Image metrics for geometric calibration of a cone-beam tomographic X-ray system based on a single plastic brick

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The exact knowledge of the geometric acquisition parameters directly influences the quality of a tomographic reconstruction. Most calibration procedures use calibration phantoms that consist of metal beads arranged in a specific order. If the exact positions of the metal beads are to be sufficiently known, the production of such calibration phantoms can become very expensive. To avoid this problem, we propose a method that uses single plastic bricks (e.g. LEGO bricks) as calibration phantom. Based on a CAD model, projections with given acquisition parameters are simulated and then compared to the real projection using a metric. The objective of our research is to evaluate which metrics are best suited for the comparison of such projections. The results of applying two metrics on simulated and real data are presented.