The present invention relates to an image plate for intra-oral dental X-ray photography, the plate being placed in a shield i which the plate is kept during photography and out of which th plate can be taken for the reading out of the image after photography.

Film which is in a foil package during photography has conven¬ tionally been used in intra-oral dental X-ray photography. X- ray film is photosensitive, for which reason the opening of th package after photography and the transfer of the film to de¬ velopment have taken place in a darkroom.

There is also known a cassette for intra-oral dental X-ray photography, which contains an image plate sensitive to X-rays The functioning of the selenium-containing image plate is base on the adherence of pigment to the plate surface. The disad¬ vantage of the system is that holding the thick and rigid cas¬ sette in the mouth is cumbersome.

The object of the present invention is to provide an image plate particularly suited for intra-oral dental photography, avoiding the above-mentioned disadvantages of prior-art sys¬ tems. The invention, in which the image plate is placed in a shield in a manner known per se, is characterized in that the shield has been made pervious to X-rays but impervious to visible light, and that the shield comprises a closed shieldin bag of plastic membrane.

The image plate according to the invention, with its bag-like plastic shield, can be made substantially thinner than the prior-known cassette which contains an image plate, and conse¬ quently its use is more comfortable for the patient. As com-

pared with intra-oral film, the advantage of the invention is that the image plate is less sensitive to external light than is film. The bag-like shield impervious to light thus consti¬ tutes a sufficient shield for the image plate between photog¬ raphy and the reading out of the plate, and the darkroom re¬ quired by films is not needed for the handling of the plate.

According to one preferred embodiment of the invention, the shield is made up of an inner bag impervious to light and a closed outer bag of plastic membrane, enveloping the inner bag. The outer bag may be of a transparent plastic material, and its sealing and opening should be maximally easy. The purpose of the outer bag is to prevent the patient's saliva from ending up in the read-out apparatus along with the inner bag and to pro¬ tect the patient from any pathogens which may have ended up on the surface of the image plate. The inner bag impervious to light may be of black plastic membrane, or alternatively of black cardboard, and it may be left open at one end.

The said inner bag impervious to light is preferably at one end open and at the other end equipped with JΞ pulling lug by which the bag can be pulled from around the image plate.„ The image plate end at the open end of the bag may further be equipped with a metal part which can be held by a magnet belonging to the pulling device used in the reading out of the image. The image plate can in this case be introduced with its bag into the read-out apparatus without the plate being exposed to out¬ side light at any stage before the apparatus. The pulling off of the bag will not take place until the pulling device has gripped the end of the plate which is protected from light in the read-out apparatus.

It is also possible that the shield comprises only one bag, which is made of a plastic membrane impervious to light and is closed during photography. After photography the bag is opened at one end, whereafter the image plate can be taken out, for

example by means of a magnet adhering to the metal part at the end of the plate in accordance with what has been stated above

When each end of the image plate is equipped with a metal part there is the further advantage that the plate can be placed in either direction in the bag open at one end. When the pulling out of the plate from the read-out apparatus and its re¬ insertion into the bag are carried out manually, these opera¬ tions can, owing to the invention, be carried out with one movement, without loosening the hold on the plate in between.

The invention also relates to a method by which the image plate, after photography, is taken out of the shield for the reading out of the image. The essential idea of the invention is that the shield, which is pervious to X-rays but impervious to visible light and comprises a closed shielding bag made of plastic membrane, is opened, that the image plate is intro¬ duced, in a bag which constitutes part of the shield, is imper vious to light and is open at one end, into a space shielded from light in the read-out apparatus, where a gripping member will grip that end of the image plate which is at the open end of the bag, and that the bag is thereafter pulled by its op¬ posite end so that it comes off from around the image plate.

When the bag end opposite to the said open end is equipped wit a pulling lug, the image plate with its bag can be introduced into the read-out apparatus so that the said pulling lug will at least in part be left outside the feed-in aperture of the apparatus, whereupon the bag will be easy to pull out of the read-out apparatus through the aperture.

