JP3447012B2 - X-ray equipment - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray apparatus, and more particularly to an X-ray apparatus.
The present invention relates to a filament tube heating circuit. 2. Description of the Related Art In an X-ray apparatus, when an X-ray photograph is taken, first a framing of a region of interest is performed by a fluoroscopic monitor image, that is, a fluoroscopic image, and then a film photographing (hereinafter, referred to as photographing). By pressing the X-ray exposure switch, the image is taken on the X-ray film. But,
A delay time of about 0.3 to 1.5 seconds usually occurs before the transition from fluoroscopy to imaging due to the characteristics of the X-ray apparatus. Explaining this delay time, an X-ray tube usually has two focal points, large and small. In fluoroscopy, a small focal point is generally used to increase the sharpness of an image, and a large focal point is generally used in radiography to increase the tube current capacity. . For this reason, at the time of transition from fluoroscopy to imaging, the large focal point is not warmed up.
It took about 5 seconds. In addition, a time for setting the anode rotation speed of the X-ray tube to a specified value, a time for charging the capacitor on the input side of the inverter to a predetermined voltage value, or a movement of the unexposed film from the retracted position to the photographing position. You also need time to do it. If this delay time exists, the imaging timing of a focused lesion may be missed in imaging of a fast moving part using a contrast agent or the like. For this reason, in the conventional apparatus, the filament voltage having a predetermined value or more is temporarily increased and applied at the beginning of the period from the start of the photographing preparation signal to the start of the exposure signal (quick start method). In the above-mentioned conventional quick start method, the voltage value to be increased and the application time are set under constant conditions. That is, the control system for supplying power to the filament is so-called constant voltage feedback for stabilizing the heating inverter input voltage to a constant value. In the steady state, the filament temperature and the application time are in a proportional relationship. However, in the transient state, the resistance value in the filament cooling state is very small, as shown in FIG. do not become. For this reason, if the type of tube or the tube current conditions are different, stabilization is not completed within the preparation period, and the degree of blackening of the film may vary in the case of continuous shooting or the like. When the heating amount of the filament is too large, the filament may be broken. SUMMARY OF THE INVENTION It is an object of the present invention to heat a filament in an unheated state at a high speed to an optimum temperature to reduce a delay time from fluoroscopy to imaging, and to prevent filament breakage due to overheating even when a different X-ray tube is used. An object of the present invention is to improve the operability and the maintainability by setting an optimum tube current value without causing the occurrence. In order to achieve the above object, the present invention provides an X-ray tube and an X-ray high-voltage device for supplying a tube current and a tube voltage applied to the X-ray tube. An X-ray apparatus comprising: a filament heating circuit for supplying electric power to a filament of the X-ray tube;
Is a filter for detecting a voltage applied to the filament.
And a current flowing through the filament.
Filament current detecting means for detecting
Of the filament voltage detecting means and the filament current detecting means.
The filament resistance of the X-ray tube is detected by each detected value
And feeds the resistance value to the filament heating circuit.
A filament resistance detecting circuit for backing, and the filament
Set the minimum value of the output current from the
The minimum current setting circuit and the
The filler is adjusted to match the resistance
To control the output voltage and output current of the
And a lament resistance control means . The output voltage is measured from the filament voltage detection circuit, and the output current is measured from the filament current detection circuit.
The output voltage and the output current are calculated and output by a divider circuit. This resistance value is fed back to the filament heating circuit and adjusted to a predetermined temperature, that is, a predetermined resistance value. Further, the minimum current limiting circuit causes the lowest current to always flow to the denominator when the division circuit is saturated, that is, when the current value on the denominator side falls below the set minimum value. As a result, the temperature of the filament can be increased at a high speed, and further, unnecessary heating is prevented. An embodiment of the present invention will be described below with reference to FIGS. First, the configuration of the present embodiment will be described. 1 is X
X-ray high-voltage device for supplying tube voltage and tube current to the tube 2
X has a large focal point 3L for photographing and a small focal point 3S for fluoroscopy.
