JPS5973897A - X-ray-tube-current controlling device - Google Patents

Abstract

PURPOSE:To obtain an X-ray-tube-current controlling device which can perform the controlling easily with a high stability and has a sufficient safety function by adopting an inverter-type heating system, and performing the controlling according to the indication of the control processor of an inverter. CONSTITUTION:In performing monitoring to prevent any excessively large current from flowing in an X-ray tube filament, an abnormality-indicating signal (d) is generated in order to prevent any excessively large current from flowing out during the detection of abnormality, thereafter being incorporated into an inverter circuit 8. For instance, during the detection of abnormality, a command signal is produced wherein the current of which can preheat the X-ray tube filament. A signal (c) corresponding to the actual current of the X-ray tube works as a feedback signal. The inverter circuit 8 performs feedback control so that the signal (c) coincides with a signal (b) by comparing their magnitudes. In addition, at the time of the generation of abnormality, it causes the preheating current to flow in the filament of an X-ray tube 10. The output of the inverter circuit 8 causes a filament current to be set through a transformer 94 thereby causing a given current to flow in the filament.

Description

[Detailed description of the invention] The present invention relates to an X-ray tube current adjustment device.

The X-ray tube current adjustment device of conventional X11 imaging equipment switches the power resistance connected to the primary side of the X-ray tube filament transformer with a contact linked to the tube current setting device, or uses an inverter heating method. In this case, each tube current setting step was provided with an adjustment volume according to the size, and these volumes were adjusted. This method has drawbacks such as a large number of parts and a large number of adjustment points. Shattered, X
71 did not provide sufficient protection against filament breakage due to excessive power supply to the X-ray tube filament or damage to the X-ray tube due to overload.

SUMMARY OF THE INVENTION An object of the present invention is to provide an X-ray tube current adjustment device that is easy to adjust, has high stability, and has sufficient safety features.

The gist of the present invention is to adopt the Karo heat method using the Inno Ku overnight method, and to control the Inno (~Yu no Ichi 1) according to instructions from the processor.Furthermore, when adopting the Inno Ku overnight method, (Fitno (tsuku) poison l).

The present invention will be explained in detail below with reference to FIG.

FIG. 1 is a diagram showing an embodiment of the present invention. 1 is an X-ray tube voltage setting device, 2 is an X-ray tube current setting device, 3 is an r/'i imaging tube selector, 4 is a logic operation circuit formed from CPU, ROM, RAM, etc.), and 6 is a DA conversion It has a function of outputting a FNA log output corresponding to the X-ray tube current to the inverter circuit 8. 7 is a DA converter, which has a function of outputting an analog output proportional to the set tube current to the inverter circuit 8. 5 is a memory for storing heating data, which is a battery-backed RAM or an electrically readable/writable ROM. 9 is a high voltage generator, 91 is a high voltage generation transformer, 92° 92A is a rectifier, 93 is an X@tube current detection resistor, and a signal proportional to the actual X-ray tube current detected by this resistor is sent to an inverter circuit 8. will be sent to. 94 is a filament heating transformer for the X-ray tube 10, the primary coil of this transformer is driven by the output from the inverter circuit 8, and the secondary coil is connected to the Xav filament. 11 is a data switch, 12 is a function switch, 13 is an X-ray photography start switch, and 14 is a write switch for storing data from the data switch 11 into the memory 5.

There are two types of processing in the above configuration. The first is a process of forming heating reference data and heating compensation data and storing them in the memory 5. The second is a process of forming heating reference data and heating compensation data and storing them in the memory 5. The second is a process of using the data stored in the memory 5 for normal use by actual It is processing. The first process is man-war machine communication k f body! : -J'-le processing.

Explain the assumptions for the operation explanation.

(1) The function switch 12 has 8-pit switches D7 to Do, and D7 and D6 specify whether the process is the first process or the second process. When D7 = ON,
It becomes an instruction to form the force/heat-reference data Fb, and D7=O
FF.

When D6=ON, it is an instruction to form heating compensation data B. On the other hand, when D7=OFF, the second processing is instructed. However, both the first process and the second process assume that the start switch 13 is ON.

The logic operation circuit 4 takes in the states of D7 and D6 and the state of the switch 13 and makes a decision. Switches D5 to Do for the lower 6 bits of the function switch 12 are used for other instructions.

