Shot sequencing based on biological equivalent dose considerations for multiple isocenter Gamma Knife radiosurgery

Area of Science:

• Neurosurgery
• Radiation Oncology
• Medical Physics

Background:

• Gamma Knife radiosurgery enables rapid delivery of multiple radiation shots.
• Optimizing the temporal sequence of shots in multi-isocenter treatments is crucial for precise biological dosing.

Purpose of the Study:

• To investigate the impact of shot delivery sequence on biological equivalent dose in Gamma Knife Perfexion treatments.
• To determine if current clinical sequences achieve optimal biological dosing.

Main Methods:

• Analyzed 20 single-target Gamma Knife Perfexion cases.
• Extracted 3D dose matrices and calculated single-fraction equivalent uniform dose (sEUD) for all possible shot sequences.
• Compared sEUD variations across sequences and correlated clinical sequences with maximal sEUD sequences.

Main Results:

• Significant variations in sEUD (>15%) were observed among different shot sequences for certain cases.
• Clinical delivery sequences closely matched optimal sequences (<3% difference, R²=0.98).
• Findings apply to tumors with varying growth rates (α/β values 2-20).

Conclusions:

• While theoretical variations exist, clinical Gamma Knife shot sequencing consistently achieves near-maximal biological target dosing.
• Current delivery protocols ensure reliable and effective biological equivalent dose delivery in multi-isocenter treatments.