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Proceedings Paper

Volumetric cone-beam CT system based on a 41x41 cm2 flat-panel imager
Author(s): David A. Jaffray; Jeffrey H. Siewerdsen
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Paper Abstract

Cone-beam computed tomography (CBCT) based upon large-area flat-panel imager (FPI) technology is a flexible and adaptable technology that offers large field-of-view (FOV), high spatial resolution, and soft-tissue imaging. The imaging performance of FPI-based cone-beam CT has been evaluated on a computer-controlled bench-top system using an early prototype FPI with a small FOV (20.5 X 20.5 cm2). These investigations demonstrate the potential of this exciting technology. In this report, imaging performance is evaluated using a production grade large-area FPI (41 X 41 cm2) for which the manufacturer has achieved a significant reduction in additive noise. This reduction in additive noise results in a substantial improvement in detective quantum efficiency (DQE) at low exposures. The spatial resolution over the increased FOV of the cone-beam CT system is evaluated by imaging a fine steel wire placed at various locations within the volume of reconstruction. The measured modulation transfer function (MTF) of the system demonstrates spatial frequency pass beyond 1 mm-1 (10% modulation) with a slight degradation at points off the source plane. In addition to investigations of imaging performance, progress has also been made in the integration of this technology with a medical linear accelerator for on-line image-guided radiation therapy. Unlike the bench-top system, this implementation must contend with significant geometric non-idealities caused by gravity-induced flex of the x-ray tube and FPI support assemblies. A method of characterizing and correcting these non-idealities has been developed. Images of an anthropomorphic head phantom qualitatively demonstrate the excellent spatial resolution and large FOV achievable with the cone-beam approach in the clinical implementation.

Paper Details

Date Published: 28 June 2001
PDF: 8 pages
Proc. SPIE 4320, Medical Imaging 2001: Physics of Medical Imaging, (28 June 2001); doi: 10.1117/12.430910
Show Author Affiliations
David A. Jaffray, William Beaumont Hospital (Canada)
Jeffrey H. Siewerdsen, William Beaumont Hospital (Canada)

Published in SPIE Proceedings Vol. 4320:
Medical Imaging 2001: Physics of Medical Imaging
Larry E. Antonuk; Martin Joel Yaffe, Editor(s)

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