JPH0221256B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention generally relates to the simultaneous imaging of biological tissues (e.g., blood vessels, ventricles), etc. for practical purposes by a combination of ultrasound Doppler blood flow measurements and pulse-echo amplitude imaging. and by said combination obtaining measurements of blood flow rates within biological tissues. This combination is obtained without any reduction in the maximum blood velocity measured by pulsed Doppler, and continuous Doppler can also be used. In the latter case, there is no limit to the maximum speed that can be measured.

The method of ultrasonic blood flow measurement based on the Doppler principle (hereinafter referred to as "Doppler measurement") and the method of echo amplitude imaging using ultrasound pulses (hereinafter referred to as "echo imaging") are considered to be well known, and this book The invention relates to the combination of these simultaneous measurements.
The method can be implemented by slightly modifying commercially available imaging and blood velocity measuring devices and interconnecting them by a central controller.

An image of the biological tissue is shown on a suitable display screen, and the area over which blood flow rate is measured is shown on the same screen. The effective spectral analysis of the received Doppler signal is also displayed on the screen and possibly printed out on a suitable printer.

It is an object of the present invention to simplify the aiming of the ultrasound head or transducer during Doppler measurements of blood velocity by utilizing echo amplitude images to determine the range over which blood velocity is measured. be.
By combining blood velocity measurements with vessel dimension measurements, it is believed that the actual flow rate in the vessel can be measured and calculated.

A very important consideration in using the type of equipment involved here is that the Doppler signal is provided in an audible format, for example by a loudspeaker. Physicians conducting investigations, especially initially, use much of the information contained in the audible Doppler signal, especially to locate points or bands within the blood system where more detailed measurements or imaging may be of interest. Therefore, it is extremely important that the audible Doppler signal be virtually undisturbed or distorted.

Instruments that create two-dimensional imaging of biological tissue in real time based on the amplitude of echoes from short ultrasound pulses are commercially available. There are two types of such known instruments: (a) Instruments based on phase-controlled transducer arrays or partial sweeps obtained by mechanically moving transducers.

(b) Instruments based on linear sweeps obtained by electronic selection of elements in a linear array of transducers or by linear mechanical movement of a single transducer.

Instruments for ultrasound Doppler measurement of blood flow velocity are also commercially available, and there are two basic methods: (a) Ultrasonic pulses. This allows depth resolution along the ultrasound beam so that small ranges of velocity can be measured. Multi-depth sampling can also be used so that velocity can be measured at several depths. This method has the disadvantage that the maximum velocity that can be measured is limited by the pulse repetition rate or frequency used.

(b) Continuous ultrasound measurement. This method does not appear to provide any depth resolution along the ultrasound beam. Instead, there is no limit to the maximum speed that can be measured. Commercial instruments are available that combine methods (a) and (b) above.

Instruments that combine echo amplitude imaging and Doppler blood velocity measurements are also commercially available. The following three principles are used: (a) Interrupt mode. The image is frozen on a suitable screen under manual control and the ultrasound head is utilized for Doppler measurements of blood velocity.

(b) Every other emitted ultrasound pulse is used for Doppler velocity measurements, and the middle pulses of the ultrasound pulses are used for echo amplitude imaging. That is, the pulses alternately serve for Doppler measurements and echo imaging.

(c) Initially, an arrangement may be proposed in which several Doppler pulses are emitted in a series with periodic interruptions to obtain a single echo amplitude imaging pulse.

The above methods of correlating echo imaging and Doppler measurements have the following deficiencies and disadvantages: (1) When the image is frozen in interrupt mode;
Movement of the measuring head or measuring object causes a false indication of the measuring speed range.

(2) The alternating emission of Doppler pulses and imaging pulses reduces the emissivity of the Doppler pulses and therefore the maximum velocity measured. (Doppler pulse measurement) (3) The third method shown has the problem of slow image updating. This is an object or/
and because it imposes limitations on the orientation response when the measuring head is moved. Another significant disadvantage of this method is that the imaging signal is audible and therefore signal listening is subject to interference.

In methods (b) and (c), continuous Doppler measurement signals may not be used. This means that the maximum velocity measured is determined by the keying frequency of the Doppler pulse mode.

These defects are caused by high image frequencies (e.g. 20
Hz) is avoided in the present invention. Furthermore, even though both pulsed signals and continuous Doppler measurement signals are used, the pulse repetition rate in pulsed mode is not reduced more than it is in pure Doppler measurement conditions.

