JPH0218089B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a dental full-mouth X-ray imaging device, and in particular to a variable envelope type full-mouth X-ray imaging device.

In a full-mouth X-ray imaging device for dental diagnosis, since the dental arch of the human body is shaped like an elliptical arc, the movement trajectory of the X-ray source and X-ray film casing during X-ray photography is shaped like an elliptical arc. be moved relative to each other by a horizontal swivel arm. At this time, the apparent center of rotation of the horizontal rotating arm, which is equipped with an X-ray source and an X-ray film casing distributed at both ends, is the envelope A shown in Figure 1.
draw

However, envelope curve A in conventional X-ray imaging equipment
The shape (trajectory) of is constant, and the fixed envelope A is simply moved back and forth in parallel as shown by the broken line according to the position of the patient's front teeth, and the cross section is also moved in parallel. The trajectory of the elliptical arc simply changed in size. This has caused problems in the following two points.

To obtain optimal images for dental diagnosis,
X-ray B needs to be irradiated perpendicularly to the dental arch C, but in order to satisfy this condition, for example, if envelope A is selected for adult men, is dental arch C
Since the tooth is small, the above conditions are not satisfied and multiple images of the tooth occur.

In the case of adults, the mandibular ramus D is more developed than in children, as shown in Figure 1, so when the molar region _C1 is photographed under the above-mentioned orthogonal X-ray irradiation state, the envelope curve A
The rotation center of the upper arm is, for example, at point A', and the X-ray B passes through the mandibular ramus D and then reaches the molar region.
C ₁ is irradiated, and shadow damage of the mandibular ramus occurs on the X-ray film side.

In order to solve this problem, the shape of the envelope A may be changed as shown in FIGS. 2 and 3.

That is, as shown in Fig. 1, the envelope A extends symmetrically toward both outsides of the molar region with the vertex a protruding toward the anterior tooth _C2 of the dental arch C at the midline O-O of the human body as a border. , and retreats in a curved line, and has a substantially triangular (or chevron-shaped) locus extending between the apex a and left and right retreat limit points b, b.
In this case, depending on the purpose of photography, the vertex a as shown in Figure 2.
When the distance r between the front teeth and the front teeth C ₂ is constant, the midline O-O from the apex a to the recession limit points b ₁ , b ₂ , b ₃
By setting the above straight line distances to l ₁ , l ₂ , and l ₃ , the shape of the envelope can be changed stepwise or steplessly to A ₁ , A ₂ , and A ₃ . In other words, if we consider the regression limit point b of the envelope A as a reference, the distance from the regression limit point b to the vertices a ₁ , a ₂ , a ₃ on the median O-O as shown in Fig. 3. This means that the straight line distance l is variable.

In such a variable envelope type, the dental arch C shown in FIG. 1 is that of an adult male, and this dental arch C
If the envelope curve when X-rays can be irradiated at right angles to the teeth is A, there will be a situation where X-rays are not irradiated at right angles to adult women and children who have smaller dental arches than adult men. , by varying the envelope as A ₁ , A ₂ , A ₃ as shown in Figure 2 or 3, the X-ray incident angle to the tooth can be changed to ₁ , _2.
Orthogonal illumination can also be obtained by changing .

Similarly, assuming that the dental arch C shown in Figure 1 belongs to an adult male, if an X-ray is taken by selecting envelope A for the teeth, envelope A overlaps mandibular ramus D. , and shadow disturbance occurs because the irradiated X-rays pass through the mandibular ramus D. At this time, by selecting the envelope curves as A ₁ and A ₂ in FIGS. 2 and 3, it is possible to eliminate the transmission of the irradiated X-rays through the mandibular ramus D.

By the way, if the shape of the envelope is changed as shown in FIGS. 2 and 3, the apparent center of rotation of the horizontal swing arm changes, and the relative relationship with the dental arch or the tomographic trajectory is disrupted. In order to eliminate such collapse of the relative relationship, it is necessary to change the feeding speed of the X-ray film in accordance with the change in the envelope shape. In other words, if the film feed speed is constant, the distance to the fault trajectory is fixed depending on the distance from the arm rotation center, so if the envelope shape changes, the fault trajectory will be connected to an unintended location, and the X Not useful for line photography. Therefore, it is necessary to vary the film feed speed in conjunction with the variation of the envelope shape. However, since there is no functional correspondence between the envelope and the X-ray film speed, it is not possible to change the film feed speed in an analog manner.

This invention was made in view of these points,
Although it is a variable envelope type that can avoid duplicate imaging of teeth and shadow problems regardless of the size of the dental arch due to individual differences, it is easy to always maintain an appropriate film feed speed in response to changes in the envelope shape. It is an object of the present invention to provide a dental full-mouth X-ray imaging device that can realize precise and clear full-mouth X-ray imaging.

Embodiments of the present invention will be described below based on the drawings.

