Patent Application
20070114428
1. Field of the Invention
The present invention relates to a radiation image capturing apparatus such as an inspection machine for performing transmission inspection of the inside of an object, or an X-ray CT apparatus or an X-ray tomography apparatus for comprehending a three-dimensional contour and to a radiation image capturing method. More particularly, the present invention relates to a radiation image capturing condition correction apparatus and a radiation image capturing condition correction method for suppressing deterioration in the accuracy and the resolution, due to image blurs and image distortion caused by radiation-source displacement that changes with irradiation time.
2. Related Art of the Invention
A technique, utilizing radiations such as X-rays, for capturing a two-dimensional or a three-dimensional radiation image has been widely employed to inspect the inner structures of products. In the case of an X-ray, by utilizing an X-ray source having a minute X-ray radiant point, making X-rays pass through an imaging subject, and capturing the obtained X-rays on an image capturing plane, an image is obtained.
In capturing the radiation image, a problem called “radiation-source displacement” has been known. As described later, in the case of an X-ray, an X-ray source, in general, generates X-rays as the secondary emission caused by the collision of an electron beam, which is emitted from a filament contained in a metal case, with a specific portion inside the case.
During image capturing, the radiation source is displaced minutely, thereby making an image being captured to be displaced on the image capturing plane; as a result, the position of the imaging subject is displaced from the position where the subject ought to be, i.e., the problem called “radiation-source displacement” is posed.
In order to cope with the foregoing problem, an image capturing apparatus is disclosed in which, by focusing attention on the correlation between the radiation-source displacement and the radiation-source temperature and providing a focus-position temperature performance obtaining unit so as to preliminarily measure and store the changing performances of the radiation-source temperature and the focus position, an image is rerendered when an actual scan is performed, by utilizing correction values obtained from the performances (e.g., refer to Japanese Patent Publication Laid-Open No. 1995-116157).
By measuring the temperature T1 and the focus position S1, the temperature T2 and the focus position S2, and the temperature T3 and the focus position S3, of the X-ray tube 202, when the X-ray tube 202 has a low temperature, when the X-ray tube 202 has an intermediate temperature, and when the X-ray tube 202 has a high temperature, respectively, the focus-position temperature performance obtaining unit 209 obtains the focus position S vs. temperature T performance of the X-ray tube 202. The focus-position temperature performance storing unit 210 stores the focus-position temperature performance obtained by the focus-position temperature performance obtaining unit 209. Based on the stored focus-position temperature performance, the focus error value providing unit 211 obtains a focus error value δx corresponding to the temperature Tx at which an actual scan is performed, and as the focus error value δ, provides the focus error value δx to the focus error correction unit of the image rerendering unit 207.
As described heretofore, the X-ray CT image-capturing apparatus performs a focus error correction utilizing relationship between the temperature of the X-ray CT and the focus position.
However, the above-mentioned conventional radiation-source correction apparatus, which performs the correction based on the correlation between the temperature and the focus position, has the following problem: A phase difference exists between the temperature to be detected and the focus position, and the X-ray tube has a structure having large volume; therefore, even though the temperature of an arbitrary position on the X-ray tube is measured, the temperature of the measurement position and the displacement of the focus position do not correspond to each other on a one-to-one basis, whereby it is difficult to carry out high-accuracy anticipation of the displacement amount.
The present invention has been implemented in order to solve the conventional problem; the object of the present invention is to provide a radiation-image capturing condition correction apparatus and a radiation-image capturing condition correction method, which can readily realize high-accuracy correction for a radiation-source shift, and a radiation-image capturing apparatus utilizing that correction apparatus and that correction method.
The 1st aspect of the present invention is a radiation image capturing condition correction apparatus for use with a) an image-capturing unit which captures a radiation image of a predetermined imaging subject; and b) a radiation generating unit which generates radiation, said radiation image capturing condition correction apparatus comprising:
a measuring unit which measures an amount of physical displacement of said radiation generating unit; and
a position correction unit for generating a correction value which is used for correcting a position at which said image-capturing unit captures said radiation image.
The 2nd aspect of the present invention is the radiation image capturing condition correction apparatus according to the 1st aspect of the present invention, wherein, the position correction unit, based on the generated correction value, performs correction in such a way that the relative positional relationships, among the radiation generating unit, the predetermined imaging subject, and the image-capturing unit, which exist when the radiation generating unit is at the predetermined position is maintained.
