Cassette for storage phosphor plate and apparatus for removing storage phosphor plate from cassette

A cassette (1) for a storage phosphor plate (2) comprises a cassette housing (4) with an opening (7) and a support (3) disposed movably within the cassette housing (4), wherein the storage phosphor plate (2) lies on the support (3). In order to simplify the structure of the cassette (1) and of the corresponding removal mechanism, provision is made such that the support (3) can be moved, together with the storage phosphor plate (2) lying on top of it, through the opening (7) of the cassette housing (4), at least partially from the inside of the cassette housing (4), and the storage phosphor plate (2) lying on the support (3) can be taken from the support (3) when the support (3) is located, with the storage phosphor plate (2) lying on top of it, at least partially outside of the cassette housing (4).

RELATED APPLICATIONS

This application claims priority to European Application No. EP05111252.2, filed on Nov. 24, 2005, which is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

One way of recording X-ray pictures is to store the image generated by X-ray radiation passing through an object, for example a patient, as a latent picture in a so-called storage phosphor layer. In order to read out the latent picture, the storage phosphor layer is irradiated with stimulation light, and so stimulated into emitting emission light. The emission light, the intensity of which corresponds to the picture stored in the storage phosphor layer, is collected by an optical detector and converted into electric signals. The electric signals are further processed as required, and finally made available for analysis, in particular for medical/diagnostic purposes in that they are displayed on a corresponding display unit, such as e.g. a monitor or a printer.

Patent application U.S. 2004/0251596 A1 discloses a cassette with a movable support within the cassette on which a flexible storage phosphor plate is located. As one starts to remove the storage phosphor plate from the cassette, the cassette is opened by opening a closure flap, and the support within the cassette is moved forward in the direction of the cassette opening until finally, it strikes a guide element disposed in the region of the cassette opening on the cassette floor, by means of which it is pressed downwards, and is in this way released from the storage phosphor plate. The storage phosphor plate is then withdrawn from inside the cassette with a mechanism, not described in greater detail, and introduced into a read-out device. During the conveyance within the cassette, the support is guided along the inner edge of the cassette by slide- or roller-bearings.

SUMMARY OF THE INVENTION

The mechanism of the cassette described above required to remove the storage phosphor plate is relatively complex. Moreover, when the closure flap is open, the storage phosphor plate can fall out of the cassette if the cassette is orientated aslant or vertically.

It is the object of this invention to provide a cassette with a simpler structure for a storage phosphor plate and a corresponding apparatus for removing the storage phosphor plate from the cassette, where in particular the storage phosphor plate is prevented in a simple way from falling out unintentionally when the closure flap is open.

This object is fulfilled using a support, together with the storage phosphor plate lying on top of it. The support can be at least partially moved out from the inside of the cassette housing by opening the cassette housing, and the storage phosphor plate lying on the support can be taken from the support when the support, with the storage phosphor plate lying on top of it, is located at least partially outside of the cassette housing.

Due to the fact that the support, together with the storage phosphor plate, is at least partially drawn out of the cassette, the complex mechanism used in the past, with which the support is only movable within the cassette, can be substantially simplified. Moreover, the storage phosphor plate which is located partially outside of the cassette can be taken from the support in a simpler way, e.g. by means of powered carrier rollers or similar, and conveyed to a read-out device.

In a preferred embodiment of the cassette according to the invention, provision is made such that the support has at least one fixing element which fixes the storage phosphor plate in place on the support when the support is located, with the storage phosphor plate lying on top of it, within the cassette housing. At the same time, the fixing element releases the storage phosphor plate when the support is located, with the storage phosphor plate lying on top of it, at least partially outside of the cassette housing so that the storage phosphor plate can be taken from the support. This embodiment of the invention is based upon the idea of achieving fixing of the storage phosphor plate in the cassette not by means of a closure flap provided on the cassette opening, but by means of a movable fixing element located on the support. In this way it is guaranteed that the storage phosphor plate located in the cassette can not fall out of the cassette when the closure flap is open with aslant or vertical positioning of the cassette.

In a preferred further development of this embodiment, provision is made such that the fixing element is counter-sunk into the support when the support, with the storage phosphor plate lying on top of it, is located at least partially outside of the cassette housing so that the storage phosphor plate is released. By counter-sinking the fixing element into the support, it is possible for the released storage phosphor plate to be taken from the support easily, in particular without having to lift the plate, and in particular be drawn away in a direction parallel to the plane of the support.

Preferably, the fixing element comprises a leaf spring which is disposed in the plane of the support and has a projection which can protrude over the plane of the support. In particular, the projection extends substantially perpendicularly to the plane of the support. In this way the fixing element according to the invention can be realised in a particularly simple and reliable way.

Moreover, it is preferred that the leaf spring is formed from a part-region of the support. In this way the support and the fixing element can be produced in a single production step and/or as one part, and therefore particularly cost-effectively.

Preferably, the leaf spring is pre-stressed against the support such that the projection protrudes out of the plane of the support, and thus fixes the storage phosphor plate in place on the support when the support is located within the cassette housing, and the projection is counter-sunk into the support when the support, with the storage phosphor plate lying on top of it, is located at least partially outside of the cassette housing. By means of the described pre-tensioning of the leaf spring, the fixing and release of the storage phosphor plate on the support are made possible in a particularly simple way.

In one embodiment of this variation, a pressing element is provided by means of which the pre-tensioned leaf spring is pressed into the support such that the projection protrudes from the plane of the support when the support is located within the cassette housing. For this, the pressing element is preferably located on the bottom of the cassette housing, beneath the support, or is formed by the bottom of the cassette housing itself.