In Fig. 4, the variable resistor POT1 extracts the rotation angle of the horizontal swing arm as an electrical signal, and as shown in Fig. 5, the output signal is controlled by the cam plate 1 that rotates together with the horizontal swing arm. Ru.
FIG. 6 shows the relationship between this cam angle and the output voltage. The variable resistor POT2 converts information corresponding to the selection of the envelope form of the horizontal rotating arm into an electrical signal and outputs the electrical signal. In the read-on memory ROM, data corresponding to various types of envelope forms are recorded as data blocks as shown in FIG. 7, and the blocks are switched by an input signal (block selection signal).

First, prior to X-ray imaging, the envelope form of the apparent rotation center of the horizontal rotating arm is set, and that information is converted into an electrical signal by the variable resistor POT2, and then selected by the A/D converter 2. It is converted into a binary digital signal corresponding to the envelope form. This signal is input to the read-on memory ROM, and a data block corresponding to the selected envelope form is selected. This data block includes a, film feed speed data, b, timing data for starting and stopping film feeding and starting and ending X-ray irradiation (hereinafter referred to as (referred to as timing data) is recorded in advance. An example of this data structure is shown in FIG. On the other hand, when the horizontal swing arm starts rotating, the arm angle is extracted as an electrical signal by the variable resistor POT1, converted to a binary digital signal by the A/D converter 3, and then input to the lead-on memory ROM. Each arm angle θ ₀ , θ ₁ , θ ₂ ... from the aforementioned selected data block.
The corresponding speed data and timing data are selected, and these data are alternately output as digital signals from the read-on memory ROM in response to a switching signal from the puncture switch 4. Then, the output digital signal is separated into speed data and timing data by the channel switch 5 and in synchronization with the puncture switching signal, and each is sent to the next stage. Of these, the speed data is stored in the temporary storage circuit 6 until the next data is output, and this data is converted into an analog voltage signal by the D/A converter 7, and then further converted into a frequency signal by the V/F converter 8. It is converted into a signal and then applied to the pulse motor drive circuit 9. The temporary memory circuit 6 prevents the film feeding pulse motor PM from wandering especially when the speed data input thereto changes. If this circuit 6 is not present, the channel switch 5 and the D/A converter The device 7 is disconnected (floating), and the rotational force of the pulse motor fluctuates uncontrollably. The timing data is input to the timing control circuit 10, and the circuit 10 performs the following operations in response to the arm angle.

○B When the arm angle reaches the film feed starting position, turn on the pulse motor drive circuit 9.

○B When the arm reaches the X-ray irradiation start position, an X-ray control signal is input to the X-ray control circuit 11 to turn on the drive of the X-ray source (not shown).

○C When the arm reaches the film feeding stop position, the input of the control signal to the pulse motor drive circuit 9 is turned off to stop the film feeding.

(2) When the arm reaches the X-ray irradiation end position, the input of the X-ray control signal to the X-ray control circuit 11 is turned off.

Therefore, in the case of the pulse motor drive circuit 9, while the speed data is being input to the circuit 9, the pulse motor PM is driven as the drive circuit control signal is input from the timing control circuit 10.

In this way, prior to X-ray imaging, when the envelope form is selected according to the individual characteristics of the patient and the purpose of imaging, the data blocks of the lead-on memory ROM are switched in accordance with this envelope form, and the envelope form is Similarly, speed data and timing data for controlling the pulse motor PM are output, and the timing control circuit 10 controls the pulse motor drive circuit 9 and the X-ray control circuit 11 in accordance with these data. Then, as the horizontal rotating arm rotates, film feeding starts according to the arm angle, film feeding speed is controlled corresponding to the selected envelope form at each arm angle, film feeding is stopped, and when X-ray irradiation starts and stops. is automatically controlled.

In addition, arm angle detection is performed using variable resistor POT1.
Instead of the combination of cam plate 1 and cam plate 1, a variable resistor that rotates directly on the arm rotation center axis P ₁ as shown in Fig. 9 is used.
It may be attached to POT3.

Also, the variable resistor in the envelope setting signal setting section
Instead of the combination of POT2 and A/D converter 3,
A digital signal may be directly obtained using a pulse encoder 12 and a counter 13 as shown in FIG. In the figure, the pulse encoder is an optical type, but other types such as a magnetic type and a contact type are also possible. In addition, 12a
1 is an encoder plate, 12b is an optical sensor, and 14 is an arm. This pulse encoder method is the first
It can also be used for arm angle detection as shown in Figure 1. 15a is an encoder plate, 15b is an optical sensor, and 16 is a counter.

FIG. 12 is a circuit diagram when the arm angle and envelope form are digitized as described above, and 12 and 15 are pulse generators such as pulse encoders. 17 and 18 are temporary memory circuits, 19
2 is a D/F converter, and 20 is a pulse generator for driving the D/F converter.

