JPS6353817B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a dental full-mouth X-ray imaging apparatus that measures the shape of a subject's dental arch and performs X-ray tomography according to the results.

Taking X-ray images of the teeth and jaws in an expanded state for dental diagnosis is known as X-ray tomography. This is done by moving the X-ray generator and the X-ray film device according to the shape of the dental arch, while keeping the angle always intersecting the dental arch at a constant angle (for example, at a right angle). For this reason, an orthopantomography method is generally known in which the shape of the dental arch is approximated by a composite curve of three circular arcs, and the X-ray generator and X-ray film device are moved along this approximated curve. In addition, methods for approximating the dental arch with an elliptical shape are also known (for example, Japanese Patent Publication No. 47-36953).
(see publication). However, since there are considerable individual differences in the shape and size of dental arches, it is impossible to approximate all of these with a compound curve of circular arcs or an elliptic curve, and the resulting X-ray image may be out of focus, etc. There is a problem in that image quality deteriorates as a result.

For this purpose, attempts have been made to directly measure the subject's dental arch and control the X-ray imaging device according to the measurement results. For example, an occlusal plate is inserted into the subject's oral cavity, and the pressure of the occlusal plate is It has been proposed to measure the shape of the dental arch of an individual subject by the switching state of the contact points (Japanese Patent Application Laid-Open No. 1986-
(See Publication No. 136500). However, since this occlusal plate method uses an occlusal pressure sensor, the measurement result obtained is the shape of the dental arch on the occlusal surface of the tooth, which is different from the dental arch on the gingival area that is clinically necessary. I can only get it. In addition, inserting a plate with electrical contacts into the oral cavity is undesirable from a safety standpoint as there is a risk of electric shock, and furthermore, when used in combination with an X-ray imaging device, the shadow of the plate may not be visible. It is necessary to remove the plate after the measurement of the dental arch is completed, and there is also the problem that the position of the patient's oral cavity, which has been carefully positioned at this time, may shift.

The present invention focuses on these points, and provides a dental full-mouth X-ray that allows accurate, easy, and safe measurement of the dental arch in the gum region, and that allows X-ray photography to be performed in the measured state. This device was developed for the purpose of providing a photographing device, in which arms each having an X-ray generator at one end and an X-ray film device at the other end arranged facing each other are rotated around an arm rotation axis. a motor; a drive motor that moves the arm rotation axis in a plane corresponding to the dental arch;
A plurality of distance measuring units each consisting of an ultrasonic distance measuring sensor and a sensor position detector that detects the amount of displacement of the ultrasonic distance measuring sensor are attached to a support member, and each ultrasonic distance measuring sensor is connected to the subject's chin. The shape of the dental arch is calculated by detecting the position of the tooth to be measured relative to the support member at each measurement point when the tooth is brought into contact with the outer surface, and the arm is rotated according to the calculated shape of the dental arch. The present invention is characterized by comprising a calculation section that issues control signals to each drive motor to cause the drive motor to move and move.

Now, the secondary X-Y that touches the maxillary and mandibular tooth rows
Considering the plane, the middle of the left and right central incisors is (X, Y) =
(0,0) coordinates, and if the X-axis is taken in the left-right direction and the Y-axis is taken in the front-back direction, the tomographic trajectory that matches the dental arch can be approximated by the following quartic equation:
Once the coordinates of the four points (X, Y) on the curve are determined, the coefficient a ₄ ~
a ₁ can be calculated.

y=a ₄ x ⁴ + a ₃ x ³ + a ₂ x ² + a ₁ x...(1) Based on this principle, the present invention provides a support member with a known shape with a plurality of distance measuring parts, and Measure the position of the ultrasonic distance measurement sensor relative to the support member using the support member as a reference, and the distance from the ultrasonic distance measurement sensor to the dental arch, and process these data in the calculation unit to determine the coordinates of each measurement point. , said
By calculating each coefficient in equation (1), the shape of the subject's dental arch is calculated, and the rotation and movement of the arm in which the X-ray generator and X-ray film device are placed are controlled according to the calculation results. be done. Therefore, regardless of individual differences such as whether the subject is an adult or a dwarf, or whether the front teeth are protruding, it is possible to always perform appropriate X-ray photography that corresponds to the shape of the subject's dental arch.

