X-ray or gamma ray systems or devices – Beam control – Scanner
Patent
1992-07-13
1997-03-04
Church, Craig E.
X-ray or gamma ray systems or devices
Beam control
Scanner
378145, G21K 510
Patent
active
056087772
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a slit radiography apparatus comprising an X-ray source, an X-ray detector for sensing radiation passing through a body to be radiographed, a slit diaphragm positioned between said X-ray source and said body for forming a substantially planar X-ray beam, means for scanning said body with said planar X-ray beam in a direction transverse to a longitudinal direction of a slit of said slit diaphragm, an absorption device comprising a plurality of electrically controllable piezoelectric tongues positioned along said longitudinal direction of said slit forming a corresponding number of sections of said planar X-ray beam, each of said tongues having a fixed end and a free end, a control device for feeding electrical control signals to said tongues for continuous vibration thereof at a predetermined frequency.
The invention also relates to a method for operating a slit radiography apparatus provided with an absorption device which interacts with a slit diaphragm and which comprises electrically controllable piezoelectric tongues, each having a fixed end and a free end and a control device which feeds electrical control signals to said tongues during operation, said method comprising feeding control signals to said tongues for continuous vibration thereof at a predetermined frequency.
Such an apparatus is known, for example, from Dutch Patent Applications 8400845 and 8601678. The apparatus known from Dutch Patent Application 8400845 comprises an X-ray source which is capable of scanning a patient or object to be examined with a flat fan-shaped X-ray beam via a slit-type diaphragm. In order to obtain an equalised X-ray image, an absorption device comprising a number of adjacently situated absorption elements which can be brought into the X-ray beam to a greater or lesser extent under the control of electrical control signals is provided near the slit diaphragm.
Each absorption element can affect a sector of the fan-shaped X-ray beam. The control signals are obtained by means of a detector which is provided behind the patient or the object and which measures the amount of radiation transmitted for each sector of the X-ray beam and provides a corresponding electrical control signal.
As absorption elements, use could be made of piezoelectric material which is clamped at one end and whose other end can be swivelled into the X-ray beam under the control of the abovementioned electrical control signals. Such tongues already absorb X-ray radiation to a certain extent themselves, but they are usually also provided with special elements which absorb X-ray radiation at the free ends. In the latter case, it is sufficient if the special elements which absorb X-ray radiation can be swivelled into the X-ray beam.
The tongues may be simple tongues of piezoelectric material which can be brought into a curved state by means of an electrical control voltage applied between the top and bottom face. The tongues may also be so-called bimorphous elements which are composed of two strips of piezoelectric material laid one on top of the other. The electrical control voltage may then be applied between the interconnected outer faces (top and bottom face) and the common central face.
The tongues can be controlled in such a manner that the position of the tongues with respect to the slit of the slit diaphragm is always matched to the amount of radiation instantaneously transmitted through the patient or the object in the associated sector of the X-ray beam, that is to say, to the instantaneous, and therefore local, transmissivity of the patient for the object.
In the Dutch Patent Application 8601678, the contents of which are regarded as included here by reference, a description is given of another method, according to which a so-called hardness modulation of the X-ray beam is used.
According to the method known from the Dutch Patent Specification 8601678, the free ends of the tongues or the absorbing elements vibrate continuously at a predetermined frequency between a position completely or largely clearing the slit
REFERENCES:
patent: 5058149 (1991-10-01), Vlasbloem
B.V. Optische Industrie "De Oude Delft"
Church Craig E.
Marn Louis E.
LandOfFree
Slit radiography apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Slit radiography apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Slit radiography apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2153116