Linac-integrated on-board spectral-CT/CBCT imaging using a photon-counting detector: a Monte Carlo study

Purpose: To investigate the feasibility of dual-modal on-board spectral-CT/CBCT imaging using a CZT photon-counting detector mounted on Linac by Monte Carlo simulations. Methods: In this proof-of-concept study, software platform Geant4 Application for Tomography Emission (GATE) and high-performance computing hardware were utilized to design validate novel spectral-CT conventional CBCT system single integrated into Linac. Through combined use simulation charge transportation model based diffusion equation, we simulated x-ray energy spectra with pixel sizes ranging 200–1,000 μm, which optimized size was determined. Spatial resolution evaluated oversampling tilted tungsten wire. A PMMA phantom, containing calcium contrast elements iodine, gadolinium, gold, demonstrate spectral CT capability K-edge method. Results: Considering trade-off between photon-peak efficiency spatial detector, determined be 400 µm. The estimated 19.2 lp/cm@10% modulation transfer function. provided sufficient structural details phantom high image contrast. Compared images differentiated four contained within very well. Conclusion: results demonstrated photon counting in