JPS6232936B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a computerized tomography apparatus that can automatically set a subject at an appropriate position so that the tomographic plane of the subject does not protrude from the imaging area.

Recently, computerized tomography (hereinafter referred to as CT) has been put into practical use as a type of tomography.

This CT consists of, for example, an X-ray tube and an X-ray detector placed opposite each other with the subject in between, and both of which are rotatable around the subject. A fan-shaped beam of X-rays that can include After obtaining X-ray absorption rate data from all directions on the tomographic plane of the subject using an X-ray detector, this data is analyzed by a computer to calculate the X-ray absorption rate at each location on the tomographic plane. The system calculates the absorption rate and reconstructs the image of the tomographic plane on a CRT, etc. at a gradation level corresponding to the absorption rate, and it is possible to analyze the composition of each part of the tomographic plane at a gradation level of, for example, 2000 levels. As a result, clear tomographic images can be obtained from soft to hard tissues, making it one of the most powerful radiological diagnostic devices for various clinical diagnoses.

The above-mentioned CT is called a third-generation CT, but in the above-mentioned CT, the X-ray tube XT and X-ray detector XD, which are placed opposite each other as shown in Figure 1, are The circle Q is rotated and moved around _one point, the center P. As mentioned above, the X-ray tube XT emits a fan-shaped beam FB that is focused at _one point and has a spread that can encompass the entire subject, and the X-ray detector XD emits a fan-shaped beam that has passed through the tomographic plane of the subject. The configuration is such that a plurality of detection elements are arranged in correspondence with the spread range so that the X-ray FB can be detected at each location. Therefore, when the X-ray tube XT and X-ray detector XD are rotated around point _P1 as the center of rotation, the trajectory drawn by the _outside line of the fan beam It becomes a circle like Q of R.

Therefore, if the subject is placed within this circle Q,
By rotating the X-ray tube XT and X-ray detector XD at least 180°,
Linear absorption data will be obtained. That is,
The area within the circle Q is the imaging area.

However, when placing the subject within this imaging area circle Q, the imaging area cannot be visually confirmed, so the movement of the bed top on which the subject is placed is controlled based on rough visual estimation. Because of this, there was a risk that the subject would protrude from the imaging area and that projection data for the protruding portion would not be obtained.

This invention is based on the above circumstances, and
An object of the present invention is to provide a computerized tomography apparatus equipped with a device capable of controlling the movement of a bed top so that the subject does not protrude from the imaging area by aligning the center of the subject with the center of the imaging area. do.

The configuration of the main parts of the present invention will be explained below with reference to FIGS. 2 to 4.

First, as shown in Fig. 2, a photographing area Q with a radius R is
On the other hand, if the subject A is placed as shown, that is, if a part of the subject A protrudes from the imaging area Q, then the center P ₁ ' of the subject A is the center P of the imaging area Q. It is only necessary to move the bed top plate TB on which the subject A is placed so that it matches ₁ .

In general, the object that can be the CT object A is the head, abdomen, etc. of a human body, but since they can be regarded as approximately circular or elliptical, the length of the longest diameter part is 1/2 , and the intersection of 1/2 the length of the diameter part perpendicular to that point is the object A.
can be regarded as the center point P ₁ '.

Therefore, if the position of the center point P ₁ ' of the subject A is detected by some means, the subject A can be placed within the imaging area Q circle.

FIG. 3 is a diagram showing an embodiment of the configuration for detecting the position of the center point P ₁ ' of the subject A. In the figure, 1a,
1b is a light emitting element that emits a narrow beam of light through a slit (not shown); 2a, 2b
is a photoelectric element that receives light rays emitted from the light emitting elements 1a and 1b through a slit (not shown) and converts it into an electrical signal. These light emitting elements 1a, 1b
and photoelectric elements 2a, 2b are arranged in parallel cross-shaped lead screws 3a, 3b, 3c, 3 so as to be able to always face each other and move in conjunction with each other in the left-right direction in the figure, that is, in the X direction, and in the vertical direction in the figure, that is, in the Y direction.
d, and are movably fitted into guide rails 4a, 4b, 4c, and 4d provided in parallel with each other.