The invention is described below in greater detail with the help of the example, with reference to the accompanying draw¬ ing, in which

Figure 1 depicts the inserting of the image plate into an inne shielding bag of plastic membrane,

Figure 2 depicts the image plate in the inner shielding bag, Figure 3 depicts the inner shielding bag enclosed in an outer shielding bag of plastic membrane,

Figure 4 depicts the removing of the outer shielding bag ac¬ cording Figure 3 from around the inner shielding bag, Figure 5 depicts the inner shielding bag and the image plate inside it, introduced into the read-out apparatus, and Figure 6 depicts the pulling off of the inner shielding bag from around the image plate adhering to a pulling device be¬ longing to the read-out apparatus.

Figure 1 shows an image plate 1 for intra-oral dental X-ray photography according to the RIM technique, the plate being made up of a substantially rigid layered plastic plate approx. 1 mm thick, with stimulable phosphor on its surface. Each end of the image plate 1 is equipped with a steel part 2.

In Figure 1 the image plate 1 is being pushed into the inner shielding bag 3, in which the plate will be during photography. The said bag 3 is made up of two opposite membranes of a plas¬ tic material which is pervious to X-rays-but impervious to visible light, the membranes being sealed to each ^" other along sealing lines 4, 5. One end 6 of the bag 3 has been left open, and a pulling lug 7 has been formed at the opposite end of the bag. The membrane material of the bag 3 may be colored black, or alternatively the membranes have been made non-transparent by means of a thin metal foil.

In Figure 2 the image plate 1 is located inside the inner shielding bag 3, so that the steel part 2 at the end of the plate is substantially at the open end 6 of the bag. The pulling lug 7 has been folded against the rest of the bag and the image plate 1 inside the bag along the sealing line 5 running across the bag 3.

In Figure 3 the inner shielding bag 3 according to Figure 2,

together with the image plate and the folded pulling lug 7, i closed along its edges in an outer shielding bag 8 made of heat-sealed plastic membrane. The outer bag 8, of which there is mainly required only the capability of being heat-sealed a opened, may be of any transparent or non-transparent plastic material, preferably, for example, polyamide. The outer bag 8 serves as a shield for the inner shielding bag 3 during photo raphy and, furthermore, it can be washed before being intro¬ duced into the mouth of a patient.

When photography has been carried out, the outer bag 8 is fir removed from around the inner bag 3 and the image plate insid it by tearing in accordance with Figure 4. The patient*s sali is removed along with the bag 8 and is thus prevented from ending up in the read-out apparatus.

Next, the pulling lug 7 of the inner shielding bag 3 is straightened so as to be parallel with the rest of the bag, o the bag with the image plate inside it is introduced into the read-out apparatus 9 for image read-out by means of a laser beam in a manner known per se. Figure 5-shows a bag 3 with th image plate, pushed through the feed-in aperture 10 into a space protected from light in the read-out apparatus, the ste part at the end of the plate in the bag adhering to the magne 12 in the pulling device 11 provided in the space. The pullin lug 7 of the bag 3 remains, in accordance with Figure 5, out¬ side the feed-in aperture 10 of the read-out apparatus, in which case it can be pulled, in accordance with Figure 6, through the aperture from around the image plate 1, while the image plate remains in the read-out apparatus.

The reading out of the image on the image plate 1 is carried out in the read-out apparatus 9 by means of a scanner and a reciprocating pulling device 11, in a manner known per se. Th read-out apparatus may also erase information from the plate that the plate is thereafter ready for a subsequent round of

use. For removing the plate from the read-out apparatus, the pulling device 11 pushes the free end of the image plate 1 out through the feed-in aperture 10. Thereafter the said end of the plate may be gripped by hand, and the plate can be pulled off the magnets 12 of the pulling device 11 and be inserted, with the end detached from the magnets first, into a shielding bag 3.

For an expert in the art it is clear that the various embodi¬ ments of the invention are not limited to the above example but may vary within the accompanying patent claims. For example, it is possible to replace the steel parts 2 at the ends of the image plate by mechanical gripping parts provided in the pulling device 11, such as an opening and closing pair of jaws by which the end of the image plate is gripped.

It is also possible to use, instead of two separate shielding bags 3, 8, one shielding bag of non-transparent plastic mem¬ brane, which bag is closed tightly before being introduced, with the image plate inside it, into- a patient's mouth and, after photography, is opened at one end -before being introduced into the read-out apparatus. ^' -