In the X-ray imaging apparatus of the present invention, as described later, an X-ray generator and an X-ray film device are provided at both ends of a rotatable arm, facing each other, and the arm moves along the X-Y plane. For example, the one described in Japanese Patent Publication No. 55-1053 filed by the present applicant can be used.

Next, embodiments of the present invention will be described with reference to the drawings. First, the dentition shape measuring section will be described with reference to FIGS. 1 to 8.

FIG. 1 is a plan view taken along a plane including the dental arch with the distance measuring unit in contact with the jaw of the subject.
In the figure, 1 is the subject's dental arch, 2 is the buccal surface, 3 is a supporting member curved in an arc shape, and 7 is a plurality of distance measuring units (four in the illustrated example) attached to the supporting member 3. The distance measuring section 7 is composed of a linear sliding type potentiometer 4 which is a sensor position detector and an ultrasonic distance measuring sensor 5.

FIG. 2 shows an example of a specific configuration of the distance measuring section 7, and shows a main body 41 of the potentiometer 4.
is fixed to the support member 3, and an ultrasonic distance measuring sensor 5 is attached by cutting a thread to the tip of a sliding rod 42 that passes through the main body 4, and 43 is a potentiometer 4.
The output lead wire 6 is a spring for pressing the ultrasonic distance measurement sensor 5 against the cheek surface 2. 51
is a sensor housing, 52 is a sensor output lead wire, 54 is a piezoelectric element for generating ultrasonic waves such as PZT, and the front part of the piezoelectric element 54 is bonded to the inner surface of a metal case 55 made of a thin plate using an epoxy adhesive or the like. An electrode 56 is bonded to the rear part using the same adhesive, and the lead wire 52 is connected to the metal case 55.
and is pulled out from the electrode 56, and the metal case 55
is bonded to the sensor housing 51 via a vibration-absorbing adhesive layer 53 such as silicone rubber adhesive. Reference numeral 57 denotes an impedance matching layer provided on the front surface of the metal case 55, which efficiently propagates the ultrasonic waves generated by the vibration of the piezoelectric element 54 to the buccal or labial surfaces, and at the same time absorbs the ultrasonic waves reflected from the teeth. In order to receive efficiently, the piezoelectric element 54 has a characteristic impedance that is the geometric mean value of the characteristic impedance and the characteristic impedance of the human cheek, and the length in the ultrasonic propagation direction is equal to the wavelength within the matching group 57 at the frequency used. It is configured to be 1/4 the size. The specific materials are:
For example, a plastic material such as epoxy resin mixed with a certain amount of rubber particles is used.

FIG. 3 is a block diagram of an electric circuit for measuring the distance between the ultrasonic distance measuring sensor 5 and the dental arch 1, and FIG. 4 is a pulse timing chart of the same circuit.

In FIG. 3, 311 is an oscillator, and the fourth
A signal with a constant frequency as shown in Figure a is continuously oscillated during measurement. 310 is a gate circuit, and an oscillator 311
The output of the power amplifier 309 is converted into a burst wave with a certain period as shown in FIG. Transmits an ultrasonic signal as shown in . The transmitted ultrasonic wave propagates inside the buccal flesh, is reflected on the tooth surface, and is received by the piezoelectric element 54 as an echo signal as shown in FIG. 4d.

