Patent Application
20080035859
A more complete appreciation of the present disclosure and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:
In describing the preferred embodiments of the present disclosure illustrated in the drawings, specific terminology is employed for sake of clarity. However, the present disclosure is not intended to be limited to the specific terminology so selected, and it is to be understood that each specific element includes all technical equivalents which operate in a similar manner.
Embodiments of the present invention include an improved CR imaging plate that has improved resistance to physical damage and/or improved resistance to ambient light while maintaining a small form and avoiding the need for automated handling equipment. Such imaging plates therefore may be ideally suited for intraoral and veterinary computed radiography. However, embodiments of the present invention should be understood to have broad uses that extend to other fields of medical radiography and radiography in general.
For example, one of the four corners 11 may be shaped with a blended chamfer, while the others of the four corners would retain the standard rounding with a 7 mm radius. The blended chamfer of the one corner 11 may allow for the imaging plate to still fit inside a conventional pouch with four rounded corners. Alternatively, another shape may be selected. Where the shape selected prevents fit into a conventional pouch, a non-standard pouch may be used.
Embodiments of the present invention may include a layer for added physical protection.
A thick protective layer 14 may be placed on the PSP layer 13. The thick protective layer 14 may be sufficiently thick and hard to resist physical and mechanical stimulus that may occur during use and handling. The thick protective coating may additionally be chemically inert and impervious to water and/or other substances. For example, the thick protective layer 14 may comprise polyethylene terephthalate polyester (PETP) or another suitable material. The thick protective layer 14 may be, for example, approximately 0.05 mm thick. The thick protective layer may be applied, for example, via heat lamination during the production of the imaging plate stock.
According to some embodiments of the present invention, the thick protective layer 14 may replace the very thin layer of aliphatic urethancynacrilate that is used to protect the PSP layer from chemically-adverse substances and hydroscopic absorption as used in the art. Alternatively, the thick protective layer 14 may be placed on top of the very thin layer of aliphatic urethancynacrilate.
The thick protective layer is thick in comparison to the very thin layer of aliphatic urethancynacrilate which is generally on the order of several microns thick. Accordingly, the thick protective layer may be approximately an order of magnitude thicker than the very thin layer.
According to some embodiments of the present invention, the thick protective layer may be highly transparent. The thick protective layer may be especially transparent at the wavelength used to stimulate the photo-stimulable layer during the scanning procedure employed after x-ray exposure has occurred. For example, where a red laser is used for stimulation, the thick protective layer may be highly transparent of red light.
The thick protective layer may also be especially transparent at the wavelengths emitted by the photo-stimulable layer after stimulation at least to the extent that such light is detectable by the photo-detectors being used. For example, because the photo-detectors used to detect the emitted light generally register light in the green-blue wavelengths, the thick protective layer may be especially transparent at green-blue wavelengths.
The thick protective layer may optionally be highly transparent at other wavelengths of light; however, according to other embodiments of the present invention, the thick protective layer may be designed to be opaque at wavelengths of light that are not used for stimulation or emission detection. This may allow for at least partial blockage of ambient light that may be responsible for image degradation or fading during periods of time that the imaging plate is exposed to ambient light. In this way, the thick protective layer serves to reduce image fading.
For example, the thick protective layer may act as an optical filter that preferentially transmits only the narrow-band wavelength required to stimulate the PSP layer (for example red) and the broad-band wavelengths which are emitted by the PSP layer and detected by the photo-detectors (for example green-blue).
Accordingly, the thick protective layer could present a degree of opacity to all other light wavelengths that are not the stimulation wavelength or the emitted wavelengths.
To achieve the desired color blocking properties, the thick protective layer may be fashioned as an optical color-band-stop filter. Alternatively, the protective coating could be optically-tailored so to preferentially transmit only the useful wavelengths precisely, for instance as a multi-band-pass interferometric filter.
In order to provide the desired optical absorption properties, the thick protective layer must be sufficiently thick. Therefore, the thick protective layer may be thick enough to offer suitable physical protection and at the same time to provide suitable optical protection. To achieve these goals, the thick protective layer may comprise multiple sub-layers, and each sub-layer may specifically provide opaqueness for particular wavelengths.
Embodiments of the present invention have been successfully tested, with several sets of different tests:
One set of tests was done to verify that the presence of thick protective layer would not detrimentally affect image quality, by comparing resolution and x-ray sensitivity achieved with imaging plates with and without thick coating layer.
Another set of test was conducted to verify the extent of protection to mechanical abuses that the extra thick coating layer can provide respect to unprotected imaging plates.
A further set of tests was conducted to reconfirm that image resolution and x-ray sensitivity achievable with the prototype PSP imaging plates coated with the extra protective layer is comparable to that of existing commercial PSP imaging plates.
