JP2640656B2 - Ultrasound diagnostic equipment - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an ultrasonic diagnostic apparatus suitable for measuring the attenuation of ultrasonic waves in a living tissue, particularly in the field of medical equipment.

[Related Art] Various tissues are distributed in a living body, and each tissue has a frequency-dependent attenuation characteristic. As described in Japanese Patent Application Laid-Open No. Sho 59-218144, a conventional apparatus for measuring such attenuation characteristics analyzes the frequency of a desired position in a tomographic image and displays the result. It used the spectrum.

[Problems to be Solved by the Invention] However, according to the above-described conventional technology, for example, due to a difference in convergence and a magnitude relationship between an analysis region of a frequency component (hereinafter, referred to as a sample volume) and a focal depth of an ultrasonic beam, for example, Frequency ZM for a sample volume at a certain depth
While the Hz component includes the first zero point and the 4 MHz component includes the second zero point, at other depths the second zero point and the fourth zero point are included, respectively.
There is a problem in that the frequency range is affected by weights such as those including up to zero.

An object of the present invention is to always keep the influence of the weight of the frequency range at the time of frequency analysis constant from a shallow part to a deep part.

[Means for Solving the Problems] The above-mentioned object is achieved by using a means for varying the transmission or reception aperture in proportion to the ultrasonic focal point as disclosed in Japanese Patent Application Laid-Open No. 52-151277, thereby making the depth from the shallow part to the deep part substantially uniform. It is achieved by a method of forming an ultrasonic beam with a high degree of convergence, or a method of correcting the frequency analysis result of a measurement object with reference to the frequency analysis result in a medium whose frequency attenuation characteristics are known in advance. You.

[Operation] The azimuth resolution d and the depth of focus Δl in the transmission or reception of the diagnostic device are approximately determined by the wavelength λ, the focal point F, and the aperture D of the ultrasonic wave when considering the directivity zero point, and d2 · λ · F / D (1) Δ14 · λ · (F / D) ² (2) In a diagnostic device in which a substantially uniform beam is formed from a shallow portion to a deep portion in the short axis direction, approximately one beam is formed in the above range in the long axis direction. It can be considered that the weight is in such a frequency range. Here, assuming that the product is the product of the sample volumes Δl or a range smaller than the product, the equations (1) and (2) show Given by

From equation (3), it can be seen that when the value of the wavelength λ is constant, the sample volume ΔV is proportional to the cube of the value obtained by dividing the focal point F by the aperture D. Therefore, if the F / D value is kept constant and the focus is changed at least for each depth of focus Δl, the frequency component is analyzed in a region having a uniform frequency range weight at any depth. be able to.

In the method described below of the problem solving means,
By comparing the characteristics of the ultrasonic beam measured with a medium having a known frequency attenuation characteristic as shown in Expression (4) and the characteristics of the medium to be measured as shown in Expression (5), (6) to As shown by the equation (7), the attenuation characteristic of the medium to be measured is obtained without being affected by the weight of the frequency range.

P _out (r, w) = H _o (r, w) × a _o (r, w) × P _in (w)
(4) P ′ _out (r, w) = H (r, w) × a (r, w) × P ′ _in (w)
… (5) _{P out (r, w),} P 'out (r, w); the received signal power _{P in (w), P'} in (w); transmission signal power _{a o (r, w),} a (r, w) Directivity characteristics H _o (r, w), H (r, w); Attenuation characteristics As described above, each parameter r, w is represented as a function of depth and frequency.

Here _{P in (w) = P '} in (w), directional characteristics if it is assumed that does not change significantly in the _{decay, a o (r, w)} ≒ a (r,
a w), when comparing the attenuation characteristics identical Sagudo, at the same frequency component, H _o (r, w) is equal to a constant K from a known value, H (r, w) is equal to unknown H . Therefore,
Equation (6) can be expressed as equation (7).

