Abadi Ehsan, Segars William P, Harrawood Brian, Sharma Shobhit, Kapadia Anuj, Samei Ehsan
Duke University School of Medicine, Carl E. Ravin Advanced Imaging Laboratories, Department of Radiology, Durham, North Carolina, United States.
Duke University School of Medicine, Medical Physics Graduate Program, Durham, North Carolina, United States.
J Med Imaging (Bellingham). 2020 Jul;7(4):042806. doi: 10.1117/1.JMI.7.4.042806. Epub 2020 Jun 1.
To utilize a virtual clinical trial (VCT) construct to investigate the effects of beam collimation and pitch on image quality (IQ) in computed tomography (CT) under different respiratory and cardiac motion rates. A computational human model [extended cardiac-torso (XCAT) phantom] with added lung lesions was used to simulate seven different rates of cardiac and respiratory motions. A validated CT simulator (DukeSim) was used in this study. A supplemental validation was done to ensure the accuracy of DukeSim across different pitches and beam collimations. Each XCAT phantom was imaged using the CT simulator at multiple pitches (0.5 to 1.5) and beam collimations (19.2 to 57.6 mm) at a constant dose level. The images were compared against the ground truth using three task-generic IQ metrics in the lungs. Additionally, the bias and variability in radiomics (morphological) feature measurements were quantified for task-specific lung lesion quantification across the studied imaging conditions. All task-generic metrics degraded by 1.6% to 13.3% with increasing pitch. When imaged with motion, increasing pitch reduced motion artifacts. The IQ slightly degraded (1.3%) with changes in the studied beam collimations. Patient motion exhibited negative effects (within 7%) on the IQ. Among all features across all imaging conditions studies, compactness2 and elongation showed the largest ( , 7.8%) and smallest ( , 2.7%) relative bias and variability. The radiomics results were robust across the motion profiles studied. While high pitch and large beam collimations can negatively affect the quality of CT images, they are desirable for fast imaging. Further, our results showed no major adverse effects in morphology quantification of lung lesions with the increase in pitch or beam collimation. VCTs, such as the one demonstrated in this study, represent a viable methodology for experiments in CT.
利用虚拟临床试验（VCT）构建体来研究在不同呼吸和心脏运动速率下，计算机断层扫描（CT）中束准直和螺距对图像质量（IQ）的影响。使用添加了肺部病变的计算人体模型[扩展心脏-躯干（XCAT）体模]来模拟七种不同的心脏和呼吸运动速率。本研究使用了经过验证的CT模拟器（DukeSim）。进行了补充验证以确保DukeSim在不同螺距和束准直情况下的准确性。每个XCAT体模在恒定剂量水平下，使用CT模拟器在多个螺距（0.5至1.5）和束准直（19.2至57.6毫米）下进行成像。使用肺部的三种通用任务IQ指标将图像与真实情况进行比较。此外，针对所研究的成像条件下特定任务的肺部病变量化，对放射组学（形态学）特征测量中的偏差和变异性进行了量化。随着螺距增加，所有通用任务指标下降了1.6%至13.3%。在有运动的情况下成像时，增加螺距可减少运动伪影。随着所研究的束准直变化，IQ略有下降（1.3%）。患者运动对IQ有负面影响（在7%以内）。在所有成像条件研究的所有特征中，紧凑度2和伸长率显示出最大最大特征最大（ ，7.8%）和最小（ ，2.7%）的相对偏差和变异性。放射组学结果在所研究的运动曲线中具有稳健性。虽然高螺距和大束准直会对CT图像质量产生负面影响，但它们有利于快速成像。此外，我们的结果表明，随着螺距或束准直的增加，在肺部病变形态学量化方面没有重大不利影响。像本研究中展示的虚拟临床试验是CT实验的一种可行方法。