The lead screws 3a, 3b, 3c, and 3d are L-shaped or U-shaped support fittings 5a, 5, respectively.
b, 5c, and 5d, respectively, via bearings (not shown), and are rotatably attached to the supports 5a, 5d.
Bevel gears 6a, 6b, 6c, 6d, 6e, 6f are provided at both ends or one end passing through the shafts 6a-6b, 6c-6d, and 6f adjacent to each other at right angles.
6e-6f are interlocked with each other. Further, the lead screws 3a, 3b and the lead screws 3b, 3c have different screws (right-hand thread and left-hand thread) cut, and the light emitting elements 1a, 1b and the photoelectric elements 2a, 2b are respectively cut by the lead screw 3.
It is attached to a nut-shaped piece fitted into parts a, 3b, 3c, and 3d. Guide rails 4a, 4
b, 4c, and 4d slidably pass through the light emitting elements 1a, 1b and the photoelectric elements 2a, 2b, respectively, and are attached at both ends to supporting metal fittings 5a, 5b, 5c, and 5d, respectively. A part of the mounting bracket 5d is rotatably passed through the tip extension of one end of the lead screw 3a via a bearing (not shown), and the reversible motor 1 is connected to the reversible motor 1 via a deceleration gear 7 and a transmission gear 8, respectively.
Connected to 0. Also, lead screw 3a
A photoelectric rotary encoder 9, for example, for measuring the movement of each frame is connected to the tip extension at the other end.

Incidentally, the lead screws 3a, 3b,
3c, 3d, etc. are all provided at locations such that the subject insertion port (h in the figure) of the rotary mount of the X-ray tube XT and X-ray detector XD in the CT described above is located at the center of the grid. Furthermore, microswitches 11a and 11b are provided at opposing ends of the support fittings 5a and 5d, respectively, and are operated when the casing of the light emitting element 1a comes into contact with them.

FIG. 4 shows a drive control circuit for the motor 10 in FIG. 3 and the drive motor for the bed top (not shown). In the figure, SW ₁ and SW ₂ are the micro switches 11a and 11b in FIG. The other ends are connected to the DC drive power supply +V via pull-up resistors R ₁ and R ₂ , respectively, and are connected to AND gates via inverters IN ₁ and IN _2, respectively.
It is connected to the first input terminals of AG ₁ and AG ₂ .
Also, SW ₀ is a push button switch for the start signal, one end of which is grounded, and the other end connected to a pull-up resistor R ₀
is connected to the DC drive power supply +V via
AND gate AG ₁ , AG ₂ through inverter IN ₀
are commonly connected to the second input terminals of the two. Further, the output terminal of the inverter IN ₁ is connected to the trigger terminal T of the mono multivibrator MM ₁ , and the output terminal of the inverter IN ₂ is connected to the trigger terminal T of the mono multivibrator MM ₂ . and gate
The output terminal of AG ₁ is an R-S type flip-flop.
Set input terminal S and OR gate of FF ₁ and FF ₃
The output terminals of AND gate AG ₂ are connected to the first input terminals of OG ₁ and the set input terminal S of RS type flip-flop FF ₂ and OR gate OG ₁ respectively.
is connected to the second input terminal of. The output terminals Q of the mono multivibrators MM ₁ and MM ₂ are connected to the reset terminals R of the flip-flops FF ₁ and FF ₂ and to the first and second input terminals of the OR gate OG ₂ , respectively. The set output terminals Q of the flip-flops FF ₁ and FF ₂ are connected to the forward rotation drive signal input terminal P and the reverse rotation drive signal input terminal N of the drive control circuit MD ₀ of the drive motor 10 in the measuring mechanism shown in FIG. 3, respectively. There is. PG ₀ corresponds to the rotary encoder 9 in the measurement mechanism shown in Fig. 3 above, and its output terminals are connected to the AND gates AG ₃ and AG _4.
It is also connected to the clock input terminal Cp of J-K type flip-flops FF ₄ and FF ₅ whose J and K input terminals are fixed to "1" via inverters IN ₃ and IN ₄ . It is connected. The set output terminals Q of flip-flops FF ₄ and FF ₅ are connected to the first input terminals of AND gates AG ₅ and AG ₆ . The second input terminals of the AND gates AG ₃ and AG ₄ are connected to the set output terminals Q of the RS type flip-flops FF ₆ and FF ₇ , and the AND gates AG ₅ and
The second input terminal of AG ₆ is connected to the set output terminals Q of RS type flip-flops FF ₈ and FF ₉ , respectively. The flip-flops FF ₆ and FF ₇ have set input terminals S commonly connected to the output terminal of the OR gate OG ₁ and reset input terminals R connected to the output terminals Q of the mono multivibrators MM ₃ and MM ₄ , respectively. For flip-flops FF ₈ and FF ₉ , the set input terminal S is a mono multivibrator.
Connected to the output terminals Q of MM ₃ and MM ₄ , respectively,
Reset input terminal R is a mono multivibrator
They are connected to the output terminals Q of MM ₅ and MM ₆ , respectively. The trigger input terminals T of the mono multivibrators MM ₃ and MM ₄ are connected to the output terminals of the photoelectric elements HS ₁ and HS ₂ in the measurement mechanism shown in Fig. 3 above.
The trigger input terminals T of _the mono-multivibrators MM ₅ and MM ₆ are connected to the output terminals of the photoelectric elements 2a and 2b _, respectively. The output terminals of AND gates AG ₃ and AG ₄ are connected to the first input terminals of OR gates _OG 3 and OG ₄ , respectively, and the output terminals of AND gates AG ₅ and AG ₆ are connected to the second input terminals of OR gates OG ₃ and OG ₄ . connected to each terminal. The output terminals of OR gates OG ₃ and OG ₄ are connected to the first and second counters CT ₁ and CT ₂ , respectively.
is connected to the count input terminal of

