DE2754920A1 - PROCEDURE AND CIRCUIT ARRANGEMENT FOR THE HEATING POWER SUPPLY OF A ROENTINE PIPE - Google Patents

Description

27S4920 / 3

Method and circuit arrangement for the heating current supply of an X-ray tube

The present invention relates to a method for generating a voltage as a function of the X-ray tube voltage and the setpoint value of the heating current of an X-ray tube, which corresponds to the X-ray tube current, and a circuit arrangement to carry out the procedure.

In X-ray technology, efforts are made to be able to set the means that intervene in the heating circuit of the X-ray tube To influence X-ray tube current in such a way that the set values of the X-ray tube current with the values actually present on the X-ray tube over the entire voltage setting range to match. Since each X-ray tube or each focal point has its own emission characteristic, such compliance with the requirement has so far only been met to a more or less rough approximation been.

As is apparent from DT-AS 1 012 000, it is known to set the X-ray tube current in the Insert heating circuit changeable resistors, and although these are dependent on the entered value of the X-ray tube voltage and the entered value

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27S492Q

of the X-ray tube current influenced. A comparison of the entered Value of the X-ray tube current to the actually resulting value of the X-ray tube current only at two points, namely at an upper and a lower limit value. The influence of the X-ray tube voltage is then carried out by trimming at an average X-ray tube current. From this it is clear that that between almost all entered and actually available values of the X-ray tube current there is one there is a more or less large deviation, which the user can only compensate by an emotional adjustment can. Replacing a defective X-ray tube with another or switching to one however, another focal point also brings about a change in the deviations. Because of this, the user is convenient unable to develop a sense of proper compensation.

For this reason, the invention is based on the object of providing a method and a method suitable for carrying out the method Specify circuit arrangement, whereby an optimal specification of the for the realization of the match between the entered and actually present X-ray tube current required heating current is possible.

According to the invention, the object is thereby achieved in terms of the method solved that the target value synthetically from the at a lower and an upper for the normal examination visit drove symptomatic X-ray tube voltages xn dependent

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The heating currents resulting from the respective set X-ray tube currents and the two symptomatic ones X-ray tube voltages, as well as one that depends on the characteristics of the X-ray tube, through the respective set X-ray tube voltage is determined by suitable means.

As a result, a stepless calibration can be carried out with the present invention.

To carry out the method can advantageously use a circuit arrangement that is characterized is that two components to simulate the symptomatic X-ray tube voltages in Depending on the set X-ray tube currents resulting heating currents are provided that these components are a component for determining the Difference between the two heating currents connected downstream is that this component with another component for the purpose of dividing this difference value by one in one associated component connected from the two symptomatic X-ray tube voltages difference value formed is that this component is another component for multiplying the division value with that of one associated component formed factor downstream 1st, and that with this component a further component for subtracting this value from the larger value of the two heating currents is connected, which at its output a signal corresponding to the nominal value of the heating current Delivery t.

Further advantages as well as features and measures of the invention The proposal is based on an exemplary embodiment shown more or less schematically in the drawing and the associated diagrams in more detail · »

1 au t e r t.

As can be seen from FIG. 1, a setting element 1 is used to set a current Ir proportional to the desired X-ray tube electrical quantity on the one hand a component

2 and on the other hand a component 3 is supplied. In these components 2 and 3, a symptomatic Röritgen tube voltage Ur * and U _R **, which are preferably 120 kV (% *) and 60 kV (U _R **), or electrical quantities proportional to them are used a dependent heating current Ijj * and Ijj ** or an electrical quantity proportional to it is formed. These two quantities are then fed to a component h in which the quantity corresponding to the heating current I,. * Is subtracted from the electrical quantity corresponding to the heating current In **. A downstream component 5 is now acted upon on the one hand with the resulting difference variable and on the other hand one in a further component 6 from the symptomatic voltage variables U * and U ** by subtracting the

