GB2477346A - Scintillator assembly for use in digital x-ray imaging - Google Patents

Abstract

A scintillator assembly for use in digital x-ray imaging, comprising an underlying substrate coated with a layer of x-ray scintillator material, and a sheet of x-ray transparent material bonded over the scintillator layer and extending beyond the edge of the underlying substrate. The substrate is a fibre optic plate (FOP) and the scintillator material is CSI.

Description

Scintillator Assembly for use in Digital X-ray Imaging The present invention relates to digital x-ray imaging and, in particular, a scintillator assembly for use in digital x-ray imaging.

It is known to use a high contrast imaging transducer, constructed using a rare earth based x-ray scintillator coating applied directly onto an underlying substrate prior to bonding it to a CCD or CMOS device, to obtain digital x-ray images. For example, a Caesium Iodide (Csl) based scintillator layer can be deposited onto a fibre optic plate (FOP) using evaporation coating technologies.

The scintillator layer converts x-ray signals to optical images, which are transferred along the fibre to the CCD or CMOS device.

The use of fibre optic plates that have been directly coated with an x-ray scintiltator layer has a number of benefits over the traditional methods of bonding an x-ray screen to a substrate, such as providing higher resolution, higher contrast and light efficiency due to elimination of light losses and optical *..S distortions and allowing for variable coating thickness for custom solutions.

A problem with these fibre optic plates that has been identified, however, is that de-lamination of the scintillator assembly can occur, which is undesirable.

According to the present invention there is provided a scintillator assembly for use in digital x-ray imaging, comprising an underlying substrate coated with a layer of x-ray scintillator material, and a sheet of x-ray transparent material bonded over the scintillator layer and extending beyond the edge of the underlying substrate.

As a result of the determination that a scintillator assembly is most prone to de-lamination when a fibre optic plate is subjected to light pressure or shock applied in a direction parallel to the face, or edge, of the scintillator, the present invention provides a scintillator assembly that is considerably more robust than existing designs.

An example of the present invention will now be described with reference to the accompanying figures, in which: Figure 1 shows the forces that have been identified to cause a scintillator layer to become delaminated from an underlying substrate; Figure 2 shows how the edges of the substrate are exposed to potentially de-laminating forces; and Figures 3A and 3B show two methods of providing a scintillator assembly according to the present invention.

As illustrated in Figure 3, a sheet of x-ray transparent material, for example PC, PMMA, PS, fibreboard, PET or similar, is bonded over the entire surface of the scintillator layer and extends beyond the extent of the underlying substrate, of the component, which in this examp'e is a fibre optic plate (FOP).

The material should be stiff and tough. The sheet of x-ray transparent material acting as a shield and should, preferably, extend beyond the limits of the scintillator coating. Similarly, the thickness of the shield should be sufficient to prevent shield deformation in the event that the component is dropped.

The resulting composite structure, comprising fibre optic plate, scintillator layer and shield, is capable of extremely rough handling, sharp impacts, shocks and being dropped. Furthermore, the fibre optic plate tends to break before de-* ..S lamination occurs. De-lamination can, however, be effected by positively accessing the edge of the scintillator at the junction of the shield but this is difficult under normal handling conditions.

. .: The shield works equally well with pressure sensitive adhesive (PSA) (or other suitable adhesive) either extending over the entire surface, or being recessed such that the outer edge of scintillator is not in contact with any other * material. These two arrangements are shown in Figure 3A and 3B, respectively.

* The first method, shown in Figure 3A, has an advantage that the surface of the scintillator is optically homogeneous. The second method, shown in Figure 3B, has an advantage that the sensitive border of the scintillator does not contact any other material.

The present invention has been tested on a scintillator coated onto a fibre optic plate that has already been covered with a layer of Parylene, a layer of paint and a second layer of Parylene. The method should work equally well if applied to the first layer of Parylene, which would eliminate the need for the layer of paint or second Parylene stage of the manufacturing process. Furthermore, it is conceivable that the method would work if the shield was applied directly to the scintillator, although this would not necessarily prevent water diffusion.

Claims (3)

1. CLAIMS1. A scintillator assembly for use in digital x-ray imaging, comprising an underlying substrate coated with a layer of x-ray scintillator material, and a sheet of x-ray transparent material bonded over the scintillator layer and extending beyond the edge of the underlying substrate.
2. 2. The structure of claim 1, wherein the substrate is a fibre optic plate (FOP).
3. 3. The structure of claim I or 2, wherein the scintillator layer is caesium iodide. * * * ****. * * * I S * So *ISS **S * * * * * S. *5* *