The 3rd aspect of the present invention is the radiation image capturing condition correction apparatus according to the 2nd aspect of the present invention, wherein, as the correction, the position correction unit moves the radiation generating unit.
The 4th aspect of the present invention is the radiation image capturing condition correction apparatus according to the 2nd aspect of the present invention, wherein, as the correction, the position correction unit moves the imaging subject and the image-capturing unit.
The 5th aspect of the present invention is the radiation image capturing condition correction apparatus according to the 2nd aspect of the present invention, wherein, as the correction, the position correction unit moves each of the radiation generating unit, the imaging subject, and the image-capturing unit.
The 6th aspect of the present invention is the radiation image capturing condition correction apparatus according to the 2nd aspect of the present invention, wherein, as the correction, the position correction unit returns the radiation generating unit to the predetermined position.
The 7th aspect of the present invention is the radiation image capturing condition correction apparatus according to the 2nd aspect of the present invention, wherein the one direction is a direction along a line perpendicular to an image capturing plane for the radiation image and the position correction unit performs correction operation in the one direction.
The 8th aspect of the present invention is the radiation image capturing condition correction apparatus according to the 7th aspect of the present invention, wherein the physical displacement amount is measured in one direction or in two directions, which are perpendicular to each other, on the image capturing plane, and the position correction unit performs correction operation in the one direction or in the two directions.
The 9th aspect of the present invention is the radiation image capturing condition correction apparatus according to the 1st aspect of the present invention, wherein, as the radiation, any one of an X-ray, an α-ray, a β-ray, a γ-ray, and a heavy-ion ray is utilized.
The 10th aspect of the present invention is a radiation image capturing apparatus comprising:
a radiation generating unit which generates radiations;
an imaging subject arrangement unit on which a predetermined imaging subject is arranged;
an image-capturing unit having an image capturing plane on which a radiation image, which is image-captured by means of the radiations, of the imaging subject is formed; and
the radiation image capturing condition correction apparatus according to the 1st aspect of the present invention.
The 11th aspect of the present invention is a radiation image capturing condition correction apparatus comprising:
a measuring unit which, in capturing on an image-capturing unit a radiation image of a predetermined imaging subject, measures an amount of physical displacement, of a radiation generating unit which generates radiations, from a predetermined position in at least one direction; and
a data correction unit which corrects data on the radiation image, based on the physical displacement amount and the relative positional relationships, among the radiation generating unit, the imaging subject, and the image-capturing unit, at the moment when the radiation generating unit has been at the predetermined position.
The 12th aspect of the present invention is the radiation image capturing condition correction apparatus according to the 11th aspect of the present invention, wherein the data correction unit utilizes, as the data on the radiation image, a predetermined amount corresponding to the physical displacement amount and performs correction in which the position of a coordinate origin defined on a detection plane of the image-capturing unit is moved by the predetermined amount.
The 13th aspect of the present invention is the radiation image capturing condition correction apparatus according to the 11th aspect of the present invention, wherein the data correction unit utilizes, as the data on the radiation image, a predetermined amount corresponding to the physical displacement amount and performs correction in which a detection position of the imaging subject on a detection plane of the image-capturing unit is moved by the predetermined amount.
The 14th aspect of the present invention is the radiation image capturing condition correction apparatus according to the 11th aspect of the present invention, wherein the one direction is a direction along a line perpendicular to an image capturing plane for the radiation image and the data correction unit performs correction operation in the one direction.
The 15th aspect of the present invention is the radiation image capturing condition correction apparatus according to the 14th aspect of the present invention, wherein the physical displacement amount is measured in one direction or in two directions, which are perpendicular to each other, on the image capturing plane, and the data correction unit performs correction operation in the one direction or in the two directions.
The 16th aspect of the present invention is the radiation image capturing condition correction apparatus according to the 11th aspect of the present invention, wherein, as the radiation, any one of an X-ray, an α-ray, a β-ray, a γ-ray, and a heavy-ion ray is utilized.
