Phosphor imaging plate and cassette handling system

X-ray or gamma ray systems or devices – Photographic detector support – Serial film or film pack changer

Reexamination Certificate

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Details

C378S174000, C250S588000

Reexamination Certificate

active

06773160

ABSTRACT:

TECHNICAL FIELD
The present invention relates both to imaging plate scanning systems and to imaging plate erasing systems. In general, the present invention relates to all forms of medical imaging plates, however, a particular preferred application of the present invention is related to storage phosphor imaging plates.
BACKGROUND OF THE INVENTION
Imaging plates, such as storage phosphor imaging plates, have become standard in the field of Computed Radiography (CR) as the medium onto which an image of a portion of the patient's body can be stored. The image on such a phosphor imaging plate is extracted by scanning the imaging plate with a scanner. Typically, a phosphor imaging plate is scanned by passing a scanning laser beam over the surface of the imaging plate while recording light emitted from the imaging plate in response to the laser beam. By recording the emission corresponding to each of the pixels of the imaging plate with a detector such as a photomultiplier, the image stored therein can be re-created (such that it can be displayed on a computer terminal).
The act of scanning an imaging plate by passing a scanning laser beam thereacross is inherently destructive (i.e.: it releases the energy stored in the phosphor screen). As such, a particular image stored on an imaging plate can only be scanned (i.e. read) once. Although such scanning of the imaging plate releases the image, thereby erasing the image, such erasure is not complete and the imaging plate may still contain ghost images, lines or other image artifacts caused or not yet fully erased by the scanning procedure itself. Accordingly, it is necessary to completely and evenly erase an imaging plate before it can be re-used to store another image thereon.
To preserve a high image quality, phosphor imaging plates are typically housed within imaging plate cassettes to protect them from light, dust, fingerprints, and other image quality reducing artifacts. Such cassettes offer protection for the imaging plates, thus ensuring a long life such that the imaging plate can be reused again and again.
To reuse an imaging plate, it must first be scanned, and then erased. Both scanning and erasing release images on the imaging plate by exposing the imaging plate to roughly the same visible wavelength of light. It is, therefore, important to ensure that the imaging plate is not inadvertently exposed to such erasing wavelengths of light prior to scanning. Accordingly, scanning and erasing of the imaging plates are typically carried out in different machines, or at widely spaced apart locations within the same machine. When separate scanning and erasing machines are used, the imaging plate is typically hand transported therebetween while stored in the imaging plate cassette. Specifically, the phosphor imaging plates are first scanned in a scanner, and then are hand carried and placed into a separate erasing machine which passes the plate under a suitable wavelength of light such that all images stored therein are released.
Therefore, it is desirable to provide a combined imaging plate scanning and erasing system such that it is not necessary to remove an imaging plate from a cassette, scan it with a scanner, remove it from the scanner, place it back into the cassette, hand carry the cassette to an erasing machine, insert the imaging plate into the erasing machine, erase the imaging plate and then return the imaging plate to the cassette for future use.
Another problem common to both scanning and erasing machines is the manner in which the imaging plates are removed from the cassette. Sometimes, this is simply done by hand (with the imaging plates then placed by hand into the scanner or eraser). In addition, a variety of bulky systems using vacuum, gravity, or friction extraction motorized devices have been used to remove an imaging plate from a cassette. One problem with such systems are that they often tend to handle the imaging plate rather roughly. This is especially true of gravity systems in which the cassette is opened such that the imaging plate simply falls into a machine.
Therefore, it is desirable to provide a system which gently and automatically removes an imaging plate from a cassette prior to scanning and gently and automatically returns the imaging plate to the cassette after the imaging plate has been erased.
Yet another problem common to existing imaging plate scanners and to existing imaging plate erasing machines is that they tend to be very large. This is especially true in the case of large combined scanning and erasing systems due to the fact that large numbers of imaging plate and imaging plate cassette designs are already in circulation. Accordingly, manufacturers tend to design scanning and erasing machinery which is adapted to deal with these pre-existing plate and cassette designs, rather than simultaneously design imaging plates, cassettes, scanners and erasing systems which would together operate to provide more spatially integrated and efficient systems. Existing cassette designs, in particular, are often poorly suited to automation, necessitating large, bulky scanning and erasing systems which are not designed to handle these imaging plates (and their associated cassettes) within small spaces.
Moreover, in many of these large existing systems, it is typically necessary to position the scanning mechanism some distance from the erasing mechanism simply to prevent light from the erasing mechanism from entering the scanning mechanism. Being so large, these existing systems must unfortunately move the imaging plate through a considerable distance therein. Such long pathways of travel (which require many separate devices to move and position the imaging plate at various locations therein) have many drawbacks. For example, complex positioning systems which move imaging plates considerable distances frequently introduce positioning errors which can cause imaging problems, or simply cause the imaging plate to jam while moving through the system. Extracting a jammed imaging plate from a location deep within a scanner or erasing system can be frustrating and time consuming.
Therefore, it is especially desirable to provide a compact combined imaging plate scanning and erasing system which is much smaller than existing systems, moving its imaging plate a shorter distance Advantages of such a system would include its portability, space saving size, reduced system complexity, and increased ease and speed of operation.
SUMMARY OF THE INVENTION
The present invention provides a small, compact combination system for both scanning and then erasing an imaging plate. Although the present invention is ideally suited for use with storage phosphor imaging plates (also known as imaging “screens”), it is not so limited.
The present system comprises a compact housing into which an imaging plate cassette is first inserted. An imaging plate infeed assembly within the housing is provided to pull the imaging plate cassette into the housing, open the imaging plate cassette (when it is positioned within the housing) and then remove the imaging plate from the imaging plate cassette for scanning followed by erasing.
In a preferred aspect, the present invention provides a combined imaging plate scanning and erasing system which comprises: (a) a housing; (b) an imaging plate infeed assembly positioned within the housing, the imaging plate cassette infeed assembly comprising: (i) a mechanism to pull an imaging plate cassette into the housing; (ii) a mechanism to open the imaging plate cassette; and (iii) a mechanism to remove an imaging plate from the cassette; (c) a scanner positioned within the housing; (d) a curved path erasing assembly positioned between the imaging plate infeed assembly and the scanner; and (e) an imaging plate transportation assembly to move the imaging plate back and forth in a path extending from the imaging plate cassette, past the erasing assembly and through a scan area adjacent to the scanner.
In preferred aspects, the entire body of the imaging plate cassette is pulled fully within the housing of the

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