JPH034843A - Ultrasonic diagnostic device - Google Patents

Abstract

PURPOSE:To improve picture quality without lowering a frame frequency and the dynamic range of blood stream velocity, and to observe blood stream from low velocity to high velocity by providing a synthesizing means, etc., to output the synthesized data of respective spectrum data to a DSC. CONSTITUTION:FFT 6a-6c are provided as plural analyzing means to respectively apply frequency analysis to blood stream information to be inputted while executing sampling in plural points N and to obtain the power spectrum data, and a spectrum synthesizer 7 is provided as the synthesizing means to synthesize the respective spectrum data from these FFT 6a-6c and to output the synthesized data to a DSC 10. Thus, respective peak detecting frequencies fr/2, fr/4 and fr/8 and bottom detecting frequencies fr/N, fr/2N and fr/4N exist in the spectrum synthesizer 7 and a detection range can be obtained from the bottom detecting frequency fr/4N to the peak detecting frequency fr/2.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention transmits and receives ultrasonic waves from an ultrasound probe to a subject, and calculates the Doppler shift from the signal obtained thereby. The present invention relates to an ultrasound diagnostic apparatus that detects a signal, converts the signal into a TV scan, and displays ultrasound information.

(Prior art) Ultrasonic diagnostic equipment has conventionally used an array-type ultrasound probe (probe) equipped with multiple ultrasound transducers. A plurality of ultrasonic transducers are defined as one unit, and this one unit of ultrasonic transducers is excited to transmit an ultrasonic beam. For example, the position of the transmitting point of the ultrasonic beam is electronically shifted by sequentially shifting the pitch by one oscillator and excitation so that the position of each unit of element changes one after another.

Then, so that the ultrasound beam is focused as a beam, the excited ultrasound transducers are shifted in excitation timing between those located in the center of the beam and those located on the sides, and the ultrasonic transducers generated thereby The reflected ultrasound waves are focused (electronically focused) using the phase difference between the sound waves generated by the vibrator. The reflected ultrasonic waves are then received by the same vibrator that was excited and converted into electrical signals, and the echo information from each transmitted and received wave is formed, for example, as a tomographic image, and the image is displayed on a TV monitor or the like.

In addition, in the case of sector scanning, the excitation timing of each transducer is set so that the transmission direction of the ultrasonic beam sequentially changes in a fan shape for each pulse of the ultrasonic beam for one unit of excited ultrasonic transducers. It is changed depending on the desired direction, and the subsequent processing is basically the same as the linear electronic scanning described above. Linear like this.

In addition to sector electronic scanning, there is also mechanical scanning in which a transducer (probe) is attached to a scanning mechanism and ultrasonic scanning is performed by moving the scanning mechanism.

Further, the ultrasonic Doppler method is a method of obtaining functional information accompanying the movement of a moving object within a living body and visualizing it, and this will be explained below. That is, the ultrasonic Doppler method utilizes the ultrasonic Doppler effect in which when an ultrasonic wave is reflected by a moving object, the frequency of the reflected wave shifts in proportion to the moving speed of the object. Specifically, by transmitting ultrasonic rate pulses to a living body and obtaining the frequency deviation due to the Doppler effect from the phase change of the reflected wave echo, we can obtain motion information of a moving object at the depth position where the echo was obtained. I can do it.

According to this ultrasonic Doppler method, it is possible to know the direction of the flow of blood at a position in the living body and the state of the flow, whether it is turbulent or regular.

Next, this ultrasonic diagnostic apparatus will be explained. In order to obtain blood flow information from ultrasound echoes, the ultrasound probe and transceiver circuit are driven to repeatedly transmit ultrasound pulses in a certain direction a predetermined number of times, and the received ultrasound echoes are phase-detected. Detection is performed by a circuit to obtain phase information, that is, a signal consisting of a Doppler signal and a clutter component. This signal is converted into a digital signal by an A/D converter, clutter components are removed by a filter, and the Doppler shift signal due to blood flow is frequency analyzed by a high-speed frequency analyzer such as an autocorrelation method, and the average value of the Doppler shift is , the variance value of the Doppler shift, the average intensity of the Doppler shift, etc. Here, by performing the above-described series of processes while scanning the ultrasound beam from one side to the other in correspondence with the sector scan screen, information on two-dimensionally distributed blood flow can be detected. Then, the blood flow information such as the two-dimensional blood flow velocity image showing the direction and velocity of the blood flow described above, and the B-mode image and M-mode image obtained with another system are processed using DSC (
Superimposed and synthesized using a digital scan converter),
Display on monitor.

