Buliev Ivan G, Badea Cristian T, Kolitsi Zoi, Pallikarakis Nicolas
Department of Medical Physics, University of Patras, Patras 26500, Greece.
IEEE Trans Inf Technol Biomed. 2003 Dec;7(4):404-11. doi: 10.1109/titb.2003.821336.
Computed tomography (CT) reconstruction methods assume imaging of static objects; object movement during projection data acquisition causes tomogram artifacts. The continuously moving heart, therefore, represents a complicated imaging case. The associated problems due to the heart beating can be overcome either by using very short projection acquisition times, during which the heart may be considered static, or by ECG-gated acquisition. In the latter case, however, the acquisition of a large number of projections may not be completed in a single breath hold, thus heart displacement occurs as an additional problem. This problem has been addressed by applying heart motion models in various respiratory motion compensation algorithms. Our paper focuses on cone beam computed tomography (CBCT), performed in conjunction with isocentric, fluoroscopic equipment, and continuous ECG and respiratory monitoring. Such equipment is used primarily for in-theater three-dimensional (3-D) imaging and benefits particularly from the recent developments in flat panel detector technologies. The objectives of this paper are: i) to develop a model for the motion of the heart due to respiration during the respiratory cycle; ii) to apply this model to the tomographic reconstruction algorithm, in order to account for heart movement due to respiration in the reconstruction; and iii) to initially evaluate this method by means of simulation studies. Based on simulation studies, we were able to demonstrate that heart displacement due to respiration can be estimated from the same projection data, required for a CBCT reconstruction. Our paper includes semiautomatic segmentation of the heart on the X-ray projections and reconstruction of a convex 3-D-heart object that performs the same motion as the heart during respiration, and use of this information into the CBCT reconstruction algorithm. The results reveal significant image quality improvements in cardiac image reconstruction.
计算机断层扫描（CT）重建方法假定对静态物体进行成像；在投影数据采集过程中物体的移动会导致断层图像伪影。因此，持续跳动的心脏代表了一种复杂的成像情况。由于心脏跳动产生的相关问题可以通过使用极短的投影采集时间来克服，在此期间心脏可被视为静止的，或者通过心电图门控采集来解决。然而，在后一种情况下，在一次屏气期间可能无法完成大量投影的采集，因此心脏移位成为一个额外的问题。通过在各种呼吸运动补偿算法中应用心脏运动模型已解决了这个问题。我们的论文聚焦于与等中心荧光透视设备、连续心电图和呼吸监测相结合进行的锥束计算机断层扫描（CBCT）。此类设备主要用于术中三维（3-D）成像，并且特别受益于平板探测器技术的最新发展。本文的目标是：i）建立一个在呼吸周期中由于呼吸导致的心脏运动模型；ii）将此模型应用于断层重建算法，以便在重建中考虑由于呼吸引起的心脏运动；iii）通过模拟研究初步评估此方法。基于模拟研究，我们能够证明可以从CBCT重建所需的相同投影数据中估计出由于呼吸导致的心脏移位。我们的论文包括在X射线投影上对心脏进行半自动分割以及重建一个在呼吸过程中与心脏执行相同运动的凸三维心脏物体，并将此信息用于CBCT重建算法。结果显示心脏图像重建中的图像质量有显著提高。
