JPH0380840A - Signal processing system for ultrasonic diagnostic device - Google Patents

Abstract

PURPOSE:To avoid the problem of saturation in a D range or a beam former at the time of a CW Doppler mode by executing a signal processing by an IF system at the time of an imaging mode, and executing a signal processing by a base band system at the time of the CW Doppler mode. CONSTITUTION:When the device functions as an IF beam former in the case of operating in an imaging mode, outputs of A/D converters 19, 20 are inputted to combination of digital Hilbert converter 32 and a combiner 33 for constituting a digital phase shifter 31, and matching of the phases is executed. Thereafter, an output of the combiner 33 is delayed for a prescribed time by a variable delaying circuit 34, and thereafter, added together with a signal from other channel inputted to an addition synthesizer 35, and brought to delay addition. On the other hand, in the case of a CW Doppler mode, the processing can be executed by only the digital Hilbert converter 32 and the combiner 33. However, in this case, the Hilbert transformation which can be applied for audio use, as well becomes long as to its sample section length, but it is executed by a DSP together with a built-in decimation filter, or it is possible to cope therewith suitably by executing it only analogously.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a signal processing method for an ultrasound diagnostic apparatus, and particularly to coexistence of imaging and CW Doppler in a phased array ultrasound apparatus having a CW Doppler function.

[Prior art and problems to be solved by the invention] Conventionally,
Some phased array ultrasonic diagnostic apparatuses employing the IF system have a CW Doppler function as an additional function. The CW Doppler is still being executed using the IF method. In CW Doppler, waves are constantly transmitted, and all clutter on the sound line leading to the target area or within a relatively loosely defined cross section is received simultaneously, so the dynamic range of the signal system (hereinafter referred to as (referred to as the D range). On the other hand, I
Although the F method does not require an amplifier in the first stage, the mixer and IF delay-and-sum system that follow determines the limit of the D range, which is more disadvantageous than the RF method.

By the way, in the case of the baseband method, when performing 0W Doppler, it is possible to "remove clutter" by cutting off the DC or low frequency immediately after each mixer, so there is no burden on the D range on the phasing and addition system. There are few Furthermore, the baseband type phased array CW Doppler is advantageous in that the phasing and addition can be performed by processing only the phase while being mounted on the audio head.

On the other hand, from an imaging standpoint, the IF method has been proven to be beneficial, especially when a digital beamformer is used. In other words, the highest performance A/D converter is not required, and suitable ones can be found on the market, and the number of channels that need to be prepared is doubled compared to the baseband method. (requires two components of in-phase i and orthogonal q), and does not suffer from DC offset or 1/f noise.

The baseband method is the IF method in almost all respects, except for the fact that DC cut can be performed immediately after each mixer (two i and q are required for each element) in the case of CW Doppler mentioned earlier. It is more disadvantageous. The baseband method was advantageous until the time when the processing speed and various performances of A/D converters and digital signal processing systems were limited, and it is not necessarily advantageous now.

This invention was made in view of this situation,
It is an object of the present invention to provide a signal processing method for an ultrasound diagnostic device that combines the advantages of the IF method in echo imaging (including two-dimensional MTI...color Doppler) and the features of the baseband method under the aforementioned special conditions. purpose.

[Means for Solving the Problems] The signal processing method of the ultrasonic diagnostic apparatus according to the present invention performs receiving beamforming using the IF method when the transmission mode is pulse echo transmission/reception, and performs receiving beamforming using the IF method when the transmission mode is pulse echo transmission/reception. This system performs receiving beamforming using a band method.

[Function] In this invention, in the case of CW Doppler, receiving beamforming is performed by the baseband method, so the CW Doppler
The problem of saturation in the D range or beamformer during Doppler is avoided.

Embodiment 1 FIG. 1 is a block diagram showing the configuration of an ultrasonic diagnostic apparatus according to an embodiment of the present invention. The probe (1) is driven by high-voltage pulses from the wave transmission driver array (2) and projects ultrasound onto the living body. The transmission driver array (2) is triggered by a trigger pulse output from the transmission delay map (3). The transmission delay map (3) is driven by the transmission waveform generator (4), which is driven by the transmission waveform generator (4), the transmission trigger circuit (5), the clock generator (6), and the transmission carrier generator (7). controlled based on the signal.

The probe (1) converts the reflected wave from the living body into an electrical signal and supplies it to the first stage amplifiers (10) and (11). The echo signal that has passed through the first stage amplifier (10), (11) is sent to the mixer (13), (
14).

At this time, if the changeover switches (12) and (15) are switched to the image side, the first stage amplifier (10) corresponding to each transducer of all the probes (1)
, (11) are respectively output to the mixer (13),
(14), and a signal of a predetermined frequency from a local oscillator (16) is input manually. And mixer (13)
In (14), an intermediate frequency signal (hereinafter referred to as IF multiplied signal) of both is obtained and output. In addition, when the changeover switches (12>, (15) are switched to the CW Doppler side (the state shown), the first stage amplifier (11) corresponding to half the transducer (1b) of the probe (() ) are input to the mixers (13) and (14).In other words, the outputs of the first stage amplifier (11) are input to the mixers (13) and (14), respectively.Furthermore, the transmitter carrier generator (7 ) are input with reference waves having phases different by 90° from each other, and only the Doppler signal corresponding to the transmission spectrum is extracted from the input echo signal.

The outputs of the mixers (13) and (14) are passed through the filter (1
7).

(t8) and the A/D converter (19y), the signal is inputted to a digital signal processing device (21) having an arithmetic function as a digital beam former via (20).

