Evaluation of four-dimensional cone beam computed tomography ventilation images acquired with two different linear accelerators at various gantry speeds using a deformable lung phantom
Evaluation of four-dimensional cone beam computed tomography ventilation images acquired with two different linear accelerators at various gantry speeds using a deformable lung phantom
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DOI：
10.1016/j.ejmp.2020.07.030
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发表时间：
2020-09-01
影响因子：
3.4
通讯作者：
Jingu, Keiichi
中科院分区：
文献类型：
--
作者：
Kadoya, Noriyuki;Nemoto, Hikaru;Jingu, Keiichi
我们评估了使用两种不同的直线加速器系统在不同机架速度下使用可变形肺体模采集的四维锥形束计算机断层扫描（4D-CBCT）通气图像（VICBCT）。4D-CT和4D-CBCT扫描使用计算机断层扫描（CT）扫描仪、安装在Versa HD中的X射线容积成像系统（Elekta XVI）和安装在TrueBeam中的机载成像仪（OBI）系统进行。在呼气峰和吸气峰图像之间进行基于强度的可变形图像配准（REDD）。通过使用两个度量标准的迭代计算得出基于VICBCT和4D-CT的通气图像（VICT）：一个基于雅可比行列式，另一个基于亨氏单位（HU）的变化。VICBCT使用了三种不同的λ正则化值（lambda）。使用逐体素斯皮尔曼秩相关系数（r）评价VICBCT和VICT值之间的相关性。在两种度量的情况下，Versa HD中机架速度为0.6度/秒的基于雅可比的VICBCT显示出所有机架速度的最高相关性（例如，λ = 0.05和r = 0.68）。因此，基于Jacobian的VICBCT的r值大于或等于基于HU的VICBCT的r值。另外，VICBCT的通气准确性在低机架速度下增加，因此，VICBCT的图像质量受到两种成像系统中机架速度变化的影响。此外，在这两种成像系统中，正则化对VICBCT有很大影响。我们的研究结果有可能有助于设计CBCT协议，将VICBCT成像到功能回避规划过程。
We evaluated four-dimensional cone beam computed tomography (4D-CBCT) ventilation images (VICBCT) acquired with two different linear accelerator systems at various gantry speeds using a deformable lung phantom.The 4D-CT and 4D-CBCT scans were performed using a computed tomography (CT) scanner, an X-ray volume imaging system (Elekta XVI) mounted in Versa HD, and an On-Board Imager (OBI) system mounted in TrueBeam. Intensity-based deformable image registration (DIR) was performed between peak-exhale and peak-inhale images. VICBCT- and 4D-CT-based ventilation images (VICT) were derived by DIR using two metrics: one based on the Jacobian determinant and one on changes in the Hounsfield unit (HU). Three different DIR regularization values (lambda) were used for VICBCT. Correlations between the VICBCT and VICT values were evaluated using voxel-wise Spearman's rank correlation coefficient (r).In case of both metrics, the Jacobian-based VICBCT with a gantry speed of 0.6 deg/sec in Versa HD showed the highest correlation for all the gantry speeds (e.g., lambda = 0.05 and r = 0.68). Thus, the r value of the Jacobian-based VICBCT was greater or equal to that of the HU-based VICBCT. In addition, the ventilation accuracy of VICBCT increased at low gantry speeds.Thus, the image quality of VICBCT was affected by the change in gantry speed in both the imaging systems. Additionally, DIR regularization considerably influenced VICBCT in both the imaging systems. Our results have the potential to assist in designing CBCT protocols, incorporating VICBCT imaging into the functional avoidance planning process.