Department of Radiation Oncology, Erasmus-MC Daniel den Hoed Cancer Center, Rotterdam, The Netherlands.
Department of Radiation Oncology, Erasmus-MC Daniel den Hoed Cancer Center, Rotterdam, The Netherlands.
Int J Radiat Oncol Biol Phys. 2015 Nov 1;93(3):532-9. doi: 10.1016/j.ijrobp.2015.07.2261. Epub 2015 Jul 17.
To evaluate a new type of marker and a new method of marker implantation and to assess interfraction cervix motion for a large population of patients with locally advanced cervical cancer by daily cone beam computed tomographic (CBCT) imaging.
We investigated the position of markers in 50 patients treated in prone position during at least 23 fractions. To reduce streaking artifacts in the planning CT scan, a new type of polymeric marker was used and compared with conventional gold markers. In addition, a new method of implantation was used in an attempt to reduce marker loss. In each fraction, a CT scan was acquired before dose delivery and aligned to the bony anatomy of the planning CT scan, simulating the clinical setup protocol. First, sufficient visibility of the markers was verified. Then, systematic and random displacement of the marker centroids was recorded and analyzed in 3 directions with regard to the planning CT and the first CBCT (to evaluate the presence of a vaginal catheter in the planning CT). Streaking artifacts were quantified with the standard deviation of the mean squared intensity difference in a radius around the marker.
Marker loss was minimal during treatment: in only 3 of the 50 patients 1 marker was lost. Streaking artifacts for the new markers were reduced compared with conventional gold markers. For the planning CT, M/Σ/σ were 0.4/3.4/2.2 mm, 1.0/5.5/4.5 mm, and -3.9/5.1/3.6 mm for the left-right, anterior-posterior, and cranial-caudal directions, respectively. With regard to the first CBCT scan, M/Σ/σ were 0.8/2.8/2.1, 0.6/4.4/4.4, and -1.3/4.5/3.6 mm.
A new type of marker and implantation method was shown to have significantly reduced marker loss and streaking artifacts compared with gold fiducial markers. The recorded marker displacement confirms results reported in the existing literature but for a larger dataset.
通过每日锥形束 CT（CBCT）成像评估一种新型标记物和一种新的标记物植入方法，并评估大样本局部晚期宫颈癌患者的分次间宫颈运动。
我们研究了 50 例接受至少 23 次分次治疗的俯卧位患者的标记物位置。为了减少计划 CT 扫描中的条纹伪影，使用了一种新型聚合物标记物，并与传统金标记物进行了比较。此外，还采用了一种新的植入方法，试图减少标记物丢失。在每个分次中，在剂量输送前采集 CT 扫描，并与计划 CT 扫描的骨性解剖结构对齐，模拟临床设置方案。首先，验证标记物具有足够的可视性。然后，记录并分析标记物质心的系统和随机位移，并针对计划 CT 和第一 CBCT（评估计划 CT 中是否存在阴道导管）在 3 个方向上进行分析。用标记物周围半径内平均平方强度差的标准差来量化条纹伪影。
在治疗过程中，标记物丢失很少：在 50 例患者中，只有 3 例丢失了 1 个标记物。与传统金标记物相比，新型标记物的条纹伪影减少。对于计划 CT，左-右、前-后和颅-尾方向的 M/Σ/σ 分别为 0.4/3.4/2.2mm、1.0/5.5/4.5mm 和-3.9/5.1/3.6mm。对于第一 CBCT 扫描，M/Σ/σ 分别为 0.8/2.8/2.1mm、0.6/4.4/4.4mm 和-1.3/4.5/3.6mm。
与金基准标记物相比，新型标记物和植入方法显示出明显减少的标记物丢失和条纹伪影。记录的标记物位移证实了现有文献中报道的结果，但数据集更大。
