Carbon ion radiography with a composite ionization chamber detector

Area of Science:

• Medical Physics
• Particle Therapy
• Radiography

Background:

• Range uncertainty in carbon ion therapy can lead to deviations in planned dose distributions, reducing treatment efficacy.
• Accurate relative stopping power (RSP) maps are crucial for mitigating range uncertainty in carbon ion therapy.
• Current methods may lack the precision required for optimal patient treatment outcomes.

Purpose of the Study:

• To develop and evaluate a composite ionization chamber detection (CICD) system prototype for precise carbon ion radiography.
• To assess the system's ability to generate accurate relative stopping power (RSP) maps.
• To establish a foundation for reducing range uncertainty in carbon ion therapy.

Main Methods:

• Developed a preliminary composite ionization chamber detection (CICD) prototype with synchronously gated integral electronics.
• Measured depth-to-dose curves and beam profiles simultaneously.
• Conducted carbon ion radiography experiments on various phantoms using the Heavy Ion Medical Machine (HIMM) beam.
• Performed Geant4 simulations to eliminate electronic noise effects.

Main Results:

• The CICD prototype achieved thickness prediction accuracies of 88.25% for sloped phantoms, with an absolute mean error (AME) of 1.07 mm.
• Electronic noise (NSR of 14.36 dB) was identified as a primary factor affecting prototype accuracy.
• Simulations demonstrated significantly improved thickness prediction accuracies (98.54%–99.07%) and reduced AME (0.09 mm–0.48 mm) after noise reduction.

Conclusions:

• The CICD prototype shows potential for refining accuracy and resolution in carbon ion radiography.
• Noise reduction techniques, like those used in simulations, are vital for maximizing the system's performance.
• This technology provides a scientific basis for minimizing range uncertainty and enhancing precision particle therapy.