Szkitsak Juliane, Karius Andre, Fernolendt Susanne, Schubert Philipp, Speer Stefan, Fietkau Rainer, Bert Christoph, Hofmann Christian
Department of Radiation Oncology, Universitätsklinikum Erlangen, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany.
Comprehensive Cancer Center Erlangen-EMN (CCC ER-EMN), Erlangen, Germany.
Phys Imaging Radiat Oncol. 2024 May 5;30:100584. doi: 10.1016/j.phro.2024.100584. eCollection 2024 Apr.
Even with most breathing-controlled four-dimensional computed tomography (4DCT) algorithms image artifacts caused by single significant longer breathing still occur, resulting in negative consequences for radiotherapy. Our study presents first phantom examinations of a new optimized raw data selection and binning algorithm, aiming to improve image quality and geometric accuracy without additional dose exposure.
To validate the new approach, phantom measurements were performed to assess geometric accuracy (volume fidelity, root mean square error, Dice coefficient of volume overlap) for one- and three-dimensional tumor motion trajectories with and without considering motion hysteresis effects. Scans without significantly longer breathing cycles served as references.
Median volume deviations between optimized approach and reference of at maximum 1% were obtained considering all movements. In comparison, standard reconstruction yielded median deviations of 9%, 21% and 12% for one-dimensional, three-dimensional, and hysteresis motion, respectively. Measurements in one- and three-dimensional directions reached a median Dice coefficient of 0.970 ± 0.013 and 0.975 ± 0.012, respectively, but only 0.918 ± 0.075 for hysteresis motions averaged over all measurements for the optimized selection. However, for the standard reconstruction median Dice coefficients were 0.845 ± 0.200, 0.868 ± 0.205 and 0.915 ± 0.075 for one- and three-dimensional as well as hysteresis motions, respectively. Median root mean square errors for the optimized algorithm were 30 ± 16 HU and 120 ± 90 HU for three-dimensional and hysteresis motions, compared to 212 ± 145 HU and 130 ± 131 HU for the standard reconstruction.
The algorithm was proven to reduce 4DCT-related artifacts due to missing projection data without further dose exposure. An improvement in radiotherapy treatment planning due to better image quality can be expected.
即使采用大多数呼吸控制的四维计算机断层扫描（4DCT）算法，单次明显较长呼吸导致的图像伪影仍会出现，给放射治疗带来负面影响。我们的研究首次展示了对一种新的优化原始数据选择和分箱算法的体模检查，旨在在不增加剂量暴露的情况下提高图像质量和几何精度。
为验证新方法，进行了体模测量，以评估在考虑和不考虑运动滞后效应的情况下，一维和三维肿瘤运动轨迹的几何精度（体积保真度、均方根误差、体积重叠的骰子系数）。没有明显较长呼吸周期的扫描用作参考。
考虑所有运动时，优化方法与参考之间的体积偏差中位数最大为1%。相比之下，标准重建在一维、三维和滞后运动中的偏差中位数分别为9%、21%和12%。一维和三维方向的测量中，骰子系数中位数分别为0.970±0.013和0.975±0.012，但优化选择的所有测量中滞后运动的平均骰子系数仅为0.918±0.075。然而，对于标准重建，一维、三维和滞后运动的骰子系数中位数分别为0.845±0.200、0.868±0.205和0.915±0.075。优化算法在三维和滞后运动中的均方根误差中位数分别为30±16 HU和120±90 HU，而标准重建的分别为212±145 HU和130±131 HU。
该算法被证明可减少因缺失投影数据导致的4DCT相关伪影，且无需进一步剂量暴露。预计可因更好的图像质量改善放射治疗计划。
