Patent ID: 6438211
Filing Date: 2002-08-20
Classification: G21K

Abstract:
An X-ray apparatus which includes an X-ray source (1) for producing X-rays (2), an X-ray detector (4) for detecting the X-rays, and a filter (14) which is arranged between the X-ray source and the X-ray detector and includes a plurality of tubular filter elements (13) having a longitudinal direction z and a circumference, whereineach filter element has an internal volume (21) for receiving a liquid filling (22) which contains at least one electrically conductive and one X-ray absorbing liquid component, the X-ray absorptivity of said filter element being dependent on the quantity of X-ray absorbing liquid component present in the internal volume (21), each filter element is provided with a first electrode (23) for applying a first electric voltage to a wall (28) of the filter element and a second electrode (29) for applying a second electric voltage to the internal volume (21) of the filter element, the first electrode is electrically isolated from the internal volume (21) of the filter element by means of an isolator layer (34) in such a manner that an electric capacitance per unit of surface area of the filter element exists between the first electrode (23) and the electrically conductive liquid component when a quantity of the electrically conductive liquid component is present in at least a part of the internal volume of the filter element (13), the X-ray absorptivity of each filter element (13) is adjustable by step-wise control of a surface level of the X-ray absorbing liquid component in the longitudinal direction z of each filter element, characterized in that the electric capacitance per unit of surface area of the wall (28) of the filter element (13) varies substantially in the longitudinal direction z of the filter element.