Thus, the present invention takes the prior art as a starting point and
Ultrasonic blood flow velocity based on the Doppler principle, especially in combination with simultaneous echo amplitude imaging (echo imaging) using ultrasound pulses to investigate living biological tissues, such as the movement of cardiac function measurements (Doppler measurements), wherein the Doppler measurements and echo imaging are updated at a frequency high enough for the echo imaging to obtain acceptable image quality, and the Doppler measurements measure velocity with a desired accuracy. The image information from the echo imaging and the display of the measurement range or measurement point for Doppler measurements can be displayed realistically on a cathode ray tube screen or the like. expressed in time, and in which a central device serves to synchronize Doppler measurements and echo imaging, and one or more transducers are used at any given time to perform either Doppler measurements or echo imaging. The above-mentioned method is activated at the moment when The novel features of the method according to the invention are primarily that the Doppler measurement is interrupted during a period consisting of non-essential time sections in order to completely or partially sweep the ultrasound beam over the image field, and that the direct current measurement The idea is that the Doppler signal is used to provide an estimate instead of the directly measured Doppler signal during all or part of the time.

Other features according to the invention are indicated in the claims, and the invention also encompasses an apparatus for carrying out the method.

The invention will be explained in detail below with reference to the drawings.

FIG. 1 shows a block diagram of an apparatus for carrying out the method according to the invention. The device comprises a central control unit 4, an echo amplitude imaging device 2 for real-time two-dimensional imaging, a Doppler device 1 with a combination device 5 represented by an MSE (missing signal estimator), and equipment, such as a cathode ray tube screen 3, for suitably displaying the Doppler spectrum.

Both the Doppler device 1 and the imaging device 2 are switched on and off electronically. Both devices are controlled by a control device 4 which operates according to principles known per se for such control. In operation, the control device 4 interrupts the Doppler measurement for short time intervals (for example 15 milliseconds) in order to perform a complete or partial sweep of the ultrasound imaging beam over the image field.
Directly measured Doppler signal to provide an estimate to replace the Doppler signal during all or part of the time only when Doppler measurements are not possible, which may occur, for example, due to interruption periods or high-pass filter transients. is used. Estimated value is MSE device 5
made by.

The echo amplitude images produced during each sweep are stored in a suitable electronic image memory which is continuously scanned to display the image on a suitable screen. Such storage methods are used in some commercial instruments.
The control device 4 provides the time structure of the Doppler and imaging measurements (echo imaging) as well as the structure of the signals for appropriate display and printout. This varies depending on the Doppler and imaging equipment used, and the design is based on the same methods of control equipment found in other time-sequenced instruments.

Also schematically shown in FIG. 1 is a Doppler transducer 10a and a transducer array 10 for echo imaging, which may for example be described in some detail in FIGS. 4 or 5 below. can be accommodated.

The function of the apparatus of FIG. 1 will be explained in detail later, particularly with respect to FIGS. 6 to 9.

Figures 2 and 3 show range 21 (second range), respectively.
Two examples of image representations of the area 31 (FIG. 3) and region 31 (FIG. 3) are shown, in which the blood velocity is measured by a phase-controlled transducer array.

These figures show aortas 26 and 3, respectively.
Hearts 25 and 35 with 6 are shown and lines 27, 28, 29 and line 3 respectively.
The extent of the image field is indicated by 7, 38, 39.

The same ultrasound heads 20 and 30 each have
Used for Doppler measurements as well as echo imaging. In FIG. 2, an ultrasound beam 22 for Doppler measurement is shown.
The eyes are directed straight ahead. In this case, it is possible to connect several elements of the transducer array to one Doppler transducer by means of suitable selectors (relays or electronic switches).

In FIG. 3, the direction of Doppler measurement 33 is offset from the centerline. To obtain this, the signal must be phase controlled in all transducer elements 30, for example by the same electronic circuit used for phase control during imaging. The method according to FIG. 2 yields better sensitivity in the case of less accurate and noisy phase control circuits.

Another transducer 4 for Doppler measurements shown in FIG.
0a can also be used, in which case the transducer array 40 serves for echo imaging by partially sweeping within the limit lines 47, 48. FIG. 5 shows a linear image sweep with a linear transducer array 50 and another Doppler transducer 50a. converter 50
and 50a are shown in contact with the patient's skin 52 with a vein 56 shown below, a portion of which is bounded by lines 57, 58 and 59. placed inside. The measurement range 51 for Doppler measurement is the vein 5
6 is shown inside.