The output terminals of the first and second counters CT ₁ and CT ₂ are connected to the first and second input terminals of the switching gate circuit CG. The switching gate circuit CG normally sends the signal from the first input terminal to the subsequent stage, and while the control signal ("1") is set to the gate control input terminal G, the signal from the second input terminal is sent. This is a circuit for sending data to the subsequent stage, and its output terminal is connected to the first input terminal of the subtracter SC. The subtracter SC has a second input terminal connected to the output terminal of the numerical value setter NS, and outputs the absolute value obtained by subtracting the numerical value from the first input terminal from the numerical value from the second input terminal. “1” when the subtraction result from the discrimination output terminal M is positive;
This circuit derives an output signal of "0" when negative, and its output terminal is connected to the first input terminal of the matching circuit CC. The coincidence circuit CC is a circuit whose second input terminal is connected to the output terminal of the third counter _CT3 , and when the signals (numeric values) from both input terminals match, the coincidence output terminal I becomes "1". The coincidence output terminal is the reset input terminal of the R-S type flip-flop _FF10 , whose R, J, and K terminals are fixed to "1".
- Connected to the clock input terminal Cp of the K-type flip-flop _FF11 via the inverter _IN7 .
The set output terminal Q of flip-flop FF ₁₀ is commonly connected to the first input terminals of AND gates AG ₇ , AG ₈ , AG ₉ , and the set output terminal Q of flip-flop FF ₁₁ is connected to AND gates AG ₁₀ , AG ₁₁ , AG _{12 .}
are commonly connected to the respective first input terminals of the first counter CT1, and are respectively connected to the clear input terminal C of the first counter _CT1 and the gate control input terminal G of the switching gate CG. Further, the reset output terminal of the flip-flop _FF11 is connected to the clear input terminal C of the second counter _CT2 , and the set input terminal S of the flip-flop _FF10 is connected to the output terminal of the OR gate _OG2 . The AND gates AG ₉ and AG ₁₂ have their second input terminals connected to the output terminals of the pulse generators PG ₁ and PG ₂ , respectively, and their output terminals are connected to the first and second input terminals of the OR gate OG ₅ , respectively. has been done. The output terminal of the OR gate OG ₅ is connected to the count input terminal of the third counter CT ₃ . The pulse generators PG ₁ and PG ₂ are photoelectric rotary encoders (not shown) that output the number of pulses corresponding to the amount of movement in the horizontal and vertical directions of the subject being moved by the bed top (not shown). ).

