Image analysis – Applications – Biomedical applications
Reexamination Certificate
2000-03-21
2003-05-13
Johns, Andrew W. (Department: 2721)
Image analysis
Applications
Biomedical applications
Reexamination Certificate
active
06563943
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 to 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.
In cases where a radiation image of an object is recorded on the two adjacent stimulable phosphor sheets, which are associated with each other such that the portions of the two sheets overlap each other, and the two radiation images having been read out from the two stimulable phosphor sheets are connected with each other, as for the overlapping regions of the two radiation images, which overlapping regions correspond to the overlapping areas of the two stimulable phosphor sheets, the image information within the overlapping region of the radiation image having been read out from the stimulable phosphor sheet located on the side close to the object should preferably be employed for the reasons described below.
Specifically, in cases where radiation carrying image information of the object is irradiated to a first stimulable phosphor sheet, which is one of the two adjacent stimulable phosphor sheets associated with each other in the manner described above and which is located on the side remote from the object, and the other second stimulable phosphor sheet, which is located on the side close to the object, the overlapping area of the first stimulable phosphor sheet, upon which the overlapping area of the second stimulable phosphor sheet overlaps, is exposed to the radiation having decayed to a dose smaller than the dose of the radiation irradiated to the other area of the first stimulable phosphor sheet, which area does not overlap the second stimulable phosphor sheet. Therefore, the image density of the overlapping region of a first radiation image having been read out from the first stimulable phosphor sheet becomes lower than the image density of the non-overlapping region of the first radiation image. Accordingly, if the image information recorded within the overlapping region of the first radiation image is employed with respect to the overlapping regions of the first radiation image and a second radiation image, which has been read out from the second stimulable phosphor sheet, and a radiation image is thereby reconstructed from the first and second radiation images, a reconstructed radiation image will be obtained in which the image density of the long, narrow overlapping region is lower than the image density of the other region. As a result, a reconstructed radiation image, which has good image quality and can serve as an effective tool in, particularly, the efficient and accurate diagnosis of an illness, cannot be obtained. However, as for the second radiation image having been read out from the second stimulable phosphor sheet, the image density of the overlapping region of the second radiation image is identical with the image density of the non-overlapping region of the second radiation image. Therefore, in cases where the image information recorded within the overlapping region of the second radiation ima
Fuji Photo Film Co. , Ltd.
Johns Andrew W.
Nakhjavan Shervin
Sughrue & Mion, PLLC
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