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Automatic online adaptive radiation therapy techniques for targets with significant shape change: a feasibility
Laurence E Court1, Roy B Tishler, Joshua Petit
1Department of Radiation Oncology, Dana-Farber/Brigham & Women's Hospital Cancer Center, 75 Francis Street, ASBI-L2, Boston, MA 02115, USA. lcourt@lroc.harvard.edu
Physics in Medicine and Biology
|May 6, 2006
Summary
This study explores online adaptive radiation therapy (ART) to correct daily patient position and shape changes. The developed algorithms show potential for managing significant anatomical variations in head and neck cancer treatment.
Area of Science:
- Medical Physics
- Radiation Oncology
- Image-Guided Therapy
Background:
- Daily variations in patient anatomy pose challenges for accurate radiation delivery.
- Adaptive radiation therapy (ART) aims to adjust treatment based on real-time anatomical changes.
- Multi-leaf collimator (MLC) positioning is critical for precise dose shaping in radiation therapy.
Purpose of the Study:
- To evaluate the feasibility of an online adaptive radiation therapy (ART) concept for correcting daily patient position and shape variations.
- To develop and assess algorithms capable of managing large and complex anatomical changes during treatment.
- To investigate the potential of automated treatment plan adaptation using pre-calculated secondary plans.
Main Methods:
- Developed algorithms to detect and correct daily patient position and shape changes using 3D and 2D image registration.
- Generated secondary treatment plans with incremental gantry angle offsets from a primary plan.
- Created daily MLC sequences by selecting nearest pre-calculated plans and applying beam's-eye-view corrections for shifts.
- Validated the technique on simulated head and neck cancer treatment scenarios with significant shape deformation.
Main Results:
- The adaptive treatment demonstrated reasonable target coverage and kept the spinal cord dose within acceptable limits.
- Significant anatomical changes, including local rotations (2-31 degrees) and shifts (-0.2 to 0.5 cm), were simulated and addressed.
- Loss of coverage was observed in specific scenarios, particularly with skew-like motions not fully accounted for by the current ART technique.
- The method successfully combined MLC sequences from different plans to adapt to positional and shape alterations.
Conclusions:
- The online adaptive radiation therapy technique shows promise for correcting substantial daily patient setup variations.
- Further refinement is needed to address specific complex motions like skew-like shoulder movements.
- The ability to combine pre-calculated plans offers a viable approach for adapting radiation therapy to dynamic anatomical changes.