Further, the numerical value setter NS includes the light emitting elements 1a, 1b and the photoelectric element 2a, in the measuring mechanism shown in FIG.
The length of 1/2 of the total travel stroke of 2b, i.e.
A numerical value corresponding to the radius of the imaging area circle Q is set. The positive/negative discrimination output terminal M of the subtracter SC is commonly connected to the first input terminals of AND gates AG ₁₃ and AG ₁₄ , and is also connected to the first input terminal of AND gates AG ₁₅ and AG ₁₆ via an inverter _IN8 . are commonly connected. The second input terminals of AND gates AG ₁₃ and AG ₁₄ are commonly connected to the set output terminal Q of flip-flop FF ₃ , and the AND gates AG ₁₅ and AG ₁₆
The second input terminals of are commonly connected to the reset output terminal of flip-flop _FF3 . The output terminals of AND gate AG ₁₃ and AG ₁₅ are OR gate OG ₆ ,
Each is connected to the first input terminal of OG ₇ , and the output terminals of AND gates AG ₁₅ and AG ₁₆ are OR gates.
They are connected to the second input terminals of OG ₆ and OG ₇ , respectively. The output terminal of OR gate OG ₆ is connected to the second input terminal of AND gate AG ₇ , AG ₁₀ , and the output terminal of OR gate OG ₇ is connected to AND gate AG ₈ ,
It is connected to the second input terminal of _AG11 . The output terminals of AND gates AG ₇ and AG ₈ are the motor drive circuits that drive the motors for horizontal movement of the bed top mentioned above.
It is connected to the forward rotation drive signal input terminal P and the reverse rotation drive signal input terminal N of MD ₁ , respectively. In addition, the output terminals of AND gates AG ₉ and AG ₁₀ are the motor drive circuits that drive the motors for vertically moving the bed top plate mentioned above.
It is connected to the forward rotation drive signal input terminal P and the reverse rotation drive signal input terminal N of MD ₂ , respectively.

The motor drive circuits MD ₁ and MD ₂ are circuits that drive the motor in forward or reverse rotation while a drive signal (“1”) is introduced into the forward and reverse drive signal terminals P and N.

Next, the operation of the configuration shown in FIGS. 3 and 4 will be explained.

That is, in FIG. 3, photoelectric elements 1a and 1b
is in the reset position (the micro switch 11a at the left end of the lead screw 3a in the figure is pressed to close), the start signal push button switch SW ₀ is closed at the timing of S ₁ in Fig. 5a. When the switch _W1 is closed, the output of the AND gate _AG1 becomes "1", and at that timing, the flip-flop _FF1 is set as shown in FIG. 5b, and the motor drive circuit _MD0 is turned on. A drive signal is introduced into the normal rotation drive input terminal P. As a result, when the motor 10 is driven to rotate in the normal direction, the reud screw 3a is rotated in the normal direction via the gears 8 and 7, and the gear 6a--
6b to the reud screw 3b, and gears 6f to 6e to the reud screw 3d.
However, the reud screws 3c are further rotated in the normal direction via the gears 6d to 6c. This results in
The light-emitting element 1a and the photoelectric element 2a continue to face each other and emit a beam of light, while the light-emitting element 1a and the photoelectric element 2a begin to move toward the right in the third figure, and similarly, the light-emitting element 1b and the photoelectric element 2b begin to move upward in the figure at the same pitch. A variable number of pulse signals is derived from the rotary encoder 9, ie the first pulse generator _PG1 .

Therefore, since the flip-flop FF ₆ is set as shown in FIG. 5c _{at the same time as the switch SW 0 is closed, the pulse signal from the pulse generator PG 1 is transmitted to} the first Counter CT ₁ is introduced and counted. After that, when the light beam emitted from the light emitting element 1a and received by the photoelectric element 2a is interrupted by the subject, the output of the inverter _IN5 (d in Figure 5) changes from "0" to "1". At the rising timing, a pulse (e in Fig. 5) is derived from the monomultivibrator _MM3 , the flip-flop _FF6 is reset (c in Fig. 5), and at the same time the flip-flop _{FF8 is} reset.
is set (Fig. 5f).