(2) The data switch 11 is directly used for the first processing and is not directly used for the second processing. In the first process, the data switch 11 sets temporary heating reference data f before forming the heating reference data Fb. Furthermore, the first
In the process, the data switch 11 sets temporary heating compensation data h for forming heating compensation data B. The processing for forming the heating reference data Fb and the processing for forming the heating compensation data B are performed separately, and therefore, it is possible to set the two data f and h using only the data switch 11. Data switch 11 consists of 8-bit switches D7-DO.

(3) The device operated by the operator is the data switch 11
, function switch 12, start switch 13
, a light switch 14, a tube voltage setting device 1, a tube current setting device 2, and a photographing tube selection device 3. In addition to this, there is a display (not shown) provided to display the actual tube current that the operator monitors. Furthermore, setting devices 1, 2 and δ
The selector 3 also has a display for displaying the set value and the selector for monitoring by the operator.

(4) FIG. 2 shows how data is stored in the memory 5.

The X-ray tube consists of multiple tubes TBI, TB2,...
Consists of TBn. Each tube TBi has a plurality of set tube current levels mAl r mA2 +..., mAt. Force n heat reference data Fbj for each set tube current level mAj
(j = 1.

2, ..., 1). Therefore, by specifying the tube number and the set tube current level as an address, the corresponding solar heat reference data Fbj can be specified. Further, heating compensation data B+ and B- are set for each tube. B+ is used for addition, and B- is used for subtraction.

FIG. 4 is an explanatory diagram of how to set and use compensation data B+ and B-. Each tube TBn has a reference tube voltage vR as a reference. For example, in Figure 4, VR = Zoo
It is called KV. There is a setting area for the set tube voltage in the area before and after the reference tube voltage. In Fig. 4, the two set tube voltages V1 = 50 KV.

V2 = 140 KV. 50Kv or less,
It is also possible to set it to 140 KV or higher. The vertical axis in FIG. 4 indicates heating compensation data B. Heating compensation data B
has characteristic 2 when the set voltage is lower than the base wall tube voltage VR, and has characteristic t2 when the set voltage is higher than the reference tube voltage VR. It is obtained for each such set-up tube voltage.

Compensated heating data F is obtained by applying the frR compensation date to the tube voltage set at that time. The calculation formula at this time is, assuming the set tube voltage is Fb, F = Fb 10B Old... Old...
Song...old/old episode...fil Compensation date is positive according to the characteristic t1 when the set tube voltage is smaller than the reference tube voltage VR, and conversely becomes negative according to the characteristic t2 when it is larger.

Furthermore,! Calculation of compensation data B corresponding to each membrane tube voltage according to temporalities tl and t2 is as follows: (Vl,,B+), (vR,o
) 6, determine the every @ line tx, and do it by interpolation.

Similarly, (VRlO), (V2, 'B-) wo4i
Thio@M line t2 is determined and performed by interpolation.

FIG. 3 shows the entire processing phase. The overall operation will be made clear in the following explanation. In FIG. 3, the process of PR1 is a process of forming reference data Fb, the process of PR2 is a process of forming compensation data Bi, and the process of PR3 is a process of normal use. However, as is clear from the figure, there are parts that repeat each other, and this division is for convenience to facilitate understanding.

First, the second process will be explained.

The start switch 13 is turned on, and the logic operation circuit 4 confirms that it is turned on. The operator selects switch D7 f: OFF' and switch D6 of the function switch 12.
Set it to iOFF. In addition to this, the operator also uses a tube voltage setting device l.
The tube voltage is set as the set tube voltage, the tube current setter 2 sets the tube current as the leg tube current, and the tube selector 3 instructs which tube to select. Data switch 1 is not used directly in the second process.

In response to such an operation, the logical operation circuit 4 takes in all the settings made by the operator. Start switch 13
7jZQN″rsp, D of function switch 12
7-OFF, D6 = OFF) state! ! 11
! The arithmetic circuit 4 recognizes that it is a 2(7) processing request. Based on this recognition, the arithmetic circuit 4 operates the tube selector 3
Set the access address of the memory 5 according to the instruction contents of the selected tube and the set tube current level of the tube current setting device 2,
Heating reference data Fbi indicated by the address and heating compensation data B-1- corresponding to the selected tube.

