Reconstruction of x-ray focal spot distribution using a rotating edge

Linxi Shi; N. Robert Bennett; Adam S. Wang

doi:10.1117/12.2549740

16 March 2020 Reconstruction of x-ray focal spot distribution using a rotating edge

Linxi Shi, N. Robert Bennett, Adam S. Wang

Proceedings Volume 11312, Medical Imaging 2020: Physics of Medical Imaging; 113122M (2020) https://doi.org/10.1117/12.2549740
Event: SPIE Medical Imaging, 2020, Houston, Texas, United States

Abstract

The size and shape of an x-ray source’s focal spot is a critical factor in the imaging system’s overall spatial resolution. The conventional approach to imaging the focal spot uses a pinhole camera, but this requires careful, manual measurements. Instead, we propose a novel alternative, simply using the collimator available on many x-ray systems. After placing the edge of a collimator blade in the center of the beam, we can obtain an image of its edge spread function (ESF). Each ESF provides information about the focal spot distribution – specifically, the parallel projection of the focal spot in the direction parallel to the edge. If the edge is then rotated about the beam axis, each image provides a different parallel projection of the focal spot until a complete Radon transform of the focal spot distribution is obtained. The focal spot can then be reconstructed by the inverse Radon transform, or parallel-beam filtered backprojection. We conducted a study on a clinical C-arm system with 3 focal spot sizes (0.3, 0.6, 1.0 mm nominal size), comparing the focal spot obtained using the rotating edge method against the conventional pinhole approach. Our results demonstrate accurate characterization of the size and shape of the focal spot.

Citation Download Citation

Linxi Shi, N. Robert Bennett, and Adam S. Wang "Reconstruction of x-ray focal spot distribution using a rotating edge", Proc. SPIE 11312, Medical Imaging 2020: Physics of Medical Imaging, 113122M (16 March 2020); https://doi.org/10.1117/12.2549740

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KEYWORDS

X-rays

Collimators

Radon transform

X-ray imaging

X-ray sources

Image resolution

Imaging systems

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