Comparative accuracy and resolution assessment of two prototype proton computed tomography scanners

Area of Science:

• Medical Imaging
• Particle Therapy Physics

Background:

• Proton computed tomography (pCT) offers accurate relative stopping power (RSP) estimation for proton therapy.
• Scanner design impacts spatial resolution and RSP accuracy, necessitating comparative studies.

Purpose of the Study:

• Directly compare spatial resolution and RSP accuracy of two pCT prototype scanners.
• Evaluate performance using the same image reconstruction algorithm at a single facility.

Main Methods:

• Scanned a phantom with known RSP inserts using phase-II and ProtonVDA pCT prototypes.
• Estimated spatial resolution via radial edge spread function.
• Evaluated RSP accuracy using mean absolute percent error (MAPE).

Main Results:

• Both scanners achieved ~0.72% MAPE (excluding one insert).
• ProtonVDA showed better overall MAPE (0.81%) than phase-II (1.14%).
• Phase-II spatial resolution (0.61 lp/mm) exceeded ProtonVDA (0.46 lp/mm).

Conclusions:

• Both pCT scanners meet the ~1% RSP accuracy requirement for proton therapy.
• Spatial resolution differences stem from distinct design philosophies: full tracking vs. position-only tracking.