CS200045B1 - Equipment for x-ray tube protection - Google Patents

Description

The invention relates to a device for protecting an X-ray tube from overload, in particular in medical and industrial X-rays.

The Klaeic X-ray machine, operating without the exposure automat, is equipped with X-ray overload protection circuits, the main part of which is a comparator that compares the X-ray load resulting from preset operating values: voltage, current, time or power with maximum allowable X-ray load. Should the realization of the presented operating values of the image lead to an overload of the X-ray tube, two solutions for its prevention are known.

In one solution, the image is blocked and the operator has to change the operating values, ie usually to increase time or reduce currents.

In the second solution, the operating values of the image are automatically adjusted to remove the overload. In doing so, care is taken not to set values that the X-ray machine is unable to realize.

These solutions have some disadvantages: The operator is forced to choose the focus itself. If this is facilitated by permanently selecting a large focus, then images that could be taken at a small focus will have greater geometric blur than can be achieved. The parameters of the optimum image, ie the shortest, must be set by the operator by trial. If this is not done, the image quality is not optimal.

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The non-stop device removes an X-ray protection device consisting of an X-ray load comparator connected both to the image operating selectors and to the permissible X-ray load evaluator according to the invention, wherein the X-ray load comparator is connected to the X-ray focus selector.

An image criterion selector circuit connected to an image selector circuit is connected to the comparator.

The invention solves the first disadvantage in that, after selecting the operating values, it first starts from a small focal point deposit. Should this be overloaded with the set image parameters, it will automatically select a large focus, while switching the nomogram of the X-ray tube to a large focus in the allowable load evaluator. The second disadvantage is that the comparator outputs another output that characterizes the degree of disagreement between the load corresponding to the preset operating values and the maximum allowable X-ray load.

The presented image values are then automatically modified so that this disagreement is nullified, that is, in case of overload, the maximum power is reached, but that the same value is achieved even when the X-ray tube is not used.

Since the requirements for the optimum image may vary and depending on the type of examination it depends on the sharpness of the geometric, sometimes the movement and sometimes the maximum contrast, and the optimal setting of image operating values for these different requirements is different. Criteria can be set as would be used by an experienced observer to achieve optimum operating values. The criteria may include a change in one or more operating values, as well as a way of proceeding if the value reaches an extreme value without canceling the disagreement. Here you can also program whether the cell should be switched to a large focus or Whether the operating parameters should be changed at a small focus or a large focus should be on.

An exemplary embodiment of the invention is shown in the accompanying drawings, in which Fig. 1 is a block diagram of the device and Fig. 2 shows schematically the wiring of the individual elements of the device.

In the block diagram (FIG. 1), the device consists of an image operating value selector 1, an X-ray load evaluator 2, which is connected to a comparator 3, the output of which is connected to the X-ray focus selector 4 and the image operating criteria criterion 5. The focus selector 4 is connected to the input of the permissible load evaluator 2. The scaling criterion 5 selector is connected to the image operating selector 1 input.

In this block arrangement, the device operates such that once the image values presented exceed the permissible load values of a small X-ray focus, a signal is generated in the comparator causing the X-ray focus selector 4 to switch to a large focus. At the same time, Comparator 3 indicates the disagreement of both its inputs including the sign, that is, which of the two is larger. From this a signal is drawn for the criterion selector 5 which, based on the operator's choice, usually adjusts the preset operating values of the diary for the entire group of examinations to achieve the full optimal X-ray load.

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The criterion for utilizing the X-ray focus load level signal in the selector 5 may be, for example, minimal motion blur, ie, minimum frame time, for selected voltages and X-ray current.

In doing so, the criterion selector 5 causes the exposure time to be reduced and the X-ray current to increase to its full capacity. Another criterion may be the maximum contrast at a given frame time. In doing so, the criterion selector 5, except for the full load of the X-ray tube, will reduce its voltage and accordingly increase the current to achieve the prescribed blackening of the image.

Another criterion may be geometric sharpness at the maximum permissible image distance.

In this case, the selector 5 adjusts the parameters first at the small focus of the X-ray tube and only when the prescribed maximum frame time cannot be maintained does it switch to the large focus.

An exemplary embodiment of the comparator 3j of the permissible load evaluator 2 and of the selectors 2 ', 3', 3 'is shown schematically in FIG. 2.

The variable resistor 11 is coupled to the X-ray voltage selector, the variable resistor 12 is coupled to the current selector, the variable resistor 13 is the permissible maximum focal point load and is coupled to the image exposure time selector, and similarly affiliated with the time selector. Together with the auxiliary resistors 15 and 16, a bridge is formed where the X-ray load generated by the image is compared with the maximum allowable value given by the focal type size. The amplifier 17 serves to amplify the deviation and from its output the load of the focus is evaluated and indicated by the measuring instrument 18,

By default, relays 19 and 21 are omitted. A small focal point is connected to the contact 21 of the relay 21 and a contact 212 of the relay 21 then a corresponding resistor 13. This condition remains unchanged if the set value of the image does not exceed the permissible values of the small focal point.

If the set values for the small focal point are not allowed, the amplifier 17 causes the relay 19 to close, which (by the contact shown here) blocks the image, and closes relay 21 by contact 19 Rel. With its own contact 213, it retains - regardless of the status of relay 19. If the set operating values of the image do not overload the large focus, relay 19 is dropped and the image blocking is canceled.

If, however, the X-ray tube is still overloaded, relay 19 remains energized and the image is blocked until the image parameters are adjusted either by the operator (e.g., by extending the image time) or automatically using the criteria selector 5.

Any change to the image parameters causes contact 20 to drop relay 21 so that the selection cycle is repeated for the new parameters.

Full X-ray load can be reached by the operator according to meter 18, according to which X-ray overload can also be checked.

The image operational criterion 5 may be (not shown) any suitable relay, electronic, and the like circuit whose outputs are connected to make adjustments to the X-ray and image exposure parameters.

Claims (2)

SUBJECT OF THE INVENTION An X-ray protection device, comprising an X-ray load comparator connected to an X-ray selector and evaluating the permissible X-ray loads, characterized in that the X-ray load comparator (3) is connected to the X-ray focus selector (4). X-ray protection device according to claim 1, characterized in that an image criterion selector circuit (5) connected to the image selector (1) circuit is connected to the comparator (3).