X-ray source tracking to compensate focal spot drifts for dimensional CT measurements

Accurate CT measurements rely on a stable X-ray focal spot. Because focal spot drift deteriorates CT data, especially at high resolutions, drift compensation is crucial. Here, we present an optical X-ray tube tracking system that does not require fiducial markers and/or radiographic image registration. To assess its performance, a calibrated, small volume (< 4 mm) multi-sphere standard was CT scanned. The deviations of unidirectional dimensional measurements were reduced by almost a factor of two when compensating for the X-ray tube drift.