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Proceedings Paper

Soft tissue visualization using a highly efficient megavoltage cone beam CT imaging system
Author(s): Farhad A. Ghelmansarai; Ali Bani-Hashemi; Jean Pouliot; Ed Calderon; Paco Hernandez; Matthias Mitschke; Michelle Aubin; Kara Bucci
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Paper Abstract

Recent developments in two-dimensional x-ray detector technology have made volumetric Cone Beam CT (CBCT) a feasible approach for integration with conventional medical linear accelerators. The requirements of a robust image guidance system for radiation therapy include the challenging combination of soft tissue sensitivity with clinically reasonable doses. The low contrast objects may not be perceptible with MV energies due to the relatively poor signal to noise ratio (SNR) performance. We have developed an imaging system that is optimized for MV and can acquire Megavoltage CBCT images containing soft tissue contrast using a 6MV x-ray beam. This system is capable of resolving relative electron density as low as 1% with clinically acceptable radiation doses. There are many factors such as image noise, x-ray scatter, improper calibration and acquisitions that have a profound effect on the imaging performance of CBCT and in this study attempts were made to optimize these factors in order to maximize the SNR. A QC-3V phantom was used to determine the contrast to noise ratio (CNR) and f50 of a single 2-D projection. The computed f50 was 0.43 lp/mm and the CNR for a radiation dose of 0.02cGy was 43. Clinical Megavoltage CBCT images acquired with this system demonstrate that anatomical structures such as the prostate in a relatively large size patient are visible using radiation doses in range of 6 to 8cGy.

Paper Details

Date Published: 20 April 2005
PDF: 12 pages
Proc. SPIE 5745, Medical Imaging 2005: Physics of Medical Imaging, (20 April 2005); doi: 10.1117/12.602148
Show Author Affiliations
Farhad A. Ghelmansarai, Siemens Medical Solutions Inc. (United States)
Ali Bani-Hashemi, Siemens Medical Solutions Inc. (United States)
Jean Pouliot, Univ. of California/San Francisco (United States)
Ed Calderon, Siemens Medical Solutions Inc. (United States)
Paco Hernandez, Siemens Medical Solutions Inc. (United States)
Matthias Mitschke, Siemens Medical Solutions Inc. (United States)
Michelle Aubin, Univ. of California/San Francisco (United States)
Kara Bucci, Univ. of California/San Francisco (United States)


Published in SPIE Proceedings Vol. 5745:
Medical Imaging 2005: Physics of Medical Imaging
Michael J. Flynn, Editor(s)

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