FR2481045A1 - HT measuring appts. for radiographic X=ray tube - has two radiation detectors covered by filters of differing absorption coefficients and feeding divider circuit - Google Patents

Abstract

The device operates on an X-ray tube in a radiodiagnostic installation without the necessity of being connected in the H.T. circuit, and includes two radiation detectors (3,4) connected through respective current-voltage converters (7,8) to a common divider (9). The two detectors are covered by respective X-ray filters (5,6) of selected different absorption characteristics. The divider output is a measure of the X-ray tube H.T. and is applied through an analogue-digital converter (11) to a memory (12) and display (13). Regulation of the tube H.T. is also effected by coupling the divider output to a comparator (14) for comparison with a preset value (15), the comparator output controlling the tube radiology generator (2). Two filters used are conveniently copper of 0.7 and 1.5 mm thick. The function of divider output with tube H.T. is known and stored in the memory to enable comparison with the actual divider output.

Description

The invention relates to a device for measuring the high voltage of the tube at

  X-rays in a radiodiagnostic system. It is known to measure the high voltage of the X-ray tube by means of a measuring sensor, for example a voltage divider, placed in the high-voltage circuit.

  of the X-ray tube. A corresponding electrical signal

  the high voltage of the x-ray tube is taken from the sensor. A disadvantage is that the measuring sensor has to be built with

  components resistant to high voltage.

  The object of the invention is to create a device for measuring the high voltage of the X-ray tube and which makes it possible to precisely determine this high voltage without it being necessary to intervene in the high-voltage circuit. Therefore it must also be possible

  to measure the high voltage of the tube during

  that there is no real value generator in the high voltage circuit, as for example in the case of

monocuve generators.

  This problem is solved according to the invention

  using two radiation detectors which are

  green, on their input faces for radiation, by two X-ray filters having different absorptions, and by a divider for the two output signals of the radiation detectors. In the device

  according to the invention, the quotient of the two different signals

  The output of the radiation detectors is a

  sure of the high voltage of the x-ray tube, that is to say that it is associated according to a function known in advance to the

  high voltage of the X-ray tube. This is why a

  termination of this high voltage is possible by

  this function. In the same way, the ripple of the high voltage effectively applied to the X-ray tube and the preliminary filtering at the level of the tube have no influence on the result of the measurement, in the case of the choice

a suitable filter.

2 2481045

  The divider output signal can be sent

  to a device for displaying the high voltage of the tube with

  In this case the display device must be

  according to the values of the high voltage. It is also possible to use the divider output signal for regulating the high voltage of the tube to

  X-rays, by means of a comparison to a con-

  sign for the high voltage of the X-ray tube and the

  yen of an order, made on the basis of this comparison.

  its, a regulator of the high voltage of the tube to

  X-rays in order to give real value to the

their deposit.

  By way of example, we have described below and illustrated

  schematically in the accompanying drawings a form of embodiment

the object of the invention.

  Figure 1 shows a diagram of a device

according to the invention.

  Figure 2 shows curves allowing

  to explain the device of Figure 1.

  FIG. 1 shows an X-ray tube 1 which is powered by a radiological generator 2. For measuring the high voltage of the X-ray tube, two radiation detectors 3 and 4 are used, the faces of which input for radiation are covered by

  two X-ray filters 5 and 6, with absorp-

  different conditions. The output signals of the detectors of

  radiation 3 and 4 are sent via

  current-voltage conditioners 7 and 8 to a divider 9.

  output signal of the divider 9 present on the output 10 con-

  3U united X-ray lehi and is sent to an analog / digital converter 11 which are born to the

  high voltage measured from the X-ray tube to a memory 12.

  The high voltage of the X-ray tube can be displayed by

a display device 13.

  The device shown is also suitable for adjusting the high voltage of the X-ray tube. For this purpose, the signal corresponding to the high voltage of the X-ray tube and present at the output 10 of the divider 9 is sent to a comparator 14 at which is also sent a target value signal delivered by a setpoint generator 15. Depending on the difference

  between the actual value and the set value of the

  the voltage of the X-ray tube, the comparator 14 delivers to the radiological generator 2 information, so that the radiological generator 2 can give the value

  of the high voltage of the x-ray tube on the

their setpoint set.

  FIG. 2 shows for two filaments

  very copper with thicknesses of 0.7 mm and 1.5

  mm, the variation of the output signal of the divider 9, that is,

  ie the dose quotient, depending on the high voltage of the X-ray tube. Therefore at each high voltage

  of the X-ray tube is associated with a determined signal of

  The curve is stored in the memory 9. During the measurement, a comparison of

  the measured value with the stored calibration values

Sees.

  Filters 5 and 6 must be adapted

  approached at the given high voltage of the ray tube

  X, in order to obtain perfect measurement results. This-

  This is necessary so that the dose quotient delivered by the divider 9 depends only on the high voltage of the x-ray tube. However, since the high voltage of the x-ray tube is generally known, It is possible to choose the appropriate combination of filters. In Figure 2 the left curve is for a 6-pulse radiograph generator, while the

  right curve is valid for a radio generator

  12-pulse logic. The curves are also valid

  for high voltages of the x-ray tube

different ripples.

Claims (4)

  1) Device for measuring the high voltage of the X-ray tube in a radiodiagnostic installation, characterized by two radiation detectors (3, 4y, whose input faces for the radiation are coated   with two X-ray filters (5, 6)   different absorptions, and by a divider (9) for the two output signals of the radiation (3, 4).   2) Device according to claim 1, characterized   in that in series and downstream of the divider (9) is connected an apparatus (13) for displaying the high voltage of the X-ray tube.   3) Device according to one of claims I or   2, characterized in that the divider (9) is located in a control circuit (1 to 10, 14, 15) for the high   X-ray tube voltage, in which the output signal   The divider (9) forms the actual value signal of the high voltage of the X-ray tube.   4) Device according to any one of the claims   1 to 3, characterized in that the output signal   of the divider (9) is sent to a memory (12) in which calibration values for the high voltage of the X-ray tube, associated with the output signals, are stored.