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SU-E-J-201: What is the Importance of Dose Recalculation for Adaptive Radiotherapy Dose Assessment?
Overlaying planned dose distributions for head and neck cancer adaptive radiotherapy (ART) dose assessment is a robust method. Dosimetric differences were minimal, indicating stable dose distributions despite anatomical changes during treatment.
Area of Science:
- Radiation Oncology
- Medical Physics
- Cancer Treatment
Background:
- Adaptive radiotherapy (ART) aims to adjust treatment based on daily anatomical changes.
- Accurate dose assessment is crucial for effective ART in head and neck cancer.
- Megavoltage CT (MVCT) on TomoTherapy enables daily imaging for dose verification.
Purpose of the Study:
- To quantify the dosimetric impact of using planned dose distributions versus recalculated distributions for ART dose assessment in head and neck cancer.
- To evaluate the robustness of planned dose distributions against anatomical variations during treatment.
Main Methods:
- 16 head and neck cancer patients treated with TomoTherapy were analyzed.
- Dose was estimated by recalculating on daily MVCT images and by overlaying planned distributions.
- Deformable image registration (DIR) was used to accumulate doses and compare dosimetric endpoints.
Main Results:
- Mean differences in PTV D95% and D05% were within ±1.4% when using planned vs. recalculated doses.
- Mean parotid D50% differed by 2.4% but showed high correlation (r2=0.97) between methods.
- Observed dosimetric variations were generally within ±5%.
Conclusions:
- Planned dose distributions can be reliably used for ART dose assessment in head and neck cancer with TomoTherapy.
- The dose distribution is robust to anatomical variations encountered during treatment.
- This simplifies ART dose assessment without compromising accuracy.
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