Read B-.

Such f3+, B- and reference 'U voltage vR and straight line t1
, t2 is calculated by the circuit 4 and the crotch T tube voltage VsK set by the tube voltage setting device 1 corresponds to) JD heat compensation data B
? Output the p force using the interpolation method. After that, the arithmetic circuit 4
=Fbi+B...Old...Mountain...
...River......Old...Calculate +21. The heating data F that is the result of this measurement is sent to the DA converter 6
The signal is sent to DA converter.

Further, the arithmetic circuit 4 sends a value corresponding to the set value set by the tube current setting device 2, such as 200-bit data of 10100O, to the DA converter 7 for DA conversion.

The inverter circuit 8 receives an analog signal a corresponding to the heating data from the DA converter 6 and an analog signal S corresponding to the setting of the DA converter 7. Furthermore, the arithmetic circuit 4 (i No. d,
The signal C corresponding to the actual Xa tube current of the X-ray pipework 0 is taken in.

The signal d is an abnormality indication No. 1 by the logical operation circuit 4. The logical operation circuit 4 monitors whether there is an abnormality in the tube current or overvoltage, and monitors whether the photographing start switch 13 is turned on. The purpose of this monitoring is to prevent destruction of the tube due to excessive current flowing through the X-ray tube filament during the various abnormalities mentioned above. There are other monitoring purposes, but they are not related to @touch, so I will not go into details.

During monitoring to prevent excessive current from flowing into the X-zoo tube filament, an abnormality display signal d is generated to prevent excessive current from flowing when an abnormality is detected, and the inverter circuit 8 is be taken in.

For example, when an abnormality is detected, a command signal of a current sufficient to completely preheat the X-ray positive filament is generated.

The signal C corresponding to the actual X-string positive current is a feedback signal, and the inverter circuit 8U compares the signal with the multiple C, and performs feedback control so that the signal C matches the signal. Furthermore, in the event of an abnormality, the inverter circuit 8 is configured to switch off the preheating power a? : Control the flow to the filament of the Xa tube 10. The output of the inverter circuit 8 sets a filament current via a transformer 94, causing a predetermined current to flow through the filament.

On the other hand, the high voltage generation transformer 91 is
A voltage is applied to the primary side of the tube, and after rectification by the rectifiers 92 and 92A, an X-ray tube current flows. XIW
The tube current is detected by a resistor 92 and inputted to the inverter circuit 8 as a signal C corresponding to the normal X-ray tube current, and is feedback-controlled so as to match the set current described above. This-
Through feedback control, the tube current finally matches the set tube current.

Next, the first process will be explained.

This first process is a process for forming the contents of the memory 5 shown in FIG. In this process, the process of forming the heating reference data Fb and the process of forming the heating compensation data B are performed by separate processes.

First, the process of forming the heating reference data Fb will be described.

In this process, the switch 104 is turned to the P side, the switch D7 of the function switch 12 is set to ON, and the start switch 13 is turned on to start the first process. Start switch 13 ON and D7=ON
The logical operation circuit 4 performs f4Jf. Furthermore, switch 1
1 to an appropriate value f. This value f has a meaning as temporary heating reference data. Logical reasoning.

The circuit 4 reads data f from the switch 11 and then sends this data to the DA converter 6. On the other hand, the arithmetic circuit 4 reads data corresponding to a reference tube current that is a reference (target) and is stored in advance in the memory 5, and sends it to the DA converter 7.

The inverter 8 is the converted analog signal a of the DA converters 6 and 7.
, b are taken in and the current to be passed through the filament transformer 94 is set. A filament current thus flows through the transformer 94, and the rectifiers 92, 9 as before.
A tube voltage is applied via 2A, causing a predetermined tube current to flow.

At this time, since the switch 104 is turned on to the P side,
Since b of the analog switch 105 is 0" and a is "H", the reswitch B is closed and the switch A is open, so the reference tube current signal is fed back from the resistor 93, which corresponds to the tube current. is not performed, and the system is an open loop.However, the tube current is displayed on a display circuit (not shown).
The operator monitors this display circuit and checks whether the tube current matches the set tube current set by the tube current setting device 2. If they do not match, the setting value f at the data switch 11
can be heating compensation data corresponding to the selected tube and the set tube current level.The operator sets a new set value f1 to the data switch 11.

