Radiation image read-out method and apparatus

Details Radiation image read-out method and apparatus Radiation image read-out method and apparatus

2001-12-20

2004-03-16

Bennett, G. Bradley (Department: 2859)

Radiant energy

Source with recording detector

Using a stimulable phosphor

Reexamination Certificate

active

06707058

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a radiation image read-out method and apparatus for reading out a radiation image stored on a stimulable phosphor sheet by exposing the stimulable phosphor sheet to stimulating light.
2. Description of the Related Art
When certain kinds of phosphor are exposed to a radiation, they store a part of energy of the radiation. Then when the phosphor which has been exposed to the radiation is exposed to stimulating rays such as visible light or a laser beam, light is emitted from the phosphor in proportion to the stored energy of the radiation. A phosphor exhibiting such properties is generally referred to as “a stimulable phosphor”. In this specification, the light emitted from the stimulable phosphor upon stimulation thereof will be referred to as “stimulated emission”. There has been put into wide use as a computed radiography a radiation image recording and reproducing system using a stimulable phosphor sheet (a sheet provided with a layer of the stimulable phosphor). In the radiation image recording and reproducing system, a stimulable phosphor sheet is exposed to a radiation passing through an object such as a human body to have a radiation image information of the object stored on the stimulable phosphor sheet, a stimulating light beam such as a laser beam is caused to two-dimensionally scan the stimulable phosphor sheet, thereby causing each part of the stimulable phosphor sheet exposed to the stimulating light beam to emit the stimulated emission, and the stimulated emission is photoelectrically detected, thereby obtaining an image signal (a radiation image signal) representing the radiation image information. In the radiation image information read-out apparatus employed in the radiation image recording and reproducing apparatus, it has been proposed to use a line light source which projects a line beam onto the stimulable phosphor sheet as a stimulating light source and to use a line sensor having an array of photoelectric convertor elements extending in the main scanning direction (the longitudinal direction of the line beam) as a means for photoelectrically reading out the stimulated emission. The line beam and the line sensor are moved relative to the stimulable phosphor sheet in the sub-scanning direction (the direction substantially perpendicular to the longitudinal direction of the line beam) by a scanning means. By the use of a line beam and a line sensor, the reading time is shortened, the overall size of the apparatus can be reduced and the cost can be reduced. See, for instance, Japanese Unexamined Patent Publication Nos. 60(1985)-111568, 60(1985)-236354, and 1(1989)-101540.
As a system using the stimulable phosphor sheet, there has been wide known an autoradiography detection system in which material labeled with radioactive labeling is administered to an organism, the organism or a part of the organism is taken as a sample, the sample is overlaid on a stimulable phosphor sheet for a predetermined time interval to have radiation image information of the object stored on the stimulable phosphor sheet, a stimulating light beam such as a laser beam is caused to scan the stimulable phosphor sheet, thereby causing each part of the stimulable phosphor sheet exposed to the stimulating light beam to emit the stimulated emission, and the stimulated emission is photoelectrically detected, thereby obtaining an image signal representing the radiation image of the sample. (See, for instance, Japanese Patent Publication Nos. 1(1989)-60784, 1(1989)-60782 and 4(1992)-3952.) In the autoradiography detection system, the stimulating light is caused to scan over the entire surface of the sample by moving the optical system in both the main scanning direction and the sub-scanning direction with a stage on which the sample is placed held stationary or by moving the optical system in the main scanning direction in which the stimulating light should scan the sample at a high speed and moving the stage in the sub-scanning direction in which the stimulating light may scan the sample at a relatively low speed.
The image signal obtained in each of the aforesaid systems is subjected to image processing such as gradation processing and/or frequency processing and a radiation image of the object is reproduced as a visible image for diagnosis on the basis of the processed radiation image signal on a recording medium such as a photographic film or a display such as a fine CRT. The doctor makes a diagnosis viewing the visible image or computer analysis is carried out on the basis of the visible image.
Further, there has been developed a microarray detection system in which known binding materials, e.g., hormones, tumor markers, enzymes, antibodies, antigens, abzymes, other proteins, nucleic acids, cDNAs, DNAs, mRNAs and the like, each of which can bond to a specific organism-derived material and properties of which such as the sequence, lengths, the composition and/or the like of bases are known are spotted by a spotter on a support such as a membrane filter to form a microarray of independent spots; an organism-derived material, e.g., hormone, tumor marker, enzyme, antibody, antigen, abzyme, other protein, nucleic acid, cDNA, DNA, mRNA or the like, which is sampled from an organic body (and is chemically processed or modified as desired) and labeled with radioactive labeling is hybridized with the known binding materials on the microarray; the microarray is kept in close contact with a stimulable phosphor sheet to expose the stimulable phosphor sheet in a pattern of distribution of the radioactive labeling on the microarray; a stimulating light beam such as a laser beam is caused to scan the stimulable phosphor sheet, thereby causing the stimulable phosphor sheet exposed to the stimulating light beam to emit the stimulated emission, and the stimulated emission is photoelectrically detected, thereby analyzing the organism-derived material sampled from the organic body. In the microarray detection system, as in the autoradiography detection system, the stimulating light beam may be caused to scan over the entire surface of the support by moving the optical system in both the main scanning direction and the sub-scanning direction with a stage on which the support is placed held stationary or by moving the optical system in the main scanning direction in which the stimulating light should scan the sample at a high speed and moving the stage in the sub-scanning direction in which the stimulating light may scan the sample at a relatively low speed. In the case of the microarray detection system, since the support is small in size, the stimulating light beam may be caused to scan the surface of the support by moving the support in the main scanning direction or in both the main scanning direction and the sub-scanning direction.
In the systems where a stimulable phosphor sheet storing thereon radiation energy is two-dimensionally scanned by a stimulating light beam and stimulated emission emitted from the stimulable phosphor sheet upon stimulation by the stimulating light beam is detected, it has been conceived that since the intensity of the stimulated emission is proportional to the power of the stimulating light beam, the stimulated emission can be detected at a higher sensitivity as the power of the stimulating light beam is increased.
However, an experiment of these inventors has revealed that the sensitivity of detection cannot be increased with increase of the stimulating light power beyond a predetermined limit but deteriorates when the stimulating light power is increased beyond the predetermined limit. Further, when the read-out pitches in the sub-scanning direction are narrowed in order to meet demand for a higher resolution, the deterioration of the sensitivity of detection becomes more significant.
When the stimulating light beam scans the stimulable phosphor sheet along a main scanning line, the stimulating light beam can stimulate the stimulable phosphor sheet not only along the main scanning line but also a

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