The 17th aspect of the present invention is a radiation image capturing apparatus comprising:
a radiation generating unit which generates radiations;
an imaging subject arrangement unit on which a predetermined imaging subject is arranged;
an image-capturing unit having an image capturing plane on which a radiation image, which is image-captured by means of the radiations, of the imaging subject is formed; and
the radiation image capturing condition correction apparatus according to the 11th aspect of the present invention.
The 18th aspect of the present invention is a radiation image capturing condition correction method for use with a) an image-capturing unit which captures a radiation image of a predetermined imaging subject; and b) a radiation generating unit which generates radiation, said radiation image capturing condition correction apparatus, comprising:
measuring an amount of physical displacement of said radiation generating unit; and
generating a correction value which is used for correcting a position at which said image-capturing unit captures said radiation image.
The 19th aspect of the present invention is the radiation image capturing condition correction method according to the 18th aspect of the present invention, further comprising, performing correction, based on the generated correction value, in such a way that the relative positional relationships, among the radiation generating unit, the predetermined imaging subject, and the image-capturing unit, which exist when the radiation generating unit is at the predetermined position is maintained.
The 20th aspect of the present invention is the radiation image capturing condition correction method according to the 18th aspect of the present invention, wherein, as the radiation, any one of an X-ray, an α-ray, a β-ray, a γ-ray, and a heavy-ion ray is utilized.
The 21st aspect of the present invention is a radiation image capturing condition correction method comprising:
measuring an amount of physical displacement of a radiation generating unit which generates radiations, from a predetermined position in at least one direction, in capturing on an image-capturing unit a radiation image of a predetermined imaging subject; and
correcting data on the radiation image, based on the physical displacement amount and the relative positional relationships, among the radiation generating unit, the imaging subject, and the image-capturing unit, at the moment when the radiation generating unit has been at the predetermined position.
The 22nd aspect of the present invention is the radiation image capturing condition correction method according to the 21st aspect of the present invention, wherein, as the radiation, any one of an X-ray, an α-ray, a β-ray, a γ-ray, and a heavy-ion ray is utilized.
The 23rd aspect of the present invention is a computer-processable storage medium in which a program is stored, the program making a computer function as a data correction unit, of the radiation image capturing condition correction apparatus according to the 11th aspect of the present invention, that corrects data on the radiation image, based on the physical displacement amount and the relative positional relationships, among the radiation generating unit, the imaging subject, and the image-capturing unit, at the moment when the radiation generating unit has been at the predetermined position.
The present invention makes it possible that a radiation-image capturing condition correction apparatus and a radiation-image capturing condition correction method that can readily realize a high-accuracy radiation-source-shift correction are put into practice. Inconsequence, a high-magnification and high-resolution radiation image capturing apparatus with reduced aliasings and artifacts can be realized.
Embodiments of the present invention will be explained below with reference to the accompanying drawings.
In
The table moving mechanism 6 is a unit for moving the imaging subject 10 on a plane perpendicular to the line that connects the X-ray radiant unit 1 and the detector 3. The detector moving mechanism 7 is a unit for moving the detector 3 along the line that connects the X-ray radiant unit 1 and the detector 3 or on a plane perpendicular to that line. The basic operation is as follows. While the table 2 and the detector 3 are revolving around the cylindrical rotation center, of the X-ray radiant unit 1, as an axis, the detector 3 performs image capturing. The captured image is preprocessed in a preprocessing unit 4a and rerendered as a tomographic image in an image rerendering unit 4b. Accordingly, it is made possible to perform without rotating the imaging subject 10 slanted-direction image capturing, which is required for rerendering of a CT image.
In Embodiment 1, the laser displacement gauges 9a to 9c are utilized as units for measuring the displacement of the x-ray radiant unit 1. The laser displacement gauges 9a, 9b, and 9c are the units for measuring the displacement amounts, of the front end of the X-ray radiant unit 1, in the x, y, and z directions, respectively. The results of the displacement measurement through the laser displacement gauges 9a˜9c are inputted to a correction value computation unit 4c. After the correction value computation unit 4c performs computation of a correction value, the image capturing position for a transmission image is corrected, by correcting an instruction to the image-capturing controller 5, based on the correction value. In addition, the x direction signifies a direction parallel to the main plane of the detector 3; the y direction signifies a direction that is parallel to the main plane of the detector 3 and perpendicular to the x direction. The z direction signifies a direction perpendicular to the main plane of the detector 3; in
As illustrated in FIGS. 2(A) and 2(B), the X-ray radiant unit 1 has a case 101 that forms the approximately cylindrical outer contour thereof, a filament 102 that is situated inside the case 101 and generates electron beams, and a radiation-source body 103 that is situated at the canopy portion of the case 101 and functions as a plane with which an electron beam generated from the filament 102 collides and from which X-rays are generated. In addition, the case 101 is made of metal such as iron; the radiation-source body 103 is made of tungsten.
