FI76234B - FOERFARANDE FOER FOTOGRAFERING AV ETT OBJEKT MED EN PANORAMAROENTGENFILMANORDNING FOERSEDD MED EXPONERINGSAUTOMATIK. TRANSFERRED PAEIVAEMAEAERAE - FOERSKJUTET DATUM PL 14 ç 11.02.86 - Google Patents

Description

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A method of capturing an object with a panoramic X-ray imaging device equipped with an exposure machine. - Förfarande för fotografering av ett objekt med en panoramaröntgenfilmanord-Ning försedd med exponeringsautomatik.

The invention relates to a method for imaging a desired object with a panoramic X-ray imaging device equipped with an exposure machine, which includes an X-ray generator, an X-ray tube and a film with a holder.

When using X-ray imaging devices, the problem is to select the correct voltage and current values for the devices for the X-ray tube so that the patient receives a successful dental X-ray. In general, a user who is new to the device will be able to evaluate and select the correct shooting values.

The general object of the invention is to provide an imaging method in which the user of the device does not have to know how to select the correct imaging values (kV, mA) with which a successful dental X-ray is obtained from the patient.

It is known from DE-A-2 650 872 to place a radiation detector of an exposure machine between the subject and the film so that the detection of the radiation dose takes place throughout the imaging. To prevent the detector from appearing in the image, a specially designed expensive detector, such as an ionization chamber detector, must be used.

A particular object of the invention is to further develop the imaging method so that a cheap radiation shading detector can be placed between the subject and the film for automatic exposure control.

This object is achieved according to the invention in that the detection of the beam passing through the object is performed before the actual imaging starts and after the detection the beam is used for imaging, which is oriented so that it passes the detector.

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In the following, the invention will be illustrated with reference to the accompanying drawings, which show some embodiments of the device used to carry out the method according to the invention.

Figure 1 shows a block diagram of a first embodiment of a device used to perform the method according to the invention.

Figure 2 shows a block diagram of a second embodiment of a device used to perform the method according to the invention.

Figure 3 shows a detail of a third embodiment of the devices used to perform the method according to the invention.

Since panoramic X-ray imaging methods and apparatus are generally known and used per se, they will not be described in more detail in this context. As conventional parts of the apparatus comprises an X-ray generator 4, 5, and the X-ray tube 5, 6 jkoka to send the object to the X-ray film for 7 8 through 7. In the film include conventional reinforcing sheets and the film holder associated with means for moving the film in the direction of the arrow Ά. The film 7 with its holder is fixed to an arm structure (not shown) common to the X-ray tube 5, by turning which the film and the X-ray tube can be rotated around the imaging object 8 in the direction of the arrows B.

A radiation measuring detector 1 is arranged in the path of the X-ray beam 6 which has passed through the object to be imaged only before the actual imaging begins. In the case of Figure 1, the detector 1 is connected to a mechanical detector transfer device 2. The detector 1 is connected to a reference and control unit 3, which in turn is connected to control the transfer device 2 and the X-ray generator 4.

3 76234 The voltage and current supplied by the X-ray generator 4, 5 by the X-ray tube 5 are separately adjustable. At the beginning of the description, a certain value pair of voltage and current is set in the device, which are, for example, 60 kV and 10 mA. At the beginning of the imaging, the X-ray device performs a measurement on the patient with X-rays whose transmittance and intensity are based on said preset pair of kV and mA values. The detector 1 in the path of the radiation beam provides information on how much radiation passed through the patient. This measurement value is compared in the comparison and adjustment unit 3 with a value at which the film darkens correctly. The value at which the film darkens properly has been determined empirically. This value is referred to herein as the reference value. The reference value is also affected by the film / reinforcement plate combination used, for which a reference value preset (density) is required.

If the value measured by the detector 1 is less than the reference value, the voltage on the X-ray tube 5 is increased as determined by the difference between these values. If the measured value is greater than the reference value, the amount of radiation is reduced by reducing the current (mA) through the X-ray tube as determined by the difference between the measured value and the reference value.

When the measurement and adjustment is completed, the transfer device 2 pulls the detector 1 out of the X-ray beam 6, whereby the rays can expose the film and the actual imaging begins. This measurement and adjustment step takes about 200 ms. The value pair used in the description remains visible on the X-ray generator 4, 5.

The embodiment of Fig. 2 differs from Fig. 1 in that the radiation measuring detector 1 is fixedly in place and the beam beam limiting blind 10 is moved in a direction perpendicular to the beam. The transfer device of the blind 10 is marked with the reference number 11 and can be implemented e.g. with an electromagnet. Before starting the shooting, the transfer device 11 moves the cropping blind 10 to a position where the beam beam delimited by it hits the detector 1. When the time required for the exposure machine has elapsed, e.g. 150 ms, the transfer device 11 76234 4 moves the

Also in the embodiment of Fig. 3, the radiation measuring detector is fixedly in place. The beam delimiting blind 12 has two beam slots 13, 14. The main beam 6 passing through the beam 13 hits the film and the auxiliary beam 9 passing through the beam 14 does not affect the image. The auxiliary beam 9 passes through the patient to the detector for the time required for the measurement, e.g. about 150 ms at the beginning of the imaging. The auxiliary beam 9 is then removed by turning the lead seal 15 in front of the beam 9. The turning device 16 operates, for example, with an electromagnet.

Claims (7)

A method of capturing a desired object with a panoramic X-ray imaging apparatus provided with an exposure automaton, consisting of an X-ray generator (4,5), an X-ray tube (5) and a film (7) as well as a holder, characterized in that detecting the beam cone (9) passing through the object is performed prior to actual taking, and after detecting, a beam cone (6) is used which is so directed that it passes past the detector (1). Method according to claim 1, characterized in that the detecting beam cone (9) is separated from the main cone (6) by a displaceable self-limiting screen (10), in whose first position the cone (9) is directed towards the stationary detector (1) and second The position of the detector (1) passing the cone (9) is directed towards the film (7). Method according to claim 1, characterized in that a main cone (6) and an auxiliary cone (9) are separated by the beam cone's defining shield (.12), which has two beam slots (13,14), the stationary detector (9). 1) arranged in the passage of the auxiliary cone (9). Method according to claim 3, characterized in that the auxiliary slit (14) of the auxiliary cone (9) is closed during taking. Method according to claim 1, characterized in that the detector (1) located between the film (7) and the object to be imaged is displaced side from the passage of the main beam cone (6). Method according to claim 5, characterized in that the detector (2) of the detector (1) controlled by a comparison and control unit (3) automatically displaces the detector (.1) from the path of the beam cone (6) as soon as a comparison is made. -