Patient positioning verification for proton therapy using proton radiography.

Area of Science:

• Medical Physics
• Radiation Oncology
• Radiotherapy Technology

Background:

• Accurate patient positioning is critical for effective proton therapy.
• Current verification methods may have limitations in precision or dose.
• Proton Range Probes (RP) have shown simulation-based potential for positioning verification.

Purpose of the Study:

• To experimentally validate the accuracy and feasibility of Proton Range Probes (RP) for patient positioning verification in proton therapy.
• To assess the detection capabilities of RP for translational and rotational positioning errors.
• To estimate the additional dose delivered to patients using RP for verification.

Main Methods:

• Experimental evaluation of RP accuracy using tissue-like samples and a multilayer ionization chamber (MLIC).
• Measurements using anthropomorphic phantoms to detect rotational and translational errors.
• Characterization of the residual integral depth dose curve (RIDDC) and comparison with Monte Carlo simulations.
• Estimation of additional patient dose by measuring local dose from a single RP.

Main Results:

• Prediction accuracy of water equivalent path length was 0.70% in tissue phantoms, with higher deviations in low-density samples (up to 5.67%).
• 1D translational and rotational errors were detected with accuracies of 1 mm and 2°, respectively, using selected RPs.
• The additional dose burden to the patient was found to be low.

Conclusions:

• Proton Range Probes (RP) are experimentally validated as a viable tool for patient positioning verification in proton therapy.
• The RP method demonstrates high accuracy in detecting positioning errors with minimal additional dose.
• RP offers a simple, fast, and low-dose solution for patient set-up verification in clinical proton therapy.