Toward a pre-clinical irradiator using clinical infrastructure.

Area of Science:

• Medical Physics
• Radiation Oncology
• Pre-clinical Research

Background:

• Pre-clinical irradiation systems often use kilovoltage x-ray systems.
• Kilovoltage beams have different radiobiological effectiveness than clinical megavoltage beams.
• Existing pre-clinical systems are costly and limited in precision for small targets.

Purpose of the Study:

• To adapt a clinical Varian TrueBeam STx linear accelerator for pre-clinical irradiation of millimeter-sized targets.
• To develop a method for delivering precise, compact dose distributions using megavoltage photon beams.
• To overcome the limitations of current pre-clinical irradiation systems.

Main Methods:

• Utilized Developer mode on a Varian TrueBeam STx linear accelerator.
• Implemented single opposed leaf pair for arc-based treatments with dynamic couch trajectories.
• Employed pre-treatment imaging for target misalignment quantification and couch correction.
• Validated dose distributions using Monte Carlo simulations and radiochromic film.

Main Results:

• Optimal dose distributions achieved with 1 mm leaf separation.
• Couch position corrections up to 2.1 mm were necessary for target alignment.
• Couch corrections improved dose profile accuracy in non-coplanar arc treatments.
• Precise dose falloff achieved for a 1 mm target: 0.3 mm (80%), 0.5 mm (50%), 1.3 mm (25%).

Conclusions:

• Successfully adapted clinical megavoltage linear accelerator for pre-clinical irradiation.
• Demonstrated the feasibility of delivering highly compact dose distributions for small targets.
• Showcased the potential of using existing clinical infrastructure for advanced pre-clinical research.