(Problems to be Solved by the Invention) By the way, in the conventional ultrasonic diagnostic apparatus described above, FFT
The ability of Doppler to detect low flow rates depends on the data length for frequency analysis. Here, the sampling frequency of the Doppler signal is fr
If the number of data is N, the data length T of the wave to be frequency analyzed is T=N/fr...
There is the following relationship (1), and the frequency resolution Δf at this time.

is Δi-1/T...
・(2) becomes. As a result, the lowest detection frequency f+la
+1m is 1, f4. . -1/T-fr/N...
・(3) becomes. Also, the highest detection frequency f, □ is fr/
It is given by 2. As a result, the dynamic range of blood flow velocity becomes 201 og (N/2) [dB], and this value changes depending on the value of the number of data N.

For example, in order to observe the diastole and systole phase of a circulatory organ such as the heart, a dynamic range in which the number N of data is about 10 is sufficient. In addition, the range of blood flow speed in the abdomen and Pv (peripheral blood vessels) is wide from low to high, so
In v, the dynamic range is improved by increasing the number of data N.

However, if the number N of data is increased, the following problem arises. In other words, between the frame frequency Fr and the ultrasonic transmission pulse repetition frequency PRF, Fr-PRF/ (MxN) (4)
There is a relationship. Here, M is the number of ultrasound rasters. (
As can be seen from equation 4), increasing the number of data causes a problem in that the frame frequency Fr decreases and the image quality deteriorates.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an ultrasonic diagnostic apparatus that can improve image quality and observe from low flow velocities to high flow velocities without reducing the dynamic range of frame frequency and blood flow velocity.

[Structure of the Invention] (Means for Solving the Problems) In order to solve the above problems and achieve the objects, the present invention takes the following measures. The present invention transmits and receives ultrasound waves from an ultrasound probe to a subject, detects a Doppler shift signal from the resulting signal using a phase detection means, and converts this detection signal into a TV scan using a DSC. In an ultrasonic diagnostic apparatus that displays ultrasound information, a plurality of filter means for band-filtering a detection signal inputted from the phase detection means at different cut-off frequencies, and a plurality of filter means provided corresponding to the plurality of filter means from each filter means. A plurality of analysis means for frequency-analyzing input blood flow information at a plurality of points to obtain power spectrum data, and a synthesis means for synthesizing each spectrum data from the plurality of analysis means and outputting the synthesized data to the DSC. It is prepared.

(Effects) By taking such measures, the following effects are achieved. When blood flow information is band-filtered with different cutoff frequencies and sampled at multiple points N depending on the observation time, multiple pieces of time-series data with different sampling time intervals are obtained. When these different time series data are frequency-analyzed, the highest detection frequency and lowest detection frequency corresponding to each observation time and sampling time interval are obtained. By combining these, a wide range from the lowest detection frequency to the highest detection frequency can be obtained. As a result, there is no need to increase the number of data N, and the rask density in the azimuth direction can be increased without reducing the frame frequency or dynamic range of blood flow velocity, improving image quality and observing in real time from low to high flow velocities. can.

(Example) Fig. 1 is a schematic block diagram showing an embodiment of an ultrasonic diagnostic apparatus according to the present invention, Fig. 2 is a schematic diagram showing a sector-type CFM scan, and Fig. 3 shows a plurality of FFs for filter bank processing.
FIG. 4 is a schematic diagram showing the output after combining the power spectrum.

