JPS59168844A - Ultrasonic examination method and apparatus - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultrasonic inspection method and apparatus for applying ultrasonic waves to dentistry, particularly for measuring the position of alveolar bone, which is a small object at a close distance. be.

More specifically, as shown in Fig. 1, alveolar bone (2) is formed outside the root of the tooth (1), and its surface is covered with gum (3). Knowing the condition of 2) is extremely important in dental treatment. This alveolar bone (
2) Since the distance from the gingival surface is short and the size is small, high resolution and short scan time are required for ultrasonic examination, and the acoustic impedance is significantly different from that of a living body. It is something. The present invention relates to a method and apparatus for measuring such objects.

Conventionally, ultrasound examinations for dental applications use a single probe.
Fix this to the front surface of the gingiva and emit an ultrasonic beam, detect the returned echo with the same probe and measure the position of the echo, then move the probe and repeat the same method. Measure with. In this way, moving one point at a time for measurement is inefficient, and the distance from the probe to the subject is extremely short, so slight fluctuations in the fixed position of the probe can cause This resulted in inaccurate tomographic images, and there was also a limit to the resolution in the depth direction.

The present invention was made to solve the above-mentioned problems, and the size of the probe is 15 x 3.5 mm or less in length, and an electronic scanning method is adopted for transmitting and receiving ultrasonic waves. In order to increase the resolution in the depth direction, the frequency is as high as possible (10 to 40 MH2), and in order to widen the directivity of the transmitted and received waves, at least the effective directivity angle at the time of wave reception is set to a wide angle of 35 degrees or more. It will be as follows.

An embodiment of the present invention will be described below with reference to the drawings.

In Figure 1, (4) indicates a probe, and this probe (
4) is a vibrating element (5□×52
)... are arranged at a constant pitch. The overall length (1), width (W), and vibrating element pitch (pl) of the probe (4) are determined as follows.

The length J-) depends on the length of the tooth (1) being examined, but at the same time, the ultrasonic waves emitted from the vibrating elements (5,) (52)... From the viewpoint of the sensitivity of the apparatus, it is important that the length is such that it can easily hit the surface of the subject (1) and that it can accurately face the subject (1). Furthermore, it is determined in consideration of operability. Specifically, it is about 8 to 151115.

Width) is medium direction resolution, vibration element (51 x 52)...
It is determined by taking into account the length of the near-field sound field (that is, the effective length of the ultrasonic wave spreads after being emitted and is proportional to the valley), sensitivity (proportional to W), operability, etc. Specifically 2
．． It should be about 5 to 3.51.

The pitch (p) of the vibration elements (51 x 52) should be set to suppress vibrations other than thickness vibrations as much as possible, to simplify the electronic circuit for control (the fewer the number of elements, the better), and to increase the fineness of the image. The number of elements is determined as appropriate, taking into consideration the shape and dimensions of the subject site, ease of probe operation, etc. Specifically, it is set to 0.2 to 0.6 m. Therefore, the vibration element (51) attached to the surface of the probe (4)
The number of X52)... is 10 to 30.

As the scanning method of the probe (4) configured as described above, an electronic scanning method is adopted. This electronic scanning method
Compared to mechanical scanning methods, there is no mechanical vibration and it is easier to operate. The electronic scan method mentioned here includes the linear scan method shown in Figure 2, and the compound (see Figure 3).
There are the linear + sector scan) method and the holographic imaging method shown in FIG.

More specifically, the linear scan method shown in FIG.
of the vibrating elements (5□×52)... are received first, and their output voltages are added. At this time, echoes are returned from the center of a group of five transducer elements. Next, the second to sixth vibration elements (52) ~
(56), 3rd to 7th vibration elements (53) to (5
□), one by one, and repeat pulse emission and echo reception at the same time. When the transmission/reception from n-4th to nth ends, the process returns to numbers 1 to 5 again. When scanning in this way, the scan hitch will move through the vibration elements (5□) (52
)... is equal to the pitch (p). In addition, in this case, 1 to 5, engineering to 6.2 to 6.2 to 7.3 to 7.3 to 8,
If you move like..., the scan pitch will be halved to 2p.

Next, the compound method shown in FIG. 3 is a combination of the linear method shown in FIG. 2 and the sector method. Here, the sector method is a so-called phased array method in which an appropriate delay time is given to the drive of each vibrating element (51×52), and the main beam is waved in a fan shape. By combining this sector method and the linear method shown in FIG. 2, for example, 1 to 5.2 to 6.
While performing linear scans such as 3 to 7, etc., at the same time, by giving unique delay times to each vibrating element (5,
This results in a scanning line with .

Next, in the holographic imaging method shown in Fig. 4, pulses are emitted by simultaneously driving a group of, for example, five vibrating elements (5m) to (sm+4), and echo signals are transmitted from all the vibrating elements (5,) to (sm+4). (5n).

In FIGS. 2, 3, and 4, the object to be examined is small and the object is to be applied to extremely short distances, so high resolution is required. Therefore, in the present invention, 1
Frequencies from 0 to 40 MHz are employed. However, even if the frequency is increased unnecessarily, there are disadvantages such as decreased sensitivity of the probe, attenuation of ultrasonic waves, and difficulty in increasing the amplification factor of the amplifier, so there is a limit to increasing the frequency. be. In addition, in order to widen the directivity of ultrasound transmission and reception, at least the maximum directivity angle (2
θ) is required to satisfy the condition that it can be viewed at a wide angle of 35 degrees or more.