This arrangement with a separate Doppler transducer, inter alia,
It has the advantage that the Doppler transducer 50a is optimized for better sensitivity in Doppler measurements. In conjunction with the mechanical imaging sweep, a separate fixed Doppler transducer 50a is used since it may be difficult to stop the movable imaging transducer fast enough for Doppler measurements.

In this regard, reference is first made to FIG. 9, which shows an exemplary time interval between echo imaging and Doppler measurement of velocity. Image time 15 ms and Doppler time
35 milliseconds gives an image speed of 20Hz. By reducing the Doppler time to, for example, 18 milliseconds, the image speed is increased to 30 Hz. Other 9th
What is shown in the figures will be explained later.

As mentioned above, the directly measured Doppler signal is
It is used to create an estimate to replace the Doppler signal at all times or when the Doppler signal is absent.
In FIG. 6, only at the above interruption time,
Or it is shown how the Doppler signal whose estimate was directly measured changes during a longer portion of time, e.g. all the time. As shown
The MSE device 65 includes a signal path 6 that transfers the measured Doppler signal directly from the wire 61 to the switch 62.
0 in parallel. Therefore, the directly measured Doppler signal passes through the upper line (solid arrow), and the lower line (dotted arrow) carries the estimated value signal from the MSE device 65 to the next part, for example the control device 4, and then For example, the signals are displayed on a display screen such as screen 3 in FIG. If the device according to the general idea of the invention is made to use the estimate signal all the time, the switch 62 will always be connected to the lower line, i.e. it will probably be connected to the signal path through the MSE device 65. seems to be sufficient. switch 6
2, by appropriate control thereof it is possible to select the portion of time in which the estimate signal is to be directly measured instead of the Doppler signal.

The estimates are generated in the MSE device 65 corresponding to the device 5 of FIG. 1 on the basis of the measured Doppler signal, for example with the associated interruption time, ie before and after this time. An estimate of the missing Doppler signal may be made, for example, in the following manner: (a) Based on the Doppler signal, e.g. at the end of the Doppler time, an estimate signal is generated, e.g. by adding broadband noise to a control filter network; can be generated. This is shown in FIG. Shown in FIG. 7 is a broadband noise generator 73, a control filter 72, and a device 71 that serves to generate filter parameter signals that control the instantaneous filter characteristics of filter 72. The filter is designed, for example, as a transversal filter in which the tapping weights are adjusted by filter parameters to obtain the desired spectrum.

(b) According to FIG. 8, the directly measured Doppler signal is continuously stored in the digital storage 82, for example by the cooperation of address jump controls in address counters 85 and 84. When an interruption is made for an image sweep, the last stored portion of the Doppler signal is read out and utilized as an estimate during the imaging period.

In the embodiment of FIG. 8, devices 82, 83 and 84 are considered to constitute the MSE device 5 shown in FIG. In a corresponding manner, the above embodiment of FIG. 7 includes devices 71, 72, 73 and 74 which may be considered as forming an MSE device.

The "directly measured" Doppler signal, indicated at 61 in FIG. 6, passes through a high-pass filter, for example filter 81 as shown in FIG. For Doppler pulse measurements, there must be inserted filters before and after the high-pass filter.

In order to obtain a smooth transition between the estimated Doppler signal and the directly measured Doppler signal, the signal may be multiplied by a window function as shown at 63 in FIG. By this method, the signal level is gradually reduced to zero before switching, and then again gradually increased to full magnitude after switching. This is illustrated in Figure 9, which shows how the signal level changes when converting from Doppler measurements to echo imaging and vice versa. An overlap between the directly measured Doppler signal and the estimate signal is also obtained by starting to increase the level of the estimate signal in the conversion from the direct signal to the evaluation signal while decreasing the level of the direct signal. The conversion from the estimate signal to the direct signal thereby initiates an increase in the level of the direct signal, while decreasing the level of the estimate signal. This smoothing or adjustment of the signal transition is particularly important at the end of each interruption period, ie when changing between the estimate signal and the directly measured Doppler signal.