The feature of this embodiment is that the BPF 5a serves as a plurality of filter means for filtering the detection signal inputted from the phase detection circuit 3a via the ADC 4 in different bands.
~5c, and F as a plurality of analysis means provided corresponding to the BPFs 5a to 5C and performing frequency analysis and obtaining power spectrum data while sampling blood flow information manually input from each BPF 5a to 5C at multiple points N.
F T 6 a to 6 c and this F T 6
It is equipped with a spectrum synthesizer 7 as a synthesizing means for synthesizing each spectrum data from a to 6c and outputting the synthesized data to the DSCIO. The BPF 5a is a bandpass filter that cuts off at a low frequency, and is inputted to the FFT 6a as manual data D1 in the ultrasonic laser beam shown in FIG. 2, for example. BPF
5b is a bandpass filter that cuts off at a mid-range frequency, and as shown in FIG.
6b. BPF5c is a bandpass filter that cuts off at a high frequency, and the input data D1
It is input to the FFT 6c as input data D3 having a frequency 1/4 of that of the input signal D3.

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. The ADC 4 converts the signal from the phase detection circuit 3a into a digital signal, and the CFM 8 (color flow mapping) performs color processing on the signal from the ADC 4. The DSCIO writes the signals from the B-mode processing section 3b, CFM 8 and power spectrum synthesizer 7, converts them into TV scans, and outputs them to the TV monitor 11.

Next, the operation of the ultrasonic diagnostic apparatus configured as described above will be explained with reference to the drawings. As shown in FIG. 2, CFM sector scanning is performed for ultrasonic rasters 1 to m-M. That is, the ultrasonic probe 1 is driven to transmit by the wave transmitting/receiving circuit 2, and the ultrasonic pulses transmitted from the ultrasonic probe 1 to a living body (not shown) are accompanied by a Doppler shift due to blood flow flowing in the living body. This becomes a received signal ', which is received by the ultrasonic probe 1 and the wave transmitting/receiving circuit 2. Furthermore, the B mode is detected by the B mode processing section 3b, and this detection signal is output to the DSCIO. Detected by the phase detection circuit 3a, a signal consisting of a Doppler shift signal due to blood flow and a clutter component is obtained. The clutter component is removed from the output of the phase detection circuit 3a to obtain a Doppler shift signal, which is converted into a digital signal by the ADC 4. As shown in FIG. 3, for example, in the ultrasonic raster m, the signal is
It is assumed that input is made in F5a to F5C. Then, the digital signal is cut off at the low frequency by the BPF 5a, and the input data D1 is passed through the FFT 6a as shown in FIG.
When sampled at multiple points N, a data length T1 (N/fr) is obtained. Further, the digital signal is cut off at the mid-range frequency by the BPF 5b, and when the input data D2 is sampled at multiple points N by the FFT 6b, the data length T2 (2N/fr) is twice the data length T1. obtain.

Further, the digital signal is cut off at a high frequency by the BPF 5c, and the input data D3 is sampled at multiple points N by the FFT 6c, resulting in a data length T3 (4N/f r
). Then, the digital signals are subjected to frequency analysis using FFTs 6a to 6C to obtain blood flow velocity data consisting of the direction of blood flow (forward flow or reverse flow) and spectrum.

Further, each of the FFT data from the FFTs 6a to 6C is subjected to power spectrum synthesis by a spectrum synthesizer 7. That is, as shown in FIG. 4, F from FFT6a
When the FT data is subjected to a power spectrum, the highest detected frequency becomes fr/2, and the data length Tl (N/fr)
Obtain the lowest detected frequency fr/N based on . Also F
When the FFT data from FT6b is subjected to power spectrum, the highest detected frequency is fr/4, and the lowest detected frequency is fr/2N based on the data length T2 (2N/fr).
get. Further, when the FFT data from the FFT 6c is subjected to a power spectrum, the highest detected frequency becomes f'/8, and the lowest detected frequency fr/4N is obtained based on the data length T2 (4N/f r).

