Linac-integrated 4D cone beam CT:: first experimental results
Linac-integrated 4D cone beam CT:: first experimental results
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DOI：
10.1088/0031-9155/51/11/017
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发表时间：
2006-06-07
影响因子：
3.5
通讯作者：
Oelfke, Uwe
中科院分区：
文献类型：
--
作者：
Dietrich, Lars;Jetter, Siri;Oelfke, Uwe
一种新的在线成像方法，直线积分锥束CT (CBCT)，在过去的几年里已经发展起来。它的优点是可以在放射治疗之前或期间直接对患者进行治疗位检查。不幸的是，呼吸器官的运动是最大的器官内运动之一，经常导致重建的三维图像中的伪影。考虑到这一点的一种方法是在图像采集期间注册呼吸相位以进行相位相关图像重建。因此，这项工作的主要焦点是提出一个系统，该系统有潜力研究内部（隔膜运动）和外部（呼吸门控系统的数据）关于呼吸相位和幅度的信息之间的相关性，使用嵌入式CBCT扫描仪。这也包括利用获取的信息进行呼吸相关四维CBCT重建的可行性研究。首先，利用运动的肺影来开发和指定所需的方法，该方法基于仅使用属于某一运动阶段的投影的图像重建。为此，必须为每个投影检测相应的相位。在这种情况下，电子信号允许人们实时跟踪运动。可用于图像重建的投影的数量取决于呼吸阶段和用于重建的投影的位置范围的大小。该范围越窄，可以更好地定位内部结构，但由于投影次数有限，图像的噪声也会增加。对这种相关性也进行了分析。在第二步，这些方法在临床应用中使用了肺肿瘤患者的数据集。在本例中，呼吸相位由外部门控系统（AZ-733V，安zai医疗有限公司）检测，该系统基于压力传感器，通过固定带连接在患者腹部。将重建的4D CBCT图像与相应的用于治疗计划的4D CT图像进行比较，为计算可能的设置误差提供了所需的信息。
A new online imaging approach, linac-integrated cone beam CT (CBCT), has been developed over the past few years. It has the advantage that a patient can be examined in their treatment position directly before or during a radiotherapy treatment. Unfortunately, respiratory organ motion, one of the largest intrafractional organ motions, often leads to artefacts in the reconstructed 3D images. One way to take this into account is to register the breathing phase during image acquisition for a phase-correlated image reconstruction. Therefore, the main focus of this work is to present a system which has the potential to investigate the correlation between internal (movement of the diaphragm) and external (data of a respiratory gating system) information about breathing phase and amplitude using an inline CBCT scanner. This also includes a feasibility study about using the acquired information for a respiratory-correlated 4D CBCT reconstruction. First, a moving lung phantom was used to develop and to specify the required methods which are based on an image reconstruction using only projections belonging to a certain moving phase. For that purpose, the corresponding phase has to be detected for each projection. In the case of the phantom, an electrical signal allows one to track the movement in real time. The number of projections available for the image reconstruction depends on the breathing phase and the size of the position range from which projections should be used for the reconstruction. The narrower this range is, the better the inner structures can be located, but also the noise of the images increases due to the limited number of projections. This correlation has also been analysed. In a second step, the methods were clinically applied using data sets of patients with lung tumours. In this case, the breathing phase was detected by an external gating system (AZ-733V, Anzai Medical Co.) based on a pressure sensor attached to the patient's abdominal region with a fixation belt. The comparison of the reconstructed 4D CBCT images and the corresponding 4D CT images used for the treatment planning provides the required information for the calculation of possible setup errors.