The ultrasonic echo signal received by the piezoelectric element 54 passes through a capacitor 301, is amplified by a first RF amplifier 302, is adjusted to an appropriate level by a semi-fixed resistor 303, and is then amplified by a second RF amplifier 3 in the next stage.
04, and a signal as shown in FIG. 4e is input to the threshold detector 305. here,
The signal is subjected to full-wave detection as shown in Fig. 4f, and a detected voltage as shown by the broken line is generated, and only when the detected voltage becomes higher than the threshold voltage _ETH shown in Fig. 4f, the fourth An output signal as shown in Figure g is obtained.

Reference numeral 306 denotes an integrating circuit that starts an integrating operation at a constant voltage or constant current at the same time as the transmission of the burst wave shown in FIG. 4b starts, and stops the integrating action at the rising edge of the output signal shown in FIG. At the same time that the waveform shown in FIG. 4 is obtained, the sample and hold circuit 307 holds the peak value of this waveform, and a hold voltage as shown in FIG. 4i is output. The value of this hold voltage is the time from the start of transmitting the burst wave to the start of receiving the echo signal. Since the size is proportional to the distance (more precisely, the round trip distance) to the
It converts it into a digital signal that can be input into the computer.

Note that when transmitting the burst wave shown in FIG. 4b, the gate circuit 301 sends a control signal shown by a broken line in FIG. 4b to the second RF amplifier 304 to reduce the gain of the second RF amplifier 304, and The receiver circuit is prevented from malfunctioning due to the transmitted burst wave during the period indicated by the broken line. Also, a in Figure 3.
.about.i indicate the signal waveforms in each circuit corresponding to those in FIG. 4 a to i with the same symbols.

Next, FIGS. 5 and 6 will be explained. Fifth
In the figure, 401 is an arithmetic unit, and 402 is an arithmetic unit 40.
1, a control panel for operating 403, a calculation unit 401;
a clock oscillator, 404, which serves as a reference for operating the
1 is the ultrasonic sensor section explained in FIGS. 1 to 4, and the output signal of the A/D converter 308 is input thereto. Further, 405 is an R/D converter that converts the output proportional to the resistance value of the potentiometer 4 shown in FIGS. 1 and 2 into a digital signal that can be input to the calculation section 401. Each data obtained by the ultrasonic distance measuring sensor 5 and the potentiometer 4 of the distance measuring section 7 is inputted.

407 is a film cassette limit switch, 408 is an arm limit switch,
This is for forcibly stopping the operation if the operation exceeds the specified range. 411
414 is a stepping motor that moves the arm rotation axis in the Y direction; 417 is a stepping motor that rotationally drives the arm; and 420 is a stepping motor that drives the X-ray film cassette. These stepping motors 411, 41
4, 417 and 420 are drive circuits 410 and 420, respectively.
413, 416, 419, each drive circuit 410, 413, 416,
419 is controlled by control circuits 409, 412, 415, and 418 based on instructions from the calculation unit 401. 421 is a high-pressure generator, 422 is a filament drive section, and 423 is an X-ray tube, and the clock oscillator 403 also serves as a pulse generator for the inverter constituting these high-pressure generator 421 and filament drive section 422.

In the above configuration, when an imaging preparation command is issued by the control panel 402, measurement result data from each distance measuring section 7 is input to the calculation section 401, and these data are processed to calculate the shape of the dental arch. Ru. Based on this, the optimal fault trajectory, tube voltage, and tube current are determined, and the tube voltage is determined by the high-voltage generator 4.
21 is the filament drive unit 4 for the tube current.
22 are set to appropriate values, and then the shooting start button on the control panel 402 is pressed, each stepping motor 411, 414, 41
7,420 is activated, and the arm rotates while its center of rotation moves on the X-Y plane along the calculated trajectory, always drawing the tomographic trajectory closest to the subject's dental arch 1 and transmitting the X-rays. Photography will take place.

