Investigating the feasibility of X-ray incident angle determination using radiophotoluminescent glass dosimeter

Abstract

Abstract Radiophotoluminescent (RPL) glass dosimeters are widely used for personal and environmental radiation monitoring purposes. However, their ability to determine irradiation geometries remains largely unexplored. In this study, we investigated the feasibility of determining X-ray incident angles using an originally developed RPL imaging system. The RPL glass samples were irradiated at angles ranging from 0 to 90° and subsequently analyzed using the smartphone-based system under UV excitation. Spatially resolved intensity distributions were extracted from the red channel of the acquired images, and quantitative analysis was performed using region-of-interest segmentation along the glass. The results revealed a clear angular dependence of the RPL signal, characterized by increasing spatial non-uniformity and a progressive decrease in distal intensity with increasing incident angle. The distal-to-proximal intensity ratio demonstrated strong sensitivity to angular variation, and the angle-dependent change in the ratio was successfully modeled using a cosine-based function within the 0–75° range of angles. A distinct deviation observed at 90° suggests the presence of additional physical effects beyond simple geometric attenuation. Consistent angular trends across multiple spatial regions confirm the robustness of the method, while the enhanced sensitivity at the distal region highlights the role of cumulative attenuation effects. These findings demonstrate the effectiveness of RPL imaging in evaluating incident angles in addition to point doses. Further studies will focus on developing a practical system that can be easily deployed in radiological emergencies.