Typically, an angular range between 116°- 152° was used for the optimized trajectories. Our results show that optimized trajectories can outperform simple partial circular trajectories in the VOI in term of image quality. We also compared our proposed trajectories to circular trajectories with equivalent angular sampling as the optimized trajectories. Furthermore, for the anatomical target the relative deviation of FSIM, UQI and CNR between the reconstructed image related to the proposed trajectory and the standard C-arm circular CBCT were found to be 5.06%, 6.89% and 8.64% respectively. We achieved a relative deviation less than 7% for FWHMavg between the reconstructed images from the optimized trajectories and the standard C-arm CBCT for all spherical targets.
Our experiments based on both the box and head phantom showed that optimized trajectories could achieve a comparable image quality in the VOI with respect to the standard C-arm circular CBCT while using approximately one quarter of projections. In order to quantify the image quality of the reconstructed image we use the average Full-Width-Half-Maximum (FWHMavg ) for the spherical target and Feature SIMilarity Index (FSIM), Universal Quality Image (UQI) and Contrast-to-Noise Ratio (CNR) for an anatomical target. The performance of the proposed framework is investigated in experiments involving an in-house-built box phantom including spherical targets as well as an Alderson-Rando head phantom.
The final optimized trajectory includes a limited angular range and a minimal number of projections which can be applied to a C-arm device capable of general source-detector positioning. Selection of the best projection views is accomplished through maximizing an objective function fed by the imaging quality provided by different x-ray positions on the digital phantom data. Such a customized trajectory should include enough information to sufficiently reconstruct a particular volume of interest (VOI) under kinematic constraints which may result from the patient size or additional surgical or radiation therapy related equipment.Ī patient specific model from a prior diagnostic computed tomography (CT) volume is used as a digital phantom for CBCT trajectory simulations. Our main aim is to enable a CBCT system to provide topical information about the target using a limited angle non-circular scan orbit with a minimal number of projections. We developed a target-based cone beam computed tomography (CBCT) imaging framework for optimizing an unconstrained three dimensional (3D) source-detector trajectory by incorporating prior image information.
0 kommentar(er)