It is a wire tube. Reference numeral 4 denotes a filament heating circuit for heating the large focal point 3L and the small focal point 3S. Reference numeral 5 denotes a filament resistance detection circuit for detecting filament resistance. The filament resistance detection circuit includes a filament voltage detection circuit 9, a filament current detection circuit 10, and a division circuit 11. Reference numeral 6 denotes a focus selection circuit for selecting one of the large focus 3L and the small focus 3S, and 7 denotes a large focus 3L and a small focus 3S.
The heating transformer 8 transforms the voltage to heat the filament. The heating transformer 8 sets the resistance set value of the filament to RsetS for small focus and Rset for large focus.
a selection switch for switching to setL; a filament voltage detection circuit 9 for measuring a filament voltage; a filament current detection circuit 10 for measuring a filament current; a division circuit 11 for calculating a quotient between the filament voltage and the filament current; Reference numeral 13 denotes a signal generator for selecting the focus selection circuit 6, the heating transformer 7, and the selection switch 8. A small focus signal or a large focus signal is output from the signal generator 13 and is switched by the focus selection circuit 6 to the heating transformer 7S or the heating transformer 7L. The signal from the signal generator 13 is also supplied to the selection switch 8 to be switched to the filament resistance set value RsetS or RsetL. A filament voltage Vf and a filament current If are supplied to the large focal point 3L and the small focal point 3S through the filament heating circuit 4, the filament resistance detecting circuit 5, and the focal point selecting circuit 6, respectively. The filament resistance detection circuit 5 calculates the filament resistance Rf 'from the output voltage Vf' and the output current If 'of the filament heating circuit 4 during fluoroscopy or imaging, and feeds it back to the filament heating circuit 4. The output voltage V is controlled by the filament heating circuit 4 so that the feedback resistance value Rf 'and the filament resistance set value selected by the selection switch 8 become equal.
f ′ and the output current If ′ are adjusted. Here, the filament resistance Rf 'is calculated from the output voltage Vf' and the output current If 'on the primary side of the heating transformer 7, that is, on the filament heating circuit 4 side.
The actual filament resistance Rf is the filament resistance Rf '.
Is the square of the turns ratio of the heating transformer 7.
Assuming that the number of primary windings of the heating transformer 7 is N1 and the number of secondary windings is N2, from the characteristics of the transformer, Vf = (N2 / N1) .Vf 'If = (N1 / N2) .If ′ Holds, and from this equation, Rf = Vf / If = (N2 / N1) · Vf ′ / (N1 /
N2) · If ′ = (N2 / N1) ² • Rf ′. Further, if voltage and current are fed back from the secondary side of the heating transformer 7 using an insulating means in the feedback system of this embodiment, it is not necessary to consider the number of turns of the heating transformer 7 in setting the filament resistance. In X-ray fluoroscopy, an operator first performs fluoroscopy to search for a region to be imaged and perform framing on a monitor. At this time, since the small focus 3S is used in the X-ray tube 2, a small focus signal is generated from the signal generator 13,
The heating transformer 7S is selected by the focus selection circuit 6, and the filament resistance set value RsetS is selected by the selection switch 8.
Then, after the fluoroscopy is completed, an image is taken on a film. At this time, while switching to the large focus signal from the signal generator 13,
The selection switch 8 also sets the filament resistance set value RsetL.
Then, the focus selection circuit 6 is also selectively switched to the heating transformer 7L. At this time, the large focus signal 3L is not heated, and since the resistance value is very small, a large current flows at the moment when a voltage is applied. However, the instantaneous resistance value is always compared with the filament resistance value RsetL and the filament value is compared with the filament resistance value RsetL. Resistance value R
It cannot be larger than setL. Also, the filament temperature can be quickly reached to the target temperature only by setting the gain of the feedback system so that the response of the resistance value becomes fast. Next, a detailed description of the filament resistance detection circuit 5 of this embodiment will be described with reference to FIG. The output voltage Vf 'of the filament heating circuit 4 is divided by voltage dividing resistors 9a and 9b, and an amplifier 9c for detecting a voltage between both ends of the resistor 9b.