Furthermore, in addition to the arm angle and envelope form, FIG. 13 shows that the arm rotational speed is detected by the arm rotational speed detector 21, and this information is sent to the D/F converter 19 via the A/D converter 22. is being entered. In other words, when the arm angle is read and the film feed speed is controlled, if the rotation speed of the arm changes due to some unexpected failure, the film feed speed is normally controlled based on the speed data assuming that this change does not occur. As a result, a positional shift occurs between the arm and the film, making it impossible to take proper photographs. Here, by correcting the film feed speed in accordance with the speed detected by the arm rotation speed detector, the correspondence between the arm rotation speed and the film feed speed can be maintained regardless of unexpected changes in the arm rotation speed. It is possible to maintain the relationship as specified and perform proper photography.

As described above, according to the present invention, in an apparatus in which the envelope form itself is varied, data for film speed control corresponding to many types of envelope forms are inputted into the memory circuit, and the selection of the envelope form is performed. In conjunction, control data corresponding to the envelope form is automatically output, so for example, for an adult male and for an adult female or child,
Depending on the size of the dental arch due to individual differences, one of the many types of envelope forms can be selected, allowing for multiple imaging of teeth and differences in the degree of development of the mandibular ramus, regardless of the size of the dental arch. Not only can shadow disturbances caused by such changes be avoided, but the appropriate film feed speed can be automatically and reliably and easily determined in response to changes in the envelope shape, allowing full-jaw processing with any envelope shape. Even in the case of X-ray photography, the effect is that accurate and clear photography can always be achieved.

[Brief explanation of drawings]

Figure 1 shows the relationship between the dental arch and the envelope;
3 and 3 are explanatory diagrams of the principle of a device for varying the envelope, FIG. 4 is a circuit diagram showing an embodiment of the present invention, and FIG. 5 is an example of an arm angle reading configuration using a cam plate. Schematic diagram, Figure 6 shows the relationship between cam angle and output voltage, Figure 7 is a conceptual diagram of the inside of the read-on memory, Figure 8 also shows the data structure, and Figure 9 shows the arm angle readout configuration. 10 is a diagram showing a modified example, and FIG. 10 is a configuration diagram in which the readout of the envelope form is digitized. FIG. 11 is a configuration diagram in which the readout of the arm angle is also digitized.
This figure and FIG. 13 are circuit diagrams showing the configuration of other embodiments, respectively. (Explanation of symbols), POT1, POT2, POT3...
...Variable resistor, ROM...Read-on memory,
PM...Pulse motor, 2, 3, 22...A/D
Converter, 4... Bank switcher, 5... Channel switcher, 6, 17, 18... Temporary memory circuit,
7...D/A converter, 8...V/F converter, 9...
...Pulse motor drive circuit, 10...Timing control circuit, 11...X-ray control circuit, 12,1
5, 20... Pulse generator, 13, 16... Counter, 19... D/F... Converter, 21... Arm rotation speed detection means.

Claims (1)

[Scope of Claims] 1. A rotating arm having an X-ray source and an X-ray film casing disposed at both ends, and an apparent center of rotation of the rotating arm moving in conjunction with the rotation of the arm. As a result, the apparent center of rotation of the rotating arm draws a symmetrical approximately triangular envelope locus toward both the left and right outer sides of the molar region, with the apex protruding toward the anterior teeth of the dental arch as the border. In the configured dental full-mouth X-ray imaging device, many types of envelope trajectories are selected by changing the straight-line distance on the human body midline between the apex of the envelope trajectory and the left and right retraction limit points in multiple stages. means for reading one envelope locus selectively set by the means; means for reading the rotation angle of the swing arm; a storage circuit for storing film feed speed data recorded in advance as multiple types of data blocks corresponding to the rotation angle of the rotating arm for each of the envelope loci, and the outputs of both the reading means; A dental full-mouth X-ray imaging apparatus, comprising: a motor drive circuit that selects one data block from among the data blocks stored in the storage circuit and controls the drive of a film feeding motor. 2. A rotating arm is provided with an X-ray source and an X-ray film housing arranged at both ends, and by moving the apparent center of rotation of the rotating arm in conjunction with the rotation of the arm, the rotating arm is A full dental jaw constructed in such a way that the apparent center of rotation draws a symmetrical, approximately triangular envelope locus toward both the left and right sides of the molars, with the apex protruding toward the anterior teeth of the dental arch as the border. In an X-ray imaging apparatus, a means for selectively setting various types of envelope trajectories by changing in multiple stages the straight-line distance on the human body midline between the apex of the envelope trajectories and left and right regression limit points. a means for reading out one envelope trajectory selectively set by the means; a means for reading out the rotation angle of the swing arm; and a means for reading out one envelope trajectory selectively set by the means; a memory circuit that stores film feed speed data and X-ray irradiation start/end control data recorded in advance in correspondence with the rotation angle of the rotating arm for each of the envelope loci as various data blocks; A motor drive circuit and an X-ray control circuit are provided for selecting one data block from among the data blocks stored in the storage circuit based on the output of the reading means and controlling the drive of the film feeding motor and the X-ray source. A dental full-mouth X-ray imaging device characterized by: 3. The device according to claim 1 or 2, characterized in that the drive circuit of the film feeding motor is configured to input rotational speed data detected by means for detecting the rotational speed of the rotating arm. equipment.