Quantitative Optimization of a Lead-Free Hybrid Active Collimator for Enhanced Radiation Protection and Image Fidelity In Mobile Fluoroscopy
Abstract
Purpose
In mobile C-arm guided interventions, reducing the radiation dose to the operator’s hands and patient’s Organ-at-Risk (OAR) is critical. Conventional collimators provide total occlusion, often sacrificing peripheral anatomical context. This study aims to develop and optimize a "see-through" hybrid active collimator using lead-free materials to achieve a balance between significant dose reduction and the maintenance of essential diagnostic visibility.
Methods
A lead-free composite of Barium Sulfate (BaSO4) and Silicon Dioxide (SiO2) was fabricated into 1 mm thick sheets. Experimental measurements were performed using a mobile C-arm (XPLUS-35FD, GEMSS Healthcare) at 93 kVp and 4.3 mA with a thorax phantom. Attenuation characteristics (HVL, TVL) and dose rates were measured using a Radcal AGMS-DM+ semiconductor detector. The impact of shielding thickness (1 to 6 mm) on image fidelity was quantitatively evaluated via Modulation Transfer Function (MTF) analysis to identify the clinical threshold for "active" collimation.
Results
The hybrid material demonstrated an HVL of 0.8 mm and a TVL of 2.9 mm. While the unattenuated dose rate was 17.38 +/- 0.2 mGy/min, the material provided effective dose reduction across all tested thicknesses. Analysis of the MTF showed that at an optimal thickness of 3 mm, the system maintained an MTF value of 0.3 at 30% contrast, preserving sufficient image quality to visualize peripheral structures. Beyond 4 mm, the image degradation became clinically unacceptable, rendering the "see-through" capability ineffective. The 3 mm thickness was determined as the optimal point for hybrid collimation, maximizing protection without compromising the surgical field of view.
Conclusion
The developed BaSO4/SiO2 hybrid collimator provides a viable solution for OAR protection in fluoroscopy. By maintaining diagnostic fidelity through optimized material thickness, this active collimation system allows for safer interventional procedures. This study establishes the physical and clinical parameters required for implementing lead-free hybrid shielding in real-time imaging environments.