As a result, the voltage enters the numerator side input of the division circuit 11 as a voltage proportional to the actual filament voltage. On the other hand, the output current If 'of the filament heating circuit 4 is converted into a voltage by the current detection resistor 10a and then enters the denominator input of the division circuit 11 as a voltage proportional to the actual filament current. At this time, both inputs of the dividing circuit 11 are proportional to the actual filament voltage / current with the same conversion. In the division circuit 11, the filament voltage Vf '
Is divided by the filament current If 'to obtain a filament resistance Rf' which is a quotient. This value can always be expressed as a value corresponding to the filament temperature according to the relationship of FIG. In these calculation systems, only the division circuit 11 requires a relatively long time for the operation, but the operation speed of the division circuit 11 is so high that there is no problem compared with the thermal time constant of the X-ray tube filament. . Next, another embodiment of the present invention will be described with reference to FIG. This is provided with a minimum current setting circuit 12 for setting the minimum value of the output current to the filament resistance detection circuit 5 described above. The output If of the filament current detection circuit 10, which is an input on the denominator side of the division circuit 11, cannot be set to zero due to the nature of the division circuit 11. This is because this state is a value that cannot be mathematically defined and the output of the division circuit 11 is saturated. Therefore, when the output If of the filament current detection circuit 10 becomes smaller than the minimum current setting value Imin, the diodes 12a and 12b switch so as to output Imin to the denominator side of the division circuit 11. In this embodiment, the operability of the X-ray apparatus can be improved by heating the unheated filament to the optimum temperature at a high speed, thereby reducing the delay time from fluoroscopy to imaging. Even with such an X-ray tube, the optimum tube current value can be set without causing filament breakage due to overheating, so that the maintainability of the X-ray apparatus is improved. Further, the filament temperature can be easily detected at high speed and with high accuracy. Then, the minimum current limiting circuit 12
, The division circuit 11 does not saturate, and the filament resistance detection circuit 5 can operate stably. Further, since all of the present embodiments are provided in the low-voltage circuit on the primary side of the heating circuit 7, it is not necessary to use various circuits relating to insulation. Furthermore, the detection accuracy is determined by the stability of the divider circuit of the amplifier. The accuracy of the resistance value is a general-purpose component, and any component having sufficient characteristics for use in an X-ray apparatus can be obtained at low cost. The dividing circuit 11 converts the detected value from A / D converted data and a filament resistance set value given by digital data into a DSP (Digital Signal Processor).
For example, a so-called digital circuit for performing a digital operation using an analog circuit or an analog circuit configured using an OP amplifier may be used. The same can be used for the minimum current limiting circuit. According to the present invention, by heating the unheated filament to the optimum temperature at a high speed, the delay time can be reduced, the operability of the X-ray apparatus can be improved, and what kind of X-ray can be obtained. The optimum tube current value can be set without causing a filament break even in the X-ray tube, and the maintainability of the X-ray apparatus is improved. Further, the filament temperature can be easily detected at high speed and with high accuracy. Since the division circuit is not saturated, the filament resistance detection circuit can be operated stably.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a configuration of the present invention. FIG. 2 is a diagram showing a relationship between a filament temperature and a filament voltage. FIG. 3 is a diagram showing a relationship between a filament temperature and a filament resistance. FIG. 5 is a circuit diagram of a filament resistance detecting circuit showing an embodiment of the present invention. FIG. 5 is a circuit diagram of a filament resistance detecting circuit showing another embodiment of the present invention. 5 Filament resistance detection circuit 6 Focus selection circuit 7S Heating transformer for small focus 7L Heating transformer for large focus 8 Selection switch 9 Filament voltage detection circuit 10 Filament current detection circuit 11 Divider circuit 12 Minimum current limiting circuit 13 Signal generator

Claims (1)

(57) Claims 1. An X-ray tube, an X-ray high-voltage device for supplying a tube current and a tube voltage applied to the X-ray tube, and an electric power supplied to a filament of the X-ray tube. an X-ray apparatus and a filament heating circuit for supplying the filament heating circuit,
Filament for detecting a voltage applied to the filament
Voltage detection means and a current flowing through the filament.
Filament current detecting means for emitting, and the filament
Each detection of the voltage detecting means and the filament current detecting means
From the output value, the filament resistance of the X-ray tube is detected.
And feed the resistance value to the filament heating circuit.
A filament resistance detection circuit for detecting
To set the lowest value of the output current from the current detection means.
The low current setting circuit and the resistance value of the filament
The filament so as to match the resistance value
Control the output voltage and output current of the heating circuit
An X-ray apparatus comprising: an element resistance control unit .