X-ray or gamma ray systems or devices – Specific application – Absorption
Reexamination Certificate
2002-10-15
2004-09-14
Church, Craig E. (Department: 2882)
X-ray or gamma ray systems or devices
Specific application
Absorption
C378S098800
Reexamination Certificate
active
06792070
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a radiation image recording method and apparatus. This invention particularly relates to a radiation image recording method and apparatus suitable for operations, wherein radiation carrying image information of an object is detected at a plurality of positions for image recording, which are set at different distances from the object, a plurality of radiation images being thereby obtained, and a phase contrast image is formed by use of the plurality of the radiation images.
2. Description of the Related Art
Radiation image recording and reproducing techniques have heretofore been used in practice. With the radiation image recording and reproducing techniques, radiation is irradiated to an object, and the radiation carrying image information of the object is detected with a two-dimensional detector, such as a stimulable phosphor sheet or a radiation detecting panel comprising a plurality of detecting devices arrayed in two-dimensional directions. In this manner, an image signal representing a radiation image of the object is obtained. The image signal is then subjected to various types of image processing, and the processed image signal is utilized for reproducing the radiation image as a visible image.
With the radiation image recording and reproducing techniques utilizing the stimulable phosphor sheet, the radiation image of the object is stored on the stimulable phosphor sheet comprising a layer of a stimulable phosphor, and the stimulable phosphor sheet, on which the radiation image has been stored, is exposed to stimulating rays, such as a laser beam, which cause the stimulable phosphor sheet to emit light in proportion to the amount of energy stored thereon during its exposure to radiation. The light emitted by the stimulable phosphor sheet is photoelectrically detected, and the image signal representing the radiation image of the object is thereby obtained. With the radiation image recording and reproducing techniques utilizing the radiation detecting panel comprising the plurality of the detecting devices arrayed in two-dimensional directions, an electric signal component corresponding to a radiation dose delivered to each of the detecting devices is formed by each of the detecting devices, and the image signal representing the radiation image of the object is obtained from the thus formed electric signal components.
In the radiation image obtained in the manner described above, a difference in intensity of radiation having passed through the object is illustrated as the image. For example, in cases where the radiation image of an object comprising a bone and a soft tissue is recorded, the radiation having passed through the bone attenuates largely, and the dose of the radiation, which has passed through the bone and is delivered to the detector, becomes small. However, the radiation having passed through the soft tissue does not much attenuate, and the dose of the radiation, which has passed through the soft tissue and is delivered to the detector, becomes comparatively large. Therefore, in the cases of the object comprising the bone and the soft tissue, a radiation image comprising a bone pattern having a low image density and a soft tissue pattern having a high image density, in which the contrast between the bone pattern and the soft tissue pattern is high, i.e. in which the quantity of information is large, is obtained.
However, in cases where the object is mainly constituted of soft tissues alone as in the cases of the radiation image for a diagnosis of mammary cancer, the difference in amount of attenuation of radiation between the soft tissues is not very large. Therefore, in such cases, a radiation image, in which the contrast between the soft tissue patterns is low, i.e. in which the quantity of information is small, is obtained.
Accordingly, phase contrast imaging techniques for visualizing a phase difference of radiation occurring due to the passage of the radiation through an object have been proposed. As in the cases of light, the radiation is an electromagnetic wave and travels and propagates as the wave. The recording of the object image with the phase contrast imaging techniques is based upon the phenomenon such that, in cases where the radiation is irradiated to two different substances, the phase of the wave of the radiation varies before the radiation passes through the substances and after the radiation has passed through the substances due to a difference in how the radiation propagates through the substances, and a phase difference is thereby caused to occur. In cases where the object is constituted of the soft tissues, the phase difference of the radiation becomes larger than the difference in amount of attenuation of radiation. Therefore, in such cases, the image recording may be performed with the phase contrast imaging techniques, and the phase difference of the radiation may be illustrated as a phase contrast image. In this manner, a fine difference between the soft tissues is capable of being visualized.
The phase contrast imaging techniques are described in detail in, for example, “Quantitative aspects of coherent hard X-ray imaging: Talbot image and holographic reconstruction” by Peter Cloetens, et al., Proc, SPIE, Vol. 3154 (1997), pp. 72-82 (hereinbelow referred to as Literature 1); and “Hard X-ray phase imaging using simple propagation of a coherent synchrotron radiation beam” by Peter Cloetens, et al., J. Phys. D: Appl. Phys. 32 (1999), pp. A145-A151 (hereinbelow referred to as Literature 2). Literature 1 and Literature 2 show that, in cases where an image recording operation is performed by use of two-dimensional detectors, such as radiation detecting panels, at a plurality of positions for image recording, which are set at different distances from the object, a plurality of image signals respectively representing a plurality of radiation images of the object are thereby obtained, and operation processing with predetermined algorithms is performed on the plurality of the image signals, a phase contrast image is capable of being formed.
In cases where a radiation image is obtained, the radiation dose delivered to a two-dimensional detector varies in inverse proportion to the square of the distance between a radiation source and the two-dimensional detector. Also, the radiation propagates in a divergent form from the radiation source, and therefore the size of the radiation image detected by a two-dimensional detector, which is located at a long distance from the object, becomes large. Accordingly, a radiation imaging apparatus, wherein a read-out gain at the time of image readout of a radiation image is adjusted in accordance with the distance between an object and a two-dimensional detector, or a magnification ratio of the radiation image is calculated in accordance with the distance between the object and the two-dimensional detector, has been proposed in, for example, Japanese Unexamined Patent Publication No. 2000-245721.
Further, a technique, wherein image size enlargement or reduction processing or image density transform processing is performed on a plurality of radiation images, which are obtained at a plurality of positions for image recording, such that a phase contrast image is capable of being obtained accurately, has been proposed in, for example, Japanese Patent Application No. 2001-146138.
However, with the techniques, wherein the read-out gain is adjusted, or the image density is transformed, a long time is required to perform the read-out gain adjustment or the image density transform, and radiation images cannot be detected efficiently.
SUMMARY OF THE INVENTION
The primary object of the present invention is to provide a radiation image recording method, wherein radiation is capable of being detected efficiently, and a phase contrast image is capable of being formed accurately.
Another object of the present invention is to provide a radiation image recording method, wherein a plurality of radiation images, from which a phase contrast image
Church Craig E.
Yun Jurie
LandOfFree
Radiation image recording method and apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Radiation image recording method and apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Radiation image recording method and apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3210436