KR100891289B1 - Ultrasound diagnostic system and method for forming i q data without quadrature demodulator - Google Patents

Abstract

An ultrasound diagnostic apparatus and method for forming IV data without an orthogonal demodulator is disclosed. The beamformer extracts at least two pairs of data having a phase difference of 90 degrees from a receiving focus output at an integer multiple of the center frequency of the analog received signal to form I and Q data.

Beamforming, Center Frequency, Integer, Extraction, IQ Data

Description

ULTRASOUND DIAGNOSTIC SYSTEM AND METHOD FOR FORMING I Q DATA WITHOUT QUADRATURE DEMODULATOR}

1 is a schematic view showing the configuration of a conventional ultrasonic diagnostic apparatus.

Figure 2 is a schematic diagram showing a method for forming IQ data using an orthogonal demodulator provided in the conventional ultrasonic diagnostic apparatus.

Figure 3 is a block diagram showing the configuration of an ultrasound diagnostic apparatus according to an embodiment of the present invention.

4 is a block diagram showing a detailed configuration of a beamformer according to an embodiment of the present invention.

5 is a schematic diagram for explaining data delay using dual port RAM according to an embodiment of the present invention;

6 is a block diagram showing the detailed configuration of the extraction unit and the detailed configuration of the interpolation unit for adjusting the amount of the digital signal according to an embodiment of the present invention.

7 is an exemplary diagram for explaining extraction of a high frequency signal and a low frequency signal according to the present invention;

8 is a graph showing the relationship between the amount of calculation and the center frequency of the digital signal output from the ultrasonic diagnostic apparatus according to the present invention.

9 to 11 are schematic diagrams for explaining a method for forming IQ data according to an embodiment of the present invention.

12 is a block diagram showing the configuration of an ultrasonic diagnostic apparatus according to another embodiment of the present invention.

<Description of Drawing>

10, 100, 200: ultrasonic diagnostic apparatus 11, 110: probe

12 and 130: beamformer 13: scan line data forming unit

13a: high-band filter 13b, 13c: multiplier

13d, 13e: low pass filter 13f: memory

14, 150: DSC 15, 160: display unit

120: ADC 140: DSP

131: outline delay unit 132: extraction unit

132a: shift register 132b: processing register

133: interpolator 133a: coefficient RAM

133b: multiplier 133c: adder

133d: register 134: control unit

The present invention relates to a method for forming an ultrasound image, and more particularly, to an ultrasound diagnostic apparatus and method for forming IV data without an orthogonal demodulator.

The ultrasound diagnosis apparatus transmits an ultrasound signal to an object to be examined, receives an ultrasound signal reflected from the object, converts the received ultrasound reflection signal into an electrical image signal, and shows an internal state of the object. It is widely used in underwater search. The ultrasonic signal is transmitted and received through a probe.

As shown in FIG. 1, the ultrasound diagnostic apparatus 10 includes a probe 11, a beamformer 12, a scanline data forming unit 13, a digital scan converter (DSC) 14, and a display unit 15. do. The probe 11 includes a plurality of transducers for converting an electrical signal into an ultrasonic signal and transmitting the same to an object, and converting the ultrasonic signal reflected from the object into an electrical signal in an analog form. The ultrasonic signal reflected from the object by the distance difference between the transducers and the object reaches each transducer at different times. The beamformer 12 converts the analog received signal generated by each transducer into a digital signal, adds an appropriate delay to the digital signal in consideration of the time to reach the transducer from the object, and adds the delayed signal to add the received focused signal (RF signal). ).

The scan line data forming unit 13 converts the received focus signal into a baseband to form scan line data. As shown in FIG. 2, the scan line data forming unit 13 includes a high band filter 13a, a cosine function multiplier 13b, a sine function multiplier 13c, and a low band for removing a DC component from an RF signal. Filters 13d, 13e and memory 13f. Cosine function multiplier 13b, sine function multiplier 13c and low band filters 13d, 13e are provided from a quadrature demodulator.

The RF signal passing through the high-band filter 13a is multiplied by a cosine function and a sine function, and then passed through the low-band filters 13d and 13e, respectively, to form an in-phase component demodulated to the baseband. Form Q data consisting of data and quadrature-phase components. The I and Q data are stored in the memory 13f and form scanline data with I and Q data pairs. In Figure 2, "fc" represents the center frequency.

The display unit 15 receives the scan converted scan line data from the DSC 14 and displays an ultrasound image.

The conventional ultrasound diagnostic apparatus 10 includes an orthogonal demodulator including a cosine function multiplier 13b, a sine function multiplier 13c, and low band filters 13d and 13e shown in FIG. 2 to form IQ data. There is a constraint that must be taken.

