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Reproducibility of irregular radiation fields for malignant lymphoma
U Mock1, K Dieckmann, A M Molitor
1Department of Radiotherapy and Radiobiology, University Hospital, Vienna, Austria.
Summary
Accurate radiation therapy for malignant lymphoma requires precise field and block placement. Regular verification film analysis improves accuracy, reducing deviations and enhancing safety margins in external radiotherapy.
Area of Science:
- Radiation Oncology
- Medical Physics
Background:
- Malignant lymphoma treatment necessitates large-field irradiation with patient-specific irregular blocks.
- Accurate determination of planning target volume (PTV) margins is crucial for effective radiation therapy.
Purpose of the Study:
- To quantitatively analyze the accuracy of radiation field and shielding block placement in malignant lymphoma patients.
- To assess deviations in different anatomical regions to inform safety margin definitions.
Main Methods:
- Forty patients with malignant lymphoma underwent irradiation using 10-MeV photons and large opposing fields.
- Verification films were compared to simulation films to evaluate field and block placement accuracy along x- and z-axes.
Main Results:
- Mean deviations for field edges were 2.0 mm (x-axis) and 3.4 mm (z-axis).
- Mean block displacements were 2.2 mm (x-axis) and 3.8 mm (z-axis), with standard deviations of 5.7 mm and 7.1 mm, respectively.
- Improved block placement accuracy was observed over time.
Conclusions:
- Systematic port film analysis aids in defining safety margins for external radiotherapy.
- Regular evaluation of verification films enhances set-up accuracy by minimizing displacements.