JPH0229242A - Response-to-refraction type ultrasonic non-linear type parameter ct - Google Patents

Abstract

PURPOSE:To reduce deterioration of the picture quality of a reconfiguration tomogram due to refraction by a method wherein a hydrophone array having a wide bore is used as an echo sounder receiver in order to prevent incurring of a wave receiving loss due to refraction of ultrasonic waves by which deterioration of the picture quality of the reconfiguration tomogram is caused mainly. CONSTITUTION:When differential frequency waves are used and when second higher harmonic waves are used, an echo sounder receiver is situated in both cases so that the center thereof is located on the sound axis of echo sounder beam. An echo sounder transmitter 2 and the echo sounder receiver 4 are scanned simultaneously in the same direction (a direction A or B), and by using a conventional algorithm, a non-linear parameter tomogram is reconfigured. In this case, when the echo sounder receiver having a small bore is used, it fails to receive ultrasonic beam which is refracted within a sample and changes its coarse. However, when an array is used, an echo sounder can be received throughout a wide range, and the receiver is prevented from failing in receipt of ultrasonic beam. This constitution enables measurement of a non-linear parameter tomogram which reduces deterioration of a picture quality due to refraction.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultrasonic medical diagnostic apparatus such as a refraction-compatible ultrasonic nonlinear parameter CT, and furthermore an ultrasonic non-destructive inspection 2.
Related to technology such as image processing.

In the conventional ultrasound nonlinear parameter CT, it is assumed that the transmitted ultrasound beam travels in a straight line, and the receiver is installed on the acoustic axis of the transmitted ultrasound beam. However, within the object, there is usually a sound velocity distribution, so the ultrasound waves do not travel straight and the propagation path of the sound waves deviates from the sound axis. Therefore, the ultrasonic waves that have passed through the object are received by a receiver. There is a problem in that the loss in the projection data caused by the loss of projection data causes deterioration in the image quality of the reconstructed tomogram of the nonlinear parameters calculated from the projection data.

The present invention was made in view of the above-mentioned circumstances.
In particular, this was done with the aim of reducing image quality deterioration of reconstructed tomograms due to the influence of refraction in ultrasonic nonlinear parameter CT that noninvasively visualizes the acoustic nonlinear parameter distribution of biological soft tissue.

In order to achieve the above-mentioned object, the present invention transmits large-amplitude ultrasonic waves as -order waves to a subject, which targets biological soft tissue, and generates them in a superimposed manner as the waves propagate. In ultrasonic nonlinear parameter CT, which reconstructs a nonlinear parameter tomogram by using the distortion components of It is characterized by the use of a wide-diameter hydrofon array. An explanation will be given below based on one embodiment of the present invention.

As mentioned above, in conventional ultrasonic nonlinear parameter CT, the image quality of the nonlinear parameter tomogram is determined by reconstructing the reception loss on the projection data caused by the refraction of the ultrasound beam within the object. was causing deterioration.

In the present invention, a wide-diameter hydro-on array is used for the receiver, so that even if the ultrasonic beam travels off the sound axis due to refraction, the receiver will not be able to receive the ultrasonic beam. It is characterized by the fact that it is In addition, instead of simply using a wide-diameter receiver, a five-structured array is used even for small-diameter hydrophones, making it possible to receive waves in a phase-insensitive manner, resulting in phase cancellation of the received sound field. It is possible to receive waves over a wide range of frequencies without being affected by errors due to

1 and 2 are block diagrams for explaining the present invention in detail, respectively. In the figures, 1, 1□, 1□ are oscillators, 2 is a transmitter, 3 is a subject, and 4 is a receiver. In the array, FIG. 1 shows an example in which a difference frequency wave is used, and FIG. 2 shows an example in which a second harmonic is used. The receiver is installed so that its center is on the acoustic axis of the transmitted beam. The transmitter 2 and the receiver 4 are simultaneously scanned in the same direction (in direction or B direction) to measure projection data. Projection data for each of the primary and secondary waves is measured from 180 degrees around the subject 3, and a nonlinear parameter tomogram is reconstructed using a conventional algorithm. Each receiving element (hydrofon)
After signal processing, the detected intensities of each part of the received sound field are added together to form projection data at that scanning position.

