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 f 50 of a single 2-D projection The computed f 50 was 0.43 Ip/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.
Original language | English (US) |
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Article number | 21 |
Pages (from-to) | 159-170 |
Number of pages | 12 |
Journal | Progress in Biomedical Optics and Imaging - Proceedings of SPIE |
Volume | 5745 |
Issue number | I |
DOIs | |
State | Published - 2005 |
Event | Medical Imaging 2005 - Physics of Medical Imaging - San Diego, CA, United States Duration: Feb 13 2005 → Feb 15 2005 |
Keywords
- Electronic portal imaging device
- Megavoltage cone beam CT
- Megavoltage soft tissue imaging
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Biomaterials
- Atomic and Molecular Physics, and Optics
- Radiology Nuclear Medicine and imaging