Comprehensive evaluation of dosimetric impact against position errors in accelerator-based BNCT under different...

Area of Science:

• Medical Physics
• Radiation Oncology
• Radiotherapy

Background:

• Accelerator-based boron neutron capture therapy (AB-BNCT) for head and neck cancer requires precise patient immobilization.
• Patient motion during the relatively long BNCT treatment can lead to significant dosimetric errors, especially in single-fraction treatments.

Purpose of the Study:

• To investigate the dosimetric impacts (DIs) of position errors in an AB-BNCT system.
• To evaluate how different treatment parameters influence these dosimetric impacts.

Main Methods:

• A cylindrical phantom was used to simulate treatment scenarios.
• Treatment plans were created in RayStation with varying collimator size, collimator-to-surface distance (CSD), and tumor-to-blood (T/B) ratios.
• Phantom shifts were introduced in anterior-posterior (AP), left-right (LR), and superior-inferior (SI) directions at different distances.

Main Results:

• Anterior-posterior (AP) shifts had the most significant dosimetric impact, particularly with smaller collimator sizes and CSD.
• Superior-inferior (SI) and left-right (LR) shifts also caused dose reductions, influenced by collimator size and CSD.
• Tumor-to-blood ratios and 10B concentrations did not significantly alter the dosimetric impacts of positional shifts.

Conclusions:

• Positional errors, especially in the AP direction, significantly affect dose delivery in AB-BNCT.
• Treatment parameters such as collimator size and CSD play a crucial role in mitigating dosimetric impacts from patient motion.