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CT verification of isocentre relocatability using stereotactic mask fixation system
V Y W Wong1, S Y Tung, T W Leung
1Department of Clinical Oncology, Tuen Mun Hospital, Hong Kong, People's Republic of China. Victy_Wong@hotmail.com
Clinical Oncology (Royal College of Radiologists (Great Britain))
|August 20, 2003
Summary
This study presents a non-invasive computed tomography (CT) verification method for accurate patient positioning in fractionated stereotactic radiotherapy. The technique ensures precise mask alignment, minimizing systematic errors for routine clinical application.
Area of Science:
- Medical Physics
- Radiotherapy Technology
- Image-Guided Therapy
Background:
- Accurate patient positioning is critical for effective fractionated stereotactic radiotherapy.
- Current methods may require invasive checks or lack precise verification.
- A reliable non-invasive method is needed for quality control of patient setup.
Purpose of the Study:
- To introduce and evaluate a non-invasive computed tomography (CT) verification method for patient positioning.
- To assess the accuracy of a mask system with a dental impression mouth bite for immobilisation.
- To enable quality control of mask positioning relative to CT images from the treatment plan.
Main Methods:
- Utilized a mask system and dental impression mouth bite for patient immobilisation.
- Employed special alignment during CT localisation for image comparison.
- Assessed patient set-up accuracy by evaluating isocentre position relative to anatomy.
- Applied planning CT images as reference for 261 cranial applications.
Main Results:
- Mean and maximum overall displacements at the isocentre were 0.7 mm and 2.5 mm.
- Mean and maximum rotational displacements in the axial plane were 0.56 degrees and 2 degrees.
- Mean translational and rotational displacements approached zero when considering direction.
Conclusions:
- The CT verification method and mask system demonstrate minimal systematic error.
- The technique offers simple set-up, 3D quantification, and short study times (10-15 min), making it practical for routine use.
- Further investigation into mask relocation is recommended to define safety margins.