@inproceedings{e073ac5d0e8543a884963569f949080e,
title = "Self-calibration of cone-beam CT geometry using 3D-2D image registration: Development and application to tasked-based imaging with a Robotic C-arm",
abstract = "Purpose: Robotic C-arm systems are capable of general noncircular orbits whose trajectories can be driven by the particular imaging task. However obtaining accurate calibrations for reconstruction in such geometries can be a challenging problem. This work proposes a method to perform a unique geometric calibration of an arbitrary C-arm orbit by registering 2D projections to a previously acquired 3D image to determine the transformation parameters representing the system geometry. Methods: Experiments involved a cone-beam CT (CBCT) bench system, a robotic C-arm, and three phantoms. A robust 3D-2D registration process was used to compute the 9 degree of freedom (DOF) transformation between each projection and an existing 3D image by maximizing normalized gradient information with a digitally reconstructed radiograph (DRR) of the 3D volume. The quality of the resulting {"}self-calibration{"} was evaluated in terms of the agreement with an established calibration method using a BB phantom as well as image quality in the resulting CBCT reconstruction. Results: The self-calibration yielded CBCT images without significant difference in spatial resolution from the standard ({"}true{"}) calibration methods (p-value >0.05 for all three phantoms), and the differences between CBCT images reconstructed using the {"}self{"} and {"}true{"} calibration methods were on the order of 10-3 mm-1. Maximum error in magnification was 3.2%, and back-projection ray placement was within 0.5 mm. Conclusion: The proposed geometric {"}self{"} calibration provides a means for 3D imaging on general noncircular orbits in CBCT systems for which a geometric calibration is either not available or not reproducible. The method forms the basis of advanced {"}task-based{"} 3D imaging methods now in development for robotic C-arms.",
keywords = "Cone-beam CT, Image-guided interventions, Imaging task, Task-based imaging",
author = "S. Ouadah and Stayman, {J. W.} and G. Gang and A. Uneri and T. Ehtiati and Siewerdsen, {J. H.}",
note = "Publisher Copyright: {\textcopyright} 2015 SPIE.; Medical Imaging 2015: Image-Guided Procedures, Robotic Interventions, and Modeling ; Conference date: 22-02-2015 Through 24-02-2015",
year = "2015",
doi = "10.1117/12.2082538",
language = "English (US)",
series = "Progress in Biomedical Optics and Imaging - Proceedings of SPIE",
publisher = "SPIE",
editor = "Webster, {Robert J.} and Yaniv, {Ziv R.}",
booktitle = "Medical Imaging 2015",
}