A microcomputer can be used as the arithmetic unit 401, and has a configuration as shown in FIG. 6, for example. In other words, 501 is the CPU, 506
507 is an address bus line, 507 is a data bus line, and 508 is a control bus line, and these bus lines are equipped with a ROM 502 as a memory.
A RAM 503 is connected, and a counter timer circuit 504 for controlling time such as preheat time and X-ray irradiation time is also connected. 505 is a parallel I/O circuit that receives commands from the control panel 402, data from the distance measuring section 7, inputs from the limit switches 407 and 408, and the ROM 502 and
The output from the RAM 503 and control signals based on the calculation results of the CPU 501 are output from this parallel I/O.
It is input and output via the circuit 505.

FIGS. 7 and 8 show other embodiments of the distance measuring section. In the figure, 58 is a piezoelectric film whose both ends are fixed to the support member 3 by the fixed poles 31, and in FIG. Therefore, a state in which the piezoelectric film 58 is pressed against the cheek surface 2 of the subject is shown.

The piezoelectric film 58 is a film-like piezoelectric element such as PVDF or PVTF that generates a voltage (charge) proportional to pressure, and its structure is shown in an expanded state in FIG. In the figure, 800 is a film-shaped piezoelectric element main body, and 801 is an electrode provided on the pressing part 44 side centering on the part pressed against the cheek surface, and this electrode 801 is formed by, for example, vapor deposition of aluminum. 802 is a lead wire, 803 is a thin electrical insulating layer made of a polymer film such as vinyl chloride provided on the side that contacts the cheek, 804 is an electrode on the cheek side;
05 is a protective layer made of a polymer film on the electrode 801 side. The material of the electrical insulating layer 803 is selected so that its acoustic impedance is between the acoustic impedance of the piezoelectric body 800 and the acoustic impedance of the cheek surface. (4 locations in the example)
The width is much larger than the thickness, and although it is film-like and continuous, there is sufficient acoustic separation between pressing points. The operation of the distance measuring section 7 of this embodiment is basically the same as that shown in FIGS. 1 and 2, and it can be used in combination with the circuits shown in FIG. 3 and subsequent figures.

FIG. 9 is a schematic diagram of an example of an X-ray imaging device,
Reference numeral 901 denotes a base, 902 denotes two Y-axis rails attached in parallel to the upper surface of the base 901, 903 denotes a first platform supported by four sliders 904 that slide on the Y-axis rails 902, and 905 906 is a second X-axis rail supported by four sliders 907 that slide on the X-axis rail 905.
It is a platform. 908 is an arm rotation shaft hanging from the second platform 906;
9 is an arm attached to the lower end of the arm rotation shaft 908; 910 is an X-ray generator supported at one end of the arm 909; 911 is an X-ray film device supported at the other end of the arm 909; And the first platform 903 has an arm rotation shaft 9.
Openings 912 and 913 are provided respectively so as not to obstruct the movement of 08. A stepping motor 414 is attached to the base 901, and the screw shaft 9 is driven by the stepping motor 414.
14 is screwed into a nut 915 provided on the first platform 903, and the first platform 903 is moved in the Y-axis direction by a stepping motor 414. Similarly, a stepping motor 411 is attached to the first platform 903.
A screw shaft 916 driven by the second platform 906 is screwed into a nut 917 provided on the second platform 906, and the second platform 906 is moved in the X-axis direction by the stepping motor 411. It's summery. Also, the second platform 906
A stepping motor 417 is attached to the arm rotating shaft 908 via gears 918 and 919.
is starting to rotate. Reference numeral 920 denotes a positioning table, which is provided with a chin rest 921 at its tip. By placing the tip of the lower jaw on the chin rest 921, the subject 922 positions the teeth and jaws on the line connecting the X-ray generator 910 and the X-ray film device 911. is positioned. The positioning table 920 is supported by a position adjustment device (not shown) so that its position can be adjusted within a certain range. A stepping motor 420 is provided in the X-ray film device.

