JPH0228974B2 - IYOCHOONPAPARUSUDOPURASOCHI - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a medical ultrasonic pulsed Doppler apparatus, and more particularly to an improvement in the dynamic range of a receiver.

(Prior Art) FIG. 6 is a diagram showing an example of a conventional ultrasonic pulse Doppler apparatus. In the figure, a probe 1 is driven by high-pressure pulses from a pulser 2 and projects ultrasonic waves onto a living body. The pulser 2 is triggered by a trigger pulse output from the wave transmission trigger circuit 3. The wave transmission trigger circuit 3 is driven by a clock obtained by dividing a clock of a predetermined frequency from a clock generator 5 by a frequency divider 4 as appropriate.

The probe 1 converts the reflected wave from the living body into an electrical signal and supplies it to the first stage amplifier 6. The echo signal that has passed through the first stage amplifier 6 is input to a Doppler echo filter 7, where only echo signals in a predetermined frequency range are extracted and input to a coherent detector 8. The coherent detector 8 extracts only the Doppler signal corresponding to the transmission spectrum from the input echo signal using reference waves having mutually different phases by 90 degrees provided by the phase shifter 9. The phase shifter 9 uses the output clock of the clock generator 5 as a carrier to obtain reference waves having a phase difference of 90° from each other. The echo signal divided into two channels by the coherent detector 8 is gated by a range gate 10, and its output is input to a Doppler filter 11, which extracts only signals in a valid frequency range as a Doppler signal.

The range gate 10 is a gate that selects a Doppler signal in an arbitrary sample volume at a depth of interest, and a control signal for controlling the range gate is provided by a range gate generation circuit 12.
The range gate generation circuit 12 generates a range gate control signal according to settings based on the wave transmission trigger.

The Doppler signal output from the Doppler filter 11 is converted into an audio frequency Doppler signal (Doppler AF signal) via the Nyquist filter 13 and output, and sent to a frequency analysis circuit (not shown) for analysis. The analysis results are displayed on an image display device (not shown). Additionally, the Doppler AF signal can be directly applied to a speaker or the like and monitored as an audible sound.

(Problems to be Solved by the Invention) However, in such a conventional ultrasonic pulse Doppler apparatus, there is a problem in that a range gate is applied after coherent detection. That is, there are strict requirements for dynamic range or linearity in the section from the coherent detector or first-stage amplifier to the Nyquist filter. This is due to the fact that since there is range gate work, it is necessary to handle signals with extremely small duty ratios.

The present invention has been made in view of the above points, and its object is to provide an ultrasonic pulse Doppler apparatus that does not encounter the dynamic range limit of the first stage amplifier, echo filter, etc.

(Means for Solving the Problems) The present invention solves the above-mentioned problems by irradiating ultrasound onto a living body and coherently detecting the reflected signal from the living body, thereby providing a Doppler that corresponds to the movement speed of a sample point of the living body. In medical ultrasound pulsed Doppler equipment that detects signals and observes the movement state of living organisms,
It is equipped with a range gate that passes only the echo signal arriving from the sample point of interest in the living body, and a pulse stretcher filter that rounds the envelope of the RF pulse signal output from this range gate. This system is characterized in that the received signal that has passed through the system is coherently detected.

(Example) Hereinafter, an example of the present invention will be described in detail using the drawings.

FIG. 1 is a diagram showing the configuration of essential parts of an embodiment of an ultrasonic pulse Doppler apparatus according to the present invention. In FIG. 1, the same parts as in the conventional example shown in FIG. 6 are given the same reference numerals. The difference from the conventional example shown in FIG. 6 is that a range gate 10 is provided before the coherent detector 8, and a pulse stretcher filter 20 is provided after the range gate 10.

With this configuration, the RF pulse signal with a high duty ratio can be stretched by the pulse stretcher filter 20 immediately after the range gate 10, so that the dynamic range requirement for the coherent detector can be reduced to the level of CW Doppler.