Next, in order to use it for dental purposes, a gel-like ultrasonic coupling agent (6
) it is desirable to emit ultrasound pulses through the For example, applying an electric shock as shown in Fig. 7 (al),
The echo signal (when receiving [3), this electrical impulse) is amplified to the saturation state (for example, 1000 times) as shown in A' in Figure 7(b), but because the diagnostic distance is short, the tail Since the tail (C1 occurs and the echo signal 03) cannot be distinguished from the echo signal 03, the influence of this tail (tc) must be removed. To remove this, vibrating element (5, X52)...
・There is a method of increasing the sensitivity and using an echo signal that is relatively higher than the level of the tailing, but this can be done by reducing the attenuation of the ultrasonic waves and increasing the sensitivity. However, since the diagnostic distance for teeth, which are objects to be examined, is extremely short, it is not preferable to use a low frequency wave and to increase the size.

Therefore, in the present invention, the hemming range is excluded and only the time (distance) that is not affected by the hemming is used. Specifically, in the case of high-frequency ultrasound of 20 MHz, z, agar gel, starch gel, Apply an ultrasonic coupling agent (6) such as Funo () gel, and apply 1.5 to 2
Provide the distance between the dragons (d).

If the probe (4) is set so that the subject (1) faces the convergence position of the emitted pulses, an image with the highest resolution can be obtained. For this purpose, a stopper (7) is attached to one or both ends of the probe (4), as shown in FIG.
) is installed. With this configuration, the fifth
As shown in the figure, after applying the coupling agent (6), just press it against the probe (4) and the subject (1) for a certain distance (
dl is maintained and operability is improved. It is not preferable to provide the stopper (7) around the entire circumference of the probe (4) because air bubbles are likely to enter the coupling agent (6) during mounting.

Next, as shown in Figure 8+2)(b), the probe (4) is automatically or manually moved to the point (P) in the vertical position.
(Ql(R,l (81) Multiple tomographic images C with shifted measurement positions by sequentially moving parallel to Tl
P) (Q) (R1(S) Obtain (T) and knead the same CRT (ii!+ of 81) as shown in Figure 9.
Display it on i'ij+i. At the same time, these tomographic images (P) (Q) (R,l (S) (Tl
Display a plane image 0) of the edge of a certain specific position, for example, the upper edge of the alveolar bone (2) on the screen of the same CRT (81). To detect, (PI Ul (R) (S) (T)
The data is extracted from the image memory of
Tomographic image (P) (Q) (RJ (8) (Point of maximum tomographic distance from Tl (p) (ql (r)
(s) (t) or tomographic image (P) (Q+
(R,) (81) It is sufficient to extract the point where the gradient of (T) changes from negative to positive.

Since the present invention provides the above-described method and apparatus, even when the distance from the probe to the subject is extremely short, such as in the case of alveolar bone, cross-sectional rrt images can be obtained efficiently and accurately. Also, multiple pieces of - no Dan JM songs + (&wo1ff
Since it is displayed on the iJ-monitor, mutual change points can be easily distinguished, and furthermore, by extracting only the change points and creating a planar image, planar changes can also be clearly recognized. Also,
Since the probe is provided with a stopper, it is possible to maintain an appropriate distance from the probe to the subject.

[Brief explanation of the drawing]

The figures are for explaining one embodiment of the ultrasonic inspection method and equipment according to the present invention. Fig. 3 is an explanatory diagram of the compound method of the electronic scanning method, Fig. 4 is an explanatory diagram of the holographic imaging method of the electronic scanning method, and Fig. 5 is an explanatory diagram of the holographic imaging method of the electronic scanning method. Figure 6 is an explanatory diagram when a stopper is provided. Figures 7 (a) and (b) are output waveform diagrams before and after amplification of electrical shock and echo signals. Figure 8 is an explanatory diagram when applied.
Figures (al(b) are explanatory views of the side and front views of the measurement points, and Figure 9 is a front view of the monitor. (1) Teeth as the subject, (2) Alveolar bone,
(3)...Secondment, (4)...Probe, (51)~(
5n)... Vibration element, (6)... Coupling agent, (
7) Stopper, (8) CRT0 patent applicant Toshiaki Furusawa, patent attorney at General Co., Ltd.

Claims (5)

[Claims] (1) Use a vertically long probe at an ultrasonic frequency of 10 to 4°■
Vibrate with Iz, transmit and receive waves by electronic scanning so that the directivity angle when receiving waves is 35 degrees or more,
An ultrasonic inspection method that displays the received signal on a monitor. (2) The ultrasonic inspection method according to claim 1, wherein a gel-like ultrasonic coupling agent is interposed between the object to be inspected and the probe. (3) The ultrasonic wave according to claim 1 or 2, in which a plurality of enhanced images of the received signal are divided and displayed simultaneously on the same monitor while the measurement position is being smoothed. Inspection method. (4) The ultrasonic testing method according to claim 3, wherein specific positions are extracted from the multi-wave multi-wave images, and planar images of these specific positions are combined and displayed on a monitor. (5) Ultrasonic testing characterized by forming a vertically elongated probe with a size of 15 x 3.5 nm or less, and attaching a stopper to this probe to maintain the proper position with respect to the object to be inspected. Device.