X-ray or gamma ray systems or devices – Specific application – Computerized tomography
Reexamination Certificate
1998-05-22
2001-01-09
Porta, David P. (Department: 2876)
X-ray or gamma ray systems or devices
Specific application
Computerized tomography
C378S010000, C378S019000, C378S146000
Reexamination Certificate
active
06173033
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed to an X-ray computer tomography apparatus of the type which is capable of producing an X-ray shadowgraph, in addition to a computed tomogram.
2. Description of the Prior Art
X-ray computed tomography apparatuses are known in which the X-ray source emits a fan-shaped X-ray beam that strikes a detector row constructed from a series of detector elements. For the production of computed tomograms, the measurement arrangement of the X-ray source and the detector rows is rotated around a system axis. From the detector output signals, produced in various projections, a computer calculates an image of the transirradiated region of the patient.
For the production of overview exposures, namely X-ray shadowgraphs, it is known from U.S. Pat. No. 4,477,922 to lock the measurement arrangement against rotation in such a computed tomography apparatus, and to carry out a relative movement between the measurement arrangement and the patient table, or at least the slab of the table, in the direction of the system axis, e.g. by displacing the patient table (or slab). The path of movement of the patient table thereby corresponds essentially to the length of the X-ray shadowgraph. Depending on the integration time of the data acquisition system, the data of a number of projections can be combined to form a line of the X-ray shadowgraph. In conventional systems, the resolution in the X-ray shadowgraph in the direction of the system axis is determined essentially by the slice collimation used for the exposure.
For the representation of the shadowgraph, the data recorded with the data acquisition system are A/D converted and transferred to a central processor. In the central processor, a normalization of the data dependent on the measurement system is conducted, the measured radiation intensities are converted to attenuation values and a sliding combination, dependent on the speed of the movement of the measurement system relative to the patient, of the projections (measured at fixed time intervals) of attenuation values is undertaken to form equidistant image lines of the shadowgraph. In a further step, the shadowgraph (obtained in a cylindrical projection) is reformated into a flat image, with pixels that are likewise equidistant in the transverse direction. A two-dimensional development of the shadowgraph, for increasing the image contrast, with simultaneous contour enhancement. follows the construction of the image. The two-dimensional filtering can take place either in a separate calculation step or on-line. corresponding to U.S. Pat. No. 5,315,628, i.e. in parallel with the data acquisition.
It is also known to expose an X-ray shadowgraph using a matrix detector, as described in U.S. Pat. No. 4,352,986, which is constructed from a series of parallel detector rows. If the matrix detector covers the entire region of examination, a relative motion between the measurement arrangement and the patient table can be avoided.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an X-ray computed tomography apparatus with a matrix detector or multirow detector wherein, besides the production of tomograms, X-ray shadowgraphs can alternatively be produced using a row of detectors or using several detector rows.
Typically, “several detector rows” designates any arrangement having a number of detector rows greater than one. The arrangement thus includes a matrix detector (array detector). The region of examination of the patient can be equal to or greater than the surface covered by the detector system.
This object is achieved according to the invention in an X-ray computed tomography apparatus having a diaphragm arrangement with a diaphragm near the tube and a diaphragm near the detector, so that, alternatively, one detector row or several detector rows can be selected from the matrix detector for use in detecting radiation, depending on whether a tomogram (one row) or a shadowgraph (multiple rows) is to be produced.
If more than one row is selected during the data acquisition, and the patient is simultaneously moved relative to the measurement system, the patient is scanned several times in chronologically displaced fashion, in a manner corresponding to the number of detector rows used. The projection data recorded with the various detector rows are summed in the central processor in a manner corresponding to the associated local position. The simultaneous data acquisition via several detector rows enables, among other things, a more rapid exposure of the X-ray shadowgraph. The blurring of the image caused by this type of acquisition can be compensated by means of a deblurring filter. In the inventive X-ray computed tomography apparatus, the computer unit is thus constructed so that a sharp imaging of the shadowgraph of the patient results, even given multiple scanning.
Given a more suitable adjustment of the diaphragms, and corresponding processing of the measurement data, the multirow detector or matrix detector can be used for the simultaneous correction of scatter radiation, and thus for further increasing the image quality.
REFERENCES:
patent: 4160167 (1979-07-01), Weiss et al.
patent: 4176280 (1979-11-01), Greschat et al.
patent: 4187430 (1980-02-01), Schmidt
patent: 4193001 (1980-03-01), Liebetruth
patent: 4324978 (1982-04-01), Kalender et al.
patent: 4352986 (1982-10-01), Pfeiler
patent: 4477922 (1984-10-01), Liebetruth
patent: 4995107 (1991-02-01), Klingenbeck
patent: 5291402 (1994-03-01), Pfoh
patent: 5315628 (1994-05-01), Guendel
patent: 5373543 (1994-12-01), Ackermann et al.
patent: 5377250 (1994-12-01), Hu
patent: 5386446 (1995-01-01), Fujimoto et al.
patent: 5430783 (1995-07-01), Hu et al.
patent: 5430784 (1995-07-01), Ribner et al.
patent: 5583903 (1996-12-01), Saito et al.
patent: 5592523 (1997-01-01), Tuy et al.
patent: 5684855 (1997-11-01), Aradate et al.
Dehner Guenter
Klingenbeck-Regn Klaus
Hill & Simpson
Ho Allen C.
Porta David P.
Siemens Aktiengesellschaft
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