The present invention provides an ultrasound diagnostic apparatus and method for forming IQ data without an orthogonal demodulator.

The present invention forms I and Q data by extracting at least two pairs of data pairs having a phase difference of λ / 4 from a focused signal outputted at an integer multiple of the center frequency of an analog received signal by a beamformer. Is the wavelength defined by the center frequency. According to the present invention, an A-mode (Amplitude mode), B-mode (brightness mode), M-mode (motion mode), color mode (doppler mode) or ultrasound image formation for the Doppler mode without the orthogonal demodulator Form IQ data.

As shown in FIG. 3, the ultrasound diagnostic apparatus 100 according to the present invention includes a probe 110, an analog-digital converter (ADC) 120, a beamformer 130, a digital signal processor (DSP) 140, and a DSC. (digital scan converter) 150 and a display unit 160.

The probe 110 converts an electrical signal into an ultrasonic signal to transmit an ultrasonic signal to an object, more specifically, a focal point within the object, and receives a ultrasonic signal reflected from the object to convert the electrical signal into an electrical signal (analog received signal). Contains the converter of. The analog received signal output from the probe 110 has a center frequency associated with the characteristics of the transducer and tissue.

The ADC 120 is provided with the number of transducers so that each transducer corresponds one-to-one to the ADC 120. The ADC 120 samples the analog signal output from the probe 110 at a constant rate, for example, 60 MHz, and converts the analog signal into a digital signal. In the ADC 120, since the sampling proceeds at a constant rate regardless of the magnitude of the center frequency of the analog signal, when the center frequency of the analog signal is low, a relatively large number of digital signals are obtained per cycle of the period defined by the center frequency. If the center frequency is high, relatively few digital signals are obtained per cycle.

The beamformer 130 extracts a part of the digital signal at an integer multiple of the center frequency to form a predetermined amount of focused signal. More specifically, the beamformer 130 delays the digital signal obtained by sampling at the ADC 120 according to a constant sampling rate, and delays a part of the digital signal delayed at a rate corresponding to an integer multiple of the center frequency of the analog signal output from the probe. Extracting and interpolating the extracted digital signal form a constant amount of focused signal. To this end, as shown in FIG. 4, the beamformer 130 includes an extractor 132 and an interpolator 133 for constantly adjusting the amounts of the digital signals output from the coarse delay unit 131 and the ADC 125. ) And the control unit 134. Furthermore, although not shown in FIG. 4, the beamformer 130 includes a transmission beam forming unit and a reception beam forming unit to implement basic functions of the beamformer included in the general ultrasonic diagnostic apparatus. The beamformer further includes a gain adjuster for compensating for attenuation.

The controller 134 controls the outline delay unit 131, the extractor 132, and the interpolator 133. According to the design of the ultrasound diagnosis apparatus 100, the controller 134 receives center frequency information from a user. Alternatively, the ultrasound diagnosis apparatus 100 may further include a center frequency information providing unit for analyzing the analog signal output from the probe 110 and providing the center frequency information to the controller 134.

The schematic delay unit 131 is implemented with dual port RAM. As shown in FIG. 5, the dual port RAM has a plurality of storage areas. The number of storage areas is less than or equal to the number of transformers. Each storage area in the dual port RAM is designated by a write pointer and a read pointer. Although not shown in FIG. 5, the dual port RAM includes a data writing pin and a reading pin, stores data input through the write pin in a storage area designated by the write pointer, and reads the data. Data stored in the area designated by the pointer is read through the read pin. The digital signal input from the ADC 120 corresponding to each transducer is stored in different storage areas. Before each transducer's digital data is written to the dual port RAM, both pointers are initialized to point to the same storage area of the dual port RAM. The data of each converter input from the ADC 120 is stored in a storage area designated by the write pointer, and each storage area is previously stored from the time when the data is stored in the storage area or from the time when the storage area is designated by the write pointer. It is specified by a read pointer after a fixed time has elapsed. The predetermined time depends on the delay profile formed by reflecting the transducer and the focal length in the object. As such, the received signal obtained by each transducer is sampled at a constant sampling rate by the ADC 120 and then delayed by the coarse delay unit 131.

The extractor 132 adjusts the amount of the digital signal based on the center frequency of the preset analog signal.

The extractor 132 adjusts the amount of the digital signal based on the center frequency of the preset analog signal. The extractor 132 includes a shift register 132a and a processing register 132b. Shift register 132a and processing register 132b are each provided with the number of receive channels of the system. On the other hand, when multiple reception scan lines are formed by a time divisional multiplexing method, the number of shift registers 132a and processing registers 132b increases according to the number of multiple reception scan lines.

