Image analysis – Applications – Biomedical applications
Reexamination Certificate
2000-03-21
2003-07-29
Johns, Andrew W. (Department: 2621)
Image analysis
Applications
Biomedical applications
Reexamination Certificate
active
06600831
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a connection processing method for radiation images and a radiation image processing apparatus for carrying out the method. This invention particularly relates to connection processing for radiation images, which is performed in cases where a radiation image of an object having been recorded on a plurality of stimulable phosphor sheets associated with one another is to be reconstructed.
2. Description of the Prior Art
Recently, as systems capable of obtaining radiation images recorded even when energy intensity of radiation, to which a recording medium is exposed, varies over a wide range, computed radiography systems (CR systems) have widely been used in practice. With the CR systems, a radiation image of an object, such as a human body, is recorded on a stimulable phosphor sheet. The stimulable phosphor sheet, on which the radiation image has been stored, is then exposed to stimulating rays, such as a laser beam, which cause it to emit light in proportion to the amount of energy stored, thereon during its exposure to the radiation. The light emitted by the stimulable phosphor sheet, upon stimulation thereof, is photoelectrically detected and converted into an image signal. The image signal is then processed and used for the reproduction of the radiation image of the object as a visible image on a recording material.
In the CR systems, stimulable phosphor sheets having various different sizes, such as a 14″×17″ size, a 14″×14″ size, a 10″×12″ size, and a 8″×10″ size, have heretofore been used in accordance with the objects whose images are to be recorded. However; in the fields of the orthopedic surgery, for the purposes of measuring the degree of bending of the spinal column, and the like, there is a strong demand for the use of a long image ranging from a pattern of the neck to a pattern of the waist as a single image. Therefore, it has been studied to utilize stimulable phosphor sheets which are longer than the aforesaid sizes in a predetermined direction.
However, in cases where the long stimulable phosphor sheets are utilized, designs of radiation image read-out apparatuses for reading out the radiation images from the stimulable phosphor sheets, such as the designs of sheet conveyance paths in the radiation image read-out apparatuses, must be altered markedly so as to be adapted to the long stimulable phosphor sheets. The radiation image read-out apparatuses must thus be designed for the exclusive use for the long stimulable phosphor sheets. Therefore, the problems occur in that the radiation image read-out apparatuses designed for the long stimulable phosphor sheets are disadvantageous in the aspect of cost.
Accordingly, a technique may be utilized, wherein two stimulable phosphor sheets having the conventional sizes are associated with each other to form an apparently long stimulable phosphor sheet, a long image is recorded on the apparently long stimulable phosphor sheet, and thereafter the two stimulable phosphor sheets constituting the apparently long stimulable phosphor sheet are subjected to image read-out operations one after the other. With the technique, the image read-out operations can be performed by utilizing the conventional radiation image read-out apparatus without its design being altered, and the problems described above do not occur.
Also, with the technique described above, three or more stimulable phosphor sheets can be associated with one another to form an;apparently long stimulable phosphor sheet, and a long image of an object can be recorded on the apparently long stimulable phosphor sheet. Also, a plurality of stimulable phosphor sheets can be associated with one another in two axis directions, which are normal to each other, in order to form an apparently wide, long stimulable phosphor sheet, and a wide, long image of an object can be recorded on the apparently wide, long stimulable phosphor sheet. Therefore, the technique described above has good adaptability to objects.
In cases where at least two stimulable phosphor sheets are associated with each other to form an apparently long stimulable phosphor sheet and an image of an object is recorded on the apparently long stimulable phosphor sheet, if the two adjacent stimulable phosphor sheets among the plurality of the stimulable phosphor sheets are considered, the two adjacent stimulable phosphor sheets may be associated with each other such that their edges are in abutment with each other. Alternatively, the two adjacent stimulable phosphor sheets may be associated with each other such that portions of the two sheets overlap each other. However, with the technique wherein the two adjacent stimulable phosphor sheets are associated with each other such that their edges are in abutment with each other, loss of image information will inevitably occurs at the boundary area between the two adjacent stimulable phosphor sheets. With the technique wherein the two adjacent stimulable phosphor sheets are associated with each other such that the portions of the two sheets overlap each other, such loss of image information does not occur.
However, with the technique wherein the two adjacent stimulable phosphor sheets are associated with each other such that the portions of the two sheets overlap each other, each of the two radiation images having been read out from the two stimulable phosphor sheets contains an image pattern of the overlapping area. Therefore, even if the two radiation images having; been read out from the two stimulable phosphor sheets are merely connected with each other without any spacing therebetween, a correct radiation image of the object cannot be reconstructed.
SUMMARY OF THE INVENTION
The primary object of the present invention is to provide a connection processing method for radiation images, wherein radiation images, which have been recorded on a plurality of stimulable phosphor sheets associated with one another with portions of adjacent stimulable phosphor sheets overlapping each other, are read out, positions of the read-out radiation images are accurately matched with one another, and a single radiation image is reconstructed from the read-out radiation images.
Another object of the present invention is to provide a radiation image processing apparatus for carrying out the connection processing method for radiation images.
In cases where two adjacent stimulable phosphor sheets are associated with each other such that portions of the two adjacent stimulable phosphor sheets overlap each other, and radiation carrying image information of an object is irradiated to the two adjacent stimulable phosphor sheets, the overlapping area of one of the two adjacent stimulable phosphor sheets, which is located on the side remote from the object, is exposed to the radiation having decayed to a dose smaller than the dose of the radiation irradiated to the other area, which does not overlap the other stimulable phosphor sheet. Therefore, an image pattern of a boundary line due to a difference in image density is formed between the overlapping area and the non-overlapping area of the stimulable phosphor sheet located on the side remote from the object. A first connection processing method for radiation images and a first radiation image processing apparatus in accordance with the present invention are characterized by detecting the thus formed boundary line image pattern and matching positions of two radiation images with each other by the utilization of the detected boundary line image pattern.
Specifically, the present invention provides a first connection processing method for radiation images, in which a single radiation image of an object is recorded on a plurality of stimulable phosphor sheets associated with one another such that portions of two adjacent stimulable phosphor sheets overlap each other, and in which connection processing is performed on a plurality of radiation images having been read out from the plurality of the stimu
Johns Andrew W.
Nakhjavan Shervin
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