Radiant energy – Source with recording detector – Using a stimulable phosphor
Reexamination Certificate
2001-10-04
2004-03-09
Porta, David (Department: 2878)
Radiant energy
Source with recording detector
Using a stimulable phosphor
C250S584000
Reexamination Certificate
active
06703637
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a radiation image read-out method and apparatus, wherein stimulating rays are irradiated to a stimulable phosphor sheet, on which a radiation image has been stored. Light, which is emitted by the stimulable phosphor sheet when: the stimulable phosphor sheet is exposed to the stimulating rays, is photoelectrically detected, and an image signal representing the radiation image is thereby obtained. This invention particularly relates to a radiation image read-out method and apparatus, wherein a radiation image is capable of being read out from a stimulable phosphor sheet, on which the radiation image has been stored with an image recording operation utilizing a stationary grid, such that adverse effects of grid patterns are eliminated
2. Description of the Related Art
Radiation image recording and reproducing systems utilizing a stimulable phosphor sheet, which comprises a substrate and a layer of a stimulable phosphor overlaid on the substrate, have heretofore been widely used in practice.
With the radiation image recording and reproducing systems, a stimulable phosphor sheet is exposed to radiation carrying image information of an object, such as a human body, and a radiation image of the object is thereby recorded on the stimulable phosphor sheet. Thereafter, stimulating rays, such as a laser beam, are caused to scan the stimulable phosphor sheet in two-dimensional directions. The stimulating rays cause an exposed area of the stimulable phosphor sheet to emit light in proportion to the amount of energy stored thereon during its exposure to the radiation. The light emitted from the exposed area of the stimulable phosphor sheet, upon stimulation thereof, is photoelectrically detected and converted into an electric image signal by photoelectric read-out means.
The image signal, which has been, obtained from the radiation image recording and reproducing systems described above, is then subjected to image processing, such as gradation processing and processing in the frequency domain, such that a visible radiation image can be obtained. In particular, the image has good image quality and can serve as an effective tool in the efficient and accurate diagnosis of an illness, for example. The image signal having been obtained from the image processing is utilized for reproducing a visible image for diagnosis, or the like, on film or displaying a visible image for diagnosis, or the like, on a cathode ray tube (CRT) display device. In cases where the stimulable phosphor sheet, from which the image signal has been detected, is then exposed to erasing light, and energy remaining on the stimulable phosphor sheet is thereby released, the erased stimulable phosphor sheet is capable of being used again for the recording of a radiation image.
Also, a radiation image recording and reproducing system aiming at enhancement of a detection quantum efficiency in the formation of the radiation image, i.e., a radiation absorptivity, a light emission efficiency, an emitted light pickup efficiency, and the like, wherein a certain type of stimulable phosphor sheet is utilized, has been proposed in, for example, Japanese Patent Application No. 11(1999)-372978. With this type of the stimulable phosphor sheet utilized in the proposed radiation image recording and reproducing system, the radiation absorbing functions and the energy storing functions of the conventional stimulable phosphor sheet are separated from each other.
The stimulable phosphor sheet utilized in the proposed radiation image recording and reproducing system contains a layer of a stimulable phosphor for energy storage, which is capable of absorbing light having wavelengths falling within an ultraviolet to visible region and thereby storing energy of the light having wavelengths falling within the ultraviolet to visible region, and which is capable of being stimulated by light having wavelengths falling within a visible to infrared region and thereby radiating out the stored energy as emitted light.
The stimulable phosphor sheet should preferably take on the form combined with a layer of a phosphor for radiation absorption, which is capable of absorbing radiation and being caused to emit light having wavelengths falling within an ultraviolet to visible region. In such cases, energy from the light having wavelengths falling within the ultraviolet to visible region, which light is emitted from the layer of the phosphor for radiation absorption when the layer of the phosphor for radiation absorption is exposed to the radiation carrying image information of an object, (the amount of the energy corresponding to the radiation image information) is stored on the layer of the stimulable phosphor for energy storage. When the stimulable phosphor sheet, on which the radiation image has thus been stored, is scanned with the stimulating rays, the light carrying the radiation image information is emitted from the layer of the stimulable phosphor for energy storage.
The stimulable phosphor sheet need not necessarily be provided with the layer of the phosphor for radiation absorption. In such cases, the stimulable phosphor sheet is utilized in combination with a fluorescent screen, which is provided with the layer of the phosphor for radiation absorption capable of absorbing radiation and being caused to emit the light having wavelengths falling within the ultraviolet to visible region.
Specifically, in such cases, the fluorescent screen is kept in close contact with the novel type of the stimulable phosphor sheet, and the radiation carrying the image information of the object is irradiated to the fluorescent screen. As a result, the light having wavelengths falling within the ultraviolet to visible region is emitted from the layer of the phosphor for radiation absorption of the fluorescent screen. Also, energy from the light emitted from the phosphor for radiation absorption (the amount of the energy corresponding to the radiation image information) is stored on the layer of the stimulable phosphor for energy storage of the stimulable phosphor sheet. When the stimulable phosphor sheet, on which the radiation image has thus been stored, is scanned with the stimulating rays, the light carrying the radiation image information is emitted from the layer of the stimulable phosphor for energy storage.
Radiation image read-out apparatuses for use in the radiation image recording and reproducing systems described above have been proposed in, for example, Japanese Unexamined Patent Publication Nos. 60(1985)-111568, 60(1985)-236354, and 1(1989)-101540. In the proposed radiation image read-out apparatuses, from the point of view of keeping the emitted light detection time short, reducing the size of the apparatus, and keeping the cost low, a line sensor comprising a charge coupled device (CCD) image sensor, or the like, is utilized as the photoelectric read-out means.
Basically, the radiation image read-out apparatuses of such types comprise:
i) stimulating ray irradiating means for linearly irradiating stimulating rays onto an area of a stimulable phosphor sheet, on which a radiation image has been stored, the stimulating rays causing the stimulable phosphor sheet to emit light in proportion to an amount of energy stored thereon during its exposure to radiation,
ii) a line sensor; which comprises a plurality of photoelectric conversion devices arrayed along the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays, and
iii) sub-scanning means for moving the stimulable phosphor sheet with respect to the stimulating ray irradiating means and the line sensor and in a direction (a sub-scanning direction) intersecting with a length direction of the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays (a main scanning direction).
The stimulating ray irradiating means for linearly irradiating the stimulating rays onto the stimulable phosphor sheet in the manner described above may be constituted so as to produce fan beam-like stimulat
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