Oblique raster scanning: an ion dose delivery procedure with variable energy layers

Area of Science:

• Medical Physics
• Particle Accelerator Technology
• Radiation Oncology

Background:

• Current ion therapy uses Equal Energy Layers (EELs) scanned by a beam spot, facing challenges in synchrotrons like energy switching delays, magnetic field ripples, and difficulties with superconducting magnets.
• These issues complicate precise dose delivery, especially for treatments requiring very short durations and for moving targets.

Purpose of the Study:

• To introduce and evaluate the Oblique Raster Scanning (ORS) procedure for mitigating dose delivery problems in ion therapy accelerator complexes.
• To demonstrate the feasibility of ORS for treating moving targets and its advantages for both synchrotron and (synchro)cyclotron-based centers.

Main Methods:

• The proposed ORS procedure synchronizes beamline magnet currents, allowing a beam spot of continuously varying energy to scan oblique layers at a constant velocity.
• Simulations and analysis were performed to assess B-field rates and the applicability of advanced target tracking techniques (3D feedback, rescanning) with ORS.
• ORS compatibility with respiratory gating and alternative variable energy production methods for (synchro)cyclotrons were also investigated.

Main Results:

• ORS can achieve low B-field rates (dB/dt = 0.1 T s⁻¹) even for rapid 13.5s irradiations of a 0.5 L target, enabling precise tracking of moving targets.
• Approximately 10¹⁰ carbon ions are sufficient for such treatments, and ORS integrates well with respiratory gating.
• ORS offers advantages for (synchro)cyclotrons, potentially replacing expensive beam transport systems with simpler, cost-effective superconducting energy acceptance systems.

Conclusions:

• Oblique Raster Scanning is a promising technique to overcome current limitations in ion therapy dose delivery, enhancing speed and precision.
• ORS provides a flexible and potentially more economical solution for various ion therapy facilities, including those using synchrocyclotrons.
• The method supports advanced treatment strategies like motion management, paving the way for more effective cancer treatments.