Figure 3 shows how waves are received when using a small-diameter receiver 4' and when using a wave receiving array 4. As a result, the reception of the ultrasonic beam that has been refracted and changed its course within the subject is impaired. However, when an array is used, it is possible to transmit the ultrasonic beam over a wide range as shown in figure (b), and the reception of the ultrasonic beam is not impaired.

FIG. 4 and FIG. 5 are diagrams for explaining the configuration of the receiver and the processing of the received signal.
In other words, the -th wave has two different frequency components + f
Using a beat wave with Z, the difference frequency components 1 to f2, which are distortion components, are used as projection data to calculate nonlinear parameters.
When reconstructing a tomogram, Fig. 5 shows that when using a second harmonic, that is, using a wave with a single frequency component in the − order wave, the second harmonic component that is the distortion component is used. 2
This shows the case where a nonlinear parameter tomogram is reconstructed using f□ as projection data, and in the figure, 4 is the receiving array.
5□, 5□, 5. is a bandpass filter, 6□.

6□, 6. is an adder, 7 is projection data of the first-order wave (f,), 8 is projection data of the first-order wave (f2), 9 is projection data of difference frequency, 10 is a bandpass filter, 111.1
1□ is an adder, 12 is projection data of the primary wave (fyu), 1
3 is the projection data of the second harmonic, 14 is the reconstruction algorithm, 15 is the nonlinear parameter distribution image, and the received signal from each array element is selected by a bandpass filter whose center frequency is the frequency of the primary and secondary waves. After that, they are added together. The received signal measured in this way is the -order wave,
Apply the energy of the sound waves that have passed through the subject to each secondary wave. The initial energy of the primary wave required for reconstruction is obtained from the received signal only underwater, where no object is present. A nonlinear parameter tomogram is obtained by applying a reconstruction algorithm used in conventional systems to the projection data of the primary wave and secondary wave obtained in this manner.

As is clear from the above explanation, according to the present invention, it is possible to measure nonlinear parameter tomograms with little deterioration in image quality due to refraction.

[Brief explanation of the drawing]

FIGS. 1 and 2 are block diagrams for explaining the present invention in detail, and FIG. 3 shows a case where a small-diameter wave receiver 4' is used (Figure (a)) and a wave receiving array. When using 4 ((b)
FIG. 4 and FIG. 5 are diagrams for explaining the configuration of the receiver and the processing of the received signal. 1.1□, 12... oscillator, 2... transmitter, 3...
・Subject. 4...Reception array, 5□, 5□, 53...Band filter. 6□, 6□, 6. . . . Adder, 7 . . . Projection data of primary wave (f), 8 . . . Projection data of primary wave (f2), 9 . . . Projection data of difference frequency, 10. ．． 10□・・
・Band filter, 11□, 112...Adder, 12・
...Projection data of the first order wave (f-engine), 13...Projection data of the second harmonic, 14...Reconstruction algorithm, 15
...Nonlinear parameter distribution image. Part <a> Illustration S skin sound field

Claims (1)

[Claims] 1. An ultrasonic method in which a large-amplitude ultrasound is transmitted as a primary wave to a subject, which targets biological soft tissues, and a nonlinear parameter tomogram is reconstructed using the distortion components that occur in a superimposed manner as the ultrasound propagates as projection data. Sonic nonlinear parameter C
In T, refraction-compatible ultrasound nonlinear parameters are characterized by using a wide-diameter hydrophone array as a receiver and eliminating reception loss due to ultrasound refraction, which is the main cause of image quality deterioration in constituent tomograms. C.T.