Dynamic image-adaptive x-ray beam limiters

The imaging capability of the dynamic spatial reconstructor (DSR), a fast (60/second), synchronous, multislice (up to 240) computed x-ray tomography scanner, has been limited by the suboptimal match of the dynamic range of the x-ray projection images with that of the image-intensified charge-coupled device (CCD) video sensors. Effective blockage of the "raw" beam component of the projection images by fixed shutters is generally impossible because of the rapid change in the multiple angles of view that result from the 15 RPM rotation of the scanner assembly about the object of study. For this reason a programmable, dynamic, image-adaptive x-ray beam shutter system has been developed to reduce the "raw" beam component of the x-ray image without degrading the image in the region of interest. This system is designed to dynamically position 28 shutters (two for each of 14 x-ray sources) continuously and independently, as a function of the angle of view, so as to selectively obscure any unattenuated "raw" x-ray beam passing alongside the object of study at all angles of view for each x-ray source.