The invention relates to a method for cephalometric imaging using an apparatus (1) which comprises an x-ray source (5), a line detector camera (8) equipped with a digital detector, which line detector camera is located to a position far away from the x-ray source (5) for carrying out cephalometric imaging while the slot of the line detector camera is substantially vertical. In cephalometric imaging, an x-ray beam (11) located substantially on the vertical plane is directed from the x-ray source (5) through the object being imaged, and the x-ray source (5) is at the same time turned about the rotation center (13) located between the x-ray source and the line detector camera (8) in order to scan the object being imaged in the horizontal direction, whereby the line detector camera (8) is moved during the scanning movement in such a way that the ray beam (11) meets the slot (14) of the line detector camera. In the method, the effective focal spot is transferred from the rotation center (13) to the focal spot of the x-ray source (5) by transferring the rotation center by means of a transverse linear movement (A) with respect to the ray beam (11).
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3. An apparatus for providing a tomographic cephalometric image comprising:
a radiation receiver;
a panoramic imaging x-ray source providing radiation along a generally horizontally extending radiation path for application to said radiation receiver;
a support for said x-ray source, said support having a vertical rotation center for rotating said x-ray source, said rotation center being positioned intermediate said radiation receiver and said x-ray source and closer to said x-ray source than to said radiation receiver;
means for rotating said x-ray source about said rotation center while otherwise maintaining the x-ray source generally stationary;
means for generally horizontally translating said rotation center in a direction generally transverse to the radiation path;
wherein the effective focal spot of the x-ray source is transferred to the general location of the x-ray source; and
means for translating said radiation receiver in a horizontal direction generally transverse to the radiation path during application of the radiation to said radiation receiver,
the motions provided to said radiation x-ray source, rotation center, and radiation receiver by the respective means producing a tomographic cephalometric image from a subject positioned in front of said radiation receiver for which the effective focal length of the x-ray source has been altered in a manner to reduce differences in the vertical and horizontal ratios of enlargement.
0. 6. A method for operating imaging apparatus to provide improved cephalometric images having reduced differences in vertical and horizontal ratios of enlargement, the method comprising the steps of:
providing an imaging apparatus comprising an x-ray source configured to apply radiation to a radiation receiver spaced apart from the x-ray source by a first distance in a lateral direction and to a radiation receiver spaced apart from the x-ray source by a second distance in the lateral direction, the second distance being greater than the first distance;
the imaging apparatus being capable of operating in a mode in which the x-ray source and the radiation receiver spaced apart from the x-ray source by the first distance are rotated about an intermediate rotation center to provide an image of an object positioned between the x-ray source and the radiation receiver spaced apart from the x-ray source by the first distance;
placing a subject for cephalometric imaging between the x-ray source and the radiation receiver spaced apart from the x-ray source by the second distance; and
taking a cephalometric image of the subject by applying radiation from the x-ray source to the radiation receiver spaced apart from the x-ray source by the second distance and simultaneously translating said rotation center in a direction generally transverse to the lateral direction so as to transfer the effective focal spot of the x-ray source towards the x-ray source in the lateral direction;
wherein the x-ray source remains substantially stationary and the effective focal spot of the x-ray source is transferred to the general location of the x-ray source.
1. A method for operating a panoramic imaging apparatus to provide improved tomographic cephalometric images, the panoramic imaging apparatus being capable of operating in a mode in which an x-ray source and radiation sensor, spaced from said radiation x-ray source at a first distance, are rotated about an intermediate vertical rotation center to provide a panoramic image from a subject positioned between the x-ray source and the radiation sensor, said method comprising the steps of:
positioning a radiation receiver to receive radiation from said x-ray source, said radiation receiver being located at a second distance from said x-ray source greater than said first distance;
placing a subject for cephalometric imaging in front of the radiation receiver;
projecting radiation from the x-ray source along a horizontal radiation path to apply radiation from the x-ray source to the radiation receiver;
carrying out a first motion comprising rotating the x-ray source about the center of rotation while otherwise maintaining the x-ray source generally stationary;
carrying out a second motion comprising horizontally translating the center of rotation in a direction generally transverse to the radiation path during application of the radiation to the radiation receiver;
wherein the effective focal spot of the x-ray source is transferred to the general location of the x-ray source; and
carrying out a third motion comprising translating the radiation receiver in a horizontal direction generally transverse to the radiation path, said first, second, and third motions producing a tomographic cephalometric image from the panoramic imaging apparatus for which the effective focal point for the x-ray source has been altered in a manner to reduce differences in vertical and horizontal ratios of enlargement.
