Variable dose interplay effects across radiosurgical apparatus in treating multiple brain metastases.

Area of Science:

• Radiosurgery
• Medical Physics
• Radiation Oncology

Background:

• Apparatus dependency significantly impacts normal brain tissue doses in multi-target stereotactic radiosurgery (SRS).
• Investigating inter-target dose interplay across contemporary SRS platforms is crucial for understanding these variations.

Purpose of the Study:

• To determine if inter-target dose interplay effects across different radiosurgical treatment platforms explain observed apparatus-dependent normal brain tissue doses.
• To compare dose delivery and treatment times for various SRS systems.

Main Methods:

• Six institutions planned SRS treatments for subsets of 12 targets using Gamma Knife Perfexion (PFX), CyberKnife, Novalis, and Varian TrueBeam FFF.
• Identical dose-volume constraints were applied across all platforms.
• Treatment plans were developed locally and results analyzed centrally.

Main Results:

• All platforms met dose-volume constraints, with minor differences in structures like the lens.
• Peripheral normal brain tissue doses were lowest with PFX and highest with TrueBeam FFF and CyberKnife.
• Volumes of normal brain receiving 12 Gy were 180-290% higher with TrueBeam FFF, Novalis, and CyberKnife compared to PFX. Treatment times were shortest with TrueBeam FFF.

Conclusions:

• Linear accelerator-based SRS platforms (TrueBeam FFF, Novalis, CyberKnife) deliver higher doses to normal brain tissue than Gamma Knife Perfexion (PFX).
• The volume of normal brain receiving therapeutic doses increases more rapidly per target with linac-based SRS.
• TrueBeam FFF offers the shortest treatment times among the evaluated SRS platforms.