This allows counter CT ₁ to have a pulse generator
The output pulse of PG ₁ is halved by flip-flop FF ₄ .
A pulse frequency-divided into is introduced via an AND gate AG ₅ and an OR gate OG ₃ . Thereafter, the light beam traverses the subject, and the light beam from the light emitting element 1a is received by the photoelectric element 2a again, and at the same time, a pulse is generated from the mono-multivibrator _MM5 (fifth illustration g).
is derived, the flip-flop _FF8 is reset (f in Figure 5), and the count pulse input to the counter _CT1 disappears. Therefore, counter CT ₁ has
A pulse (h in FIG. 5) is introduced while flip-flop FF ₆ and flip-flop FF ₈ are being set.

In this case, the number of pulses introduced into the counter CT ₁ while the flip-flop FF ₆ is set is equal to the distance from the starting position of the light emitting element 1a and the photoelectric element 2a to one end of the subject in FIG. It is equivalent. Furthermore, while flip-flop FF ₈ is set, the number of pulses introduced into counter CT ₁ is 1/1/2 of the lateral thickness of the object.
Corresponds to 2. Therefore, the count value of the counter _CT1 becomes a value corresponding to the X-coordinate position of the center of the subject.

On the other hand, in parallel with the above-described operation, a pulse is also introduced into the second counter _CT2 due to the movement of the light emitting element 1b and the photoelectric element 2b. That is, the flip-flop FF ₄ is set at the same time as the switch SW ₀ , the output pulse of the pulse generator PG ₁ is introduced into the counter CT ₂ via the AND gate AG ₄ and the OR gate OG ₄ , and the light beam from the light emitting element 1a is directed to the subject. When the light is finally cut off and no longer received by the photoelectric element 2b, the flip-flop _FF7 is reset, the flip-flop _FF9 is set, and the output pulse of the pulse generator _PG1 is divided into 1/2 by the flip-flop _FF5. Counter via , andgate AG ₆ , orgate OG ₄
Introduced in CT ₂ . After that, when the light beam is received by the photoelectric element 2b again, the flip-flop _FF9 is reset, so the counter _CT2 has a counter.
As with CT ₁ , from the start position to the center of the subject
The value corresponding to the coordinate position is being counted.

After that, the light emitting elements 1a, 1b and the photoelectric element 2
When each pair of a and 2b reaches the right end and the bottom end in the third figure, respectively, and completes the entire scan stroke, the micro switch 11b, ie, SW ₂ , provided at one end of the mounting bracket 5a is closed. switch
Mono multivibrator by closing SW ₂
A pulse (i in Figure 5) is derived from MM ₁ and the flip-flop FF ₁ is reset (b in Figure 5).
However, the motor drive circuit MD ₀ loses the drive signal,
The motor 10 stops and the measurement operation ends.

The output pulse of the monomultivibrator _MM1 (i in FIG. 5), which is the measurement operation end signal, sets the flip-flop FF ₁₀ (j in FIG. 5). On the other hand, in the subtracter SC, for example, the 8-bit count value of the first counter CT ₁ and the same value of the numerical value setter NS
8-bit output value, that is, the light emitting elements 1a and 1b
(2a, 2b) is subtracted from the value corresponding to the center position of the movement stroke (the center P ₁ of the imaging area described above), and the result is introduced into the coincidence circuit CC. In the subtracter SC, if the subtraction result is positive, its positive/negative discrimination output terminal M becomes "1", and conversely, if the subtraction result is negative, it becomes "0". Also, in this case, flip-flop FF ₃ is connected to AND gate AG ₁ at the start of the measurement mentioned above.
It is in the set state by the output “1” of
Further, at the position of the center point P ₁ ' of the subject shown in the third figure, the output of the positive/negative discrimination output terminal M is "0". Therefore, the output of OR gate OG ₆ is "0" because the outputs of AND gates AG ₁₃ and AG ₁₅ are both "0", and the output of OR gate OG ₇ is "0", and the output of AND gates AG ₁₄ and AG ₁₆ is "0". ”,
Since it becomes "1", it becomes "1".

