and 4, and residual multiple echoes are reduced.

Further, since the first few data of Na 1 of NQ, 4 are small in quantity, the residual echo can be reduced accordingly.

However, in the case of a two-stage alternating scan as shown in Figure 6, in the case of ultrasonic raster No. 2, the first five data (2a to 2e) include residual echoes from No. 1 (lh to ld). The latter three data (2f to 2h) are affected by the residual echo from raster No.3 (3a to 3c). Therefore, the multiple color noise caused by the residual echo cannot be reduced with the alternating two-stage constant-interval alternating scan. Therefore, in this case, the scanning method is sequentially switched to the alternate scanning method.

Here, in the various modes of diagnosis described above, a case will be described in which a diagnostic image of a shallow part of the subject, that is, a region located at a short distance from the body surface is obtained. First, the operator inputs desired diagnostic depth data D1 for the subject into the controller 12 by operating the panel switch 10 in FIG. This causes the scan controller 15a to operate, refer to the data on the probe information table shown in FIG.
), constant interval alternating scan is selected as the ultrasonic beam scan mode, and if D1 or more, sequential alternating scan is selected, and this selection signal is supplied to the wave transmitting/receiving circuit 2, MTI 4, etc.

In this way, when a depth region of, for example, 10 (an) or more is selected for the subject, ultrasonic beam scanning is performed in the normal manner in sequential alternating scans, but for example, less than 10 (1) If the shallow region of
Since this is performed using alternating scans at regular intervals, it is possible to obtain diagnostic images in which the influence of time phase differences is alleviated.

Note that the present invention is not limited to the embodiments described above. In the above-mentioned embodiments, an alternate four-stage scan method and an alternate two-stage scan method have been described, but an alternate scan method with a different number of stages may be used. In addition, various modifications can be made without departing from the gist of the present invention.

[Effects of the Invention] As described above, according to the ultrasonic diagnostic apparatus of the present invention, when obtaining a diagnostic image of a shallow part of a subject, that is, a short distance region from the body surface, the operator can perform a diagnosis desired by the operator. When the depth position is less than a predetermined depth position, constant interval alternating scan is selected as the ultrasonic beam scan mode, and when the depth position is above a predetermined depth position, sequential alternating scan is selected, so the influence of time phase difference can be suppressed. .

[Brief explanation of the drawing]

FIG. 1 is a schematic block diagram showing an embodiment of the ultrasonic diagnostic apparatus according to the present invention, FIG. 2 is a schematic diagram showing the functions of the scan controller, and FIG. Fig. 4 is a schematic diagram showing other functions of the scan controller; Fig. 5 is a schematic diagram showing another embodiment of fixed interval alternating scan with four alternating stages; FIG. 7 is a schematic diagram showing another embodiment of regular interval alternating scan by stages; FIG. 7 is a schematic configuration diagram showing a conventional scan pattern; FIG. 8 is a schematic diagram showing an example of a conventional ultrasonic diagnostic apparatus; 1 and 10 are schematic configuration diagrams showing an alternate scanning method using a conventional ultrasonic diagnostic apparatus, respectively, and FIG. 11 is a schematic diagram showing the generation of residual multiple color noise. DESCRIPTION OF SYMBOLS 1... Ultrasonic probe, 2... Wave transmission/reception circuit, mutual wave circuit, 3b... B mode processing part, 45... FFT, 6
...DSC, 7...Monitor, channel SW, 12...
Controller, 15a controller. 3a...place...MTI, 10...pa...scan agent patent attorney rule Noriyuki Chika agent patent attorney Takeshi Kondoll11Figure lI 2 figure figure note) fl, DI-10cm Figure Figure Figure Figure True 10

Claims (1)

[Claims] In an ultrasonic diagnostic apparatus that transmits and receives ultrasound waves from a probe to a subject using a wave transmitting/receiving means, detects a Doppler shift signal from the obtained received wave signal, and displays ultrasound information based on this, means for selecting a display depth region or display magnification in a specimen; and means for sequentially transmitting and receiving ultrasound waves at a plurality of predetermined sample points of the same ultrasound raster, and rate the sequential transmission and reception to different ultrasound rasters at a predetermined number of raster alternations. The wave transmitting/receiving means is configured to perform switching between sequential alternating scanning, which is performed alternately at each rate, and constant interval alternating scanning, which alternately scans ultrasonic rasters with different rates at different raster alternating numbers. An ultrasonic diagnostic apparatus characterized by comprising control means that performs control according to a frequency for driving the probe, selection information by the display depth region or display magnification selection means.