In the foregoing configuration, the X-ray radiant unit 1 corresponds to a radiation generating unit as termed in the present invention; the laser displacement gauges 9a to 9c correspond to measuring units as termed in the present invention. The correction value computation unit 4c, the image-capturing controller 5, the table moving mechanism 6, and the detector moving mechanism 7 correspond to position correction units as termed in the present invention and configure a radiation image capturing condition correction apparatus as termed in the present invention.
The X-ray CT image-capturing apparatus is an example of a radiation image capturing apparatus as termed in the present invention; the table 2 corresponds to an imaging subject arrangement unit as termed in the present invention; the detector 3 corresponds to an image-capturing unit as termed in the present invention.
The operation of an X-ray CT image capturing apparatus, having the foregoing configuration, according to Embodiment 1 of the present invention will be explained; through the explanation of the operation, an embodiment of a radiation image capturing condition correction method as termed in the present invention will be explained.
The principle of the present invention will be explained first. Radiation-source-shift correction through conventional technologies takes into account, as a cause of the radiation-source shift, the effects of heating of the filament 102, the case 101, and the like inside the X-ray radiant unit 1 illustrated in FIG. 2; however, the correction has a significant disadvantage that, due to each the structure having large volume of the case 101 and the radiation-source body 103, it is difficult to comprehend which portion of the X-ray radiant unit 1 shows temperature change that corresponds most to the radiation-source shift, whereby the anticipation of the direction and the extent of correction is difficult to perform actually.
In contrast, the present invention is characterized by focusing attention on the relationship between the change in the contour of the X-ray radiant unit 1 and the radiation-source shift, caused by the temperature change in the case 101 and the like, due to the lighting of the filament 102. In other words, due to the heating of the filament 102, case 101 and the radiation-source body 103 both of which are made of metal expand; because the electron-beam collision position P, inside the X-ray radiant unit 1, from which X-rays are generated are situated on the radiation-source body 103, the collision position P also shifts by the expansion amounts of the case 101 and the radiation-source body 103.
The arrangement of a radiation image formed on the image capturing plane of the detector 3, the X-ray radiant unit 1, the table 2, and the detector 3 is fixed; therefore, when a positional change in any portion is produced, it is possible to geometrically detect the positional change as a change in any one of the rest portions. Accordingly, as long as the table 2 and the detector 3 are fixed, it is conceivable that the radiation image detected by the detector 3 is shifted, this shift is occured as the shift of the X-ray radiation source.
Thus, by measuring an alternation of the physical contour or the placement of the outer contour of the X-ray radiant unit 1 (especially the vicinity of the radiation-source body 103 that actually generates) in each direction of X, Y and Z axis from the state when the measure starts, if the alternation (hereafter referred to as a “physical displacement amount”) is produced, the physical displacement amount is considered as the shift of the X-ray radiation source. And in accordance with the direction and the magnitude of the physical displacement amount, the positional relationships among the radiation source, the imaging subject, and the detector are corrected. The metal expansion in the vicinity of the radiation-source body 103 can be considered to be isotropic, compared to the temperature distribution.
Accordingly, accurate comprehension of the direction and the magnitude of a radiation-source shift is enabled, whereby high-accuracy radiation-source correction can be performed.
Embodiment 1 will be explained in detail below with reference to a flowchart in
Next, in Step S1, the x-direction displacement, of the front end of the X-ray radiant unit 1, with respect to the reference point is measured by the laser displacement gauge 9a. Next, in Step S2, the obtained displacement amount is stored as an x-direction correction value Δx. In Step S3, the y-direction displacement, of the front end of the X-ray radiant unit 1, with respect to the reference point is measured by the laser displacement gauge 9b. In Step S4, the obtained displacement amount is stored as a y-direction correction value Δy. Similarly, in Step S5, the z-direction displacement, of the front end of the X-ray radiant unit 1, with respect to the reference point is measured by the laser displacement gauge 9c. In Step S6, the obtained displacement amount is stored as a z-direction correction value Δz.
