Maximum kinetic energy considerations in proton stereotactic radiosurgery

Area of Science:

• Medical Physics
• Radiation Oncology
• Radiotherapy Physics

Background:

• Stereotactic radiosurgery (SRS) is a precise radiotherapy technique.
• Proton therapy offers potential advantages in dose distribution for SRS.
• Determining optimal proton beam parameters is crucial for effective SRS delivery.

Purpose of the Study:

• To establish the maximum proton kinetic energy needed for stereotactic radiosurgery (SRS) patient treatment using coplanar arc-based proton therapy.
• To analyze the influence of gantry angle number and location on proton energy requirements.
• To correlate treatment arc length with required proton beam energy.

Main Methods:

• Analysis of treatment plans from 100 SRS patients.
• Utilized in-house software to simulate proton pencil beam spot placement from 51 gantry angles.
• Calculated radiological path length and determined maximum proton energy as a function of treatment arc length.

Main Results:

• 100% of patients could be treated with 118 MeV if only one gantry angle was used.
• Maximum proton energy requirements increased with treatment arc length: 127 MeV (90°), 145 MeV (180°), 156 MeV (270°), and 179 MeV (360°).
• Proton energy requirements showed a linear increase with the size of the treatment arc.

Conclusions:

• A significant portion of SRS patients can be treated with lower proton energies when gantry angles span smaller arcs.
• The maximum proton kinetic energy needed is directly proportional to the treatment arc length.
• Optimizing gantry angle selection in arc-based proton therapy can potentially reduce maximum energy requirements for SRS.