As a result, the output of the AND gate AG ₈ becomes " ₁ " from the setting of the flip-flop FF ₁₀ (j in FIG. The bed top starts moving to the left in the third diagram.
On the other hand, the gate of the AND gate AG ₉ is opened by the set signal of the flip-flop FF ₁₀ , and the pulses generated from the second rotary encoder, that is, the second pulse generator PG ₂ according to the amount of movement of the top plate are sent to the OR gate OG ₅ . to the third counter _CT3 . Thereafter, when the count value of the counter _CT3 reaches the output value of the subtracter SC, a match signal "1" is introduced from the output terminal I of the match circuit CC, resets the flip-flop _FF10 , and at the same time resets the flip-flop via the inverter _IN7 . Set FF ₁₁ and clear counter CT ₃ . When the flip-flop FF ₁₀ is reset, the gate of the AND gate AG ₈ is closed and the drive motor for moving the bed top plate left and right stops.

At the same time, the flip-flop _FF11 is set, so that the first counter _CT1 is cleared and the gate control terminal G of the switching gate circuit CG becomes "1", and the output value of the second counter _CT2 is changed to the subtracter SC.
The value is subtracted from the output value of the numerical setter NS. In this case, the center point of the object shown in Figure 3
At the position _P1 ', the positive/negative discrimination terminal M of the subtractor SC is located above the position of the center point _P1 of the imaging area mentioned above in the figure, that is, the numerical value corresponding to the position is large.
The output value of is "0". Therefore, orgate
The outputs of OG ₆ and OG ₇ are “0” and “0” respectively as described above.
As a result, the gate of the AND gate _AG11 is opened, and the reverse drive signal "1" is sent to the top vertical drive circuit _MD2 by the set signal "1" of the flip-flop _FF11 . As a result, the bed top (not shown) starts to be driven in reverse, that is, to move downward in FIG. 3, and at the same time, pulses corresponding to the amount of movement are derived from the rotary encoder, ie, the pulse generator PG ₃ in FIG. 3. This output pulse is generated by the AND gate AG ₁₂ whose gate is opened by the set signal of flip-flop FF ₁₁ and the OR gate.
It is introduced via OG ₅ into a third counter CT ₃ and counted. In this case, AND gate _AG9 is closed at the same time as flip-flop _FF10 is reset. When the output value of the counter _CT3 reaches the output value of the subtracter SC, a match signal "1" is derived from the output terminal I of the match circuit CC, the flip-flop _FF11 is reset, and the second counter _CT2 is cleared and at the same time the AND gate AG ₁₂
When the gate of AND gate AG ₁₂ is closed, the third counter CT ₃ is cleared, and the drive motor for vertically moving the bed top plate is stopped.

Therefore, the bed top plate (not shown) is as shown in the third diagram d _x
Therefore, the center P ₁ ' of the _subject shown in the third drawing is the center point of the imaging area shown in the third drawing. This corresponds to P ₁ .

Note that the light emitting elements 1a and 1b are shown in the other reset position (the liquid screw 3) in FIG.
When the micro switch 11b at the left end in the illustration of a and 3b is pressed to close it,
In FIG. 4, switch SW ₁ is opened and switch SW ₂ is closed, contrary to the above. Therefore, when the start switch _SW0 is closed in this state, the output of the AND gate _AG2 becomes "1" at the closing timing, and the flip-flop _FF2 is set. As a result, the motor drive circuit MD ₀ receives the reverse drive signal and drives the motor 10 in the reverse direction, and as a result, in FIG. starts moving upward in the figure. The flip-flop _FF3 is reset by the output "1" of the AND gate _AG2 , and contrary to the above, the Q output terminal becomes "1" and the output terminal becomes "0". Therefore, the output of the positive/negative discrimination output terminal M of the subtracter SC transmits positive/negative ("1", "0") in reverse, and the light emitting elements 1a, 1b and the photoelectric element 2
Even if the horizontal movements of a and 2b are reversed, the corrected moving direction of the bed top will be appropriate.

As described above, according to the present invention, even if the subject is placed outside the imaging area, the position of the subject is automatically moved to the most appropriate position where the center of the subject matches the center of the imaging area. be done. Therefore, the position of the subject can be set extremely quickly and accurately, greatly improving the imaging function of CT.