Perform similar operations based on this setting value. Hereafter, change the setting values until they match. If they match, the set value f at that time is set as the caloric heat reference data Fbi, and the operator turns on the light switch 14. The logic operation circuit 4 receives the ON state of the light switch 14 and stores the contents of the data switch 11 at that time in the memory 5. This storage address is an address that can be specified by the tube selected by the tube selector 3 and the tube current level set by the tube current setting device 2.

Incidentally, since the setting value f at the data switch 11 is determined by trial and error, it is wise to set the value as small as possible at the start according to the selected tube, and gradually change it from small to large. This is because if a too large value is set depending on the selected tube, the filament may burn out due to overheating.

Next, the process of forming heating compensation data B will be described.

In this process, switch 13 is ON, switch 12 is D
7 is operated as OF'F and D6 as ON, and the sword performance circuit 4 fully recognizes this state as a process for forming the heat compensation data B. On the other hand, the data switch 11 is
Set h+ to the upper 4 bit switches and h- to the lower 4 bit switches.

The data switch 11 h-4-, h
- is taken in as temporary 7JlI heat compensation data. Furthermore, the heating reference data Fbi is read out from the address corresponding to the selected tube of the tube selector 3 and the set tube current level of the tube current setter 2, which have already been stored in the memory 5 in the above process.

Curved heating reference data Fbi and provisional heating compensation data h+
, h-. First, the sum of Fbi and h+ is sent to the DA converter 6. The inverter circuit 8 outputs filament heating power for the X-ray tube 10 to the transformer 94 in accordance with this added value. Due to the output of this inverter,
The official current flows in the same way as before. A circuit (not shown) allows the operator to display whether the tube current is the set tube current or not.
This is done by monitoring. If they do not match, set another h0, and similarly set data switch 1 with the matching violet.
Change the setting value of 1. When they match, the temporary h+ at that time is determined as the actual heating compensation data, and by turning on the light switch 14, h+ is written to the address of the memory 5 as B+.

Similar operations and processing are performed for h- to set the true B- remainder and store it in the memory 5.

During the above operation, the contents of the data switch 11 are changed to adjust the tube voltage so that the set tube current is maintained over the entire range from a low value to an aggressive value.

Incidentally, by changing the modifier page 11 from a small value of 1- to a large value, overheating due to erroneous operation can be prevented. Another method is to set the maximum allowable value to memory 5.
, and the operation may be performed only when the value is within the permissible maximum value. Furthermore, accurate compensation is possible by obtaining three points or general multi-point percentage notes in addition to two points.

In the above explanation, the upper 4 bits of the data switch are B+,
The lower 4 pits are set to B-, but by setting D6 of the function switch 12 to B+ for heating compensation and D5 to B-, all 8 bits of the data switch 11 are used as compensation data to separately set B+ and B-. It can also be set.

FIG. 2 shows an embodiment of the inverter circuit 8. In FIG. 81°82
is a Calo calculator, 83.84il- is an inverting amplifier, and 85 is a voltage follower circuit. 86 changes the output power instantaneously depending on the input signal from the voltage follower circuit 85. The output of the i7arter 86 is supplied to the primary coil of the heating transformer 94 in FIG. 87 to 98 are resistors, 99, 100, 101 are diodes, 102
is an AND circuit, and one input terminal receives a timer signal from a timer circuit not shown in FIG.

A signal from the changeover switch 104 is connected to the remaining one.

The selector switch 104 is turned on to the P side during data adjustment and to the q side during normal use. When the P side is ON, the output is 0.
When the side is ON, the output is 1.

The analog switch 105 is A 1.1l during normal use.
Turn it on to select the output of the JV and device 81. When adjusting data, turn on the B side and select the ground side. The selection of the A side ON is performed by inputting ゝXl// to the terminal a. This ゝゝ1〃 occurs under the condition that the q1 law of the switch 104 is ON and the timer output e is 1\l〃. The B side ON selection is performed by inputting the terminal b K'l /'. This ゝ\1〃 is when the AND circuit 102 output 1\0 and the inverter 103 output ゝ\l〃.

