Optimized anti-scatter grids for flat panel detectors

Markus Lendl

doi:10.1117/12.709386

14 March 2007 Optimized anti-scatter grids for flat panel detectors

Markus Lendl

Proceedings Volume 6510, Medical Imaging 2007: Physics of Medical Imaging; 65102L (2007) https://doi.org/10.1117/12.709386
Event: Medical Imaging, 2007, San Diego, CA, United States

Abstract

Anti-scatter grids are well established in the field of X-ray projection imaging. In general these grids consist of a large number of parallel lead lamellae separated by X-ray-transparent material. This regular structure defines the characteristic grid frequency. Modern X-ray imaging systems apply digital receptors, i.e. image intensifiers coupled to a CCD camera or solid state flat-panel detector. Combining a digital detector and an anti-scatter grid may lead to Moire artifacts. This results from sampling an analog X-ray image with signal components higher than half the sampling frequency. Especially in high dose DSA images (Digital Subtraction Angiography) these irritating artifacts may be visible to the user. In this paper we present a concept for minimizing these grid artifacts: Signal propagation in the detector is modeled by three steps, scintillator MTF, aperture MTF, and sampling. Since the scintillator MTF is irrelevant for the grid optimization process, we focus on aperture MTF and sampling. From the given geometry of the detector elements the corresponding 2D Fourier transform is calculated. An evaluation for typical grid frequencies, i.e. arcs around the origin of the 2D Fourier transform, results in profiles exhibiting pronounced minima. From the respective angle values for these minima, grid orientation can be optimized for minimum Moire disturbances. Simulation results for typical detector pixel geometries and for grid frequencies used in practice are validated by measurement for two different anti-scatter grids on a Siemens angiographic system with a digital flat-panel detector.

Citation Download Citation

Markus Lendl "Optimized anti-scatter grids for flat panel detectors", Proc. SPIE 6510, Medical Imaging 2007: Physics of Medical Imaging, 65102L (14 March 2007); https://doi.org/10.1117/12.709386

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KEYWORDS

Sensors

Modulation transfer functions

X-rays

Scintillators

X-ray imaging

Fourier transforms

Lead

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