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WE-C-217BCD-11: Coupled Radiative and Optical Geant4 Simulation of MV EPIDs Based on Thick Pixelated Scintillating
D Constantin1,2, M Sun1,2, E Abel1,2
1Stanford University, Stanford, CA.
Medical Physics
|May 19, 2017
Summary
This study validates megavoltage (MV) CT detector performance using Geant4 simulations, achieving excellent agreement with experimental data. The findings suggest using optically opaque, specular septa to enhance detector efficiency for improved medical imaging.
Area of Science:
- Medical Physics
- Imaging Science
- Detector Physics
Background:
- Metal artifacts in kilovoltage (kV) CT imaging reduce diagnostic quality.
- Megavoltage (MV) photons offer a solution by penetrating high-Z objects, reducing artifacts.
- High detective quantum efficiency (DQE) MV detectors are crucial for dose-efficient imaging.
Purpose of the Study:
- Validate coupled radiation and optical Geant4 simulation results against experimental data for prototype pixelated scintillator MV detectors.
- Determine essential optical parameters influencing MV detector performance.
- Establish a comprehensive DQE model for MV detectors.
Main Methods:
- Experimental data from 8 different detectors (CsI, CdW, BGO scintillators) using a 6MV source were analyzed.
- Accurate Geant4 models were developed, incorporating coupled radiation and optical simulations.
- Optical properties were optimized by minimizing differences in modulation transfer functions (MTF) between simulated and experimental data.
- Simulation validation was performed against normalized noise power spectrum (NNPS(f)) and DQE(f) curves.
Main Results:
- Optimal optical parameters were identified: 10% top surface reflectivity, 95% crystal-septa surface reflectivity, and 90% Lambertian component for reflected beams.
- The absolute difference between experimental and simulated data remained below 10% across all datasets.
- The developed Geant4 model demonstrated high fidelity in predicting detector performance.
Conclusions:
- This study presents the first comprehensive optical and radiative DQE(f) model using Geant4 with excellent experimental validation.
- The model highlights the potential for improved MV detector performance.
- Utilizing more specular and optically opaque septa is recommended for enhanced detector efficiency.