First, the first process, which is normal use, will be explained.

During normal use, under the condition that the q side of the switch 104 is ON and the timer output e is ■l, the a side of the switch 105 becomes SS 1 // through the AND circuit 102, and A
Il] turns ON. Specify the timer output FiX-ray exposure period.

Signals a, b, c, d, and e during normal use are as follows.

Signal a: A signal corresponding to F=Fb+B read out from the memory 5.

Signal b: A signal corresponding to the tube current set by the tube current setting device 2.

Signal C: A signal corresponding to the real tube current for feedback detected by the resistor 93.

Signal d...This is an abnormality display signal of the circuit 4, and is a binary signal of \\0 when abnormal and ゝゝ1〃 when normal.

Signal e: Indicates the X-ray irradiation section, during the irradiation section X1
Otherwise, it is a binary signal of \0.

7J[] Rule 2 unit 81 calculates the deviation of the signal between the signal S and C (c-
b) Output. 13 of the inverting amplifier 83
The inverted output of No. a and the above deviation (c-b) are taken in and an added output is generated. Additionally, the output of inverting amplifier 83 enters inverting amplifier 84 .

Diodes 99, 100, 101 and resistor 97 form an analog OR circuit. Diode 99, 100
, 101, the lowest level of the voltage inputs becomes the output of the analog OR circuit and is sent to the voltage follower 85.

The abnormality display signal d is V″l〃 at normal time, and “1 //
= H level, and other diodes 99, 10
Assuming that the input level to 0 is lower than the above H level in any case, the diode 101 continues to be OFF as long as the signal d is -1.

Under such normal conditions, the lowest value among the inputs of diodes 99 and 100 is selected. The diode 99 receives an added value of the reference signal a and the feedback deviation (Cb), and the diode 100 receives a signal obtained by multiplying the reference signal a by, for example, 1.degree.

When the added value is lower than the signal obtained by multiplying the reference signal by 1.2, the addition I1. The value input is selected, and when the signal obtained by multiplying the reference signal a by 1.2, for example, is lower than the added value, the signal obtained by multiplying the reference signal a by 1.2, for example, is selected.

The selected output is input to a voltage follower circuit 85 and then taken to an inverter 86. The inverter 86 is the circuit 8
5, the output is controlled according to the selected output.

As a result, the actual gnL current is controlled to always be constant, and the tube current is always added.

On the other hand, when an abnormality occurs, the signal d reaches a level of \0 -, only the diode 101 is turned on, and an output corresponding to the level of the signal d is input to the voltage follower circuit 85. This signal d causes the inverter 86 to flow a current sufficient to preheat the X-ray filament.

The analog OR circuit is set so that the lowest level among them will not overheat the filament, no matter how many three people are working on it. For example, it is set to about 1.1 to 1.2 times the rating. This is achieved by increasing the amplification rate of the inverting amplifier 84, which inverts and amplifies the reference signal a, by 1.1 to 1.2 times. Accordingly, it is possible to prevent the X-ray tube from being overheated due to the excessive deviation (c - d, .) due to feedback, which would result in an excessive u value with respect to the reference signal a.

The selection of B based on the calculation of the reference heating signal F = Fb + B becomes B-, B+ depending on the magnitude relationship between the basic tube voltage ■R and the set tube voltage vs, and F = Fb + B
or F=Fb-B. This allows compensation using the tube voltage.

Compensation for heating using tube voltage corrects tube current fluctuations due to so-called space charge limitations, which is a general characteristic of X-ray tubes, such that even under the same heating conditions, the higher the tube voltage, the more current flows. Loaded with stuff. During X-ray irradiation, such compensation seems meaningless because the actual tube current is detected and fed back, but due to the influence of the thermal inertia of the filament,
It is not stable immediately after irradiation. This is necessary in order to stably irradiate X-rays over one peak during the entire period of X-ray irradiation.

In addition, feedback control based on detection of the actual tube current during irradiation compensates for biased magnetization of the heating transformer due to the Xi tube current flowing through the filament heating transformer during irradiation, and decreases in tube current due to fluctuations in current. You can also do it.

Next, the process of forming heating reference data by the inverter circuit 8 will be explained.

In this process, 'switches 104 and 105, signal a
~e is as follows.