The X-ray imaging device has this configuration,
Each stepping motor 411, 414, 417,
420 is driven, the arm 909 rotates while moving on the X-Y plane, and moves according to the dental arch of the subject 922 to perform X-ray tomography.

Since FIG. 10 shows the tip of the positioning base 920, the support member to which the distance measuring unit 7 is attached is 3
It is divided into two parts, a and 3b, and is rotatably attached to the positioning base 920 by the support part 32. 10a and 10b show the state when measuring the shape of the dental arch, and support members 3a and 3b
The ultrasonic distance measuring sensor 5 of the distance measuring unit 7 is brought into contact with the chin of the subject 922 to perform measurement, and then the supporting members 3a, 3
X-ray photography is performed by tilting down the distance measuring section 7 to a position where it does not interfere with X-ray photography. During this time, subject 922 rested his lower jaw on the chinrest 9.
21 and by appropriately fixing the head with a fixing member (not shown), the position of the dental arch can be prevented from changing between measurement and X-ray photography.

As is clear from the description of the embodiments above, the present invention supports a plurality of distance measuring units each including an ultrasonic distance measuring sensor and a sensor position detector that detects the amount of displacement of the ultrasonic distance measuring sensor. The position of the dental arch relative to the supporting member is measured, the shape of the subject's dental arch is calculated by the calculation unit, and the positions of the X-ray generator and the X-ray film device are determined according to the calculation results. The shape of the dental arch can be easily and safely measured, and the shape of the dental arch can be accurately measured in the clinically necessary area.
Moreover, since X-ray photography is performed using the measurement results as they are without moving the position of the oral cavity, there are advantages such as the ability to easily obtain clear X-ray images useful for diagnosis.

[Brief explanation of the drawing]

The figures all show embodiments of the present invention; Fig. 1 is a plan view of the distance measuring section in use, Fig. 2 is a partially cutaway side view of the distance measuring section, and Fig. 3 is a partially cutaway side view of the distance measuring section. A block diagram of the electric circuit, Fig. 4 is a pulse timing chart of the same circuit, Fig. 5 is a block diagram of the electric circuit of the entire device, Fig. 6 is a block diagram of the calculation section, and Fig. 7 is a diagram of other parts of the distance measuring section. A plan view of the embodiment,
8a and 8b are a front view and a plan view of the piezoelectric film of the same embodiment, FIG. 9 is a schematic side view of the main part showing an example of an X-ray imaging device, and FIGS. 10a and 1
FIG. 10b is a perspective view and a plan view of the positioning table in a used state, and FIG. 10c is a perspective view of the positioning table in another used state. (Explanation of symbols), 1... Dental arch, 2... Buccal surface,
3, 3a, 3b... Support member, 4... Potentiometer (sensor position detector), 5... Ultrasonic distance measuring sensor, 7... Distance measuring section, 54... Piezoelectric element, 58... Piezoelectric film , 401... calculation section,
411, 414, 417, 420...Stepping motor (drive motor), 908...Arm rotation axis, 909...Arm, 901...X-ray generator,
911...X-ray film device, 920...positioning table, 922...subject.

Claims (1)

[Claims] 1. A drive motor that rotates an arm having an X-ray generator at one end and an X-ray film device at the other end facing each other around an arm rotation axis;
It consists of a drive motor that moves the arm rotation axis within a plane corresponding to the dental arch, an ultrasonic distance measurement sensor, and a sensor position detector that detects the amount of displacement of this ultrasonic distance measurement sensor, and is attached to a support member. The position of the tooth to be measured with respect to the support member at each measurement point is detected by placing a plurality of distance measurement units and each ultrasonic distance measurement sensor in contact with the outer surface of the subject's jaw, and detecting the position of the tooth to be measured relative to the support member. A dental full-mouth X-ray comprising: a calculation unit that calculates the shape of the dental arch and issues a control signal to each drive motor so as to rotate and move the arm according to the calculated shape of the dental arch. Photography equipment.