In order to suppress strong reflections from the tissue boundaries of biological tissues, the Doppler apparatus is equipped with a high-pass filter 81 (FIG. 8) with high edge selectivity. When starting the Doppler measurement after the imaging time (interruption time),
It seems that there is a transient phenomenon in the high-pass filter.
Directly measured Doppler signals may not be applicable during the high-pass filter transient signal time, so estimates must also be used during this time. Therefore, the evaluation time appears to be longer than the image sweep time shown in FIG.

The transient phenomenon time of the high-pass filter is shown in Figure 8.
The signal is multiplied and reduced before the filter by a window function denoted by . The signal level before filter 81 is then slowly increased from zero to its fixed magnitude.

The reduction in transient time in the high-pass filter also
obtained by changing the frequency response of the filter during the transient period. An example of a prefilter network 100 that does this is shown in FIG. 11, which incorporates a voltage controlled resistor 102 with a control signal input 103. When a Doppler measurement begins, the value of control resistor 102 is very low, ie, approximately equal to zero, so that the amplification of filter 100 is low and the shear frequency is high. The value of control resistor 102 is then increased to its maximum value for 2 milliseconds after switching on the Doppler device after the image sweep.

Furthermore, in addition to an actual prefilter network consisting of a capacitor 101 and a control resistor 102, FIG.
05 and the required buffer amplifier 104 is shown, the transient period of which should be reduced. The prefilter network is incorporated as part of the high pass filter.

It is clear that in the prefilter network 100 of FIG. 11, the capacitor 101 is a variable capacitor and is voltage controlled instead of the resistor 102, ie both these components can be voltage controlled. What is important here is that the described property changes are obtained.

FIG. 12 shows a preferred transducer array for use in a device according to the invention, which is particularly relevant to the embodiment of FIG. As shown in the example of FIG. 12, a number of transducer elements are placed along the line. The central 16 elements, or perhaps all elements, are used for continuous Doppler measurements, with half of these elements being transmitting elements and the other half being receiving elements. This is obtained by electronic switching or perhaps by a relay in a manner known per se. In the pulsed mode of Doppler measurements, both halves, each containing 8 transducer elements, are interconnected so that the 16 central elements operate in parallel.
During echo imaging, the generic transducer elements are assumed to operate in a control manner known per se. It is clear that this array has transducers other than the 32 transducers shown in FIG. Furthermore, with continuous Doppler measurements, the subdivision of the number of transducers used may differ from the situation where half of the elements are used for transmitting and the other half for receiving.

Finally, it should be mentioned that the ratio of the respective time intervals for Doppler measurements and echo imaging is different from that described with respect to FIG. Thus,
Depending on the desired accuracy in velocity measurements, Doppler measurements can occupy a shorter portion of time than imaging (interruption time).

[Brief explanation of drawings]

1 is a block diagram of an apparatus for carrying out the method according to the invention; FIG. 2 is a schematic diagram of a first type of image display by the apparatus according to the invention; and FIG. 3 is a second type of image display by the apparatus according to the invention. FIG. 4 is a schematic diagram showing a variation of the arrangement of FIG. 2 with another Doppler transducer; FIG. 5 is a schematic diagram showing a variation of the array of FIG. Schematic diagram showing another form of usage-based display, No. 6
7 shows a schematic diagram of one embodiment for constructing an estimate of the Doppler signal; FIG. 8 shows the evaluation FIG. 9 is a schematic diagram showing the time division between echo imaging and Doppler measurement as well as some signal processing (window function); FIG. Time diagrams similar to those shown in FIG. 9, but a particular embodiment based on the use of a high-pass filter; FIG. 11 is an example of a prefilter network to be arranged before the high-pass filter of the device; FIG. 12; is an example of a transducer array for use in a device according to the invention. Explanation of symbols, 1... Doppler measuring device, 2... Echo imaging device, 3... Cathode ray tube screen, 4...
...Central control unit, 5...MSE (Missing Signal Estimator).