Next, in Step S7, by, through the image-capturing controller 5, utilizing the table moving mechanism 6 and the detector moving mechanism 7, the table 2 and the detector 3 are moved to the positions, which are obtained through computation, corresponding to the respective positions of the table 2 and the detector 3 at the moment when the front end of the X-ray radiant unit 1 was situated at the reference point. In this situation, it is assumed that a correction value computed by the correction value computation unit 4c, based on the stored correction values Δx, Δy, and Δz, is a predetermined amount to be required to move the table 2 and the detector 3.
Accordingly, the movement, in accordance with the correction values, of the able 2 and the detector 3 returns the relative positional relationships among the radiation source inside the X-ray radiant unit 1, the table 2, and the detector 3 in the image capturing apparatus to the relative positional relationships among the respective elements at the moment when the front end of the X-ray radiant unit 1 was situated at the reference point. In this regard, however, the arrangement positions of the table 2 and the detector 3 in the X-ray CT image-capturing apparatus are changed.
In Step S8, by, through the image-capturing controller 5, controlling the X-ray radiant unit 1 and the detector 3, a transmission image is captured and stored.
The Step S8 is repeatedly performed for a certain number of images necessary for image rerendering. Additionally, in Step S9, after being processed by the preprocessing unit 4a, the stored image is converted by the image rerendering unit 4b into a tomographic image; in Step S10, the resultant image is stored and, in Step S11, outputted to the image display apparatus 8.
As discussed heretofore, according to Embodiment 1, by measuring the physical displacement amount of the front end of the X-ray radiant unit 1, the change in the radiation-source position can accurately be anticipated and corrected. Accordingly, by preliminarily removing the effect of the radiation-source position that changes with time, a clear and high-resolution tomographic image can be obtained that has no blur such as an aliasing or an artifact.
In addition, in Embodiment 1, a tomography is realized by a method in which the imaging subject 10 is not rotated; however, the X-ray CT image-capturing apparatus may be configured in such a way that a tomography is realized by a method in which the imaging subject 10 is rotated. Moreover, as a unit which measures the physical displacement amount of the front end of the X-ray radiant unit 1, the laser displacement gauges 9a to 9c are utilized; however, the measuring unit of the present invention is not limited thereto; for example, contact-type displacement gauges may be utilized.
Still moreover, in the foregoing explanation, correction is performed, by, through the table moving mechanism 6 and the detector moving mechanism 7, moving by a predetermined amount the table 2 and the detector 3; however, as illustrated in
Furthermore, the X-ray CT image-capturing apparatus according to the present invention may be configured in such a way that the table moving mechanism 6, the detector moving mechanism 7, and the X-ray radiant unit moving mechanism 11 are all provided, and correction is performed by moving the table 2 and the detector 3 by a predetermined amount and, in response to the movement, returning the X-ray radiant unit 1 by the amount corresponding to the traveling amount of the table 2 and the detector 3. In this case, the relative positional relationships among the respective portions inside the X-ray CT image-capturing apparatus differ from the original ones; however, in the image capturing apparatus at the moment after correction has been performed, the relative positional relationships among the radiation source inside the X-ray radiant unit 1, the table 2, and the detector 3 coincide with the relative positional relationships among the foregoing elements at the moment when the front end of the X-ray radiant unit 1 was situated at the reference point. The foregoing configuration is effective in the case where the respective traveling ranges of the table moving mechanism 6, the detector moving mechanism 7, and the X-ray radiant unit moving mechanism 11 are restricted.
In summary, the present invention has only to be configured in such a way that the condition in which the X-ray radiant unit 1 is situated at a predetermined position where a user consider that correction through radiation-source shift is not required is assumed to be the reference condition, and the X-ray radiant unit 1, the imaging subject 10 placed on the table 2, and the detector 3 move so that the relative relationships, under the reference condition, among the respective elements can be maintained, whereby correction is performed. Thus, the present invention is not limited by an actual moving procedure or moving subjects. In addition, the method of determining the predetermined position may arbitrarily be specified by a user, in accordance with the utilization condition of the apparatus.
