JPS626455B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultrasonic tomographic diagnostic apparatus that removes multiple reflected echoes during ultrasonic irradiation and obtains clear tomographic images.

In general, this type of tomographic diagnostic equipment has a large number of transducer elements arranged in a linear manner, and pulses are emitted from a certain group of the transducer elements, and after the echoes are received by the same transducer element, they are emitted by the next group of transducer elements. A similar operation is performed to complete one parallel scan, and pulses are emitted from the first group of vibrating elements again.

In this case, in addition to the original echo signal, the original echo signal is reflected again on the transducer surface, which is further reflected inside the living body and returned to the transducer element group as an echo signal. Next,
If we call the tertiary, ……… reflection multiple reflections,
Although multiple reflections gradually attenuate, they appear periodically, and their intensity increases, especially when there is a strong echo source inside the living body.As a result, they become mixed with the original echo signal of the transducer group. As a result, the image obtained by combining the original echo signals from the vibrating element group becomes unclear, and in some cases, this may cause misdiagnosis.

It is an object of the present invention to provide an ultrasonic diagnostic apparatus that solves this problem and obtains a clear image by removing noise based on multiple reflections that adversely affects the original echoes from an ultrasonic tomographic image based on echo synthesis. That is the purpose.

The present invention will be described below based on embodiments with reference to the drawings.

FIG. 1 is an explanatory diagram showing the relationship between a vibration element and an echo source inside a living body. The pulse α emitted from the vibrating element 10 is reflected by the echo source 20 and returns β, but is again reflected γ by the vibrating element 10, and further reflected by the echo source 20 to return γ to the vibrating element 10. Here, as shown in Fig. 2, if the arrival time of the primary echo signal 1 is t, echoes 2 and 3 due to multiple reflections return at intervals of 2t and 3t, respectively. It happens. However, in this case, as shown in Figure 2,
Compared to the original echo 1, the multiple reflection echoes are gradually attenuated in the order of their arrival.

The principle of the device of the present invention is that, as shown in FIG. The purpose is to obtain the state shown in the figure after processing. That is, in the present invention, a digital memory system is used in which the value of multiple echoes estimated from the first echo is stored in an address and removed. Now, to simplify the explanation, we will discuss the removal of double multiple echoes. After A/D converting the echo signal, it is stored as the original signal in the memory at address _A1 according to the depth, and at address ( 2×A ₁ ) and address (2×A ₁ +1) by performing a ratio calculation necessary for removing multiple echoes and storing the calculated value as a negative value. Furthermore, the following echo signal is
The data at the address (A ₂ ) corresponding to the depth is read out, summed with the new echo signal, written to that address, and (2×A ₂ ) and (2×A ₂
+1) is also stored with a negative value in the same manner as above. In this way, multiple echoes can be eliminated, and an echo signal without multiple echoes can be obtained by D/A conversion.

In this case, more accurate removal is possible by comparing the removed signal with surrounding signals and returning it to the arithmetic unit.

Of course, echo signals due to multiple reflections are not generated only between the vibrating element and the echo source, but they are generated periodically at least every n times the arrival time t of the primary echo signal (n is an integer). If the returning echo signals are removed, the blurring of the image due to noise will be significantly reduced, and this effect was confirmed in the experimental results.

Thus, the present invention is an extremely useful device in that images based on the synthesis of echoes in conventional ultrasonic tomographic diagnostic devices become even clearer, making it possible to make correct diagnoses.

[Brief explanation of the drawing]

FIG. 1 is a diagram illustrating echoes and their reflections accompanying ultrasonic emission, and FIG. 2 is a diagram illustrating the principle of the apparatus of the present invention.

Claims (1)

[Claims] 1. In an ultrasonic diagnostic apparatus in which a large number of vibrating elements are arranged in a straight line to form a probe, and a set of a certain number of vibrating element groups among these are sequentially switched electronically to scan a tomographic image, the vibration Among the ultrasonic echoes emitted from the element group, in order to eliminate the multiple reflection signals that arrive at a time n times the arrival time of the first echo signal (where n is an integer), the first echo signal that arrives is A/D conversion is performed and stored in the address A ₁ memory according to the depth, and a negative value corresponding to the multiple echo to be removed from the strength of the first echo is stored in the address (nA ₁ ) and address (nA ₁ +1). An ultrasonic tomographic diagnostic apparatus characterized in that a digital memory system is used, which calculates the ratio of the values of and stores the respective values, erases the negative values, and performs D/A conversion to obtain an echo signal free of multiple echoes.