Therefore, the spectrum synthesizer 7 receives each of these highest detected frequencies f r/2 . f r/4° f r/8
and the lowest detection frequency f r /N * f r /2N
, f r/4N, it is possible to obtain a detection range from the lowest detection frequency fr/4N to the highest detection frequency f'/2. As a result, the dynamic range of blood flow velocity is 201og (2N). [dB], and the dynamic range can be significantly improved.

On the other hand, the signal from the ADC 4 is subjected to color flow mapping, and these data are written to the DSCIO together with the data from the spectrum synthesizer 7, and then TV scan converted and ultrasound diagnostic information is displayed on the TV monitor 11. .

In this way, according to this embodiment, blood flow information is transmitted from BPF5a to
Band filtering with different cutoff frequencies by 5C,
If these are sampled at a plurality of points N depending on the observation time, a plurality of time series data with different sampling time intervals are obtained.

Then, when frequency analysis is performed on these different time series data,
The highest and lowest detected frequencies corresponding to each observation time and sampling time interval are obtained. By combining these, the lowest detected frequency is f
It can be improved to r/4N, and the maximum detection frequency fr can be improved to f'
/2, and can obtain a wide range from the lowest detection frequency to the highest detection frequency. As a result, there is no need to increase the number of data N, and the raster density in the azimuth direction can be increased without reducing the frame frequency Fr or the dynamic range of blood flow velocity, improving image quality and allowing real-time processing from low to high flow velocities. Since it can be observed and, for example, a backflow surface and a fold can be distinguished, an appropriate diagnosis can be made.

Note that the present invention is not limited to the embodiments described above. In the above-mentioned embodiment, the explanation was given for the ultrasonic raster m, but the invention can be similarly applied to other ultrasonic rasters. Also, the highest detection frequency is f r/2. fr
/4. Although f r/8 is used, other highest detection frequencies may be set and the corresponding lowest detection frequencies may be obtained.

In short, it goes without saying that various modifications can be made without departing from the gist of the present invention.

[Effects of the Invention] According to the present invention, when blood flow information is band-filtered with different cutoff frequencies and sampled at a plurality of points N depending on the observation time, a plurality of time series data with different sampling time intervals are obtained. When these different time series data are frequency-analyzed, the highest detection frequency and lowest detection frequency corresponding to each observation time and sampling time interval are obtained. By combining these, a wide range from the lowest detection frequency to the highest detection frequency can be obtained. As a result, there is no need to increase the number of data N, and the raster density in the azimuth direction can be increased without reducing the dynamic range of frame frequency or blood flow velocity, improving image quality and allowing real-time observation from low to high flow velocities. We can provide ultrasonic diagnostic equipment that can

[Brief explanation of the drawing]

FIG. 1 is a schematic block diagram showing an embodiment of an ultrasonic diagnostic apparatus according to the present invention, FIG. 2 is a schematic diagram showing a sector-type CFM scan, and FIG. 3 is a schematic diagram showing a plurality of FFs for filter bank processing.
FIG. 4 is a schematic diagram showing the output after combining the power spectrum. 1... Ultrasonic probe, 2... Transmission/reception circuit, 3a...
・Phase detection circuit, 3b...B mode processing section, 4...
ADC15a ~5c-BPF, 68~6
c-・FFT, 7-・spectrum synthesizer,
8...CF M unit, 1°...DSC, 11.
...TV monitor.

Claims (1)

[Claims] Ultrasonic waves are transmitted and received from the ultrasound probe to and from the subject, a Doppler shift signal is detected from the signal obtained by this using a phase detection means, and this detection signal is converted into a TV scan using a DSC to obtain ultrasound information. In the ultrasonic diagnostic apparatus for displaying, a plurality of filter means for band-pass filtering the detection signal inputted from the phase detection means at different cutoff frequencies, and a blood flow inputted from each filter means provided corresponding to the plurality of filter means. A plurality of analysis means for frequency-analyzing information at a plurality of points to obtain power spectrum data, and a synthesis means for synthesizing each spectrum data from the plurality of analysis means and outputting the synthesized data to the DSC. Features of ultrasonic diagnostic equipment.