Under the control of the control unit 134, the digital signal in the storage area designated by the read pointer is transferred to the shift register 132a. Preferably, the digital signal corresponding to each transducer is transferred to the shift register 132a corresponding to that transducer. Under the control of the controller 134, the extractor 132 is configured to convert some digital signals from the digital signals stored in each shift register 132a at a rate of n times the center frequency of the analog signal received from the probe, where n is an integer. Extract the signal. That is, some digital signals are extracted from the digital signals stored in the shift register 132a and transferred to the processing register 132b at a rate corresponding to n times the center frequency of the analog signal output from the probe. Preferably, the extraction rate is defined as in Equation 1 below.

In Equation 1, fc is the center frequency of the analog signal output from the probe, n is an integer. When the bandwidth is guaranteed to be twice the center frequency of the analog signal, the maximum frequency is twice the center frequency. According to the Nyquist theorem for the purpose of reducing aliasing, the sampling rate (i.e. the extraction rate) must be at least twice the maximum frequency, so the integer n is preferably 4, but is not limited thereto. It doesn't work.

As a part of the digital signal is extracted from the digital signal stored in the shift register 132a at a rate n times the center frequency of the analog signal, in the case of a received signal having a high center frequency (that is, one period from the ADC 120). When a relatively small digital signal is output, the digital signal can be extracted at a relatively high rate compared to an ADC output using a constant sampling rate. In addition, in the case of a received signal having a low center frequency (that is, when a relatively large number of digital signals are output from the ADC 120 per cycle), the digital signal is extracted at a lower rate than the ADC output using a constant sampling rate. do. In other words, when the density of scanline and frame rate are the same, the sampling rate is constant when the center frequency of the analog signal is high (high frequency signal) as shown in FIG. Extracting digital signals at a rate higher than the rate, and extracting the digital signal at a relatively low rate when the center frequency of the analog signal is low (low frequency signal), resulting in too much data using a high extraction rate at low frequencies. Is prevented from being extracted and compensated for the lack of data by using a low extraction rate at high frequencies. (For convenience of description, the waveforms of the high frequency signal and the low frequency signal are shown as the waveforms of the analog signal. Digital in high frequency or low frequency signals in the form of digital signals The call is extracted). Therefore, an almost constant amount of digital signal can be output from the beamformer regardless of the amount of signal output from the ADC120 (see FIG. 8). The degree of attenuation of the signal is proportional to the frequency, and as the frequency increases, the visible depth (transmission depth) decreases. In general, the maximum transmission depth is almost 512 times the wavelength defined by the center frequency, and the amount of digital signal output from the ADC depends directly on the center frequency. However, in the present invention, by using the extraction rate defined as in Equation 1 in consideration of the relationship between the center frequency and the degree of attenuation, the amount of digital signal output per one cycle can be controlled. Therefore, a relatively constant amount of digital signals can be extracted regardless of the magnitude of the center frequency.

The interpolator 133 interpolates the digital signal output from the processing register 132b. To this end, the interpolator 133 includes a coefficient ram 133a, a multiplier 133b, an adder 133c, and a register 133d as shown in FIG. . Coefficient ram 133a provides a look-up table of interpolation filter coefficients. Interpolation includes a process in which the multiplier 133b multiplies the digital signal input from the processing register 132b by the interpolation filter coefficients stored in the coefficient RAM 133a and adds the output signal of the multiplier 133b in the adder 133c. The output signal of the adder 133c, that is, the reception focus signal, is stored in the register 133d.

Referring back to FIG. 3, the DSP 140 forms IQ data for forming an ultrasound image such as an A, B, C, M, or D mode from the received focus signal output from the beamformer 130. . The DSP 140 extracts at least one pair of focused focus signals having a phase difference of λ / 4 from the received focused signals output from the beamformer 130 at a rate n times the center frequency of the analog received signal, and performs I, Q For example, as shown in FIG. 9, the DSP 140 selects the reception focus signals d, for example, d1, d2, d3, and d4 at a rate four times the center frequency of the analog reception signal. d1 and d2 have a phase difference of λ / 4, and d2 and d3, d3 and d4 also have a phase difference of λ / 4. When the reception focus signal selected by the DSP 140 is d1, d2, d3, d4, d5, d6, d7, d8 ... in order, the nth Q data is given a (-1) ^{n + 1} sign to Q. D1, -d3, d5, -d7, and the like are stored in the data memory in this order, and (-1) ^{n + 1} codes are assigned to the ^nth I data, and d2, -d4, d6, -d8, and I data memory. Save the ... in order. IQ data pairs such as (d1, d2), (-d3, -d4), (d5, d6), (-d7, -d8) ... as the nth stored data in the Q data memory and the I data memory, respectively. To form. When the beamformer output corresponding to n times the center frequency is output, n pairs of I and Q data are obtained per two periods of the center frequency.

