University Medical Center Hamburg-Eppendorf, Martinistr. 52, Hamburg, 20246, Germany.
Siemens Healthcare GmbH, Siemensstr. 1, Forchheim, 91301, Germany.
Radiat Oncol. 2017 Jun 19;12(1):100. doi: 10.1186/s13014-017-0835-7.
Respiration-correlated CT (4D CT) is the basis of radiotherapy treatment planning of thoracic and abdominal tumors. Current clinical 4D CT images suffer, however, from artifacts due to unfulfilled assumptions concerning breathing pattern regularity. We propose and evaluate modifications to existing low-pitch spiral 4D CT reconstruction protocols to counteract respective artifacts.
The proposed advanced reconstruction (AR) approach consists of two steps that build on each other: (1) statistical analysis of the breathing signal recorded during CT data acquisition and extraction of a patient-specific reference breathing cycle for projection binning; (2) incorporation of an artifact measure into the reconstruction. 4D CT data of 30 patients were reconstructed by standard phase- and local amplitude-based reconstruction (PB, LAB) and compared with images obtained by AR. The number of artifacts was evaluated and artifact statistics correlated to breathing curve characteristics.
AR reduced the number of 4D CT artifacts by 31% and 27% compared to PB and LAB; the reduction was most pronounced for irregular breathing curves.
We described a two-step optimization of low-pitch spiral 4D CT reconstruction to reduce artifacts in the presence of breathing irregularity and illustrated that the modifications to existing reconstruction solutions are effective in terms of artifact reduction.
呼吸相关 CT（4D CT）是胸腹部肿瘤放射治疗计划的基础。然而，目前临床 4D CT 图像存在由于呼吸模式规律假设未得到满足而产生的伪影。我们提出并评估了对现有低螺距螺旋 4D CT 重建方案的修改，以克服各自的伪影。
所提出的高级重建（AR）方法包括两个相互依赖的步骤：（1）对 CT 数据采集过程中记录的呼吸信号进行统计分析，并为投影 binning 提取患者特定的参考呼吸周期；（2）将伪影度量值纳入重建中。对 30 名患者的 4D CT 数据进行了标准相位和局部幅度重建（PB、LAB）和 AR 重建的图像进行比较。评估了伪影的数量，并将伪影统计数据与呼吸曲线特征相关联。
与 PB 和 LAB 相比，AR 将 4D CT 伪影的数量减少了 31%和 27%；对于不规则的呼吸曲线，减少的幅度最为明显。
我们描述了一种用于降低呼吸不规则时低螺距螺旋 4D CT 重建中伪影的两步优化方法，并说明了对现有重建解决方案的修改在减少伪影方面是有效的。