The pulse stretcher filter 20 is a rounding filter (tuning circuit) for rounding the envelope of the RF pulse signal. This is equivalent to a second-order or higher-order low-pass filter with its frequency axis shifted, and as shown in Figure 2, the RF
When the burst signal A is input, its energy is conserved and the waveform is made to have a not very high duty ratio as shown in the figure B. Examples of this filter include LC, crystal, ceramic,
A mechanical or other bandpass filter can be used. Another way to look at the function of a pulse stretcher filter is to extract one of the many emission line spectra of this signal that are periodically observed on the frequency axis, as shown in Figure 3. I can say that it is. however,
The role of the stretcher is not necessarily limited to the extraction action as shown in the diagonal line, but even a wide stretcher as shown in the broken line can serve a substantially sufficient role.

According to the ultrasonic pulse Doppler apparatus having such a configuration, the probe 1 is driven by the high-voltage pulse Tr shown in FIG. 4A, and an echo signal a as shown in FIG. 4B is obtained. This echo signal a is a signal obtained after passing through the first stage amplifier 6 and the Doppler echo filter 7. This echo signal a is subjected to a range gate as shown in Figure C to extract a Doppler signal at the depth of interest as shown in Figure D. Range gate output b is passed through pulse stretcher filter 2
0 and stretch it as shown in the figure. The signal expanded in this manner is input to the coherent detector 8 as in the conventional case, and a Doppler signal corresponding to the transmission spectrum is extracted. In this case, the dynamic range for the coherent detector may be approximately CW Doppler.

In addition, although the Doppler echo filter 7 is used in the embodiment, it is not necessarily necessary. Further, this device can also be applied to B-mode imaging, and in that case, the received signal for B-mode imaging can be extracted by branching the output of the first stage amplifier 6.

Additionally, this device can also be configured to coexist with CW Doppler. When functioning as a CW Doppler, the waves are transmitted from the CW generator 31 as shown in Figure 5.
Pass the CW output through the CW transmitter 32 (make it high voltage)
The echo signal is transmitted to the probe 1, and the echo signal is received through the same route as in the case of pulsed Doppler. In the case of CW Doppler, the range gate is kept in the on state (through state). Also, reception is
As shown by the broken line in the figure, the output signal of the probe may be applied to the input end of the range gate, the input end of the pulse stretcher filter 20, or the input end of the coherent detector 8.

(Effects of the Invention) As described above in detail, according to the present invention, it is possible to realize a system that does not encounter the dynamic range limit in the first stage amplifier, Doppler echo filter, etc. In other words, there is no need to apply signals containing high-level signals or unnecessary signals (clutter, etc.) to the range gate or coherent detector, and this is significantly improved compared to conventional methods in terms of the dynamic range resistance of the device. be advantageous to

[Brief explanation of drawings]

FIG. 1 is a block diagram of main parts showing an embodiment of the ultrasonic pulse Doppler device according to the present invention, FIGS. 2 and 3 are diagrams for explaining the function of a pulse stretcher filter, and FIG. 4 is a diagram of the device. FIG. 5 is an explanatory diagram of another embodiment of the present invention, and FIG. 6 is a configuration diagram of a conventional ultrasonic pulse Doppler apparatus. 1... Probe, 2... Pulser, 3... Transmission trigger circuit, 4... Frequency divider, 5... Clock generator,
6... First stage amplifier, 7... Doppler echo filter, 8... Coherent detector, 9... Phase shifter,
10... Range gate, 11... Doppler filter, 12... Range gate creation circuit, 13... Nyquist filter, 20... Pulse stretcher filter.

Claims (1)

[Claims] 1. Detect a Doppler signal corresponding to the movement speed of the sample point of the living body by irradiating the living body with ultrasound and coherently detecting the reflected signal from the living body,
A medical ultrasonic pulse Doppler device that observes the movement state of a living body uses a range gate that passes only echo signals arriving from sample points of interest on the living body, and a pulse stretcher filter that rounds the envelope of the RF pulse signal output from this range gate. A medical ultrasonic pulse Doppler device, comprising: a pulse stretcher filter for coherent detection of a received signal passing through the range gate and the pulse stretcher filter.