[Estimation of collimator scatter factor, S(c), of rectangular fields by a saturation model]

Area of Science:

• Medical Physics
• Radiation Oncology
• Radiotherapy Physics

Context:

• Accurate calculation of the collimator scatter factor (S(c)) is crucial for precise dose delivery in external beam radiotherapy.
• Existing methods for determining S(c) can be complex and time-consuming, especially for non-standard field shapes.
• The need for efficient and accurate S(c) estimation tools is paramount for optimizing radiation treatment planning.

Purpose:

• To develop and validate a practical two-component scatter model for estimating the collimator scatter factor (S(c)) for symmetric rectangular fields.
• To construct an S(c) table for symmetric rectangular fields using measured in-air output data.
• To assess the applicability of the developed S(c) table for calculating S(c) values in asymmetric rectangular fields.

Summary:

• A two-component scatter model, incorporating primary collimator/flattening filter and collimator jaw scatter, was applied to measured in-air output data for symmetric rectangular fields.
• The model was fitted to width and length direction data, enabling the construction of an S(c) table for symmetric fields.
• Calculations for asymmetric fields using the generated S(c) table showed good agreement with measured values, demonstrating the method's precision.

Impact:

• Provides a precise and practical method for constructing S(c) tables for symmetric rectangular fields in radiotherapy.
• Enables accurate calculation of S(c) for a wide range of symmetric and asymmetric rectangular fields, enhancing treatment planning accuracy.
• Facilitates improved dose calculations and potentially better patient outcomes in radiation therapy through more reliable scatter factor estimation.