In-beam PET imaging for on-line adaptive proton therapy: an initial phantom study

Area of Science:

• Medical Physics
• Nuclear Medicine
• Radiotherapy Technology

Background:

• Proton therapy requires precise beam range verification for effective and safe treatment.
• Online image-guided adaptive proton therapy necessitates real-time monitoring capabilities.

Purpose of the Study:

• To develop and investigate a positron emission tomography (PET) system for on-line image-guided adaptive proton therapy.
• To assess the PET system's capability for intra-fraction proton beam range verification.

Main Methods:

• A novel PET system with dual rotating depth-of-interaction measurable detector panels (SSPM arrays, LYSO scintillators) was designed.
• Data acquisition involved irradiating a phantom with a 179.2 MeV proton beam and acquiring PET data during and after irradiation at multiple angles.
• Image reconstruction and analysis were performed to measure positron activity range and system performance.

Main Results:

• The PET system demonstrated high sensitivity and uniform resolution, achieving sub-millimeter activity range accuracy.
• Minimal acquisition time (6s) and three spills were sufficient for accurate measurements.
• Minor energy photo-peak shifts due to neutron exposure were observed but corrected offline.

Conclusions:

• The developed prototype PET system is feasible for intra-fraction proton beam range verification in adaptive proton therapy.
• The system shows promise for real-time applications, enabling faster and more accurate treatment adjustments.
• Further development is needed for a clinical translation of this on-line PET system.