0. 13. A method for operating an imaging apparatus to provide improved cephalometric images having reduced differences in vertical and horizontal ratios of enlargement, the method comprising the steps of:
providing an imaging apparatus extending in three dimensions, including a length dimension, a width dimension that is generally perpendicular to the length dimension, and a height dimension that is generally perpendicular to the length dimension and generally perpendicular to the width dimension;
wherein the imaging apparatus comprises an x-ray source configured to apply radiation in the length dimension to a radiation receiver spaced apart from the x-ray source by a first distance in the length dimension and to a radiation receiver spaced apart from the x-ray source by a second distance in the length dimension, the second distance being greater than the first distance;
the imaging apparatus being capable of operating in a mode in which the x-ray source and the radiation receiver spaced apart from the x-ray source by the first distance are rotated about an intermediate rotation center to provide an image of an object positioned between the x-ray source and the radiation receiver spaced apart from the x-ray source by the first distance;
placing a subject for cephalometric imaging between the x-ray source and the radiation receiver spaced apart from the x-ray source by the second distance; and
taking a cephalometric image of the subject by applying radiation from the x-ray source to the radiation receiver spaced apart from the x-ray source by the second distance and simultaneously translating said rotation center generally in the width dimension so as to transfer the effective focal spot of the x-ray source towards the x-ray source in the length dimension;
wherein the x-ray source remains substantially stationary and the effective focal spot of the x-ray source is transferred to the general location of the x-ray source.
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The present application is a continuation application of U.S. patent application Ser. No. 10/204,104, filed Oct. 10, 2002, now U.S. Pat. No. 6,731,717.That application is the U.S. national stage application of International Application PCT/FI01/00137, filed Feb. 14, 2001, which application was published on Aug. 23, 2001 as International Publication WO 01/60257. The International Application claims the priority of Finnish Patent Application 20000369, filed Feb. 18, 2000.
The present application is a reissue application of U.S. patent application Ser. No. 10/795,638, filed Mar. 8, 2004, now U.S. Pat. No. 6,891,921. That application is a continuation of application Ser. No. 10/204,104, filed as Application No. PCT/FI01/00137 on Feb. 14, 2001, now U.S. Pat. No. 6,731,717. The International Application claims the priority of Finnish Patent Application 20000369, filed Feb. 18, 2000.
The present invention relates to a method for cephalometric imaging using an apparatus which comprises an X-ray source, a line detector camera equipped with a digital detector, which line detector camera is located to a position far away from the X-ray source for carrying out cephalometric imaging while the slot of the line detector camera is substantially vertical, whereby in cephalometric imaging, an X-ray beam located substantially on the vertical plane is directed from the X-ray source through the object being imaged, and the X-ray source is at the same time turned about the rotation centre located between the X-ray source and the line detector camera in order to scan the object being imaging in the horizontal direction, whereby the line detector camera is moved during the scanning movement in such a way that the ray beam meets the slot of the line detector camera. The publication U.S. Pat. No. 5,511,106 discloses this type of scanning method for cephalometric imaging.
When cephalometric imaging is carried out in the manner described above, the vertical ratio of enlargement remains the same as without the scanning movement, but the horizontal ratio of enlargement, on the other hand, changes because the rotation centre changes into the effective focal spot instead of the focal spot of the X-ray source. Accordingly, the object of the present invention is to provide a method by means of which the ratios of enlargement in cephalometric imaging can be maintained the same in the vertical and horizontal directions in cephalometric imaging, which is carried out by means of the turning movement taking place about the rotation centre of the X-ray source. A further object is to provide a method which can be implemented by using existing panoramic X-ray imaging apparatuses, which already comprise the means needed to perform the required movements. To achieve this object, the method relating to the invention is characterised in that in the method, the effective focal spot is transferred from the rotation centre to the focal spot of the X-ray source by transferring the rotation centre by means of a transverse linear movement with respect to the ray beam.
The invention is described in greater detail in the following, with reference to the accompanying drawings, in which:
The apparatus 1 according to
To the support part 2 is connected a supporting arm 3, at the other end of which is the cephalometric imaging apparatus 10, which comprises a line detector camera 8 to be placed behind the object being imaged, and a secondary collimator 9 to be placed in front of the object being imaged. In cephalometric imaging, the patient's head is scanned by means of the ray beam 11 from right to left or vice versa.
In the method according to the invention, cephalometric imaging is carried out by turning the X-ray source 5 about a rotation centre 13 to image the patient's head 12 by means of a vertically positioned ray beam 11.
It is for this reason that, according to the invention, in cephalometric imaging the rotation centre 13 is arranged to be transferred by linear movement transversely with respect to the ray beam 11, as shown by reference marking A in FIG. 1.
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