Proton range verification through prompt gamma-ray spectroscopy.

Area of Science:

• Medical Physics
• Nuclear Physics
• Radiotherapy Research

Background:

• Proton therapy offers precise radiation delivery but requires accurate range verification.
• Current methods for range verification can be limited by tissue composition uncertainties.
• Prompt gamma-ray emissions present a promising signal for in-beam range monitoring.

Purpose of the Study:

• To experimentally validate a novel method for proton therapy beam range verification using prompt gamma-ray emissions.
• To assess the method's ability to simultaneously determine beam range and elemental composition (oxygen and carbon).
• To evaluate the method's performance in phantoms with varying compositions.

Main Methods:

• Measured differential cross sections for prompt gamma-ray lines from proton interactions with carbon-12 and oxygen-16 up to 150 MeV.
• Modeled discrete prompt gamma-ray emissions along proton pencil beams using measured cross sections.
• Fitted detected prompt gamma-ray counts to the models to determine beam range and elemental concentrations.
• Assessed performance using a prototype detector in two phantoms with different elemental compositions.

Main Results:

• Simultaneously determined absolute proton beam range with a standard deviation of 1.0-1.4 mm.
• Detected relative range shifts with a standard deviation of 0.3-0.5 mm.
• Achieved accurate determination of oxygen and carbon concentrations in phantoms.

Conclusions:

• Quantitative prompt gamma-ray measurements, utilizing nuclear reaction cross sections, enable precise proton range verification.
• This method is effective even in the presence of unknown tissue compositions.
• The findings support the clinical application of prompt gamma-ray spectroscopy for real-time proton therapy monitoring.