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19 March 2008 Effects of digital geometry and phantom size on cone-beam CT point spread function measurement
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The three-dimensional point spread function (3D PSF) of cone-beam computed tomography (CBCT) can be measured through the use of point phantom or edge phantom. In cone-beam tomography theory, an input of delta impulse function will produce an output of a delta function (except a scale factor) under the assumption of continuous geometry, thus manifesting spatial shift invariance over the scan field of view (SFOV). For a practical CBCT system, its 3D PSF is of spatial variant distribution over the SFOV, due to the digital geometry in discrete projection detection and gridded volume reconstruction. In principle, the 3D PSF of a CBCT system can be measured either by a micro point-like phantom (<1mm) by approaching a delta impulse function, or by a macro edge phantom (>1mm) by analyzing the edge blurring mechanism. We found that there exists ambiguity and controversy among the 3D PSF measurement and characterization, varying with the size of the phantom. In this work, we will investigate the effects of digital geometry and phantom size on the 3D PSF measurement. In the results, we will propose an experimental protocol for eliminating the uncertainty associated with the 3D PSF characterization of a CBCT system.
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Zikuan Chen and Yang Tao "Effects of digital geometry and phantom size on cone-beam CT point spread function measurement", Proc. SPIE 6913, Medical Imaging 2008: Physics of Medical Imaging, 691350 (19 March 2008);

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