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In search of a one plan solution for VMAT post-mastectomy chest wall irradiation
T T Monajemi1,2, P A K Oliver1,2, A Day1
1Department of Radiation Oncology, Dalhousie University, Halifax, Nova Scotia, Canada.
Journal of Applied Clinical Medical Physics
|June 28, 2020
Summary
This study compared skin doses in VMAT and tangent radiotherapy, finding that bolus use can achieve similar superficial doses. Hospital gowns and blankets also increase surface dose, impacting treatment planning.
Area of Science:
- Medical Physics
- Radiotherapy Physics
- Radiation Oncology
Background:
- Accurate skin dose assessment is crucial in radiotherapy for effective treatment and minimizing side effects.
- Volumetric Modulated Arc Therapy (VMAT) and 3D tangential techniques are common treatment modalities for chest wall irradiation.
- Bolus materials are often used to compensate for tissue deficits or to increase superficial dose.
Purpose of the Study:
- To evaluate and compare skin dose distributions in VMAT and tangential radiotherapy for chest wall treatments.
- To identify optimal bolus protocols that yield comparable superficial doses between different treatment techniques.
- To investigate the dosimetric impact of common materials like hospital gowns and blankets on skin dose.
Main Methods:
- Utilized phantom measurements with Optically Stimulated Luminescence Dosimeters (OSLDs) and EBT3 film to assess skin dose.
- Investigated various bolus materials including Superflab (3, 5, 10 mm) and brass mesh.
- Compared measured doses with Eclipse treatment planning system (TPS) predictions and conducted patient measurements.
Main Results:
- Without bolus, VMAT generally resulted in lower skin doses compared to tangents.
- With bolus, both techniques showed increased skin doses, with Superflab achieving doses close to prescription.
- Eclipse TPS predictions showed good agreement with measurements, within 5% for Superflab and 15% for no bolus.
- Hospital gowns and blankets demonstrated a bolusing effect, increasing surface dose by approximately 10%.
Conclusions:
- The choice of bolus thickness and material can be tailored to achieve desired skin doses for both VMAT and tangential techniques.
- Understanding the bolusing effect of everyday materials is important for accurate dose delivery.
- These findings support the development of specific bolus protocols for optimizing superficial dose in chest wall radiotherapy.
