Automated evaluation of setup errors in carbon ion therapy using PET: feasibility study.

Area of Science:

• Medical Physics
• Radiation Oncology
• Nuclear Medicine

Background:

• Carbon-ion therapy offers precise dose delivery but requires accurate patient positioning.
• Patient mispositioning can compromise treatment efficacy and increase toxicity.
• Positron emission tomography (PET) is being explored for real-time monitoring in particle therapy.

Purpose of the Study:

• To evaluate the efficacy of automated image registration-based particle therapy PET for detecting patient mispositioning during carbon-ion therapy.
• To assess the performance of this technique across various tumor sites including head and neck, pelvic, lung, and brain regions.

Main Methods:

• Biologically optimized carbon ion treatment plans were created.
• Monte Carlo simulations generated reference β(+)-activity distributions.
• Simulated setup errors (shifts, rotations) were introduced to computed tomography (CT) data.
• Pearson's correlation coefficient (PCC) compared simulated PET images to reference distributions.
• Inbeam and inroom PET scenarios were evaluated.

Main Results:

• Automated PCC detection identified cranio-caudal shifts of ≥4 mm in head and neck, lung, and brain regions.
• Detection was not feasible for prostate tumors due to homogeneous pelvic region.
• Lung tumor detection sensitivity varied with location, down to 2 mm shifts for central tumors.
• Rotational shifts of ≥6° were detectable in head and neck and lung regions.
• Inroom PET with longer measurement times showed advantages.

Conclusions:

• Automated particle therapy PET is a viable technique for detecting patient setup errors in carbon-ion therapy.
• The method shows promise for clinical implementation to enhance treatment accuracy.
• Further optimization of PET monitoring strategies is warranted for diverse clinical scenarios.