X-ray or gamma ray systems or devices – Specific application – Dental panoramic
Patent
1997-02-07
1998-10-27
Wong, Don
X-ray or gamma ray systems or devices
Specific application
Dental panoramic
378 39, 378 40, A61B 614
Patent
active
058287213
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention is directed to a radiation diagnostic installation for producing panorama tomograms, of the type having means for tomographically scanning a subject with radiation and for generating electrical signals dependent on the radiation shadow of the subject, and having signal processing means including a memory for storing the electrical signals during the tomographic scanning and a computer for calculating signals corresponding to a tomogram of the subject in a desired slice position. The present invention is also directed to a method for producing panorama tomograms.
DESCRIPTION OF THE PRIOR ART
A radiation diagnostic installation of the above type is disclosed in German OS 41 33 066, corresponding to U.S. Pat. No. 5,195,114. This known installation has a swivel unit at which an X-ray source and an X-ray image detector are arranged lying opposite one another. The X-ray image detector acquires the X-rays that have penetrated through an exposure subject arranged between the X-ray source and the X-ray image detector. While the X-ray source and the X-ray image detector are rotated around the exposure subject, the image data received from the X-ray image detector are supplied to an image memory that sequentially stores the received image data as individual images. For producing a panorama image, an image processing means is provided that reads individual images from the image memory at predeterminable derivation intervals, shifts these by a selectable shift amount and adds the derived and the shifted individual images. The position of the tomographic image layer of a panorama image produced in this way is dependent on the interval for the derivation of the image information from the image store arrangement as well as on the amount of the shift of the image information at the point in time of the addition. A further panorama image in a further tomographic image slice can be calculated by selecting a different derivation interval and a different shift amount. In order to eliminate influences superimposed on the first panorama image that, for example, arise from an object that lies in a tomographic image slice differing from the desired tomographic image slice, it is known to calculate a second panorama image in a second image slice. The second panorama image is converted into a projected panorama image that is generated by projecting the second panorama image onto the predetermined tomographic image slice. This projected panorama image is subtracted from the first panorama image in order to obtain a panorama image that is free of these undesired effects. A clear and definite panorama image can thus be produced in the defined tomographic image slice.
Since it is not assumed that the desired image slice is directly found by entering the derivation interval and the shift amount relevant thereto, a manual approximation method is implemented by selecting different derivation intervals and shift amounts until a panorama image is calculated in a desired image slice. This manually implemented approximation method is very time-consuming. Moreover, the time required for the calculation of the panorama images is great in this approximation method. By viewing the calculated panorama images, the personnel must identify the desired image slice themselves.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a radiation diagnostic installation and method wherein the time required for the determination of the desired slice position for a panorama image to be calculated is slight.
In a radiation diagnostics installation of the type initially described, this object is inventively achieved in a method and installation wherein the desired slice position is calculated in a computerized manner from the calculation of individual slice positions and their evaluation.
An advantage of the invention is that the derivation intervals and the shift amounts no longer need be manually entered, and instead the computer determines the desired, diagnostically ideal slice position of a
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"Matching of Tomographic Slices for Interpolation," Goshtasby et al., IEEE Trans. on Med. Imaging, vol. 11, No. 4, Dec. 1992, pp. 507-516.
Plotz Josef
Schulze-Ganzlin Ulrich
Sirona Dental Systems GmbH & Co. KG
Wong Don
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