Dose quantification in carbon ion therapy using in-beam positron emission tomography

Area of Science:

• Medical Physics
• Radiotherapy
• Nuclear Medicine

Background:

• Accurate dose distribution is critical for effective carbon ion therapy.
• Positron emission tracking offers a potential in-vivo method for dose verification.
• Fragment decay analysis provides insights into particle interactions within the target volume.

Purpose of the Study:

• To develop and validate an iterative method for estimating absolute dose distribution in carbon ion therapy.
• To utilize positron annihilation signals from fragment decays for dose reconstruction.
• To improve the precision of dose delivery monitoring in carbon ion radiotherapy.

Main Methods:

• Decomposition of positron annihilation distributions into contributions from ¹¹C, ¹⁰C, and ¹⁵O.
• Construction of a basis function library via simulation of monoenergetic ¹²C irradiations.
• Iterative fitting of fragment profile library to acquired annihilation data, incorporating total variation regularization.
• Combination of fitted weights with monoenergetic dose profiles for total dose estimation.

Main Results:

• The method accurately calculates dose profiles with low mean relative errors (0.8% for ¹¹C, 1.0% for ¹⁰C, 1.6% for ¹⁵O).
• Accurate estimation of the Spread-Out Bragg Peak (SOBP) distal edge position (within 0.7 mm, 1.9 mm, and 1.2 mm for the respective isotopes).
• Successful evaluation across 14 diverse polyenergetic ¹²C dose profiles, including flat, randomized, and complex distributions.

Conclusions:

• The proposed iterative method effectively reconstructs absolute dose distributions in carbon ion therapy using positron annihilation data.
• This technique offers a promising approach for in-vivo dose verification and quality assurance in particle therapy.
• The findings support the clinical translation of positron emission tracking for real-time dose monitoring during carbon ion treatments.