R **

Size U _n ** H _{supplied by the difference size U n} * formed. From these differences Ijj ** - Ijj * and Un * - U **, a variable is now formed in this component 6 by dividing I ** - I * by U * - U ** which corresponds to a further »η Haue Lenient 7 is fed. In this Bui & ement 7 this size is combined with a

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supplied by a further component 8, one from the respectively set X-ray tube voltage U and

multiplied by the factor F representing the electrical quantity derived from the emission characteristics of the X-ray tube. The resulting variable is now fed to a component 9 , where it is subtracted from the variable that is also supplied and is proportional to the heating current I **.

is hed, i.e. at the output of this component there is a value proportional to the setpoint of the heating current electrical quantity, which is represented as a formula as follows?

τ ** - T ♦ H H

U * - U ** R R

* ^F

The diagram according to FIG. 2 shows the values of the heating current at the various X-ray tube voltages Must assume that the value of the X-ray tube current at the X-ray tube matches the entered value Value matches. The course of the X-ray tube voltage depends on the characteristics of the respective X-ray tube addicted. Investigations have shown that for the respective, arbitrarily chosen Rontge ^ nsxr ^ life practically constant change ratios for the assigned There are heating currents with constant changes in the X-ray tube voltage. Based on this fact According to the present invention, by means of suitable curve generators, two are the characteristics of the respective X-ray tube parameters, namely U *

and U ** formed, the two frequently occurring in practice - R

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corresponding, i.e. symptomatic, X-ray tube voltages. Since - as mentioned above - practically constant conditions prevail for all other X-ray tube voltages, can now all other parameters and thus also the other heating currents by introducing a Factor F can be determined and thus specified. This factor is indicated in FIG. 3, with constant Conditions for the individual X-ray tube voltages have been assumed, so that the factor F result in linear relationships. In reality, these relationships are not 100%, but they are the aforementioned solution represents an optimal approximation of the ideal case, and this approximation is special good in the range between the two symptomatic X-ray tube voltages U * and U **. For this

R R

Basically, the symptomatic X-ray tube voltage U ** was used as the starting point; selected, ie the factor F is here equal to zero. With smaller X-ray tube voltages, the factor F becomes negative and with larger X-ray tube voltages it becomes positive, whereby the two symptomatic Höntgenrolrrrensetungen are preferably at U ₁₃ ** = 60 kY and V * = 12Ο kV «

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Claims (3)

KOCH & STERZEL Essen, November 29th, 1977 GmbH & Co Bt / Os Claims ί 1.) / process experience and circuit arrangement for generating a setpoint value of the heating current of an x-ray tube, which is dependent on the X-ray tube voltage and the x-ray tube current, characterized in that the setpoint value is synthesized from the lower and upper values which are symptomatic for normal examination operation e X-ray tube tension varies depending on the set X-ray tube currents resulting in heating currents and the two symptomatic X-ray tube voltages, and one that depends on the characteristics of the X-ray tube and is determined by the X-ray tube voltage set in each case Factor is formed by suitable means. 2.) The method according to claim 1, characterized in that the factor is formed such that it is positive and negative Can assume values and has the value zero at the lower symptomatic X-ray tube tension. 909824/0341 / 2 3.) The method according to claim 1, characterized in that the lower symptomatic X-ray tube voltage to about 6O kV and the upper symptomatic X-ray tube voltage is set to about 120 kV. k.) A circuit arrangement according to claim 1, characterized in that two structural elements (2-3) are provided to simulate the in the symptomatic X-ray tube voltage in dependence on the respectively set X-ray tube currents resulting heating currents that these components, a component (k) to determine the Difference between the two heating currents is connected downstream, that this component (^) is connected to a further component (6) for the purpose of dividing this difference value by a difference value formed in an associated component (5) from the two symptomatic X-ray tube voltages, that this component (5) a further component {7} for multiplying the division value with the factor formed by an assigned component (8) is connected downstream, and that this component (?) is connected to a further component {9) subtracting this value from the larger value of the two heating currents, that at its exit a dem The setpoint of the heating current supplies the corresponding signal. 909824/0341