JPS6133439B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a highly sensitive ultrasonic probe.

BACKGROUND ART Ultrasonic tomography devices, which are used as medical devices and can view tomographic images of the heart and abdomen in real time, have recently become popular. This is because these methods are characterized by being non-stretchy and capable of obtaining a large amount of information from a tomographic image of a living body without any danger. Ultrasonic diagnostic methods include the pulse reflection method, Doppler method, transmission method, etc., but the pulse reflection method is currently in practical use. The principle of pulse reflection method is the same as that of emitting ultrasonic pulses of 1 MHz to 10 MHz from an ultrasonic transducer (piezoelectric element), and echoes due to impedance mismatch are returned from the interface of tissues (substances) with different acoustic impedances. A tomographic image of a living body can be obtained by receiving an echo using a transducer, applying brightness modulation to a cathode ray tube based on the intensity of the received signal, and displaying the position and intensity of the echo.

Important characteristics of this ultrasonic probe include sensitivity and separation ability. Good sensitivity means that the size of the echo is large relative to the emitted signal, and good resolution means that the amount of information brought by the echo is also large, and the S/N ratio is also large. In order to increase this separation power, at least two things are necessary. One is to increase the ultrasonic frequency and shorten the wavelength. In other words, half a wavelength is required just to measure distance, and the speed of sound in a living body is
1500m/s, so 1MHz ultrasound is 0.75mm
The separation power is only . Therefore, the wavelength is shortened, and generally a frequency of 2MHz to 5MHz is used. Another method is to appropriately damp the Q of the vibrator to absorb unnecessary waveforms and absorb ultrasonic waves coming from the opposite direction. Therefore, the vibrator is used by pasting it on a material with a low Q value, such as rubber, called bucking material. Furthermore, in order to increase the separation ability, the frequency can be increased, but as the frequency is increased, the attenuation of the ultrasound waves in the living body increases, so the echo signal becomes smaller. However, the current trend is that frequencies are moving toward higher frequencies due to the development of control electronic circuits.
Therefore, in order to increase the sensitivity, a device with an acoustic impedance between the transducer and the living body is installed to achieve matching, so that ultrasonic waves can be more efficiently introduced into the living body. For this matching layer, it is effective to use a thermosetting resin such as epoxy resin with a wavelength of 1/4 of the frequency used by the vibrator, both in terms of acoustic impedance and acoustic matching. Therefore, the higher the frequency, the thinner the vibrator and matching layer need to be. For example, at a frequency of 5MHz, the thickness of the resonator is approximately 130μ for a 200μ matching layer.
It is an object of the present invention to provide a method for simply manufacturing a thin matching layer for such a small thin vibrator with good performance. Embodiments of the present invention and conventional examples will be described below based on the drawings. FIG. 1 shows the general structure of a probe, in which numeral 1 denotes a vibrator made of a piezoelectric element having electrodes 2 on its front and back surfaces, and is attached to a backing material 3. The piezoelectric element is used by dividing it into a plurality of elements (as shown in the figure) or by dividing a single vibrator into electrodes. 4,
5 is a lead taken out from the electrode, 5 is a common ground, and 4 is taken out from each vibrator. Second
The figure shows a matching layer (Matsuting layer) on the probe in Figure 1.
In this cross-sectional view, a matching layer 6 having a thickness of λ/4 (λ is the wavelength) is uniformly attached to the upper surface of each vibrator 1. The matching layer is an acoustically matched thermosetting resin such as epoxy. Conventionally, this matching layer 6 is applied by dipping a thick layer of λ/4 or more onto the probe shown in Fig. 1, attaching it, heating and hardening, and polishing it to a specified thickness, or by pre-setting it to a specified thickness. It was manufactured by pasting together the finished pieces with resin of the same type. However, as the frequency increases, the layers must be made thinner, and the former method does not provide dimensional accuracy, and the latter method requires a certain amount of space and lacks mechanical strength, making it difficult to manufacture. It is particularly difficult to take measures when the layer contains air bubbles. The present invention improves these and makes it possible to manufacture the device, and will be explained below with reference to FIGS. 3 and 4.
FIG. 3 shows the overall structure of the probe, in which a large number of vibrators 7 are stuck on a backing material 6, and each electrode is electrically connected to a terminal 9 through a lead 8. The vibrator 7 may be divided into elements,
Alternatively, only the electrodes may be divided. Now, on top of the vibrator 7, small resin pieces 10 made of the same material as the matching layer and having a predetermined thickness are pasted in advance at four or more locations. Thereafter, as shown in FIG. 4, a thin transparent sheet 12 made of polyethylene, polyvinylidene fluoride, etc. is placed on a flat plate 11, and uncured resin 13 is poured onto the resin piece 10.
Place the probe through the tube and heat to harden. After that, it is sufficient to remove the sheet 12 with the sheet 12 still attached. If the sheet is a flexible film, it can be used while attached to the human body close to the acoustic impedance, or it can be removed by peeling it off or by lightly polishing it. Before curing this resin matching layer, the air between each vibrator 1 is naturally degassed by vacuum degassing, but depending on the viscosity of the resin, it may not be possible to remove the air, and in many cases, air bubbles may remain. be. If air bubbles remain, they will cause acoustic mismatching and deteriorate the characteristics, so it is necessary to eliminate the air bubbles. If the sheet 12 is made transparent, even if air bubbles occur, they can be seen through the sheet, making it easy to fill the air bubbles with resin by making small holes in the air bubbles and impregnating them with resin again.

As described above, according to the manufacturing method of the present invention, a matte layer of an ultrasonic probe can be easily applied with good performance.

[Brief explanation of the drawing]

Figure 1 is a perspective view of a portion of a typical element-divided ultrasound probe, Figure 2 is a cross-sectional view of the same ultrasound probe with a matting layer added, Figures 3 and 4.
The figures are a perspective view and a partially sectional view of an ultrasound probe manufactured by the method of manufacturing an ultrasound probe of the present invention. 6... Bucking material, 7... Vibrator, 8... Lead,
9...Terminal, 10...Resin piece, 11...Flat plate,
12...Sheet, 13...Resin.

Claims (1)

[Claims] 1. A piezoelectric element is pasted on a backing material, the piezoelectric element is divided into a plurality of vibrators by electrode division or element division, and then 1/4 of the wavelength of the frequency used is applied to the surface of the vibrator. A matte layer of thermosetting resin with a thickness of A method for manufacturing an ultrasonic probe, characterized by making it by pouring a resin. 2. Ultrasonic waves according to claim 1, characterized in that a very thin transparent sheet of polyvinylidene fluoride or the like is placed on a flat plate, and a probe is placed on the sheet to form a matting layer. Probe manufacturing method.