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Immobilizing and Positioning Patients for Radiotherapy
1Department of Radiation Oncology, University of California, San Francisco, CA, USA
Seminars in Radiation Oncology
|April 1, 1995
Summary
Accurate patient positioning and rigid immobilization are crucial for effective radiotherapy. Improving these techniques minimizes margins, reduces normal tissue dose, and enhances tumor control probability.
Area of Science:
- Radiation Oncology
- Medical Physics
- Radiotherapy Technology
Background:
- Accurate patient positioning and rigid immobilization are critical for effective radiotherapy.
- Small reductions in tumor dose can significantly decrease local control probability.
- Advanced treatment planning necessitates precise target localization.
Purpose of the Study:
- To emphasize the importance of accurate patient positioning and immobilization in radiotherapy.
- To explore how improved accuracy can lead to reduced margins and better outcomes.
- To highlight the role of new technologies in achieving higher positioning precision.
Main Methods:
- Review of radiobiological principles and their relation to dose-response curves.
- Discussion of advancements in immobilization materials and techniques.
- Integration of computed tomography (CT)-based planning with imaging technologies like electronic portal imagers.
Main Results:
- New immobilization methods allow for 3 mm accuracy in most patients, enabling 5 mm margins.
- Intracranial and head/neck targets can achieve 1-2 mm accuracy, even with invasive methods.
- Real-time tracking with portal imagers, video cameras, or radiography allows for positional adjustments during treatment.
Conclusions:
- Optimizing immobilization and positioning reduces target uncertainties, forming the basis for treatment margins.
- Minimizing these uncertainties can lead to increased uncomplicated local tumor control.
- Quantitative studies are essential for each site and method to refine margins and improve outcomes.