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Evaluation of mechanical precision and alignment uncertainties for an integrated CT/LINAC system
Laurence Court1, Isaac Rosen, Radhe Mohan
1The Department of Radiation Physics, The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030, USA.
Medical Physics
|July 11, 2003
Summary
This study evaluated uncertainties in an integrated CT/LINAC system for radiation therapy. A protocol using fiducial markers achieved higher precision (0.5 mm) for patient setup correction.
Area of Science:
- Medical Physics
- Radiation Oncology
- Imaging Technology
Background:
- Integrated CT/LINAC systems offer potential for accurate interfractional setup error correction in radiotherapy.
- Accurate patient positioning is crucial for effective radiation delivery and minimizing off-target dose.
Purpose of the Study:
- To identify and quantify sources of uncertainty in an integrated CT/LINAC system.
- To measure the overall precision of patient setup correction using different protocols.
Main Methods:
- Systematic evaluation of eight sources of uncertainty, including couch position, digital readout, couch sag, CT coordinate precision, fiducial marker identification, and alignment.
- Phantom studies to assess the precision of two distinct patient setup protocols.
Main Results:
- The largest uncertainties were identified in couch position on the CT side (0.5 mm) and contour alignment (0.4 mm).
- A protocol utilizing fiducial markers demonstrated superior precision (0.5, 0.4, 0.4 mm in SI, RL, AP directions) compared to a purely mechanical protocol (0.6, 0.7, 0.6 mm).
Conclusions:
- Understanding individual uncertainty sources is key to optimizing radiotherapy patient setup.
- The fiducial marker-based protocol offers improved precision for CT-LINAC integrated systems, enhancing radiotherapy accuracy.