Clinical Linear Accelerator-Based Electron FLASH: Pathway for Practical Translation to FLASH Clinical Trials

Area of Science:

• Medical Physics
• Radiation Oncology
• Radiotherapy Technology

Background:

• Ultrahigh-dose-rate (UHDR) radiation therapy (RT) shows promise for reduced toxicity and comparable tumor control via the FLASH effect.
• Current clinical trials for UHDR RT primarily utilize specialized equipment.
• Exploring UHDR RT feasibility on standard clinical linear accelerators (LINACs) is crucial for broader clinical application.

Purpose of the Study:

• To investigate the technical feasibility of delivering ultrahigh-dose-rate (UHDR) electron radiation therapy using a standard clinical linear accelerator (LINAC).
• To assess the potential for adapting existing LINACs for UHDR electron delivery without hardware modifications.

Main Methods:

• A standard clinical LINAC was modified by tuning its electron energy for UHDR delivery.
• Respiratory gating was employed to control pulse delivery.
• A short source-to-surface distance (SSD) electron setup with a standard scattering foil was configured and tested on an anthropomorphic phantom.
• Dosimetry was evaluated using radiochromic film and an ion chamber profiler for various field sizes.

Main Results:

• Mean dose rates of up to 112.83 Gy/s were achieved at different SSDs.
• At 80 cm SSD, a mean dose rate of approximately 60 Gy/s was achieved for all collimated field sizes, with an R80 depth of 6.1 cm (17.5 MeV).
• Dose heterogeneity was consistently below 5.0%, with asymmetry ranging from 2.2% to 6.2%.

Conclusions:

• The technical feasibility of UHDR electron delivery on a standard clinical LINAC was demonstrated.
• A short SSD setup and optimized electron beam current allow for homogenous UHDR electron delivery across clinically relevant field sizes and depths.
• This approach is easily reversible to standard clinical use, facilitating practical implementation of UHDR RT.