Embodiment 2 will be explained below with reference to a flowchart in
Next, in Step S17, the image rerendering unit 4d obtains correction values Δx, Δy, and Δz from the correction value computation unit 4c and based on the correction values, computes to correct positions of the coordinate origin that is supposed to be located on the detection plane of the detector 3. Specifically, the computation is performed as follows.
As illustrated in
In contrast, in Step S17, by shifting the coordinate origin O by adding Δx, Δy, and Δz as predetermined amounts, the whole coordinate system is shifted on the detection plane 30. As a result, as illustrated in
Next, when, in Step S8, by, through the image-capturing controller 5, controlling the X-ray radiant unit 1 and the detector 3, a transmission image is captured, the transmission image is formed at a corrected coordinate position on the detector 3; therefore, a captured image can be obtained that is located at the same coordinates as those of the image to be captured under the initial condition.
In addition, processing may be implemented in which the correction in Step S17 is omitted, and instead of shifting the coordinate origin O, Δx, Δy, and Δz are subtracted as predetermined amounts, as illustrated in
As discussed heretofore, according to Embodiment 2, by measuring the physical displacement amount of the front end of the X-ray radiant unit 1, and utilizing the obtained physical displacement amount and the positional relationships, under the initial condition, among the X-ray radiant unit 1, the table 2, and the detector 3, a radiation-source shift represented as data can be corrected before or after image capturing by the detector 3. Accordingly, by accurately anticipating change in the radiation-source position, a clear and high-resolution tomographic image can be obtained that has no blur such as an aliasing or an artifact. Moreover, the correction can be performed by means of software; therefore, Embodiment 2 has an advantage in that, by omitting the operation and the processing of moving the table and the detector only for the purpose of correction, the operation of the apparatus can be simplified.
In FIGS. 7(A) to 7(D), an x-y coordinate system is utilized as a coordinate system 31 for simplicity; however, in the case where z-direction correction is involved, the radiation-source shift and the effect of correction, as described later, appear as dimensional changes in an image at the detection position 32.
In the foregoing configuration, an X-ray CT apparatus that generates a 3-dimensional image has been utilized as an example, and it has been explained that, in order to obtain 3-dimensional coordinates, correction is performed in the x-, y-, and z-directions; however, in a correction apparatus and a correction method according to the present invention, it is not necessarily required to perform correction in all the three directions; thus, correction may be performed only in any one or two of the three directions.
For example, in the case where a configuration is employed in which only a z-direction physical displacement amount is detected and corrected, the configuration has the following advantage. In other words, generally, the foregoing radiation-source shift in a direction along the line that connects the X-ray source with the detector causes a blur or the like of the imaging-subject outline in a tomographic image and considerably affects the magnification ratio for a radiation image to be image-captured, in particular; however, all the exemplified conventional radiation-source correction methods are each to disclose only the position correction on a plane the normal to which is the line that connects the radiation-source with the detector, and there has not been any method to cope with the radiation-source shift in a direction along the line that connects the X-ray source with the detector. According to the present invention, by performing correction in the z-direction as the projection of the radiation-source shift in a direction along the line that connects the X-ray source with the detector, an appropriate focal position in accordance with the magnification ratio for an image to be image-captured can be ensured.
In particular, in the case where, as in foregoing embodiments, the positional relationships of the X-ray radiant unit 1, the imaging subject 10 placed on the table 2, and the detector 3 are not in coaxial (the cylindrical rotation axel of the X-ray radiant unit 1) relationships with one another, as illustrated in
In the case where the X-ray radiant unit 1, an imaging subject placed on the table 2, and the detector 3 are arranged in such a way as to image-capture the imaging subject fixed coaxially with the rotation axel, correction may be performed only along the x-direction and the y-direction.