The digital signal processing device (21) converts the signal into, for example, an audible frequency Doppler signal (Doppler AF signal), sends it to a speaker (23) via a D/A converter (22), and monitors it as an audible sound. . It is also sent to a frequency analyzer (24) and analyzed, and the results are displayed on an image display device (25).

Next, the case of operating in the imaging mode will be described. Here it is a changeover switch (12).

It is assumed that (I5) is switched to the imaging side.

High voltage pulses from the transmitter driver array (2) are sent to the probe (
Ultrasonic signals are applied to all the transducers of (1) and projected onto the living body, and each probe (1) receives the reflected waves from the living body and converts them into electrical signals.The received signals are sent to the first stage amplifier ( 1
0), (11). And the first stage amplifier (
The outputs of 10) and (11) are respectively connected to the mixer (13).
, (14) manually, and mixer (13), (1
4), a signal of 4.2 MHz, for example, is manually inputted from the oscillator (1B), the two signals are mixed, and the IF multiplied signal is extracted. This IF multiplied signal, for example, DC ~ 1.4MH
It becomes a signal in the range of z.

IF multiplied signal filters (17) corresponding to each of all the transducers (la) and (lb) of this probe (1);
(18) is input. This filter (17), (
[1] is, for example, a band pass filter of 70 Hz to 1.4 MH2, and components in that frequency range are extracted and DC components are cut. In the IF method, even during imaging, there is no need for DC coupling after the mixers (1a) and (14), so the A/D converters (19) and (
There is no problem even if the DC cut is left on until the point 20) is reached.

The outputs of the filters (17) and (18) are sent to the A/D converter (
19).

(20), where it is converted into a digital signal. In this example, the IF multiplied signal A/D from DC to 1.4MHz
Since it is input to the converters (19) and (20), for example, the sampling rate is set to 5 to 6Mf (z, resolution 8 to 10b).
Just make it IT. A/D converter (19), (20)
The output of is input to the digital signal processing circuit (21),
Then, while determining the azimuth, focus, etc., a phase-combined Doppler output is obtained.

Next, the case of operating in CW Doppler mode will be described. Here, it is a changeover switch (12).

It is assumed that (15) is switched to the CW Doppler side.

In CW Doppler mode, half of the transducers (la) of the probe (1) are used for transmitting waves, and the other half of the transducers (1b) are used for receiving waves. child (l)
The received signal in b) is amplified by the first stage amplifier (11), and its output is input to mixers (13) and (14).

For example, the output of the amplifier (lla) is
2) is input to the mixer (13a) via
It is input to the mixer (14a). Mixer (13a)
In addition to the output of the amplifier (lla), a 90° phase reference wave is input from the transmitting carrier generator (7), and both signals are mixed. The mixer (14a) includes an amplifier (11a).
) as well as the output from the transmit carrier generator (7).

The phase reference wave is manually input and both signals are mixed. The signals mixed by the mixers (13a) and (14a) in this way are filtered by the filters (17a), respectively.
), (18a) and A/D converter (19a),
The signal is input to the digital signal processing device (21) via the input echo signal (20a), and a Doppler signal corresponding to the transmission spectrum is extracted from the input echo signal, and a Doppler output is obtained by phase-synthesizing the azimuth, focus, etc.

Here, the A/D converters (19) and (20) are originally ones with a moderate speed suitable for the IF acid component (however, they are much faster than those for audio), so In this case, this can be used (even if the number of bits is slightly insufficient) to perform higher-order oversampling (for example, 1
After that, a rounding filter is applied to perform decimation (thinning, for example, 16:1). This decimation function is performed by the subsequent digital signal processing circuit (2
1) Achieves the digital filter function while obtaining process gain.

FIG. 2 is a circuit diagram of a beam former built into the digital signal processing device (21).

When this device is functioning as an IF beamformer, the outputs of the A/D converters (19) and (20) are connected to a digital Hilbert converter (32) and a combiner (33) which constitute a digital phase shifter (31). After that, the outputs of the combiner (33) are each delayed for a predetermined time in the variable delay circuit (34), and then the outputs of the combiner (33) are input to the adder/synthesizer (35). It is added together with the signals from the channels and delayed summed.

On the other hand, in the case of CW Doppler mode, the variable delay circuit (3
4) is not required, and the digital Hilbert converter (32
) and the combiner (33) alone.

However, in this case, the Hilbert transform, which can also be applied to audio, has a longer sample interval length, but is performed by the DSP together with a built-in decimation filter (not shown).
Alternatively, it may be possible to respond appropriately by doing it in an analog manner.

[Effects of the Invention] As described above, according to the present invention, signal processing is performed using the IF method in the imaging mode, and signal processing is performed using the baseband method in the CW Doppler mode. Imaging and CW with avoidance of saturation issues in the D range or beamformer
A device that coexists with Doppler is realized.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an ultrasonic diagnostic apparatus according to an embodiment of the present invention, and FIG. 2 is a block diagram of a digital signal processing circuit. In the figure, (1) is the probe, (10), (11) is the first stage amplifier, (12) is the changeover switch, (13),
(14) is a mixer (15) is a changeover switch, (16) is a local oscillator, (17) and (18) are filters, (19) and (20) are A/D converters, (2
1) is a digital signal processing circuit.

Claims (1)

[Claims] In the signal processing method of a phased array type ultrasound device having a CW Doppler function, reception beamforming is performed using the IF method in the pulse echo transmission/reception mode, and reception is performed using the baseband method in the CW Doppler mode. A signal processing method for ultrasound diagnostic equipment that uses wave/beamforming.