Dual-energy head cone-beam CT using a dual-layer flat-panel detector: physics-based material decomposition

Flat panel detector (FPD) based cone-beam computed tomography (CT) has made tremendous progress these days, with many new medical and industrial applications keeping emerging from diagnostic imaging and image guidance for radiotherapy and interventional surgery. However, current cone-beam CT (CBCT) is still suboptimal for head scan whose requirement for image quality is extremely strict. Recently, the dual-layer flat panel detector technology is under development and is promising to further advance CBCT from qualitative anatomic imaging to quantitative dual-energy CT. Its potential of enabling head CBCT applications has yet been investigated. The relatively moderate energy separation from the dual-layer FPD and the overall low signal level especially for the bottom layer detector, raise significant challenges in performing high quality dual-energy material decomposition. In this work, we propose a physics based material decomposition algorithm that attempts to fully use the detected X-ray signals and prior-knowledge behind head CBCT using dual-layer FPD. Specifically, projection data from the two layers of detector are first adaptively combined to generate conventional CT images with reduced noise. A physics model based dual-layer multi-material spectral correction (dMMSC) is then developed to make the combined image reconstruction beam-hardening free. After a regular projection-domain material decomposition (MD) being conducted, the corresponding beam-hardening free projections from the dMMSC will be taken as a guidance to further enhance the dual-layer MD performance, leading to significantly improved robustness of MD and suppressed low-signal artifact in our preliminary results.