title: Quantifying cross-scatter contamination in biplane fluoroscopy motion analysis systems.
abstract: Biplane fluoroscopy is used for dynamic in vivo three-dimensional motion analysis of various joints of the body. Cross-scatter between the two fluoroscopy systems may limit tracking accuracy. This study measured the magnitude and effects of cross-scatter in biplane fluoroscopic images. Four cylindrical phantoms of 4-, 6-, 8-, and 10-in. diameter were imaged at varying kVp levels to determine the cross-scatter fraction and contrast-to-noise ratio (CNR). Monte Carlo simulations quantified the effect of the gantry angle on the cross-scatter fraction. A cadaver foot with implanted beads was also imaged. The effect of cross-scatter on marker-based tracking accuracy was investigated. Results demonstrated that the cross-scatter fraction varied from 0.15 for the 4-in. cylinder to 0.89 for the 10-in. cylinder when averaged across kVp. The average change in CNR due to cross-scatter ranged from 5% to 36% CNR decreases for the 4- and 10-in. cylinders, respectively. In simulations, the cross-scatter fraction increased with the gantry angle for the 8- and 10-in. cylinders. Cross-scatter significantly increased static-tracking error by 15%, 25%, and 38% for the 6-, 8-, and 10-in. phantoms, respectively, with no significant effect for the foot specimen. The results demonstrated submillimeter marker-based tracking for a range of phantom sizes, despite cross-scatter degradation.
authors.affiliation: Marquette University , Department of Biomedical Engineering, 1515 W. Wisconsin Avenue, Milwaukee, Wisconsin 53233, United States.
authors.forename: Janelle A
authors.initials: JA
authors.lastname: Cross
authors.affiliation: Marquette University , Department of Biomedical Engineering, 1515 W. Wisconsin Avenue, Milwaukee, Wisconsin 53233, United States.
authors.forename: Ben
authors.initials: B
authors.lastname: McHenry
authors.affiliation: Marquette University , Department of Biomedical Engineering, 1515 W. Wisconsin Avenue, Milwaukee, Wisconsin 53233, United States.
authors.forename: Taly Gilat
authors.initials: TG
authors.lastname: Schmidt
keywords: biplane fluoroscopy; contrast-to-noise ratio; cross-scatter; marker-based tracking; scatter fraction
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