u = H / K → H = u · K (7) [Embodiment] An embodiment of the present invention will be described below with reference to the drawings. First
FIG. 1 is a block diagram showing a configuration example of the present invention. In the figure, 1 is an ultrasonic transmission / reception probe constituted by arranging a plurality of ultrasonic transducers, 2 is an aperture selection circuit for selecting an ultrasonic transmission / reception aperture, and 3 is a transmission / reception aperture. A transmission / reception switching circuit for switching a signal transmission path, a transmission driving circuit for exciting and driving each transducer of a transmission aperture, and a reception phasing for performing phase matching and addition of reflected signals obtained by each resonator of a reception aperture. A circuit, 6 a signal processing circuit for performing various signal processing required for the configuration of the B-mode image, 7 a frequency analysis circuit for calculating the distribution of frequency components, and 8 a B-mode image, a result required for displaying the frequency analysis result and the like. An image memory for storing data, 9 is an image display device, and 10 is a signal processing control circuit for controlling each circuit.

In such a configuration example, at the time of transmission, first, the transmission aperture is selected by the aperture selection circuit 2 by the signal processing control circuit 10, and the three transmission / reception switches 3 are set to the transmission mode. Thus, for example, if the focus and aperture are selected as shown in FIG. 2A, a beam having a substantially constant width from the shallow portion to the depth as shown by the solid line in FIG. 4 is formed. The transducer excitation signal phase-controlled by the transmission drive circuit 4 is transmitted to the probe 1 via the transmission / reception switch 3 and the aperture selection circuit 2 to emit ultrasonic waves. Ultrasonic waves radiated into the human body are reflected on tissues or organ boundaries having different acoustic impedances and return to the probe again. At the time of reception, similarly, for example, the reception aperture as shown in FIG. 2A is sequentially selected by the aperture selection circuit 2 by the signal processing control circuit 10, and the transmission / reception switch 3 is set to the reception mode. As a result, a beam similar to the transmitted wave is formed. The received signals are sent to the wave receiving and phasing circuit 5 via the above circuits. In the wave receiving phasing circuit 5, the phases of the above-mentioned received signals are shifted and added according to the probe shape, the element arrangement interval, the reception focus, and the like, the phasing output is performed, and the signal processing circuit 6 and the frequency analysis are performed. Send to circuit 7. Signal processing circuit 6
Then, after a logarithmic compression process, a detection process, and the like of a signal necessary for the configuration of the B-mode image are performed, the signal is A / D-converted to an address corresponding to the aperture position and the reception time of the B-mode image storage area of the image memory 8. Remember. The frequency analysis circuit 7
Then, a received signal at a certain time with respect to each time is added, the signal is subjected to frequency analysis by FFT or the like, the distribution of the frequency component is obtained, and then the same as the above in the analysis result storage area of the image memory 8. Store it in the address.

The above operation is repeated by sequentially moving the transmission / reception aperture in the transducer array direction, thereby obtaining data for one screen, and displaying a B-mode image on the nine image display devices.

In the display of the frequency analysis result, as shown in FIG. 3, the operator designates an arbitrary analysis region position on the screen while observing the B-mode image displayed on the display device 9. Upon receiving this signal, the diagnostic apparatus main body displays a marker at a specified position on the screen, and reads out data of an address corresponding to the specified position from the frequency analysis result storage area of the image memory 8, for example, as shown in FIG. Display as shown on the left. In this example, the horizontal axis represents the frequency, the vertical axis represents the intensity, and the axis in the depth direction is displayed as a three-dimensional display.

FIG. 5 shows another embodiment of the present invention. In FIG. 5, 1 to 10 are the same as in FIG.
11 to 14 have the same configuration as 3 to 5. Where 2
5 and 7 are focuses suitable for frequency analysis (Focu
s), a frequency analysis circuit that performs signal processing by selecting an aperture. Numerals 11 to 14 and 6 are suitable for reproducing a B-mode image. For example, Focus, as shown in FIG. This is a circuit for a B-mode image that selects an aperture and performs signal processing.

The operation of each circuit is the same as that described in FIG.
In this embodiment, the circuit can be switched between the frequency analysis (a side) and the B-mode image reproduction (b side) by SW1 and SW2. Therefore, as shown in FIG. 4, when capturing a B-mode image, a narrow beam having a width as shown by a broken line is used as a high-resolution image, and a beam having a constant width from a shallow portion to a deep portion such as a solid line is obtained during frequency analysis. Perform attenuation measurement with. With such a configuration, it is possible to analyze the frequency components without deteriorating the B-mode image. Although the present embodiment has two circuits as described above, the present invention is not limited to this, and the same effect can be obtained by using one system of circuits in a time-division manner. Needless to say.