Moreover, it is preferred that the support has at least one recess by means of which a conveyance device can engage with the storage phosphor plate lying on the support, and thus take the storage phosphor plate from the support, and in particular draw it away in a direction parallel to the plane of the support. The storage phosphor plate can thus be taken from the support in a simple way.

Preferably, the conveyance device comprises at least one mating roll with a first and a second roller, the first roller pressing onto the storage phosphor plate from below by means of the recess, and the second roller pressing onto the storage phosphor plate from above. The first and/or second roller is mechanically powered.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1a) to1e) show a cassette1according to the invention in different phases during the removal of a storage phosphor plate2. The cassette1comprises a cassette housing4with an opening which is sealed from light by means of a pivotable closure flap5. Within the cassette housing4, there is a level support3on which the storage phosphor plate2lies.

The storage phosphor plate2usually substantially consists of a storage phosphor layer10which is applied to a substrate11. The storage phosphor layer10is made up, for example, of powdery storage phosphor particles which are applied to the substrate11by means of a suitable binder. Alternatively, the storage phosphor layer10can comprise a plurality of needle-shaped phosphor structures which are preferably produced by vaporisation on the substrate11. The corresponding storage phosphor plates are therefore also called Powder Image Plates (PIP) or Needle Image Plates (NIP).

The substrate11is preferably a thin, flexible foil made of a material through which X-rays can pass, such as e.g. synthetic. The storage phosphor plate2lies with its substrate11loose on the support3, and is substantially held on the support3by friction forces and/or form-fit, e.g. by means of one or more peripheral elements6and/or fixing elements.

FIG. 1b) shows a first phase of the removal process in which the front-side opening7of the cassette1is released by raising a pivotable closure flap5. A removal device16engages with the edge of the support3and conveys the latter, as shown inFIG. 1c), together with the storage phosphor plate2lying on top of it, out of the cassette1in direction E to the region of a conveyance device which, in the example shown, has a first and second carrier roller11and12.

In the phase of the removal process shown inFIG. 1d), the carrier rollers11and12lie on both sides of the storage phosphor layer2, and can draw these away from the support3in direction R, as shown inFIG. 1e).

FIG. 2shows a section of a cross-section through the cassette1according to the invention when the support3is located, together with the storage phosphor plate2, fully within the cassette1. In the preferred embodiment of the invention shown here, there is a leaf spring8located in the plane of the support3which has a projection9protruding from the plane of the support3. The projection9prevents the storage phosphor plate2from being able to fall out of the cassette1through the opening7in the cassette housing4when the closure flap is open (not shown here) when the cassette is in a vertical or slanted position.

FIG. 3shows a section of a cross-section through the cassette when a part of the support3, together with the storage phosphor plate2lying on top of it, is located outside of the cassette1. In this state, the leaf spring8leaves the plane of the support3in a downwards direction. The projection located on the leaf spring8is in this way also sunk downwards and moved out of the plane of the support3. The storage phosphor plate2is thus released, and can be drawn away from the support3in direction R.

As can be seen fromFIGS. 2 and 3, the leaf spring8is pre-tensioned such that the projection9is moved downwards, out of the plane of the support3, when the latter is located at least partially outside of the cassette1, and moved back into the plane of the support3when the support3is located within the cassette1. The leaf spring8is pressed here by the bottom14of the cassette itself, or by a pressing element (not shown) disposed on the bottom14of the cassette in the direction of the plane of the support3.

FIG. 4shows a top view of an example of the support3. The storage phosphor plate2lying on the support3is indicated by a dashed line. The support3has two leaf springs8, the projections9of which fix the storage phosphor plate2in place on the support3when the latter is located within the cassette (as described by means ofFIGS. 2 and 3). In this way, the storage phosphor plate2is prevented from falling out of the open cassette in a simple and reliable way.

The support3is preferably produced from a material, in particular a synthetic, through which X-rays can pass. The leaf springs8in particular are made of the same material as the support3, and can be produced together with the support3in one production step, e.g. using the injection moulding method. Alternatively however, the leaf springs8can be obtained after production of the support3by sawing them out of the support3. In the latter case, the aforementioned pre-tensioning of the leaf springs8can be implemented by heating and corresponding forming of the leaf springs8.

If the support3is located, together with the storage phosphor plate2lying on top of it, outside of the cassette (seeFIG. 3), the leaf springs8together with the projections9located on top of them are sunk perpendicularly to the plane of the drawing, and release the storage phosphor plate2so that the latter can be drawn away from the support3in the direction R and be conveyed to a read-out device.

In the example shown, the storage phosphor plate2is drawn away from the support3by powered carrier rollers11and12(seeFIG. 1e). For this, the support3has recesses13through which the respective first carrier roller11located beneath the support3can engage with the storage phosphor plate2. Opposite the first carrier roller11, the second carrier roller12presses from above onto the storage phosphor plate2. At least one of the two carrier rollers11and12is powered and enables the storage phosphor plate to be conveyed away from the support3in direction R.

FIG. 5shows a detailed illustration of a cross-section of the cassette1according to the invention1with an open closure flap5, shown as a side view. The support3is located, together with the storage phosphor plate2lying on top of it, partially outside of the open cassette1, the projection9being moved out of the plane of the support by the leaf springs8and releasing the storage phosphor plate2which is drawn away from the support3in direction R by the first and second carrier rollers11and12. The first carrier roller11passes through the support3via one of the recesses13(FIG. 4) and presses on the lower side of the storage phosphor plate2.