Impact of Inorganic Scintillators on Dose Response: A Gate Modeling Study
Abstract
Purpose
Inorganic scintillating detectors offer high-precision and high spatiotemporal resolution dosimetry for small-field radiotherapy applications such as SRS, SBRT, and SFRT. This study examines the impact of detector materials and volume on dose distributions to ensure accurate dose measurement and clinical calibration.
Methods
Comprehensive clinical dose measurement modeling was performed using Monte Carlo simulations in GATE based on GEANT4. The detection channel was modeled according to the sensitive volume geometry and scintillator material composition to evaluate dose quantification and perturbation analysis. A realistic clinical setup was implemented using treatment room geometry, clinical phantoms, and an Elekta LINAC source. A 6 MV photon beam with field sizes of 0.5 × 0.5 cm2, 3 × 3 cm2, and 10 × 10 cm2 was simulated using TPS data. Two inorganic scintillating detectors with sensitive volumes of 2 × 10-5 mm³ and 5 × 10-3 mm³ were evaluated, including the addition of thin material layers to assess material-dependent effects on absorbed dose measurements.
Results
The detector with the smallest sensitive volume(2 × 10-5 mm³) showed no measurable impact on dose distributions. In contrast, a tenfold increase in scintillating volume using the same material produced average dose deviations of approximately 2.5% for the smallest field (0.5 × 0.5 cm2) and about 1% for larger fields (3 × 3 cm2 and 10 × 10 cm2). The addition of an external amplification layer(~ 200 μm aluminum coating) introduced a negligible dose perturbation (<0.1%) for all fields in both cases. Overall, simulation results show improved accuracy in dose distributions for the smaller-volume detector relative to the larger-volume.
Conclusion
The study shows that scintillator volumes above a critical threshold value can perturb dose distributions and measurements. These results highlight the importance of designing geometry-controlled sensitive volume detectors for accurate small-field dosimetry and have the potential for multi-modality applications.