3D range-modulator for scanned particle therapy: development, Monte Carlo simulations and experimental evaluation

Area of Science:

• Medical Physics
• Radiation Oncology
• Biomedical Engineering

Background:

• Particle therapy offers precise radiation delivery but can involve lengthy treatment times.
• Modulating beam energy is crucial for conformal dose distribution, but multi-energy plans are time-consuming.
• Interplay effects in scanned particle beams can compromise dose homogeneity, especially for moving targets.

Purpose of the Study:

• To design and manufacture a 3D range-modulator for scanned particle therapy.
• To achieve highly conformal dose distributions using a single fixed beam energy.
• To substantially reduce overall treatment time and mitigate interplay effects.

Main Methods:

• A 3D range-modulator was designed using thin pins of varying lengths to modulate the Bragg peak.
• Rapid prototyping was employed for modulator fabrication.
• FLUKA Monte Carlo simulations, including a custom user routine and intensity-modulated scanning, were used to model dose distribution.
• Experimental validation was performed using 400.41 MeV/u 12C beam at Heidelberg Ion Beam Therapy Center.

Main Results:

• Simulated and measured dose distributions showed good agreement.
• A monoenergetic raster plan with the 3D range-modulator took only 3 seconds, a 20-fold reduction compared to a 16-energy plan.
• The modulator effectively modulated the Bragg peak for a spherical target at 25 cm depth in a water phantom.

Conclusions:

• The 3D range-modulator enables highly conformal dose distributions with a single energy, drastically reducing treatment time.
• This approach significantly reduces or eliminates interplay effects, enhancing dose homogeneity for moving targets.
• The technology shows promise for rapid and reliable clinical application, particularly for lung tumors.