Further, in the present embodiment, a one-dimensional array in which the degree of convergence of the ultrasonic beam is not intense in the short axis direction and the weight of the frequency region is uniform has been described. Needless to say, the present invention is applied to an annular array that can be changed or a two-dimensional array that can change the aperture as well as the major axis, and the effect of the present invention is further increased.

FIG. 6 shows still another embodiment of the present invention. In FIG. 6, 1 to 10 are the same as in FIG.
Reference numeral 15 denotes a data correction circuit for correcting the obtained frequency analysis result with data representing the weight of the frequency range of the ultrasonic beam stored in advance.

The correction circuit 15 stores information corresponding to data representing the weight of the frequency range of the ultrasonic beam measured in a medium with little attenuation, such as underwater, and the information is stored in correspondence with the frequency-analyzed position. Read and correct the analysis result. The correction circuit 15 includes a circuit for calculating information for correction and a RAM (random access memory) or R
It is composed of a storage circuit such as an OM (Read Only Memory), and is configured so that the information for correction can be updated as appropriate.

[Effects of the Invention] According to the present invention, it is possible to analyze a frequency component deviated from the influence of the weight of a frequency range caused by a difference in convergence of an ultrasonic beam and a magnitude relationship between a focus search and a sample volume. effective. Further, there is an effect that the attenuation characteristic of the medium to be measured can be obtained without being affected by the weight of the frequency range.

[Brief description of the drawings]

1, 5 and 6 are block diagrams showing an embodiment of the present invention, FIG. 2 is a table showing the relationship between Focus and aperture, FIG. 3 is a schematic diagram of a display example on a display, FIG. The figure is a depth-azimuth distance characteristic diagram of the ultrasonic beam. DESCRIPTION OF SYMBOLS 1 ... Probe, 2 ... Diameter selection circuit, 3 ... Transmission / reception switch, 4 ... Transmission drive circuit, 5 ... Reception phasing circuit, 6 ...
Signal processing circuit 7, frequency analysis circuit 8, image memory 9, image display device 10, signal processing control circuit.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Keiyoshi Katakura 1-280 Higashi Koikebo, Kokubunji-shi, Tokyo Inside the Central Research Laboratory of Hitachi, Ltd. (56) References JP-A-59-218144 (JP, A) JP-A-61 JP-A-48343 (JP, A) JP-A-52-151277 (JP, A) JP-A-58-55850 (JP, A)

Claims (1)

(57) [Claims] 1. An ultrasonic transmitter / receiver comprising a plurality of ultrasonic transducers for transmitting an ultrasonic wave to an inspection object and receiving a reflected signal from the inspection object, and transmitting the ultrasonic wave in accordance with a focal length. An aperture selection circuit for selecting an aperture for reception, and a transmission / reception switch for switching between transmission and reception of ultrasonic waves,
A transmission driving circuit that performs transmission driving of the ultrasonic transceiver,
A reception phasing circuit for phasing a reception signal by the ultrasonic transceiver, a signal processing circuit for processing an output of the reception phasing circuit to obtain an intensity distribution image of the reflected signal, A frequency analyzer for analyzing the frequency of the output of the wave phasing circuit, a correction circuit for correcting the frequency analysis result by the frequency analysis circuit, a memory for storing the output of the signal processing circuit and the frequency analyzer, and the intensity An image display device that displays the distribution image and the frequency analysis result, and a unit that specifies a region in which the frequency analysis result is displayed in the intensity distribution image displayed on the image display device, The region is displayed on the display device in superposition with the intensity distribution image, and the correction circuit is measured with respect to the inspection target with respect to the received signal power measured in advance with a medium having a known frequency attenuation characteristic. By calculating the product of the ratio of the received signal power and the known frequency attenuation characteristic, the output of the frequency analyzer for the specified area of the inspection target is corrected, and the specified area of the inspection target is corrected. An ultrasonic diagnostic apparatus, wherein a frequency attenuation characteristic is obtained.