Feasibility study for dose calculation with a radiation treatment planning system using a fixed-size electron cone...

Area of Science:

• Medical Physics
• Radiation Oncology
• Dosimetry

Background:

• Commercial treatment planning systems (TPS) often lack native support for small, fixed-size electron cone applicators.
• Accurate radiation dose calculation is critical for effective and safe electron beam therapy.

Purpose of the Study:

• To assess the feasibility of using a commercial TPS for treatment planning with small fixed-size electron cone applicators.
• To validate the accuracy of monitor unit (MU) calculations and dose distributions generated by the TPS for these applicators.

Main Methods:

• Compared dosimetric characteristics (beam profiles, output factors) of a 6 MeV electron beam using a fixed-size cone versus a general applicator with cerrobend cutouts.
• Measured output factors and compared monitor units (MUs) from TPS with direct measurements.
• Validated TPS dose distributions against Gafchromic film measurements.

Main Results:

• Gamma analysis demonstrated high agreement for depth dose (>95% with 1%/1 mm) and beam profiles (>99% with 2%/2 mm).
• Indirect TPS calculations for the fixed-size electron cone applicator showed MU differences within 1.0% of direct measurements.
• 2D dose distribution agreement exceeded 99% (3%/3 mm) between film measurements and TPS calculations.

Conclusions:

• Commercial TPS can be feasibly adapted for treatment planning with small fixed-size electron cone applicators.
• The proposed method, incorporating relative output factors, provides a reliable approach for dose calculation in specialized electron therapy.