Here, the reception focus data of each pair are selected at different times. Thus, this time difference is compensated for. Compensation may be made by using a filter coefficient of an interpolation filter for fine delay.

If a pair of focused signals is considered to be selected at the same time, a new pair may be obtained through combination with another pair. For example, (d1-d3, d2-d4) may also be a pair of new focused signals having a phase difference of λ / 4.

As another example, the DSP 140 may further include a compensator for compensating for a difference in selection time of each pair of reception focus signals instead of an interpolation filter for fine delay of the beamformer.

The DSC 150 scan-converts to display the image data input from the DSP 140, and the display unit 160 receives the scan-converted image frame data and displays the ultrasound image.

As shown in FIG. 12, the ultrasound diagnosis apparatus 200 according to another embodiment of the present invention includes a personal computer (PC) 210 in place of the DSP 140 and the DSC 150 shown in FIG. 3. In other words, the DSP and DSC functions are implemented in software through the PC 210.

According to the method for forming IQ data of the present invention, an ultrasonic signal reflected from an object is converted into an analog signal, the analog signal having a center frequency, and the analog signal is converted to obtain a plurality of digital signals. Extract a portion of the digital signal at an integer multiple rate to form a receive focus signal, extract at least one pair of data having a phase difference of λ / 4 from the receive focused signal, and phase of λ / 4 from the receive focused signal At least one pair of data having a difference is extracted, and the interpolation unit processes the phase difference of each data pair to be a phase difference obtained in the same time zone, thereby forming IQ data in the same time zone.

The present invention made as described above provides an advantage that the system can be more easily designed by forming IQ data without an orthogonal demodulator.

In addition, the present invention has an advantage that the processing power of an image processor such as a DSP or a PC does not act as a significant limitation in the design of the ultrasonic diagnostic apparatus by outputting a focusing signal having a relatively constant amount of calculation from the beamformer.

Claims (12)

A probe for converting and providing an ultrasound signal reflected from an object into an analog signal, the analog signal having a center frequency, the wavelength being defined by the center frequency; An analog-digital converter converting the analog signal input from the probe to form a plurality of digital signals; A beamformer extracting a portion of the digital signal at an integer multiple of the center frequency and forming a reception focus signal from the extracted digital signal; And At least one pair of reception focus signals having a phase difference of λ / 4 is selected from the reception focus signals sequentially output from the beamformer to form I and Q data, respectively, for the selected n th I data and n th Q data, respectively. (-1) A digital signal processor which gives ^{n + 1} codes and forms the I and Q data as nth I and Q data pairs Ultrasonic diagnostic device comprising a. The method of claim 1, And selecting the at least one pair of focused signals for one period defined by the center frequency. The method of claim 1, The digital signal processing unit, And a beam upper portion for compensating different selection times of the pair of reception focus signals of each pair. The method according to any one of claims 1 to 3, The beamformer, And an extractor for extracting a portion of the digital signal at an integer multiple of the center frequency to adjust the amount of the focused signal. The method of claim 4, wherein The extraction unit, A shift register for storing a digital signal input from the analog-digital converter; And And a processing register for storing the digital signal extracted from the shift register at an integer multiple of the center frequency. The method of claim 5, The beamformer further includes an interpolation unit for performing interpolation using a digital signal output from the extraction unit. The method of claim 6, The interpolation unit, Coefficient RAM for providing a look-up table of interpolation filter coefficients; And A multiplier for interpolating the digital signal by reflecting the interpolation filter coefficients in the extracted digital signal; And And an adder for adding the output of the multiplier to form the focused signal. The method of claim 4, wherein The probe comprises a plurality of transducers, The beamformer includes a delayer for delaying data corresponding to each transducer by reflecting the position of each transducer. The method of claim 8, And the retarder is comprised of dual port RAM. Converts the ultrasonic signal reflected from the object into an analog signal, the analog signal having a center frequency, the wavelength λ being defined by the center frequency, Converting the analog signal to obtain a plurality of digital signals, Extracting a portion of the digital signal at an integer multiple of the center frequency to form a received focus signal, At least one pair of receiving focus signals having a phase difference of λ / 4 from the reception focus signal is selected to form IQ data, and (-1) ^{n + 1} codes are respectively applied to the selected nth I data and nth Q data. And forming the I, Q data as an nth I, Q data pair. The method of claim 10, And forming the IQ data by compensating for different selection times of the pair of receive focus signals. The method according to claim 10 or 11, wherein IQ data forming method for selecting the at least one pair of the focused signal during a period defined by the center frequency.

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