SU-E-T-494: Variation of Mucosal Dose in Head-And-Neck Radiotherapy: A Phantom Study Using Monte Carlo Simulation

Area of Science:

• Medical Physics
• Radiation Oncology
• Radiotherapy Dosimetry

Background:

• Head-and-neck radiotherapy often involves small photon fields, posing challenges for accurate mucosal dose assessment.
• Understanding mucosal dose variations is crucial for predicting and mitigating treatment-related complications.

Purpose of the Study:

• To investigate how mucosal dose is affected by photon beam energy, beam angle, multi-beam configurations, and mucosal thickness in small photon fields used in head-and-neck radiotherapy.

Main Methods:

• Cylindrical phantoms with varying mucosal thickness (1-3 mm) and heterogeneities (bone, air) were used.
• Simulations employed 6 and 18 MV photon beams with varied angles (0°, 90°, 180°) and multi-beam setups (2, 4, 8 beams).
• Monte Carlo simulations (EGSnrc code) calculated doses along the central-beam axis in mucosal tissue.

Main Results:

• At 0° beam angle, mucosal surface doses decreased with increased thickness, more significantly for 6 MV than 18 MV.
• At 180° beam angle, mucosal thickness had an insignificant effect on surface dose.
• Increasing the number of beams reduced the impact of mucosal thickness on dose.
• Heterogeneity effects on mucosal dose varied with beam energy, angle, and thickness.

Conclusions:

• Mucosal dose is significantly influenced by beam energy, angle, multi-beam configuration, and mucosal thickness in small photon fields.
• This dosimetric information is vital for developing optimized head-and-neck intensity-modulated radiotherapy (IMRT) strategies.
• Consideration of these factors can lead to minimized mucosal complications for patients.