The switches 104...P 11111 are turned on, so the AND circuit 102 outputs the signal o.

Switch 105...terminal a via inverter 103
SS 1 // is applied to , switch A is OFF',
Switch B is turned on. As a result, the adder 81 is disconnected and is no longer involved in the processing at all. Therefore, once the signal is turned on, the signal C becomes irrelevant, and no feedback control is performed at all.

Signals S, C, @... have nothing to do with the operation.

Signal a: A signal corresponding to temporary heating reference data set by the data switch 11.

Signal d: This signal d may be unrelated to the operation, but
There is a need to check everything to see if it is normal or not while forming data F! ! Because it is righteous, when it is normal ゝ＼1 //, when it is abnormal it is 10“
Make the most of it as much as possible.

Under the above conditions, the operator monitors whether the current value set by the tube current setting device 2 is obtained by the signal a using a display (not shown), and presses the data switch 1 until a match is obtained.
Change the setting data in step 1.

The set value of the data switch 11 when a match is obtained is Fb
Then, turn on the light switch 14 and set the setting device 2゜3.
The above Fb is stored at the address specified by .

The process of forming heating compensation data B by the inverter circuit 8 will be explained.

In this process, the switches 104 and 105 are in the same state as in the previous heating reference data Fb formation process, and the B side of the switch 105 is turned on. Therefore, feed pack control is not performed. In addition, signals a and d are as follows.

Signal a: Fb read from the address of the memory 5 determined by the tube current level of the setting device 2 and the selected tube of the selector 3 and the data h of the upper 4 bits or lower 4 bits of the data switch 11 are added. The resulting signal is signal a. The upper 4 bits are set as compensation data for a set voltage lower than the reference tube voltage, and the lower 4 bits are set as compensation data for a set voltage higher than the reference tube voltage.

Signal d: Handled in the same manner as in the reference theme Fb formation process described above.

Under such signal conditions, the inverter 86 receives a signal corresponding to the signal a and causes a tube current to flow. At this time, adjustments are made by changing the contents of the data switch 11 so that the set tube current is achieved over the entire tube voltage region by repeatedly irradiating X-rays over the entire tube voltage region from low to high. When the compensation data is determined, switch 14 is turned on, and the contents of data switch 11 at that time are set as compensation data B.
It is written into memory 5 as . The above operation is performed for each of the upper and lower 4 bits of the data switch 11.

As explained above, according to the present invention, tube current adjustment can be achieved with small parts such as a function switch, data switch, light switch, etc., and since the data switch can be shared for multiple adjustments, it can be achieved in a small size and at low cost. Furthermore, data that is not valid at the time of data input is restricted, and the heating feedback system based on actual tube current detection is also safe because it has a built-in protection circuit to prevent overheating. Furthermore, the feedback circuit works to ensure stable X-ray output at all times. In addition, heating reference data and compensation data are stored separately in memory, so that only a small amount of reference data is required for compensation data, so memory capacity can be greatly limited.

[Brief explanation of drawings]

FIG. 1 is an embodiment of the present invention, FIG. 2 is a data composition diagram of the memory, FIG. 3 is a flowchart of the overall processing of the present invention, FIG. 4 is a diagram explaining the setting of compensation data B, and FIG. FIG. 5 is an example diagram of an inverter circuit. l...Tube voltage setting device, 2...Tube current setting device, 3...
・Tube selector, 4...Logic operation circuit, 5...Memory, 6゜7...DA converter, 8...Inverter circuit,
9...Commercial voltage generator, 10...X@tube, 11...
・Data switch, 12...Function switch. Patent applicant Hitachi Medical Co., Ltd. Agent Patent attorney Masami Akimoto - Figure 1 il; 2N

Claims (1)

[Claims] 1. A tube selector that indicates the type of tube, a tube current setting device that indicates the tube current, a tube voltage setting device that indicates the tube voltage, a data switch, a function switch, a start switch, and a light. The status of the switch, data switch, function switch, start switch, light switch, tube selector, tube current setting device, and tube voltage setting device is taken in, and the heating standard data creation mode is certified and processed, and the heating compensation data is created. An X-ray tube current adjustment device equipped with a logical operation circuit that performs mode recognition and processing and necessary calculations.