Additionally, in the foregoing configuration, the relative positional relationships among the X-ray radiant unit 1, the table 2, and the detector 3 are utilized for performing correction; the positional relationships are ensured by the assumption that the electron-beam collision position P inside the X-ray radiant unit 1 is constant (the change in the contour of the X-ray radiant unit 1 corresponds to the change in the collision position P, on a one-to-one basis), the detection plane is fixed on the detector 3, and the imaging subject 10 is placed on the table 2, while the shape thereof is kept constant. Among the relationships, the artificial manipulation during correction and image capturing affects the relationship between the table 2 and the imaging subject; therefore, it is desirable to place the imaging subject on the table 2 in such a way as not to be deformed and displaced, under the initial condition, during correction, and during image capturing.
After the physical displacement amount of the X-ray radiant unit 1 is detected, a configuration is employed in which, as described in Embodiment 1, a position correction unit is provided that moves the X-ray radiant unit 1, that moves the table 2 and the detector 3, or that moves the X-ray radiant unit 1, the table 2, and the detector 3 so that the relative positional relationships among the X-ray radiant unit 1, the table 2, and the detector 3 can maintain the reference condition; or a configuration is employed in which, as described in Embodiment 2, a data correction unit is provided that performs correction through software, prior to or during image capturing by the detector 3; however, a configuration may be employed in which both the position correction unit and the data correction unit are provided. In this case, by, based on the physical displacement amount, distributing and allocating correction values to the position correction unit and the data correction unit, thereby making the both correction units operate, it is made possible that, even though a radiation-source shift is produced, an X-ray image is obtained that is rendered on the same coordinates as those of the image obtained by being image-captured under the initial condition.
In the case where, for example, a large radiation-source shift is produced that makes it impossible that, only by mechanical movement of the X-ray radiant unit 1, the table 2, and the detector 3 through the position correction unit, the relative positional relationships in a condition under which no correction is required is maintained, the configuration having the position correction unit and the data correction unit can be utilized with correction through software as a supplementary means, software; therefore, that configuration is effective when there is restriction on the shape and the size of a radiation image capturing apparatus and the like.
In addition, in the foregoing embodiments, it has been explained that the radiation image capturing condition correction apparatus according to the present invention is incorporated in an X-ray CT apparatus as an example of a radiation image capturing apparatus; however, the correction apparatus can be utilized not only in the image capturing apparatuses illustrated in
Still moreover, a radiation image capturing condition correction apparatus according to the present invention may not preliminarily be integrated with a radiation image capturing apparatus, but may be utilized as a separated apparatus, in combination with an existing radiation image capturing apparatus. In particular, the correction apparatus according to Embodiment 2 performs correction through software; therefore, it has an advantage in weight saving and universality.
Additionally, a program according to the present invention makes a computer perform functions of all or part of the units (or devices, elements, circuits, units, and the like) of the foregoing radiation image capturing condition correction apparatus according to the present invention; the program may operate in collaboration with a computer.
Additionally, the present invention provides a medium that carries a program for making a computer perform functions of all or part of the units of the foregoing radiation image capturing condition correction apparatus according to the present invention; a medium may be employed that can be read by a computer and the program read out of which by the computer performs the foregoing functions in collaboration with the computer.
In addition, the foregoing term “part of the units” according to the present invention signifies some units among the units or part of the functions of a single unit.
Additionally, a storage medium in which a program according to the present invention is stored and that can be read by a computer is included in the present invention.
Moreover, one of the utilization forms for a program according to the present invention may be a mode in which a program is stored in a storage medium that can be read by a computer and the program operates in collaboration with the computer.
Still moreover, one of the utilization forms for a program according to the present invention may be a mode in which a program is transmitted through a transmission medium, read by a computer, and operates in collaboration with the computer.
The storage medium also includes a ROM.
The foregoing computer according to the present invention is not limited to a computer that includes a pure hardware such as a CPU, but may be a computer that includes firmware, an OS, or a peripheral device.
As explained heretofore, a configuration according to the present invention may be realized through software or through hardware.
The present invention demonstrates an effect with which, in capturing a radiation image, high-accuracy correction for a radiation-source shift is readily realized, whereby the present invention is useful for a radiation image capturing condition correction apparatus and the like; for example, in capturing a radiation image, the present invention enables a high-magnification and high-resolution tomographic image with reduced aliasings and artifacts to be obtained, whereby the present invention can be applied to an X-ray CT apparatus, a tomography apparatus, and the like.
| Number | Date | Country | Kind |
|---|---|---|---|
| JP 2005-334805 | Nov 2005 | JP | national |
