FLASH radiotherapy treatment planning and models for electron beams

Area of Science:

• Medical Physics
• Radiation Oncology
• Radiotherapy Technology

Background:

• The FLASH effect, observed at ultra-high dose rates (>40 Gy/s), offers normal tissue sparing in radiotherapy while maintaining tumor control.
• High-energy electrons (HEE) are currently used for superficial tumors, with very-high-energy electrons (VHEE) proposed for deep-seated tumors.

Purpose of the Study:

• To review treatment planning system (TPS) developments for high-energy electron (HEE) and very-high-energy electron (VHEE) FLASH radiotherapy.
• To discuss beam models, characteristics, and future FLASH applications in radiotherapy.

Main Methods:

• Review of existing literature on treatment planning for electron FLASH RT.
• Analysis of dosimetric modeling for UHDR HEE and VHEE RT devices.
• Evaluation of in silico dosimetric performance of VHEE techniques.

Main Results:

• UHDR HEE treatment planning focused on accurate dosimetric modeling for clinical transfer.
• VHEE treatment planning showed promising dosimetric performance compared to photon RT.
• Multiple metrics for quantifying the FLASH effect exist, but experimental validation is needed.

Conclusions:

• Accurate and validated modeling of the FLASH effect in treatment planning is essential.
• Treatment planning for electron FLASH RT will become increasingly important for complex clinical applications.
• Further research is needed to improve experimental characterization and understanding of the FLASH effect.