G4RT — Geant4-Based Simulation Platform for Radiotherapy Phantom Studies

We introduce G4RT, a reproducible simulation framework that transforms complete computer-aided design assemblies into Geant4-compatible detector geometries via a fully auditable computer-aided design-to-database (CAD → DB) workflow. Exports from the Fusion 360 CAD platform (3MF and CSV) are normalized into a schema-constrained database and processed by a database-driven geometry builder, which preserves hierarchical structure, material definitions, and spatial transformations while generating tessellated solids and registering sensitive detector volumes. Physics settings, cut-offs, sources (analytic or International Atomic Energy Agency phase-space files), and scoring parameters are centrally configured using TOML, a human-readable configuration file format. We assess geometry fidelity, dosimetric accuracy via gamma analysis, and computational performance under multithreading, demonstrating reduced iteration times and enhanced auditability compared to hand-coded geometries. This approach is particularly suited for experiments employing 3D-printed scintillator phantoms under clinically realistic beam conditions.