Feasibility of enhanced electron density maps based on spectral CT for abdominal radiation treatment planning and dose calculation

During Computed tomography (CT) simulation, iodine contrast agents are typically injected to assist in more precise contouring. However, contrast agents are absent during radiotherapy planning and treatment, and the presence of iodine can potentially affect dose calculations. To improve dose calculation accuracy and clinical efficiency, this study explores the feasibility of using enhanced electron density(EED) maps for dose calculation. Twenty patients who underwent enhanced spectral CT scanning for abdominal tumors from June 2023 to October 2024 were retrospectively included. Relative differences in relative electron density(RED) values of EED maps versus non-contrast electron density (NCED) maps and Hounsfield unit (HU) values of enhanced CT (ECT) versus non-contrast CT (NCCT) were compared. Dose calculation comparisons were made based on radiotherapy plans generated from EED, NCCT and NCED maps, and evaluation metrics included, dose-volume histogram (DVH) parameters, and gamma pass rates. The differences in RED values between EED and NCED were minimal (−0.07 % to −1.22 %), whereas the differences in HU values between NCCT and ECT were significant(-15.33 % to −70.85 %). The comparison of DVH parameters between the EED and NCCT plans revealed no statistically significant differences for most parameters in both PTV and OARs, with the maximum discrepancy being only 0.24 Gy. No statistically significant differences were observed in any DVH parameters between EED and NCED plans. Gamma pass rates showed a high degree of agreement in the dose distributions between the EED and NCCT plans, and between the EED and NCED plans, with a Gamma pass rate of more than 94 % at the 1 %/1 mm criterion. We have preliminarily validated that EED based on spectral CT can be used for dose calculation for radiotherapy planning, and that this method is effective in reducing errors, improving clinical workflow, and reducing image dose to patients.