Note that the present invention is not limited to the above configuration, and for example, in the above embodiment, light emitting elements 1a and 2a and photoelectric elements for measuring the width of the subject in the X direction (horizontal direction) and Y direction (vertical direction) are used. 1b and 2b are each driven simultaneously by one driving source,
Although the configuration is such that a movement measuring circuit is provided for each, each pair is sequentially driven by a separate drive source with a measurement time difference, and one movement measuring circuit is sequentially switched and measured. It's fine. It goes without saying that the arithmetic control circuit can also be easily configured to perform analog operations similar to those described above by using potentiometers in place of the rotary encoders described above. It goes without saying that other modifications may be made as appropriate without changing the gist.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining the CT according to the present invention, and FIG. 2 is a diagram for explaining the CT according to the present invention.
FIG. 3 is a diagram showing an embodiment of the configuration for measuring the center point of a CT object in the present invention, and FIG. 4 is a diagram illustrating the measurement mechanism in FIG. 3. 5 is an electric circuit diagram showing the configuration of an embodiment of the control circuit and measurement calculation circuit of
FIG. 3 is a signal waveform diagram for explaining the operation shown in the figure. 1a, 1b...Light emitting element, 2a, 2b...Photoelectric element, 3a, 3b, 3c, 3d...Lead screw, 4a, 4b, 4c, 4d...Guard rail, 5
a, 5b, 5c, 5d...Mounting bracket, 6a, 6b,
6c, 6d, 6e, 6f...Bevel gear, 10...Motor, 9...Rotary encoder, 11a, 11b...
Micro switch, PG ₁ , PG ₂ , PG ₃ ...Pulse generator, MD ₀ , MD ₁ , MD ₂ ...Motor drive circuit,
SW ₀ , SW ₁ , SW ₂ ...Switch, SC...Subtractor,
CT ₁ , CT ₂ , CT ₃ ...Counter, CC...Coincidence circuit,
NS...Numerical setting device, FF ₁ to FF ₁₁ ...Flip-flop, MM ₁ to _{MM 6} ...Mono multivibrator,
AG ₁ to AG ₁₂ ...AND gate, OG ₁ to _{OG 7} ...OR gate, IN ₁ to IN ₈ ...inverter, CG...gate switching circuit.

Claims (1)

[Scope of Claims] 1. Move a predetermined stroke in the X direction and the Y direction while holding the tomographic plane of the subject placed on the bed top 2.
A pair of light emitting elements and photoelectric elements, a signal generator that derives signals according to the amount of movement of the light emitting elements and photoelectric elements, and a center point of the tomographic plane of the subject is calculated based on the output value of this signal generator. a measurement calculation circuit that calculates the amount and direction of movement of the subject in the X and Y directions until the center point coincides with the center point of the imaging area; A computer tomography apparatus comprising a motor drive circuit for moving a bed top in the X direction and the Y direction. 2. The computerized tomography apparatus according to claim 1, wherein a lead screw and a lead screw provided in parallel thereto are configured to move the two pairs of light emitting elements and photoelectric elements by predetermined strokes in the X direction and the Y direction, respectively. A computerized tomography apparatus characterized in that guardrails are assembled into parallel cross-sections, and each lead screw is driven by a single motor. 3. In the computer tomography apparatus according to claim 1 or 2, the measurement calculation circuit receives the movement amount of the light emitting element and the photoelectric element in a pulse amount, and starts the movement of the light emitting element and the photoelectric element. The light beam is counted at a predetermined pulse rate from the position to the position where it touches the subject, and while it crosses the subject it is counted at a pulse rate that is 1/2 of the predetermined pulse rate, and the sum of both counts is calculated as the subject. A computerized tomography apparatus characterized by performing measurement calculations based on the center position of a specimen. 4. In the computer tomography apparatus according to any one of claims 1 to 3, the light emitting element and the photoelectric element may start moving at any end of the predetermined stroke as the starting position. A computerized tomography apparatus patented in that a movement direction switching control circuit is provided in the measurement calculation circuit so as to operate the computer tomography apparatus.