Patent Number: 
Section: abstract

An X-ray apparatus is equipped with an X-ray filter having adjustable absorption properties in order to reduce the dynamic range of an X-ray image. The filter includes a matrix of filter elements 13, 13xe2x80x2, 13xe2x80x3 in which a level of an X-ray absorption liquid can be varied. The amount of the X-ray absorption liquid within an individual filter element determines the value of the X-ray absorption within this filter element. It is necessary that the resultant amount of the X-ray absorption liquid within each filter element is reproducible. Such an X-ray filter (12) is mounted near the X-ray source and is rotated together with the gantry when an X-ray image is required with some angulation with respect to an object. When the X-ray filter is angled (xcex2) with respect to the vertical direction (g), the hydrostatic pressure within filter elements varies with respect to the calibrated state and the resultant amount of the X-ray absorption liquid is not reproducible. In order to compensate the variation of the hydrostatic pressure within the filter, the latter is provided with a hydrostatic pressure control system (131, 160).