Claims (1)

[Claims] 1. Ultrasonic Doppler blood flow velocity measurement, pulsed wave or continuous wave mode, pulse-echo amplitude imaging,
A combination device for examining biological tissue,
The combination device is configured to perform the Doppler measurement and the amplitude imaging alternately at a fast alternating speed such that the Doppler measurement and the amplitude imaging can be observed simultaneously by a user, comprising: sweeping the amplitude imaging; Each time period for the scanning velocity of the ultrasound beam over a complete or significant portion of the image range is such that the amplitude of the imaging itself is not lower than that of an independent imaging device, and the scanning speed of the ultrasound beam is a complete sweep over that image range. each time period for a Doppler measurement has a minimum length determined by the Doppler measurement frequency to obtain a calibration value with the required accuracy. , said amplitude imaging together with a representation of the Doppler measurement area, which consists of a small confined area for pulsed wave measurements, or includes an overlapping area of pulsed waves between the transmitting and receiving beams of the transducer for continuous wave Doppler measurements. represented in real time on a display device, the combination device comprising: a Doppler measurement device providing a pulsed or continuous wave mode measurement output; a pulse-echo amplitude imaging device; and at least one for Doppler measurement and amplitude imaging. an ultrasound transducer, the transducer being within a range where signals can be transmitted between the Doppler measuring device and the imaging device, and synchronizing Doppler measurements and amplitude imaging; A control device configured to provide at least one of imaging and spectral Doppler data in real time by displaying the data in combination, and within a range where signal transmission between the Doppler measurement device and the imaging device is possible. and said controller in signal communication therewith; said Doppler measurements being repeatedly interrupted to provide, at least in a significant portion, a complete sweep of the ultrasound beam over the amplitude imaging range, and for each interruption means for sufficiently updating the image; and means for generating an estimated signal having a spectral content close to the signal of the Doppler measurement, the means being within the signal transmission range of the Doppler device and in signal communication with the Doppler device; and said means for determining said estimated signal based on said Doppler measurements, wherein said estimated signal is determined based on said Doppler measurements after being filtered through a Doppler device high-pass filter, at least when no useful Doppler measurements are taken. As a result, it replaces the output device of the combined Doppler signal, thereby providing an independent imaging without reducing the maximum velocity measured alone by the Doppler device itself or independently. An ultrasonic device characterized in that it provides an approximation of instantaneous Doppler measurements, pulsed or continuous wave, and amplitude imaging without reducing the beam scanning speed for amplitude images produced solely by the device. A device that combines sonic Doppler blood flow measurement and pulse-echo amplitude imaging. 2. The apparatus of claim 1, wherein the means for generating the estimated signal is adapted to form an estimated value for each estimation period on the basis of a Doppler signal curve during a time associated with each estimation period; The apparatus wherein the estimated value replaces the Doppler signal of the Doppler measurement during the estimation period. 3. The apparatus according to claim 1, further comprising a storage device for continuously storing Doppler measurements and reading out the final storage of the Doppler measurements to form an estimate during each estimation period. The device comprising: 4. The device according to claim 3, further comprising: means for determining the characteristics of the Doppler measurements; a control filter with an instantaneous filter characteristic adjusted on the basis of the characteristics of the Doppler measurements, e.g. the power spectrum; a broadband noise source sustained in the filter such that the output provides an estimate of a Doppler measurement. 5. Apparatus according to claim 4, further comprising means for introducing a window function before the high-pass filter to reduce transients in the high-pass filter. 6. The apparatus of claim 1, wherein the estimation is performed in a Doppler measurement path after the high-pass filter. 7. The apparatus of claim 6, wherein the high-pass filter characteristic is varied from an increasing frequency limit to a low cut-off frequency during a time period of the same magnitude as the transient period of the high-pass filter. Said device. 8. The device according to claim 7, wherein a prefilter network is incorporated into the high-pass filter, the prefilter network having a series capacitor filter and a parallel resistor, the capacitor or resistor being voltage controllable. said device, said device being adapted to supply a control voltage which is present and which changes the filter characteristics. 9. The device according to claim 1, further comprising means for adjusting or smoothing the Doppler measurement signal or the estimation signal at the transition between Doppler measurement and echo imaging, in particular at the end of the estimation time. Said device. 10. Apparatus according to claim 9, characterized in that the smoothing device is adapted to multiply the signal or signals by a suitable windowing function, for example a cosine function. 11. The apparatus of claim 1, wherein at least one of said very high frequency transducers has a number of transducer elements arranged along a straight line, some of which transducer elements act as transmitters in Doppler measurements. , while the remaining part of the transducer elements operates as a receiver, and the entire number of transducer elements in the array is adapted to be activated during echo imaging. 12. The apparatus of claim 1, wherein the output device provides an audible output of the combined Doppler signal.