In the first set of such tests, four intraoral imaging plates each with a PSP layer of thickness 0.180 mm were tested. In a first test imaging plate, the PSP layer was coated with only the standard very thin layer of aliphatic urethancynacrilate. A second test imaging plate added a thick protective layer of thickness 0.05 mm on top of the thin aliphatic urethancynacrilate layer. A third test imaging plate added a thick protective layer of thickness 0.20 mm on top of the thin aliphatic urethancynacrilate layer. A fourth test imaging plate lacked the thin aliphatic urethancynacrilate layer and had only a thick protective layer of thickness 0.05 mm. A commercial, conventional Fujifilm BAS PSP imaging plate was also tested for comparison. The PSP layer thickness of the Fujifilm BAS is believed to be approximately 0.090 mm thick.
The test imaging plates and the conventional plate were exposed using a 65 kV, 7 mA, DC x-ray source at Source-Detector Distance=33 cm. The first test imaging plate exhibited a sensitivity that was approximately 2.6 times greater than the Fujifilm BAS imaging plate. The second and third test imaging plate exhibited a sensitivity that was approximately 2.1 times greater than the Fujifilm BAS imaging plate. The fourth imaging plate exhibited a sensitivity that was approximately 2.3 times the Fujifilm BAS imaging plate.
It should be noted that an enhanced sensitivity coincides with a reduced dynamic range of approximately the same factor.
Accordingly, it was determined that the presence of the thick protective layer did not significantly reduce imaging plate sensitivity.
In another test, the maximum visually-detectable spatial resolution in line pairs per millimeter (lp/mm) was evaluated with a converging-line-pair test object, limit resolution 10 lp/mm, positioned at 30° from the scanning axis. Exposures were made at 40 ms and 80 ms. The test imaging plates were compared against data obtained from a conventional Fujifilm BAS imaging plate. Scanning was performed at different scanning resolutions, as possible with the Gendex DenOptix PSP scanner, that is 600 DPI and 300 DPI (DPI=Dot-per-Inch). The results were as follows:
Accordingly, the maximum visually-detectable spatial resolution was comparable for each test imaging plate, whether coated or uncoated, suggesting that the thick protective layer did not substantially adversely effect maximum visually-detectable spatial resolution.
At 600 DPI, the Fujifilm BAS conveys a perception of better crispness than each of the test plates. This phenomenon was not observed at 300 DPI. This perception of better crispness is believed to be the result of the thinner PSP layer used by the Fujifilm BAS. Accordingly, it was concluded that reducing the PSP layer in the test plates, for instance to 0.090 mm or less, would allow embodiments of the present invention to achieve crispness comparable to or better than the Fujifilm BAS imaging plate.
In mechanical abuse testing, the second, third and fourth test imaging panels were tested for scratch resistance against a Fujifilm BAS imaging plate. The test procedure included dragging a 1 mm spherical point needle across each plate at a force ranging from 100 to 800 mN in 100 mN increments prior to x-ray exposure and image capture. The second and fourth test imaging panel required approximately 10 times more pressure to produce the same image defect as the standard imaging plate. The third test imaging panel required in excess of 26 times more pressure to produce the same image defect as the Fujifilm BAS imaging plate.
Accordingly, it was demonstrated that the test imaging plates including the thick protective layer provided substantially better physical protection than the imaging plates that lacked the thick protective coating.
In subsequent sensitivity testing, a test plate having a PSP layer thickness of 0.090 mm and a thick protective layer of thickness 0.05 mm and a test plate having a PSP layer of 0.090 mm without a thick protective layer were tested against the standard Fujifilm BAS imaging plate.
In sensitivity testing, the sensitivity response of both test plates appeared to be 2.3 times higher than that of the Fujifilm BAS imaging plate with the sensitivity of the test plate without the thick protective layer being approximately 10% higher than the test plate with the thick protective coating. Therefore, the reduction of sensitivity caused by the thick protective layer appeared to be within acceptable margins.
In further testing of spatial resolution, the maximum visually-detectable spatial resolution in line pairs per millimeter (lp/mm) was evaluated with a converging-line-pair test object, limit resolution 10 lp/mm, positioned at 30° from the scanning axis. Exposures were made between 50 ms and 160 ms. The test imaging plates were compared against data obtained from a conventional Fujifilm BAS imaging plate. The results were as follows:
Accordingly, it was demonstrated that image performances with the test imaging plate having the thick protective coating was about as good as, or better than, the conventional imaging plate, and the presence of the thick protective coating did not significantly reduce the resultant image quality.
The observance of marginally lower spatial resolution respect to the Fujifilm BAS imaging plate is believed to be inconsequential, especially at the 300 DPI scanning resolution that is most frequently used for dental imaging.
A further set of test was conducted with imaging plates having a PSP layer of approximately only 0.05 mm, and a protective layer of 0.05 mm. It was found that both resolving power (in lp/mm) and sensitivity were comparable and very close to those achieved with Fujifilm BAS imaging plates.
The above specific embodiments are illustrative, and many variations can be introduced on these embodiments without departing from the spirit of the disclosure or from the scope of the appended claims. For example, elements and/or features of different illustrative embodiments may be combined with each other and/or substituted for each other within the scope of this disclosure and appended claims.
