Dosimetry of large, irregularly shaped fields by the circle method. A feasibility study

Area of Science:

• Medical Physics
• Radiation Oncology
• Radiotherapy Dosimetry

Background:

• Accurate dose calculation is crucial for effective radiotherapy, especially for irregularly shaped radiation fields.
• Existing methods may require complex separation of radiation components or lack precision for non-standard fields.

Purpose of the Study:

• To introduce and validate the Circle Method, an algorithm for dose calculation in irregularly shaped fields.
• To assess the accuracy of the Circle Method by comparing calculated doses with experimental measurements.

Main Methods:

• Developed the Circle Method algorithm based on measurements from circle fields on the therapy machine.
• Integrated Clarkson's sector-integration method and an off-axis correction into the algorithm.
• Did not require separation into primary and scattered radiation components.

Main Results:

• The Circle Method demonstrated good agreement between calculated and experimental dose values.
• Agreement was within +/- 2.8% in the primary treatment field.
• Accuracy was maintained even under block shieldings.

Conclusions:

• The Circle Method provides a simplified yet accurate approach to dose calculation for irregular radiotherapy fields.
• The algorithm's efficiency and accuracy make it a valuable tool in radiation oncology practice.