X-ray or gamma ray systems or devices – Specific application – Computerized tomography
Reexamination Certificate
2000-03-02
2001-06-05
Kim, Robert H. (Department: 2882)
X-ray or gamma ray systems or devices
Specific application
Computerized tomography
C378S015000
Reexamination Certificate
active
06243436
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed to a CT (computed tomography) device of the type for imaging slices that are inclined toward the system axis with a measuring unit having a detector system and an X-ray source that is displaceable around a system axis for scanning an examination subject, whereby the examination subject and the measuring unit can be adjusted relative to one another in the direction of the system axis for scanning a volume of the examination subject.
2. Description of the Prior Art
CT devices of this general type are known wherein the measuring unit is tilted relative to the system axis for imaging slices that are inclined toward the system axis.
A disadvantage of such known devices is the considerable technical outlay that is associated with the realization of a measuring unit that can be tilted.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a CT device of the type described above wherein the imaging of slices inclined toward the system axis is possible with reduced technical outlay.
According to the invention, this object is achieved in a CT device for imaging slices inclined toward the system axis with a measuring unit having a detector system and a radiation source that is displaceable around a system axis for scanning an examination subject, whereby the examination subject and the measuring unit are adjustable relative to one another in the direction of the system axis for scanning a volume of the examination subject, and having an input means for entering the position of at least one slice, which is to be imaged and which is inclined toward the system axis. The input unit cooperates with a control unit of the CT device such that the control unit adjusts the measuring unit in the direction of the system axis for scanning a volume of the examination subject so that the slice, which is to be imaged and which is inclined toward the system axis, is completely contained in the scanned volume. An electronic computer initially constructs planar tomograms from the data acquired during the scanning of the volume and constructs the tomogram of a slice, which is to be imaged and which is inclined toward the system axis, by multi-planar reconstruction from the planar tomograms.
In the inventive CT device, a mechanical tilting of the measuring unit is therefore not necessary for imaging slices that are inclined toward the system axis. Rather, the display of such inclined slices is digitally enabled by means of software by scanning the volume of the examination subject, which contains the slice to be imaged and which slice is inclined toward the system axis, and obtaining the tomogram of the desired slice that is inclined toward the system axis, by the known method of multi-planar reconstruction, from the tomograms of slices of the scanned volume that reside in planes at a right angle to the system axis and that have been reconstructed on the basis of the acquired data. Thus, the size of the scanned volume does not significantly exceed the size required for the acquisition of the slice that is to be imaged and that is inclined toward the system axis.
Not only is the mechanical outlay considerably reduced by avoiding the mechanical tilting of the measuring unit, since all mechanical components, which enable the tilting of the measuring unit, are avoided, but also a considerable facilitation of the control unit is also possible, since, for example safety checks regarding the danger of squeezing to the examination subject when tilting the gantry, can be reduced. The financial advantages that are achieved by the inventive structure are not only of importance for medical applications but also for industrial applications.
Further, the inventive CT device occupies less space, so that mobile use, for example on a motorized cart, is facilitated. Since the selection of the slice that is to be imaged and that is inclined toward the system axis ensues by means of software, a gain in time is also achieved when examinations are conducted, since the time required for the tilting of the measuring unit, which only ensues with low angular velocity, is saved.
Another advantage is that the diameter of the measuring opening of the measuring unit, through which the examination subject extends when an examination is conducted, does not represent a limitation for the maximum inclination that slices to be imagined can exhibit. Rather, it must only be observed that the diameter of the measuring opening is no larger than this necessary in order to be able to place an examination subject of a fixed maximal size in the measuring opening. This advantage is particularly beneficial with respect to corpulent patients. Besides, the examination subject or the support bed carrying the examination subject can be lowered in the measuring opening without any danger, so that there is no danger of collision as in the case of a mechanically tilted measuring unit. This is particularly beneficial with respect to the therapy planning.
When the tilting of the measuring unit is foregone, a support bed that is provided for the examination subject can be rigidly combined with the measuring unit, so that the outlay, which is required for the stabilization of the position of the center plane of the measuring system relative to the bed, is drastically reduced. Corresponding software modules can be omitted in the control unit, for example. Further, the outlay of testing that is required with respect to the initial operation and maintenance of the CT device is also reduced when a mechanical tilting of the measuring unit is foregone.
The inventive CT device thus enables significant cost savings.
In a version of the invention the CT device displays the tomogram of the slice to be imaged and which is inclined toward the system axis on a monitor, without prior display of the planar tomograms, and this display forms the basis for the acquisition of this inclined tomogram,.
In a preferred version of the invention, the input unit are allows entry of a spatial area that contains a number of slices that are inclined toward the system axis, so that it is possible to examine volumes that are inclined toward the system axis.
Also in a preferred embodiment, the input unit includes a display unit for displaying an X-ray shadow image (referred to as a topogram or “scout view”), which is picked up with the CT device and which is stored in the CT device, and a marking arrangement by means of which a spatial area, which contains at least one slice that is to be imaged and that is inclined toward the system axis or which contains a number of slices that are to be imaged and that are inclined toward the system axis, can be marked in the X-ray shadow image. It is thus assured that, in fact, the volume that is required imaging the slice(s) inclined toward the system axis is scanned, so that it is highly unlikely that examinations must be repeated or that the desired slice will be incompletely imaged.
In order to assure that, in fact, only the volume that is required for imaging a spatial area, which contains a slice or slices inclined toward the system axis, is scanned in so as to avoid unnecessary radiation loads, in an embodiment of the invention the computer determines an initial position and an end position on the basis of the entered position of the aforementioned spatial area. Between the initial position and the end position, the control unit adjusts the measuring unit in the direction of the system axis for scanning this spatial area.
If the slice, which is to be imaged and which is inclined toward the system axis, fills only one section of the image format of the display format on the monitor, in an embodiment of the invention the computer causes the tomogram to be displayed on the monitor in a format-filling manner, so that the full format of the monitor can be utilized, even when only details are to be imaged.
REFERENCES:
patent: 4246484 (1981-01-01), Fetter
patent: 5247556 (1993-09-01), Eckert et al.
patent: 5430783 (1995-07-01), Hu et al.
patent: 54
Hahn Guenter
Hupke Rolf
Kiknadze Irakli
Kim Robert H.
Siemens Aktiengeseuschaft
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