Assessment of image intensifier and distortion for DSA localization studies.

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Abstract
The authors present methods of correcting pincushion and S distortions of an image intensifier, and of measuring the geometrical parameters of the imaging device used for localization from digital subtraction angiography brain studies. Pincushion and S distortions of the image intensifier are corrected by a calibration grid. A test pattern is used to study effectiveness of the corrections. Intrinsic geometrical parameters (source-to-image distance, centre of X-ray projection) of the apparatus are measured by the use of a calibration phantom. Short-range and long-range time drift of the distortion, as well as influence of the parameters of image acquisition on the accuracy of the localization results, are considered. The results obtained successfully demonstrate the accuracy of the correction, provided that the apparatus is warm.