Advancing carbon ion therapy with dual-energy CT: Enhanced elemental decomposition for precise range and secondary...

This study introduces a parameterization method to predict elemental mass ratios through DECT and extending to the dose estimation of carbon ion therapy.

An extensive dataset comprising 85 biological tissues was utilized to calculate the effective atomic number and the electron density ratio. A parameterization technique was developed to estimate elemental mass fractions. The method incorporated an arctan function to constrain the mass fractions of hydrogen and carbon, with concurrent consideration of other elements. Besides, the method was applied to the ICRP110 human phantom to ascertain its elemental composition. Monte-Carlo simulations were conducted to irradiate the phantom with carbon ion beams, yielding dose distributions for primary and secondary particles. The results were compared to the existing SECT and DECT methods.

The proposed DECT method improves the accuracy of determining density of six elements about twofold compared to the SECT method and reduces the uncertainty in range prediction of a 400 MeV/u carbon ion beam by 50 %. With the ICRP110 human phantom irradiated with a 350 MeV/u carbon ion beam, this method improved peak position prediction by 2.0 mm (1.0 mm), gamma passing rates of dose by 12 % (9 %) and secondary dose by up to ∼25 % (∼16 %) over the SECT method (existing DECT method).

The proposed DECT method can accurately predict elemental densities in human tissues, improving the accuracy of primary and secondary dose distributions compared to existing methods, which shows potential in precise estimation of linear energy transfer and relative biological effects of carbon ion therapy.