Kadoya Noriyuki, Cho Sang Yong, Kanai Takayuki, Onozato Yusuke, Ito Kengo, Dobashi Suguru, Yamamoto Takaya, Umezawa Rei, Matsushita Haruo, Takeda Ken, Jingu Keiichi
Department of Radiation Oncology, Tohoku University School of Medicine, Sendai, Japan.
Department of Radiation Oncology, Tohoku University School of Medicine, Sendai, Japan.
Pract Radiat Oncol. 2015 Sep-Oct;5(5):e505-e512. doi: 10.1016/j.prro.2015.03.001. Epub 2015 Apr 18.
The purpose of this study was to clarify the dosimetric impact of 4-dimensional computed tomography (4D-CT)-derived, ventilation-guided functional avoidance for stereotactic body radiation therapy (SBRT) with 3-dimensional conformal radiation therapy.
Eleven lung cancer patients with peripheral tumors no greater than 5 cm in size were studied (average planning target volume, 42.4 ± 32.5 cm(3)). Four-dimensional-CT ventilation imaging was performed using deformable image registration for spatial mapping of the peak-exhale 4D-CT image to the peak-inhale 4D-CT image and computation of the Jacobian-based ventilation metric. For each patient, anatomical and functional plans were created using 7 to 9 noncoplanar beams for SBRT (40-56 Gy/4-8 fractions). The anatomical plan was generated without incorporating ventilation information. In the functional plan, functional dose-volume constraints were applied in planning to spare the high-functional lung that was defined as the 90th percentile functional volume. The beam directions of the 2 plans were automatically determined by beam angle optimization.
The percentage of volume receiving a dose of ≥5 Gy (V5), V10, V20, and mean dose to the high-functional lung were 20.5%, 15.6%, 7.8%, and 4.6 Gy, respectively, for the anatomical plan, whereas they were 12.3%, 8.2%, 4.6%, and 3.2 Gy, respectively, for the functional plan. No significant differences in minimum dose, maximum dose, and conformity index of the planning target volume and in all dosimetric parameters for normal tissues between the anatomical and functional plans were seen.
We compared anatomical and functional plans for SBRT with 3-dimensional conformal radiation therapy for the first time. Our results demonstrated that a functional plan for SBRT reduced the dose in the high-functional regions without a significant change in the total lung or planning target volume even if the radiation technique cannot modulate beam intensity. Thus, this technique can be safely used in functional planning for SBRT.
本研究旨在阐明三维适形放射治疗立体定向体部放射治疗（SBRT）中，基于四维计算机断层扫描（4D-CT）的通气引导功能避让的剂量学影响。
研究了11例周围型肿瘤大小不超过5 cm的肺癌患者（平均计划靶体积，42.4±32.5 cm³）。使用可变形图像配准进行四维CT通气成像，将呼气末四维CT图像空间映射到吸气末四维CT图像，并计算基于雅可比行列式的通气指标。对于每位患者，使用7至9个非共面射束创建SBRT（40 - 56 Gy/4 - 8分次）的解剖学和功能计划。解剖学计划的生成未纳入通气信息。在功能计划中，计划时应用功能剂量体积约束以保护被定义为第90百分位数功能体积的高功能肺。两种计划的射束方向通过射束角度优化自动确定。
解剖学计划中，高功能肺接受≥5 Gy剂量的体积百分比（V5）、V10、V20以及平均剂量分别为20.5%、15.6%、7.8%和4.6 Gy，而功能计划中分别为12.3%、8.2%、4.6%和3.2 Gy。解剖学计划和功能计划在计划靶体积的最小剂量、最大剂量和适形指数以及正常组织的所有剂量学参数方面均未观察到显著差异。
我们首次比较了SBRT的解剖学计划和功能计划与三维适形放射治疗。我们的结果表明，SBRT的功能计划降低了高功能区域的剂量，即使放射技术不能调节射束强度，全肺或计划靶体积也无显著变化。因此，该技术可安全用于SBRT的功能计划。
