X-ray or gamma ray systems or devices – Beam control – Filter
Reexamination Certificate
1999-11-16
2001-06-26
Kim, Robert H. (Department: 2882)
X-ray or gamma ray systems or devices
Beam control
Filter
C378S158000, C378S157000
Reexamination Certificate
active
06252939
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to an X-ray examination apparatus which includes
an X-ray source,
an X-ray detector,
an X-ray filter which includes a plurality of filter elements and is arranged between the X-ray source and the X-ray detector,
an electric voltage source and a control system for selectively applying electric voltages to individual filter elements,
which control system includes voltage lines, and
the filter elements being connected to the electric voltage source by way of voltage lines, and
the X-ray absorptivity of the individual filter elements being adjustable by adjustment of a quantity of X-ray absorbing liquid in individual filter elements on the basis of the electric voltages applied to the individual filter elements.
2. Description of Related Art
An X-ray examination apparatus of this kind is known from international patent application WO 97/03449.
The X-ray examination apparatus is used to form an X-ray image of an object to be examined, for example a patient to be radiologically examined. The X-ray source irradiates the object by means of an X-ray beam and an X-ray image is formed on the X-ray detector due to local differences in the X-ray absorption within the object. The X-ray filter ensures that the range of brightness values of the X-ray image remains limited. The X-ray filter is adjusted in such a manner that on the one hand parts of the X-ray beam which are only insignificantly attenuated by the object are slightly attenuated by the X-ray filter and that, on the other hand, parts of the X-ray beam which are significantly attenuated by the object are transmitted by the X-ray filter practically without attenuation. Because the brightness values of the X-ray image lie within a limited range, the X-ray image can be very readily processed further in order to achieve a good rendition of even small details of low contrast.
The X-ray filter of the known X-ray examination apparatus is provided with a bundle consisting of a very large number of capillary tubes, each of which communicates with the X-ray absorbing liquid by way of one end. The quantity of X-ray absorbing liquid present in the individual capillary tubes is influenced by the electric voltage applied to the wall of the capillary tubes. It has been found that the adhesion between the wall of the capillary tubes and the X-ray absorbing liquid is dependent on the electric potential difference between the wall of such a capillary tube and the X-ray absorbing liquid.
The voltage lines extend between the capillary tubes in the X-ray filter of the known X-ray examination apparatus. The capillary tubes are connected to one of the voltage lines by way of a respective field effect transistor. The field effect transistors are arranged between the capillary tubes. It is a drawback of the X-ray filter of the known X-ray examination apparatus that a rather large amount of space is required for the voltage lines to extend between the capillary tubes. Consequently, the active surface area of the known X-ray filter is significantly smaller than the overall surface area of the X-ray filter. Moreover, the field effect transistors are arranged in a region which is exposed to X-rays during operation of the X-ray examination apparatus. The X-rays may affect the field effect transistors so that the service life of the known X-ray filter is limited.
Citation of a reference herein, or throughout this specification, is not to construed as an admission that such reference is prior art to the Applicant's invention of the invention subsequently claimed.
SUMMARY OF THE INVENTION
It is an object of the invention to provide an X-ray examination apparatus which includes an X-ray filter which is adjustable on the basis of respective quantities of X-ray absorbing liquid in individual filter elements and has an active surface area which is larger than that of the known X-ray filter.
It is a further object of the invention to provide an X-ray filter whose service life is significantly longer than that of the known X-ray filter.
This object is achieved by means of an X-ray examination apparatus according to the invention which is characterized in that:
the filter elements are formed by spaces between plates which are locally attached to one another, and
the voltage lines are provided at least partly on one or more of the plates.
The filter elements have the shape of capillary tubes which are formed by spaces between the plates. Preferably, the plates are provided with separating members. The separating members separate neighboring filter elements from one another between neighboring plates. The separating members are formed, for example by protrusions which are formed transversely of the plates. Alternatively, use can be made of corrugated plates; the corrugations of the plates then constitute the separating members. The individual filter elements are provided with respective electrodes which are arranged on the parallel plates, for example on the side of the parallel plates which faces the inner side of the relevant filter elements. If desired, the electrodes can be covered with an electrically insulating dielectric layer and/or with a hydrophobic coating layer. The electrodes receive the electric voltage whereby the quantity of X-ray absorbing liquid present within the respective filter elements is influenced. The electric voltages are applied to the electrodes via the voltage lines.
Because the voltage lines extend across the plates, between the filter elements hardly any additional space is required for the voltage lines. Consequently, the voltage lines do not take up any active space of the X-ray filter so that the active surface area of the X-ray filter is larger than that in the known X-ray examination apparatus. The active surface area of the X-ray filter is the surface area of the X-ray filter via which the absorption of the X-rays can be controlled.
The voltage lines can be readily continued across the parallel plates so as to reach a region which is not traversed by the X-ray beam during operation of the X-ray examination apparatus. Switching elements can then be positioned in such a region which is not traversed by the X-ray beam and the electrodes can be connected to the switching elements by way of the voltage lines extending across the parallel plates. In that case the switching elements are not exposed to X-rays during operation of the X-ray examination apparatus. Degrading of the switching elements by the X-rays is thus avoided and hence the service life of the X-ray filter is prolonged. The switching elements form part of the control unit and the voltage lines are connected to the electric voltage source via the switching elements. The respective electrodes of the individual filter elements are thus connected to the electric voltage source via the respective voltage lines and the switching elements. The electric voltage is applied to the associated filter element, specifically to the electrode of said filter element, by closing a switching element as desired. Preferably, the switching elements are formed by thin-film transistors which can be switched by applying a gate voltage to a gate contact of such a thin-film transistor. Furthermore, the individual thin-film transistors are connected to the electrodes of the filter elements, for example by way of their respective drain contact, and to the voltage lines by way of their respective source contact. The switching elements may also be constructed as integrated circuits in semiconductor technology, for example silicon.
The corrugated plates are preferably formed by flexible wall foils. In that case the filter elements are preferably formed by locally attaching the wall foils in a stack of wall foils to one another and by subsequently expanding the stack of wall foils essentially transversely of the surface of the wall foils, for example by stretching. Between neighboring, essentially parallel wall foils, spaces are thus formed at the areas where the neighboring wall foils are not attached to one another, which spaces
Giesbers Jacobus B.
Linders Petrus W. J.
Prins Menno W. J.
Van Nes Andreas C. M.
Weekamp Johannes W.
Dunn Drew A.
Kim Robert H.
U.S. Philips Corporation
Vodopia John F.
LandOfFree
X-ray examination apparatus including an X-ray filter does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with X-ray examination apparatus including an X-ray filter, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and X-ray examination apparatus including an X-ray filter will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2496975