A Novel 2D Scintillation Dosimeter Using Long Scintillating Fibers
Abstract
Purpose
Two-dimensional dosimetry for radiotherapy quality assurance commonly relies on planar detector arrays or radiochromic film. While these methods provide high spatial resolution, they are often time-consuming, single-use, and do not provide real-time feedback. This work presents a simulation-based validation of a two-dimensional dosimetry concept using long plastic scintillating fibers combined with tomographic reconstruction. The objective is to enable accurate dose reconstruction from a limited number of projections while supporting non-rotating acquisition strategies and optimizing key design parameters for a compact and mechanically simple QA dosimeter.
Methods
High-statistics Monte Carlo simulations were performed using TOPAS with a 6~MV photon phase space provided by the IAEA. Reference square and H-shaped radiation fields were generated in water and used as ground truth. Dose reconstructions were evaluated using filtered back-projection, the simultaneous iterative reconstruction technique, and the simultaneous iterative reconstruction technique with total variation regularization. The effects of projection number, rotating versus non-rotating multi-stack acquisition, depth and beam divergence corrections using percentage depth dose scaling and pitch variation, and fiber sampling density were quantified using profile-based metrics, including field size, penumbra width, mean absolute error, and one-dimensional gamma analysis using a 3%/3mm criterion.
Results
The SIRT+TV achieved the best agreement with reference dose profiles, with a mean absolute error of 3.22 % and a gamma pass rate of 93.5 %. Reducing the number of projections from nineteen to ten preserved field size within one millimeter with moderate penumbra broadening. A non-rotating multi-stack configuration achieved a MAE of 4.19 %, compared with 2.66 % for a rotating configuration.
Conclusion
Accurate two-dimensional dose reconstruction can be achieved using limited-angle and non-rotating plastic scintillation fiber configurations. The proposed dosimeter offers reusability, real-time dose readout, and mechanical simplicity, making it suitable for routine radiotherapy quality assurance and enabling future extension toward quasi-three-dimensional dose verification using stacked layers.