(Tuesday, 7/31/2018) 1:15 PM - 1:45 PM
Room: Exhibit Hall | Forum 8
Purpose: Aiming at improving the precision of radiotherapy, dual energy imaging with dual filter was proposed to be designed for Brainlab ExacTrac clinical stereoscopic image guidance system to further enhance the image quality for both, bone-only (spin SBRT) and soft-tissue-only (lung SBRT) DE imaging. Hence, there is a need to develop an accurate and reliable computational methods with a comprehensive characterization of the existing ExacTrac x-ray platform, which is the main objective of this work.
Methods: X-ray spectra for different tube potentials were thoroughly characterized by simulation and experimental measurements. The simulation was performed using SPEKTR 3 toolkit. To validate the simulation results, the x-ray spectra of an ExacTrac system were acquired for 60-140 kVp range using a CdTe detector with multiple added collimators. For the same kVp range, half value layer (HVL) in mm of Aluminum (Al) were measured using a calibrated RaySafe detector. The raw spectra were calibrated using 57Co source and corrected for the escape peaks and detector efficiency. The simulation input parameters were varied until the simulated spectra matched the measured spectra for full kVp range. Using this optimized input parameters, the SPEKTR HVLs were calculated and compared to the measured values.
Results: The best match between simulation and measured spectra for full kVp range was achieved with SPEKTR parameters of 1.6 mm Al inherent filtration, 2.9 mm added Al, and -0.002 mm Tungsten (W) for the small anode angle correction. As another validation, the simulated and measured HVLs were matched satisfactorily within 3% for all kVps.
Conclusion: The ExacTrac stereoscopic imaging x-ray tube was extensively investigated and characterized using simulation and experimental measurements of both spectra and HVLs. The SPEKTR code with optimized parameters will be employed confidently in identifying filter materials and their thicknesses in a future dual energy study for dual filter design.
Funding Support, Disclosures, and Conflict of Interest: The authors acknowledge financial support from the Atlantic Canada Opportunities Agency (ACOA) Atlantic Innovation Fund (AIF)
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