Bedos Ludovic, Riou Olivier, Aillères Norbert, Braccini Antoine, Molinier Jessica, Moscardo Carmen Llacer, Azria David, Fenoglietto Pascal
Radiation Oncology Department, Institut régional du Cancer de Montpellier (ICM), Val d'Aurelle, 208 avenue des Apothicaires, 34298 Montpellier cedex 5, France.
Rep Pract Oncol Radiother. 2017 Mar-Apr;22(2):132-140. doi: 10.1016/j.rpor.2016.07.007. Epub 2016 Nov 12.
To evaluate the tumor repositioning during gated volumetric modulated arc therapy (VMAT) for liver stereotactic body radiotherapy(SBRT) treatment using implanted fiducial markers and intrafraction kilovoltage (kV) images acquired during dose delivery.
Since 2012, 47 liver cancer patients with implanted fiducial markers were treated using the gated VMAT technique with a Varian Truebeam STx linear accelerator. The fiducial markers were implanted inside or close to the tumor target before treatment simulation. They were defined at the maximum inhalation and exhalation phases on a 4-dimensionnal computed tomography (4DCT) acquisition. During the treatment, kV images were acquired just before the beam-on at each breathing cycle at maximum exhalation and inhalation phases to verify the fiducial markers positions. For the five first fractions of treatment in the first ten consecutive patients, a total of 2705 intrafraction kV images were retrospectively analyzed to assess the differences between expected and actual positions of the fiducial markers along the cranio-caudal (CC) direction during the exhalation phase.
The mean absolute intrafractional fiducial marker deviation along the CC direction was 1.0 mm at the maximum exhalation phase. In 99%, 95% and 90% cases, the fiducial marker deviations were ≤4.5 mm, 2.8 mm and 2.2 mm, respectively.
Intrafraction kV images allowed us to ensure the consistency of tumor repositioning during treatment. In 99% cases, the fiducial marker deviations were ≤4.5 mm corresponding to our 5 mm treatment margin. This margin seems to be well-adapted to the gated VMAT SBRT treatment in liver disease.
使用植入的基准标记物和剂量输送过程中采集的分次千伏（kV）图像，评估肝脏立体定向体部放射治疗（SBRT）的门控容积调强弧形治疗（VMAT）期间的肿瘤重新定位。
自2012年以来，47例植入基准标记物的肝癌患者使用Varian Truebeam STx直线加速器的门控VMAT技术进行治疗。在治疗模拟前，将基准标记物植入肿瘤靶区内或附近。在四维计算机断层扫描（4DCT）采集中，在最大吸气和呼气阶段对其进行定义。在治疗过程中，在每个呼吸周期的最大呼气和吸气阶段，在束流开启前采集kV图像，以验证基准标记物的位置。对前十例连续患者治疗的前五个分次，回顾性分析总共2705幅分次kV图像，以评估呼气阶段基准标记物沿头脚（CC）方向的预期位置与实际位置之间的差异。
在最大呼气阶段，沿CC方向的平均绝对分次基准标记物偏差为1.0毫米。在99%、95%和90%的病例中，基准标记物偏差分别≤4.5毫米、2.8毫米和2.2毫米。
分次kV图像使我们能够确保治疗期间肿瘤重新定位的一致性。在99%的病例中，基准标记物偏差≤4.5毫米，与我们5毫米的治疗边界相对应。该边界似乎非常适合肝脏疾病的门控VMAT SBRT治疗。
