Hatamikia Sepideh, Biguri Ander, Kronreif Gernot, Figl Michael, Russ Tom, Kettenbach Joachim, Buschmann Martin, Birkfellner Wolfgang
Austrian Center for Medical Innovation and Technology, Wiener Neustadt, Austria.
Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria.
PLoS One. 2021 Feb 9;16(2):e0245508. doi: 10.1371/journal.pone.0245508. eCollection 2021.
Cone beam computed tomography (CBCT) has become a vital tool in interventional radiology. Usually, a circular source-detector trajectory is used to acquire a three-dimensional (3D) image. Kinematic constraints due to the patient size or additional medical equipment often cause collisions with the imager while performing a full circular rotation. In a previous study, we developed a framework to design collision-free, patient-specific trajectories for the cases in which circular CBCT is not feasible. Our proposed trajectories included enough information to appropriately reconstruct a particular volume of interest (VOI), but the constraints had to be defined before the intervention. As most collisions are unpredictable, performing an on-the-fly trajectory optimization is desirable. In this study, we propose a search strategy that explores a set of trajectories that cover the whole collision-free area and subsequently performs a search locally in the areas with the highest image quality. Selecting the best trajectories is performed using simulations on a prior diagnostic CT volume which serves as a digital phantom for simulations. In our simulations, the Feature SIMilarity Index (FSIM) is used as the objective function to evaluate the imaging quality provided by different trajectories. We investigated the performance of our methods using three different anatomical targets inside the Alderson-Rando phantom. We used FSIM and Universal Quality Image (UQI) to evaluate the final reconstruction results. Our experiments showed that our proposed trajectories could achieve a comparable image quality in the VOI compared to the standard C-arm circular CBCT. We achieved a relative deviation less than 10% for both FSIM and UQI metrics between the reconstructed images from the optimized trajectories and the standard C-arm CBCT for all three targets. The whole trajectory optimization took approximately three to four minutes.
锥形束计算机断层扫描（CBCT）已成为介入放射学中的一项重要工具。通常，采用圆形源 - 探测器轨迹来获取三维（3D）图像。由于患者体型或额外医疗设备导致的运动学限制，在进行全圆旋转时常常会与成像仪发生碰撞。在之前的一项研究中，我们开发了一个框架，用于为圆形CBCT不可行的情况设计无碰撞、针对患者的轨迹。我们提出的轨迹包含足够的信息来适当地重建特定的感兴趣体积（VOI），但约束条件必须在干预前定义。由于大多数碰撞是不可预测的，因此进行实时轨迹优化是很有必要的。在本研究中，我们提出一种搜索策略，该策略探索一组覆盖整个无碰撞区域的轨迹，随后在图像质量最高的区域进行局部搜索。使用先前诊断CT体积上的模拟来选择最佳轨迹，该CT体积用作模拟的数字体模。在我们的模拟中，特征相似性指数（FSIM）用作目标函数来评估不同轨迹提供的成像质量。我们使用Alderson - Rando体模内的三个不同解剖目标研究了我们方法的性能。我们使用FSIM和通用质量图像（UQI）来评估最终的重建结果。我们的实验表明，与标准C形臂圆形CBCT相比，我们提出的轨迹在VOI中可以实现相当的图像质量。对于所有三个目标，优化轨迹重建图像与标准C形臂CBCT之间的FSIM和UQI指标的相对偏差均小于10%。整个轨迹优化大约需要三到四分钟。
